PREAMBLE (NOT PART OF THE STANDARD)

END OF PREAMBLE (NOT PART OF THE STANDARD)

Indian Standard
GUIDE FOR TREATMENT AND DISPOSAL OF EFFLUENTS OF FERTILIZER INDUSTRY

i

Chairman	Representing
Dr T. R. Bhaskaran	Geo Miller & Co Pvt Ltd, Calcutta
Members
Shri S. Bhoothalingam	Kerala State Board for the Prevention & Control of Water Pollution, Trivandrum
Shri J. D. Joysingh (Alternate)
Chief Water Analyst, King Institute, Madras	Director of Public Health, Government of Tamil Nadu, Madras
Shri L. M. Choudhry	Haryana State Board for the Prevention & Control of Water Pollution, Chandigarh
Shri M. L. Prabhakar (Alternate)
Shri M. V. Desai	Indian Chemical Manufacturers’ Association, Calcutta
Shri Mangal Singh (Alternate)
Shri H. P. Dubey	National Test House, Calcutta
Shri B. K. Dutta	The Fertilizer (Planning & Development) India Ltd, Sindri
Shri G. S. Ray (Alternate)
Shri R. C. Dwivedi	Uttar Pradesh Water Pollution Prevention and Control Board, Lucknow
Shri R. N. Sen (Alternate)
Shri P. Ganguly	The Alkali & Chemical Corporation of India Ltd, Calcutta
Shri P. K. Chakravarty (Alternate)
Shri K. L. Ghosh	Regional Research Laboratory (CSIR), Bhubaneshwar
Dr P. K. Gupta	National Physical Laboratory (CSIR), New Delhi
Shri Jitendra Rai (Alternate)
Dr M. I. Gurbaxani	The Tata Iron & Steel Co Ltd, Jamshedpur
Shri S. Hanumanth Rao	Karnataka State Board for Prevention & Control of Water Pollution, Bangalore
Shri C. H. Govinda Rao (Alternate)
Shri C. P. Jain	Central Electricity Authority, New Delhi
Shri J. Jha (Alternate)

© Copyright 1981 BUREAU OF INDIAN STANDARDS This publication is protected under the Indian Copyright Act (XIV of 1957) and reproduction in whole or in part by any meant except with written permission of the publisher shall be deemed to be an infrigement of copyright under the said Act.

1

Members	Representing
Shri Mallinath Jain	Delhi Water Supply & Sewage Disposal Undertaking, New Delhi
Shri K. R. Sahu (Alternate)
Joint Director (Chem), RDSO, Railway Board (Ministry of Railways) Lucknow.
Assistant Chemist & Metal
Lurgist, N. E. Rly, Gorakhpur (Alternate)
Shri M. S. Krishnan	Bhabha Atomic Research Centre, Bombay
Shri V. N. Lambu	Ion Exchange (India) Ltd, Bombay
Shri M. S. Bidiakar (Alternate)
Shri S. Mahadevan	Bharat Heavy Electricals Ltd, Hyderabad
Shri G. Krishnayya (Alternate I)
Dr A. Prabhakar Rao (Alternate II)
Shri V. K. Malik	All India Distillers Association, New Delhi
Shri K. Suriyanarayanan (Alternate)
Shri K. Manivannan	Director of Industries, Government of Haryana, Chandigarh
Prof R. S. Mehta	Gujarat Water Pollution Control Board, Gandhinagar
Shri M. D. Dave (Alternate)
Shri S. K. Mitra	West Bengal Prevention & Control of Water Pollution Board, Calcutta
Municipal Analyst	Municipal Corporation of Greater Bombay
Shri D. V. S. Murthy	M. P. State Prevention & Control of Water Pollution Board, Bhopal
Shri P. K. Banerjee (Alternate)
Shri R. Natarajan	Bombay Chamber of Commerce & Industry, Bombay
Shri B. M. Rahul (Alternate)
Shri S. K. Neogi	Institution of Public Health Engineers, India, Calcutta
Dr M. Banerjee (Alternate)
Dr V. Pachaiyappan	The Fertiliser Association of India, New Delhi
Dr R. N. Trivedi (Alternate)
Shri R. Paramasivam	National Environmental Engineering Research Institute (CSIR), Nagpur
Shri M. V. Nanoti (Alternate)
Prof S. C. Pillai	Indian Institute of Science, Bangalore
Shri A. K. Poddar	Steel Authority of India Ltd, New Delhi
Shri A. K. Das (Alternate)
Shri H. S. Puri	Punjab State Board for the Prevention and Control of Water Pollution, Patiala
Shri Qimat Rai (Alternate)
Shri B. B. Rao	Ministry of Works & Housing
Dr I. Radhakrishnan (Alternate)
Shri B. V. Rotkar	Central Board for the Prevention & Control of Water Pollution, New Delhi
Dr K. R. Ranganathan (Alternate)
Shri K. Rudrappa	Engineers India Ltd, New Delhi
Shri S. N. Chakrabarti (Alternate)

2

0. FOREWORD

0.1

This Indian Standard was adopted by the Indian Standards Institution on 5 June 1981, after the draft finalized by the Water Sectional Committee had been approved by the Chemical Division Council.

0.2

A number of nitrogenous and phosphatic fertilizer factories have been commissioned in India in the last three decades and more are either under installation or planned for installation in the coming years. These fertilizer factories are located throughout India, depending on the proximity of the raw material source, availability of water and power and distribution of finished product. The effluent disposal facility has also been considered recently in deciding the factory site.

0.3

The production of fertilizers requires a huge quantity of water for various uses. A substantial part of this water after use in the process finds its way out contaminated with various pollutants. These effluents finally flow to the nearby inland surface waters, coastal waters, or on land causing water pollution problems.

0.4

Considerable work has been done in India and abroad on proper treatment and disposal of these effluents and information and data on the subject are now available. These data and information have formed the basis for the preparation of this standard. While realizing that any effluent treatment process has the inherent scope for being further improved, the Committee responsible for the preparation of this standard has given careful consideration to the feasibility of the methods available in literature and has been of the view that effective measures can now be taken for abatement of pollution. It is hoped that the industry, public health authorities and other agencies concerned with water pollution control in different parts of the country will find this standard useful.

0.5

The object of this standard is to compile information on methods of treatment of effluents and to make definite recommendations for their treatment in India. The standard does not seek to provide detailed information on the working of a plant or on the designing and operation of the effluent treatment plant.
Further, the methods recommended for adoption have been selected taking into consideration the practicability of their adoption by the industry.
3When better and more economic methods of treatment become available, revision of this standard will be taken up. A list of relevant references is given in Appendix A.

0.6

It is recommended that plants located near the sea may preferably discharge their effluents into the marine coastal area rather than into inland surface water. The extent of pollution of marine coastal areas permitted by discharge of effluents is laid down in IS : 7967-1976*.

0.7

The extent of pollution of inland surface waters permitted by discharge of effluents is laid down in IS : 2296-1974†. The following Indian Standards lay down tolerance limits for industrial effluents :

IS : 2490 (Part I)-1974	Tolerance limits for industrial effluents discharged into inland surface waters : Part I General limits (first revision)
IS : 2490 (Part VIII)-1976	Tolerance limits for industrial effluents discharged into inland surface waters: Part VIII Phosphatice fertilizer industry (first revision)
IS : 2490 (Part IX)-1977	Tolerance limits for industrial effluents discharged into inland surface waters: Part IX Nitrogenous fertilizer industry (first revision)
IS : 3306-1974	Tolerance limits for industrial effluents discharged into public sewers (first revision)
IS : 3307-1977	Tolerance limits for industrial effluents discharged on land for irrigation purposes (first revision)
IS : 7968-1976	Tolerance limits for industrial effluents discharged into marine coastal areas.

0.8

Methods of sampling and test for industrial effluents are covered in various parts of IS : 2488‡.

1 SCOPE

1.1

This standard covers methods of treatment and disposal of effluents from nitrogenous and phosphatic fertilizer industry. It includes available data and information on the sources, characteristics, volumes, pollutional effects of the effluents, ways of waste prevention and methods of their treatment and disposal.
*Criteria for controlling pollution of marine coastal areas.
†Tolerance limits for inland surface waters subject to pollution (first revision).
‡ Methods of sampling and test for industrial effluents:

Part I - 1966
Part II - 1968
Part III - 1968
Part IV - 1974
Part V - 1976

4

2. DESCRIPTION OF PROCESSES INVOLVED

2.0

General—Nitrogenous fertilizer industry is mainly concerned with the production of fertilizers like urea, ammonium sulphate, ammonium nitrate, calcium ammonium nitrate (CAN), ammonium chloride, etc. Phosphatic fertilizer category manufactures mainly single superphosphates, triple superphosphates, nitrophosphates, ammonium phosphates, etc.

2.1 Nitrogenous Fertilizer Industry

2.1.1

Ammonia Production—in the production of nitrogenous fertilizer ammonia is the basic intermediate product. Ammonia is produced by reaction of hydrogen with nitrogen. This reaction is carried out in a converter in the presence of iron catalyst promoted with metal oxides at elevated pressure, which favours ammonia formation. The raw material source of nitrogen is atmospheric air or pure nitrogen from an air liquefaction plant. Hydrogen on the other hand is obtained from a variety of sources, namely naphtha, fuel oil, coal, natural gas, coke-oven gas, hydrogen rich refinery gas, electrolytic hydrogen off-gas, etc. The production of ammonia from the above feed stock involves three main steps : preparation of raw synthesis gas, purification of the gas mixture and synthesis of ammonia.

2.1.1.1

The process adopted for synthesis gas preparation depends on the feedstock used. Where a cheap source of electricity is available, electrolysis of water yields hydrogen off-gas with the production of heavy water. In India only one such unit is operating at present. In the partial oxidation process hydrocarbon feedstock and oxygen or oxygen enriched air are preheated and reacted at high temperature and pressure to form carbon monoxide and hydrogen. The raw gas is scrubbed with water for removal of the carbon formed during gasification and after desulphurization is sent to the shift conversion unit. In the steam reformation process, desulphurized naphtha or natural gas is subjected to catalytic reforming in a primary reformer in the presence of steam to form carbon monoxide and hydrogen. Since the reaction is incomplete in the primary reformer, a secondary reformer is used for converting the remaining hydrocarbons. Air is injected into the secondary reformer to burn the unreatcted hydrocarbons and supply the nitrogen requirement of the raw gas. Coal gasification process involves pulverised coal gasification in the presence of oxygen and steam. The raw gas produced is cleaned up before it goes for shift reaction for purification.

2.1.1.2

Purification of raw gas—The first step in the purification of raw synthesis gas is the shift conversion of carbon monoxide to carbon dioxide which is accomplished by reacting carbon monoxide with steam over activated iron oxide catalyst; carbon dioxide thus produced with hydrogen is removed by absorption process by use of scrubbing solutions. The absorbents normally used are hot potash activated with arsenic in Vetrocoke
5process, hot potash activated with a small quantity of vanadium, arsenic, etc, in the Ben field process, chilled methanol in the Rectisol process, monoethanolamine process, etc. Carbon dioxide is recovered and reused. The residual carbon monoxide is removed by met ha nation or absorbed by liquid nitrogen wash.

2.1.1.3

Ammonia synthesis—Pure hydrogen and nitrogen in the required quantities are made to react under elevated pressure and temperature over activated iron oxide catalyst to produce ammonia. The ammonia produced is cooled so that it condenses and is recovered in a liquid-gas separator.

2.1.2

Urea Production—Urea is the main nitrogenous fertilizer in India. Urea is produced from ammonia and carbon dioxide obtained from ammonia plant normally located at the site of the urea plant. Urea synthesis can he divided into three main sections, namely, synthesis, decomposition/recovery and finishing sections. In the synthesis section ammonia and carbon dioxide are com pressed in an autoclave at elevated temperature and pressure to form a solution of urea, ammonium carbonate and water. The product stream from the urea reactor is a mixture of urea, ammonium carbonate, water, unreacted ammonia and carbon dioxide. An excess of ammonia is always maintained, so that carbon dioxide concentration in the exit stream is low. The next section, in the urea process is the decomposition section where the solution from the autoclave is heated to decompose ammonium carbonate. The decomposed ammonium carbonate along with excess and unreacted ammonia and carbon dioxide is recycled in the autoclave, while 70 to 75 percent urea solution is recovered. In the finished section, the urea solution leaving the decomposition section is further processed. The urea solution is concentrated under vacuum or at atmospheric pressure in a specially designed evaporator of falling film type to raise the urea concentration above 98 percent. The molten urea from the concentrator is pumped to the top of the prilling tower where it is sprayed downward against an upward stream of cold air. The urea prills from the tower are cooled, screened and stored.

2.1.3

Ammonium Sulphate Production—Ammonium sulphate is produced from three sources.

2.1.3.1

The production of coke from coal results in the production of coke oven gas which contains a significant amount of ammonia. This ammonia is converted into byproduct ammonium sulphate by reacting it with sulphuric acid.

2.1.3.2

Ammonium sulphate is produced by neutralizing synthetic ammonia with sulphuric acid and the ammonium sulphate crystals formed are separated from the mother liquor by filtration or centrifuging.
6

2.1.3.3

Ammonium sulphate is also manufactured from natural or byproduct gypsum. The ground gypsum is reacted with ammonium carbonate producing ammonium sulphate and chalk. The chalk is separated by filtration and the liquor is evaporated and crystallized. The ammonium sulphate crystals are separated by filtration and dried.

2.1.4

Ammonium Nitrate and Calcium Ammonium Nitrate Production—Ammonia reacts with nitric acid in a neutralizer producing ammonium nitrate. Ammonia and nitric acid are preheated with the vapours of the neutralizer. In the neutralizer, concentrated ammonium nitrate solution is produced which is further concentrated m vacuum concentrators. In ammonium nitrate production, the concentration is carried out up to molten nitrate which is then sprayed from a prilling tower against an upward stream of air to produce prilled ammonium nitrate. In the case of calcium ammonium nitrate (CAN), the concentrated liquor is pumped and sprayed into the granulator which is also fed with a measured quantity of limestone powder and recycle fines. The hot granules are dried, screened, cooled and coated with soapstone dust in a coating drum and stored.

2.1.5

Nitric Acid and Sulphuric Acid Production—In the industries where ammonium nitrate and ammonium sulphate are produced, nitric acid and sulphuric acid production plants are also installed. Sulphuric acid and nitric acid are also required for the production of phosphatic fertilizers. Nitric acid is produced by oxidation of ammonia over a noble metal catalyst and absorbing in water Sulphuric acid is normally produced by burning sulphur to form sulphur dioxide which is then oxidized to sulphur trioxide over vanadium catalyst; sulphur trioxide is then absorbed in concentrated sulphuric acid.

2.1.6

Ammonium Chloride Production—Ammonium chloride is normally obtained as a byproduct in the production of soda ash. Sodium chloride is reacted with ammonium bicarbonate producing ammonium chloride and sodium bicarbonate. The ammonium chloride solution is filtered, evaporated and crystallized. Ammonium chloride is also manufactured by direct neutralization of ammonia with hydrochloric acid gas.

2.2 Phosphatic Fertilizer Industry

2.2.1

Phosphoric Acid—In the manufacture of phosphatic fertilizers, the production of phosphoric acid is the basic building block. The first step involved in phosphoric acid production is grinding of rock phosphate. Ground phosphate rock is mixed with sulphuric acid after the acid has first been diluted with water to 55 to 70 percent sulphuric acid concentration. The acidulated rock is digested and retained for several hours in attack vessels. The rock phosphate is converted into gypsum and phosphoric acid. Some of the fluorine contained in the rock phosphate is evolved from the attack vessels as silicon tetrafluoride and hydrofluoric acid. Both silicon
7fluoride and hydrofluoric acid are collected in the wet scrubber unit. Some quantity of fluorine and P₂O₅ remains along with the byproduct gypsum which poses disposal problems. After the reaction in the digester, the mixture of phosphoric acid and gypsum is pumped to the filter where gypsum is separated from phosphoric acid. Dilute phosphoric acid, thus produced is further concentrated to 40 to 54 percent phosphorus pentoxide under reduced pressure. During concentration, the evolved fluorine together with minor quantities of phosphoric acid passes to the barometric condensers and these contaminate the condenser water.

2.2.2

Single Superphosphate—Single superphosphate is produced by the reaction of sulphuric acid with ground rock phosphate. After reaction, the mixture is transferred to a den where sufficient retention time is provided for solidification. At the end, it is taken to storage for curing.

2.2.3

Triple Superphosphate—Ground rock phosphate and phosphoric acid are mixed in a tank with agitation. After reaction the slurry is distributed on to the recycled dry product. It is dried in rotary driers and sized in vibrating screens before storage.

2.2.4

Ammonium Phosphates—Two primary raw materials for the production of ammonium phosphates are ammonia and phosphoric acid. Different grades of ammonium phosphate vary only in the nitrogen and phosphate contents. Therefore, by controlling the degree of ammoniation during the neutralization of phosphoric acid, different grades of ammonium phosphate can be obtained. Ammonia is reacted with phosphoric acid in vertical cylindrical vessels with or without agitation. The resultant slurry is then distributed on to dry recycled product. The product is then discharged into rotary driers from where it passes to storage.

2.2.5

Nitrophosphates—Nitric acid acidulation differs from sulphuric acid acidulation in that phosphoric acid is not separated as a product from the acidulation reaction mixture. Nitric acid and rock phoshpate are mixed in a series of reaction vessels with agitation. In the first few vessels, the reaction products—calcium nitrate and phosphoric acid-remain in a mixed liquid form. At this point, either phosphoric or sulphuric acid is added together with ammonia to produce a specific mix of calcium compounds, ammonium nitrate and phosphoric acid. This is then converted into a dry product.

3 SOURCES, VOLUMES AND CHARACTERISTICS OF EFFLUENTS

3.1 Nitrogenous Fertilizer Industry (Sources of Effluents)

3.1.1 Ammonia Plant

3.1.1.1

From raw material handling, storage and preparation sections, normally a small stream of effluent containing mainly some coal dust, fuel oil or naphtha is discharged, depending on the feed stock used
8

3.1.1.2

Where coal is used as feedstock, a considerable quantity of quenched ash is discharged continuously from the coal gasification section. The ash slurry from the direct scrubber recirculating water settling system containing some cyanides is also discharged to the ash pond.

3.1.1.3

When naphtha is used as feed stock, the effluents from the oil gasification section and carbon recycle section contain high concentration of oil, in addition to the carbon particles and sulphide impurities. Catalytic steam reformation process is mostly adopted when naphtha is used feedstock. No liquid effluents are produced in this process.

3.1.1.4

In the partial oxidation process, finely divided carbon is produced Some built-in facility in the plant exists for recycle and reuse of this carbon in the process itself, but due to unforeseen accidental failure of the system, some carbon slurry may be discharged for a short period. This carbon slurry may also contain some cyanides and sulphides.

3.1.1.5

Depending on the absorbent used for the purification of raw gas, some toxic chemicals, namely, arsenic, MEA, vanadium, methanol and some alkali are discharged in a small stream.

3.1.1.6

From the CO-conversion unit, some quantity of condensate containing ammonia and catalyst dust is discharged.

3.1.1.7

During the commissioning of the plant and initial start-up some quantity of ammonia is discharged when the catalyst reduction operation is carried out. Normally, this effluent emanates once every 2 to 3 years.

3.1.1.8

From the ammonia synthesis section, a stream of condensate containing oil is discharged.

3.1.1.9

Some effluent containing ammonia is sometimes discharged from the storage and recovery sections of some plants.

3.1.1.10

A continuous purge from recirculating cooling water is discharged which contains conditioning chemicals and biocides.

3.1.2 Urea Plant

3.1.2.1

From the carbon dioxide compression section some effluent containing oil is discharged.

3.1.2.2

Considerable quantities of ammonia and urea arc discharged continuously along with the vacuum condensate. In modern urea plants, the quantities of ammonia and urea discharged has been reduced appreciably be process modification. When urea solution is concentrated at atmospheric pressure, no liquid effluent is produced in the urea plant, as no barometric condenser is needed for vacuum generation.
9

3.1.2.3

Some urea and ammonia are occasionally discharged which originate from spillage, leakage of glands, flanges, joints, etc, floor washings and also from drainings during shutdown and startup of plants, In modern plants these discharges are collected and recyled.

3.1.2.4

A stream of cooling water purge containing conditioning chemicals and biocides is discharged from the cooling tower continuously.

3.1.3 Ammonium Nitrate and Calcium Ammonium Nitrate Plant

3.1.3.1

The scrubber liquor from the neutralization section contains ammonia and nitric acid which may or may not be recycled.

3.1.3.2

Some ammonium nitrate is discharged from the vacuum concentration section.

3.1.3.3

Occasional spillage and leakage from process may give rise to an effluent containing ammonium nitrate.

3.1.3.4

The cooling water blowdown containing some conditioning chemicals and biocides is discharged continuously.

3.1.4 Ammonium Sulphate Plant

3.1.4.1

From the reaction and filtration section of the gypsum process, some effluents are discharged which contains ammonium sulphate, ammonia, chalk, etc.

3.1.4.2

Where direct neutralization is done, a small quantity of ammonia may be released in the effluent.

3.1.4.3

From the concentration, evaporation and crystallization section, an effluent containing ammonia and ammonium sulphate is discharged.

3.1.4.4

Spillage and leakages also form another effluent stream effluent containing mainly ammonium sulphate.

3.1.4.5

Cooling tower blowdown containing conditioning chemicals and biocides is discharged continuously.

3.1.5

Ammonium Chloride Plant—The effluents are mixed up with soda ash plant effluent and contain ammonia and ammonium chloride. However, this effluent is discharged in a limited quantity.

3.1.5.1

In the direct process, the main effluent is the wash water used to wash the gases before they are let out. This will be of considerable volume and will contain ammonia.
10

3.2 Phosphatic Fertilizer Industry (Sources of Effluents)

3.2.1 Phosphoric Acid Plant

3.2.1.1

During the digestion of rock phosphate with acid, silica, fluorine and other impurities present in it are evolved as silicon fluoride, hydrofluoric acid, dust, etc. These off-gases are scrubbed with water. A part of the scrubber liquor is discharged continuously.

3.2.1.2

In the phosphoric acid concentration section, fluorine together with minor quantity of phosphoric acid passes to the barometric condenser. The condenser discharge contains 2 to 3 percent H₂SiF₆.

3.2.1.3

From the gypsum filtration section also, some quantity of effluent is discharged which contains suspended matter, phosphorus pentoxide and fluorine.

3.2.1.4

Normally, the gypsum obtained as a by-product is collected in a pond; the overflow from this pond contains suspended matter, phosphate, fluorine, etc.

3.2.2

Single Superphosphate—During the production of single superphosphate, dust, fluorine, phosphate bearing waste water is discharged from scrubbers of the digestion section and scrubber liquor of the exit off-gases from the dens.

3.2.3

Triple Superphosphate—In the manufacture of triple superphosphate dust, fluorine, phosphate bearing off-gases from the reaction vessels, granulator and dryer are scrubbed with water. A part of this scrubber liquor finds its way out in the effluent stream.

3.2.4

Ammonium Phosphates—The main effluent normally discharged from ammonium phosphate plant contains ammonia, phosphate, fluorine, dust, etc. The contaminants indicated above are evolved during the neutralization reaction, and granulation, drying and sizing operations. These off-gases are scrubbed with phosphoric acid and the entire scrubber liquor is put into the reactor.

3.2.5

Nitrophosphates—In nitrophosphate production also, dust, fluorine, phosphate, ammonia, etc, containing off-gases from digestion and ammoniation section and also from drying, granulation and sizing sections are scrubbed with water for reduction of the pollutants in the emissions of nitrophosphate plant. A portion of the scrubber liquor is discharged as effluent continously.

3.2.6

During the processes of manufacture of phosphoric acid and phosphatic fertilizers considerable quantity of recirculating cooling water is used. A continuous stream of cooling water blowdown containing conditioning chemicals and biocides is discharged from the cooling towers.
11

3.2.7

Sulphuric Acid Plants—When there are leakages, the cooling water gets contaminated with sulphuric acid.

3.2.8

Nitric Acid Plant—When there are leakages, the cooling water gets contaminated with nitric acid.

3.3

Quantity of Effluent—The total quantity of finally treated effluent discharged from fertilizer industries varies widely, depending on the raw material used, the end product obtained and the process adopted for the production of fertilizers. A 1 000 tonnes per day urea plant having recirculating cooling water system and all the auxiliary facilities required for production, generally discharges 8000 to 12000 m³/day effluents, while a phosphatic fertilizer plant with recirculating cooling water system and auxiliary facilities and having a production capacity of about 100 tonnes of P₂O₅ per day as fertilizer generally discharges 3000 to 6000 m³/day effluents.

3.4 Characteristics of Effluents

3.4.1

The main pollutants from the nitrogenous and phosphatic fertilizer industry along with the auxiliary facilities are indicated below:

1. Ammonia and ammonium salt;
2. Suspended solids and ash;
3. Acids and alkalis;
4. Oil;
5. Arsenic, MEA and methanol;
6. Nitrates;
7. Urea;
8. Cooling water conditioning chemicals like chromate, phosphates, biocides, etc;
9. Cyanides and sulphides;
10. Biochemical oxygen demand;
11. Fluorides; and
12. Phosphates, etc.

3.4.2

Nitrogenous Fertilizer—Typical ranges of contaminant concentrations* from various operations are given below:
*Data based on Revised Draft Report on Fertilizer Industry Pollution and Control Measures submitted to the Central Board for Prevention and Control of Water Pollution by Tata Consulting Engineers, Bombay.
12

3.4.2.1 Cooling tower blowdown

	Contaminant	Concentration Range (mg/l)
a)	Suspended solids	30-3 000
b)	Dissolved solids	300-3 200
c)	Free ammonia	0.4-40
d)	Ammoniacal nitrogen	20-400
e)	Phosphates	10-30
f)	Chromium	6-8
g)	Chlorides	8-18
h)	Sulphates	20-50
j)	Calcium	80-240
k)	Zinc	Traces
m)	Oil	10-1 000

3.4.2.2

Water treatment plant—The effluents from the water treatment plant of a nitrogenous fertilizer unit varies from 380 1/tonne of urea to 2000 1/tonne of urea, depending upon the quantity of raw water used. The dominant contaminants in a water treatment plant effluent are anions and cations. In a typical nitrogenous fertilizer unit manufacturing urea the amount of sodium hydroxide in the water treatment plant effluent is 11.6 kg/tonne of urea manufactured. The total sulphate ion quantity is 18.2 kg/tonne of urea. Besides these, when a process condensate is treated for use as boiler feed water, ammonia finds its way into the water treatment plant effluent.

3.4.2.3 Boiler blow-down

	Contaminant	Concentration Range (mg/l)
a)	Phosphorus	10
b)	Dissolved solids	100
c)	Suspended solids	10
d)	Free ammonia	2
e)	Ammoniacal nitrogen	2
f)	Oil	30

13

3.4.2.4 Ammonia plant

	Contaminant	Concentration Range (mg/l)
a)	Suspended solids	100-1 5000
b)	Dissolved solids	1 000-3 000
c)	Ammoniacal nitrogen	200-1 500
d)	Arsenic	0-2
e)	Carbon dioxide	5 000
f)	Chlorides	80
g)	Sulphates	200
h)	Calcium	25
j)	Cyanides	7
k)	Sodium	75
m)	Vanadium	0.1

3.4.2.5 Urea plant

	Contaminant	Concentration Range (mg/l)
a)	Suspended solids	100
b)	Dissolved solids	1000-3 000
c)	Ammoniacal nitrogen	500-2 000
d)	Urea	340-20 000
e)	Sulphates	200
f)	Chlorides	80
g)	Calcium	20
h)	Phosphates	5

3.4.3

Phosphatic Fertilizer—Typical ranges of contaminant concentrations* from various operations are given below:
*Data based on Revised Draft Report on Fertilizer Industry Pollution and Control measures submitted to the Central Board for Prevention and Control of Water Pollution by Tata Consulting Engineers, Bombay.

3.4.3.1 Cooling tower blowdown

	Contaminant	Concentration Range (mg/l)
a)	Dissolved solids	380
b)	Volatile solids	50
c)	Fluorides (as F)	1 14
d)	Chromates	Traces
e)	Chlorides (as Cl)	52
f)	Sulphates (as SO4)	30
g)	Calcium (as Ca)	10

3.4.3.2 Boiler blowdown

	Contaminant	Concentration Range (mg/l)
a)	Dissolved solids (fixed)	9 661
b)	Sulphates (as SO4)	918.3-3 813
c)	Alkalinity (as CO3)	2 150-2 950
d)	Hydroxide	450-575
e)	Silica (as SiO2)	0.80
f)	Zinc	0.10

3.4.3.3 Superphosphate plant

	Contaminant	Concentration Range (mg/l)
a)	Suspended solids	150-600
b)	Dissolved solids	644-980
c)	Biochemical oxygen demand (5 day at 20°C), Max	35-175
d)	Fluorides (as F)	1 920-2 163
e)	Chlorides (as Cl)	42-234
f)	Sulphates (as SO4)	40-336
g)	Calcium	32-86
h)	Phosphates (as PO4)	0.4-1

3.4.3.4 Blending unit

	Contaminant	Concentration Range (mg/l)
a)	Total dissolved solids	1480
b)	Dissolved oxygen	6.7
c)	Biochemical oxygen demand (5 days at 20°C), Max	1
d)	Chlorides (as Cl)	488 15
e)	Sulphates (as SO4)	200
f)	Ammoniacal nitrogen	10
g)	Phosphates (as PO4)	5
h)	Oil and grease	Traces

4. METHODS OF TREATMENT, UTILIZATION AND DISPOSAL

4.1

General—In the preparation of any scheme of treatment for effluents it is essential that each source of effluent be studied regarding its flow over a 24-hour period for several days and the maximum, minimum and average flow be ascertained. Installation of flowmeter or weir of continuous recording type is useful. Otherwise, readings of flow have to be recorded at hourly intervals normally. In case no measurement device can be installed, the effluents should flow to a holding tank where the level has to be recorded hourly. While locating the source of effluent, due consideration should be given to occasional discharges due to leakage and floor washings, etc, and also the effluents which may be discharged during malfunctioning of the plants and during the start-up or shutdown of the plant.

4.1.1

Each effluent source has to be analysed individually over a 24-hour period with samples drawn hourly. The samples may be collected hourly and made into 3 to 6 composite samples, depending on the variation of flow and composition.

4.2

Segregation of Effluents—The effluent streams have to be segregated according to the nature of pollutants present in them and their concentration. As a general practice, all effluents containing high concentration of total ammonia nitrogen should be combined. Normally effluent containing ammonia nitrogen above 100 mg/l should fall in this category. However, effluents with 50 to 100 mg/l ammonia nitrogen may also be collected in this stream if the volume is large. The following steps should be followed, wherever applicable :

1. Effluents containing suspended solids above 100 mg/l should be combined together as far as practicable;
2. Oil bearing effluents should be combined as far as possible;
3. Highly acidic and alkaline effluents should be separated from the rest of the effluent streams;
4. Urea bearing effluents which also contain high concentration of ammonia should be separated from ammonia bearing effluent;
5. All cooling tower purge water containing chromate, phosphate and biocides should be separated from the rest of factory effluents;
6. Ash slurry should be separated from the rest of the effluents;
7. Effluents containing carbon slurry should be stored separately; 16
8. Arsenic and cyanide bearing effluents should be stored separately;
9. Effluents containing fluorides and phosphates are to be segregated from other effluents;
10. Sewage effluents should be treated separately as far as possible and
11. Storm water and drain water should not mix with individual plant effluents.

However, many of the above effluents may be combined, depending on their characteristics, flow and type of treatment to be adopted.

4.2.1

After assessment of the individual effluent streams regarding their volume, pollutant content, frequency of discharge etc, the volume and concentration of various pollutants in the final effluent discharged beyond the factory boundary limit have to be ascertained. These figures along with the prevailing standard of the effluents and the receiving water and also the local regulation will indicate the degree of specific type of treatment of the individual segregated effluents that will be necessary for adoption for treatment of the effluent. Accordingly, various methods of treatment available are to be studied to suit the requirements for individual pollutants. Once the treatments for the pollutants are finalized, a broad scheme is developed and in the same scheme integration of all the treated effluents is made (Fig. 1).

4.2.2

While studying the different treatment schemes, preference should always be given to such schemes where some recovery of waste products for reuse in the process or recovery for direct marketing can be made from the wastes. Sometimes the effluent water after adequate treatment can be recycled in the process. This reduces water consumption as well as the final effluent volume discharged.

4.2.3

Sometimes the segregated effluents can be combined in such a way that one can be utilized for the treatment of the other. This type of judicious combination reduces the cost of chemicals and also increases the efficiency of treatment rendered.

4.2.4

The various processes available at present for the treatment of individual pollutant parameters relevant to the fertilizer industry have been compiled below for study before final adoption according to the suitability of a particular process depending on the degree of treatment considered necessary.

4.3 Treatment of Effluents for Specific Pollutants

4.3.1

Ammonia Nitrogen—Various processes have been developed for removal/recovery of ammonia nitrogen from effluents. These processes basically fall in two categories: (a) Physio-chemical, and (b) biological.
17
18

Effluent Streams Effluent containing suspended carbon, cyanide, sulphide, etc Condensate containing oil Cooling tower blowdown containing CrO4 and PO4 Process condensate containing ammonia Catalyst reduction NH3 Reactor draining, overflow of tanks and plant washings Vacuum condensate containing ammonia and urea Cooling tower  blowdown containing CrO4 and PO4 Condensate containing oil Acidic effluent Alkaline effluent Acidic effluent Raw water treatment plant sludge Boiler blowdown Ash slurry Oily effluent Concentrated fluosilicic acid solution Effluent containing fluorine and phosphate Gypsum slurry Effluent containing fluorine and phosphate Sewage effluent from toilets and washings Uncontaminated effluent stream Final effluent of the factory after treatment

Treatment of Effluent Suspended matter settling Cyanide, sulphide removal system Oil separator Evaporation of ammonia Collection pit for ammoniacal effluent Air/steam stripping of ammonia with recovery of ammonia in case of steam stripping Thermal urea hydrolysis ammonia recovery Chromate phosphate removal system Neutralization Oil separation Ash settling pond Oil separation Recovery of fluosilicic acid Fluorine and phosphate removal system Gypsum settling pond Sewage treatment Biological treatment Mixing pond

19

4.3.1.1 Physico—chemical processes

1. Air stripping—The concentration of ammonia nitrogen in effluent can be reduced considerably by adopting air stripping of ammonia from the effluent at an elevated pH Ammonium ions (NH₄⁺) in water exist in equilibrium with NH₃ as follows:
   NH₄+ ⇌ NH₃°
   At pH level above 7.0 the equilibrium is shifted progressively towards the right, so that ammonia is liberated as gas. This dissolved gaseous ammonia in the effluent is stripped of by flowing air through the effluent.
   In actual operation, the pH of the waste water is brought to a pH level between 10.0 and 11.0 by adding alkali; the waste water is then pumped to the top of the cooling tower type packed tower and distributed evenly to cover the full surface of the packings (Fig. 2). The waste water moves down through the packing countercurrent with the air flow. The tower for ammonia stripping may be either crossflow or counterflow type with induced or forced air circulation. The ammonia present in the waste water is stripped off before it leaves at the bottom of the tower. The extent of ammonia removal depends on many factors of which pH temperature, ammonia concentration, contact time with air and water-air-water ratio, etc, are very important and these factors are to be considered adequately while designing an air stripper for ammonia removal. In a well designed plant, the concentration of ammonia in the effluent can be reduced to 50 mg/l adopting this process.
2. Steam stripping—Steam stripping of ammonia (Fig. 2) is a well established process. The process is adopted by the coke-oven industries for the recovery of by product ammonia. Here also stripping of ammonia from waste water depends on how the ammonia exists in the water. In neutral solution, ammonia does not exist as dissolved NH₃ gas at ambient temperature. Therefore, the pH and the temperature are increased, so that the reaction proceeds progressively further to the right, namely, in favour of the formation of NH₃. In a suitably designed distillation unit, the ammonia can be stripped off by steam with or without raising the pH as the case may be and the resultant ammonia can be covered by condensing as dilute ammonia solution or as ammonium sulphate solution after neutralizing it with sulphuric acid. Under ideal operating conditions, 90 to 99 percent ammonia removal efficiency can be obtained.
3. Ion exchange—Ion exchange is a unique effluent waste water treatment method. Ion exchange can accomplish purification of the 20
   
   Fig. 2 Ammoniacal Effluent Treatment By Steam/air Stripping
   21waste water to a quality that could comply with zero pollutant discharge criteria or that would permit complete recycle of waste waters. The ion exchange process can also accomplish complete recovery of waste products being lost along with the waste water stream and can provide for efficient recycle of the recovered products into the plant processes. This may be represented as follows:
   
   When the recovery of ammonia by ion exchange is aimed at from ammoniacal waste waters and no recovery of waste water is envisaged, a simple process based on adsorption of ammonium ion by hydrogen form of a cation exchanger is incorporated (Fig. 3). The clarified ammoniacal waste water is passed through the exchange column where ammonium ion would be absorbed in the exchanger replacing hydrogen ion. When the exchanger approaches exhaustion (indicated by residual ammonium ion in the treated effluent at the outlet of the exchanger), it is regenerated to the hydrogen form with a suitable concentration of sulphuric/nitric acid. The regeneration process is adopted to get minimum regenerant use and maximum concentration of product solution. The product ammonium sulphate or ammonium nitrate solution is concentrated and processed in the process plant for the production of fertilizer and the waste water with very low concentration of ammonia is neutralized before discharge along with the other effluent streams.
   When the recovery of waste water is also envisaged, in addition to a cation exchanger, an anion exchanger is incorporated (Fig. 4). This unit can be used for the treatment of waste waters containing both ammonium ions and other acidic ions. The ammonium salt contaminated waste water after proper clarification first flows through a bed of strongly acidic cation, resin operating in the hydrogen form. The ammonium ion combines with the cation, while the hydrogen ion combines with the nitrate/sulphate ion to form nitric/
   22
   
   Fig. 3 Ammoniacal Effluent Treatment By Cation Exchange
   sulphuric acid. The acidic water then passes through the bed of anion resin in base form where the acidic ions are absorbed. The effluent water from the second bed is very low in ammonium salts, and can be reused in the process as make up water in boiler feed water treatment plant and may be used in the boilers after polishing in mixed bed ion exchange system. The cation exchange resin holding the ammonium ion can be regenerated using sulphuric or nitric acid to form ammonium sulphate or nitrate solution. The anion resin holding the acidic ion is regenerated using a solution of ammonium hydroxide to form more ammonium sulphate or nitrate solution. The ammonium salt solution thus produced may be used in the process for the production of ammonium sulphate or nitrate, provided such facilities are available at site. It may be noted that soluble inorganic contaminants in the waste water will also find their way into the product.
   

4.3.1.2 Biological processes

1. Biological nitrification and denitrification—Biological nitrification and denitrification can reduce ammoniacal nitrogen content of the final effluent to a very low level. This process is being adopted in municipal waste treatment for years. In the treatment of industrial waste, this treatment may be adopted as a secondary or tertiary treatment where the ammonia nitrogen content of the influent is comparatively low and also a high degree of treatment for the removal of ammoniacal nitrogen is desired. The treatment is based on the reaction of ammonia nitrogen with, oxygen in an aerated pond or lagoon to form nitrites and finally to the nitrate nitrogen form in the presence of a specialized group of
   23
   
   Fig. 4 Ammoniacal Effluent Treatment By Ion Exchange
   24nitritying organisms (Fig. 5). The nitrates in turn reacted in another anaerobic pond in the presence of biodegradable carbon compound employing the denitrifying process form elemental nitrogen. The process may be represented as follows:
   
   The first step nitrification takes place in the presence of aerobic bacteria which converts the ammonia nitrogen into nitrates. This reaction is affected by degree of aeration, water temperature, initial ammonia nitrogen content, bacterial population, pH of solution, etc. As destruction of alkalinity is associated with the reaction, sufficient alkalinity should be present in the waste in the nitrification tank, otherwise alkalinity should be supplemented to the waste water. Similar supplementation may be required for other bacterial nutrients like phosphate, potassium, magnesium, iron, etc if these are not originally present adequately in the waste water. This step can be carried out in tank, pond, lagoon, trickling filter, etc.
   The denitrification step is an anaerobic process which occurs when the biological micro-organisms cause the nitrates and the organic carbon to be broken down into nitrogen gas and carbon dioxide. As the organisms responsible for denitrification can utilize only organic carbon as their carbon source, a supplement of a readily biodegradable soluble organic compound is required to be added to the nitrified effluent prior to its entry into the denitrification unit. The organic carbon used for such a process is methanol, sewage effluent or organic waste from industries. In case methanol is used as the organic carbon source, 2 to 2.5 g of methanol is required for denitrification of lg of nitrate nitrogen. This reaction is carried out in a tank, pond or lagoon under anaerobic conditions. The reaction requires very low or nil dissolved oxygen in the effluent, neutral pH range, proper supply of organic carbon, suitable detention time, etc.
2. Algal uptake—Since ammonia nitrogen is an algal nutrient, algae are capable of extracting this nutrient from the waste water. Algae growing in waste water stabilization ponds utilize ammonia nitrogen of the waste water to form cell tissue in the presence of sunlight. Adequate carbon dioxide and some other nutrients are also required in this process. For fixing up 1 g of nitrogen into algal cell material to 12 g of carbon as carbon dioxide gas is normally required. 25
   
   Fig. 5 Dilute Ammonia and Urea Bearing Effluent Treatment
   26Oxidation pond-like ponds may be used for the culture of algae (Fig. 6). Carbon dioxide may be supplied by biodegradation of organic matter or dilute carbon dioxide may be diffused through a network of carbon dioxide diffusers in the pond. Other necessary nutrients for algal cultures may be supplemented in the pond. With suitable detention time, depth of the pond, concentration of algae, concentration of ammonia nitrogen, sunlight, etc. the uptake of ammonia nitrogen in the cell formation of algal cells is quite appreciable. Algae thus produced may be harvested using a suitable process and utilized as manure.
   

4.3.2 Urea and Nitrate Nitrogen

4.3.2.1

In modern urea manufacturing technology, thermal urea hydrolysis with recovery of ammonia of the waste water (Fig. 7) is being incorporated in the plant itself. This system, if provided, is expected to reduce the quantity of urea in the effluent appreciably. The use of hydrolyser stripper should be considered as an alternate arrangement.

4.3.2.2

Urea nitrogen can be removed from effluents by hydrolyzing urea in the presence of enzyme urease secreted by some bacteria formed in the soil (Fig. 5). The dilute urea solution is hydrolyzed by the above bacteria in the presence of organic carbon compounds to give ammonia and carbon dioxide.

NH₂CONH₂ + 2H₂O → (NH₄)₂CO₃

The pH increases with the progress of hydrolysis; under properly maintained conditions, over 95 percent of urea can be hydrolyzed in 24 h. The hydrolyzed solution containing ammonia can be treated by any of the methods described under ammonia removal.

4.3.2.3

Reduction of nitrates can be effected by the denitrification process (Fig. 5) described under 4.3.1.2 (a).

4.3.3

Suspended Solids—Suspended solids originate from various sources in the fertilizer industry. The process water clarification plant sludge, ash slurry from coal gasification plants, steam generation plants or phosphoric acid plant effluent during neutralization of effluent with lime, etc, suspended solids in different particle sizes find their way into the effluent. These effluents containing suspended solids are settled in a suitably designed settling basin and the clear overflow passes out. In some cases, particularly where the particle size is comparatively small, mechanical clarifier having proper arrangements of dosing coagulants or polyelectrolytes are required for quick settling. The sludge discharged from the bottom of the clarifier may be drawn out mechanically, dewatered and disposed of as solid waste as required.
27

28

4.3.4

pH—Sometimes the effluents are highly acidic or alkaline in nature. When both acidic and alkaline waste waters are found, they may be mixed suitably for neutralization. Otherwise for neutralization of acidic effluent, lime or soda ash may be used and for neutralization of alkaline effluent sulphuric acid may be used. In the process of neutralization proper mixing is very important. This can be effected by flash mixing or mixing by agitation or recirculation.

4.3.5

Oils and Greases—Oils and greases normally discharged in fertilizer industry effluents are mostly in non-emulsified form. Furthermore, a majority of these insoluble oils are lighter than water and therefore they will float on its surface. Insoluble oils lighter than water are usually separated in settling tanks provided with an adjustable skimming weir (Fig. 8). These settlers are usually termed as gravity type mechanical oil separators. The oils readily float on these separators and the depth of the weir is adjusted according to the amount of oil present in the waste water. The collected oil is skimmed by mechanical means periodically. A properly designed oil separator can reduce the oil content of the effluent below 50 mg/l. If a greater degree of oil removal is desired, the effluent from the oil separator may be passed through active carbon or a porous coke bed by which the oil and grease content of the effluent is reduced to 2 to 10 mg/l.

4.3.6

Arsenic—In fertilizer industry, arsenic is a constituent of absorbent liquids used for carbon dioxide removal. Normally adequate arrangements are provided in the plant so that arsenic does not find its way out in the effluent. But in actual practice, due to leakages in pump glands, flanges, joints, etc, and also from spillages, some arsenical solution is discharged. The quantity of this arsenical solution can be controlled within reasonable limits by good housekeeping. The arsenic solution which is discharged even after taking all the precautions is completely separated from other waste waters. The waste water containing arsenic is then filtered, concentrated, further filtered through active carbon filter if necessary and recycled in the process. When it is not possible to take it into the process, the arsenical solution is evaporated to dryness and the solids are placed in concrete drums, sealed properly and buried underground or disposed of into the deep sea far away from the coastline.

4.3.7

Chromate and Phosphate—Fertilizer industry requires a high quantity of cooling water during processing of fertilizers. In most of the fertilizer factories, cooling water is recycled through cooling towers. Suitable inhibitors for control of scaling/corrosion properties of circulating water are dosed into the cooling water system. Various inhibitors are used depending on the local conditions. Most of the plants use combinations of chromate, phosphate and zinc in different proportions. Normally, zinc is used in a very low concentration, therefore, any specific treatment for the removal of zinc is not considered necessary. In the treatment for removal of chromate
29
30from waste water, phosphate is also simultaneously removed, so specific treatment for removal of phosphates is not considered necessary.
The basic principle of chromate removal is the reduction of hexavalent chromium to trivalent form and precipitation of chromium as chromium hydroxide (Fig. 9).

The cooling tower blowdown which contains chromate is collected in a tank and the pH of the water is lowered to the range 2 to 4 by adding sulphuric acid. After mixing with the acid, ferrous sulphate, sodium sulphite, sodium metabisulphite or sulphur dioxide is added to reduce hexavalent chromium. For removal of lg of CrO₄ about 10 g of ferrous sulphate, 2.5 g of sodium sulphite or 1.5 g of sulphur dioxide is required. After reduction, lime is added to the effluent for raising the pH and precipitation of chromium. The settled effluent is allowed to be discharged along with other effluents of the factory. The reactions which take place during the above operations are as follows:

1. When ferrous sulphate is used for reduction:
        Na₂Cr₃O₇ + 6FeSO₄ + 7 H₂SO₄→ Cr₂(SO₄)₃ + 3Fe₂(SO₄)₃ + 7 H₂O + Na₂SO₄
2. When sodium sulphite is used for reduction:
        Na₂Cr₂O₇ + 3Na₂SO₃ + 4H₂SO₄→ 4Na₂SO₄ + Cr₂ (SO₄)₃+ 4 H₂O
3. When sulphur dioxide is used for reduction:
        Na₂Cr₂O₇ + 3 SO₂ + H₂SO₄→ Cr₂ (SO₄)₃ + H₂O + Na₂SO₄

31Lime treatment for precipitation of chromium also partially precipitates out phosphate which is added to the cooling towers as sodium hexameta phosphate.
Recently, another iron process based on reduction with ferrous ion provided by electrolysis using iron electrode has been developed. This process can operate at pH 6 to 8. The chromium hydroxide and iron hydroxide are precipitated together and can be separated as a sludge by clarification. It consumes only electricity and metallic iron.

4.3.7.1

Many fertilizer units use furnace oils containing about 4 percent sulphur in their boilers; the boiler stack contains around 0.2 percent SO₂ which is a reducing agent. The chemistry of the process is:
The reaction takes place quite rapidly at low pH (2 to 3). The SO₃ present in the flue gas helps in attaining the low pH of this order; under this condition even a small percentage of SO₂ is able to reduce the hexavalent chromium. In this arrangement the problem of air contamination is also reduced due to utilization of SO₂ and SO₃.
The resulting trivalent chromium as chromium sulphate is much less toxic. To fully overcome the toxicity problem, it is necessary to convert soluble chromium sulphate into chromium hydroxide at pH 10 to 11 through the addition of alkali as suggested in 4.3.7. However, to further reduce the cost of disposal, the ammonia containing waste water itself may be utilized as an alkali to bring about the precipitation of chromium hydroxide. Effluents from fertilizer plants happen to be rich in plant nutrients and can be a secondary source of fertilizers. These effluents can, therefore, after suitable treatment, be applied on land for irrigation with the prior permission of local authorities. Experiments have shown that the effluents from fertilizer plants can be usefully employed to raise various crops and vegetables due to their high nitrogen and phosphorus contents.

4.3.8

Cyanide—Depending on the process and raw material, cyanides are sometimes encountered in the fertilizer factory effluent. Usually cyanide containing effluents are completely segregated from other waste waters and are treated or disposed of separately. When the cyanide content is low, the effluent can be discharged at a controlled rate along with the other waste water, so that cyanide content of the final effluent does not go beyond speci-fied limits. When the cyanide content of the effluent is comparatively high, some suitable treatment is required.
32

4.3.8.1

When cyanide content is high and the effluent volume is low it can be removed by stripping with steam and acidic gas (Fig. 10). The residual cyanide after stripping may be treated further, if required.

4.3.8.2

Cyanide bearing effluents may be treated by alkaline chlorination process (Fig. 10) which oxidizes cyanide ultimately into carbon dioxide and nitrogen. Cyanide forms cyanogen chloride according to the equation:
In the presence of caustic soda cyanogen chloride is converted into sodium cyanate as follows:
The sodium cyanate produced in the above reaction is much less toxic and may be discharged along with other effluents. If complete treatment is desired, sodium cyanate is further oxidized by the addition of chlorine to carbon dioxide and nitrogen.
In order to have simplified operation and control, a single vessel is used for cyanide removal. The pH is maintained at about 8.5 by dosing caustic soda, and chlorine is added from chlorinators of suitable capacity. The requirement of chlorine for complete oxidation of cyanide is 9 to 10 g for 1 g of cyanide. The process is quite satisfactory for treatment of effluents from fertilizer industries.

4.3.9

Sulphides—Sulphides are sometimes present in small quantities in fertilizer factory effluents. Water containing sulphides in excess of 0 5 mg/l has offensive (rotten egg) odour and is also very corrosive. The sulphides
33present in fertilizer factory waste water normally do not require any special treatment. Natural dilution by the other waste water from the factory is sufficient to bring down the level of sulphides within specified limits. Sulphides are present in acidic pH range as hydrogen sulphide and in alkaline pH range as sulphide salts. Hydrogen sulphide is usually removed by aeration process in the acidic pH range, In this process hydrogen sulphide removal is by stripping rather than oxidation. Sometimes chemical oxidation by dosing chlorine is also resorted to for removing sulphides from effluents.

4.3.9.1

Sulphides can also be precipitated chemically.

4.3.10

Fluorides and Phosphates—The main source of fluorides and phosphates in the phosphatic fertilizer industry arc scrubber liquors from various unit operations involving scrubbing of the off-gases, floor washings and gypsum and water. In the effluent, fluorides are present as fluosilicic acid with small amounts of soluble salts as sodium and potassium fluosilicates and hydrofluoric acid. Phosphorus is present principally as phosphoric acid with minor amounts of soluble calcium phosphates. For the removal of fluorides and phosphates two-stage treatment with chalk followed by lime or double lime treatment is adopted (Fig. 11).

In the former case, in the first stages the effluent is treated with chalk or finely divided calcium carbonate at a pH of about 3.0. The requirement of calcium carbonate is 3 to 3.5 g for 1 g of F and 0.6 to 0.7 g for 1 g of PO₄. The following reactions are believed to take place:
In the above reactions, almost all the fluorides are precipitated as calcium fluoride. Silica is also precipitated out. However, most of the phosphates remain in solution as monocalcium phosphate. During the second stage treatment, the product of the first stage is further treated with lime at a pH
34of about 8.5. In this reaction, calcium hydroxide requirement is 2.1 to 2.3 g for 1 g of residual F and 1.0 to 1.1 g for 1 g of residual PO₄.
It is believed that in the second stage the under mentioned reaction takes place:
In the second stage, residual fluorides and phosphates from the first stage are converted into insoluble calcium fluoride and calcium hydroxy apatite at pH around 8.5 and precipitated out. The overall fluoride and phosphate removal efficiency is above 99 percent in the above two stage treatment.
In double lime treatment, lime is used in place of chalk or powdered calcium carbonate as indicated earlier in the two stage treatment.
The effluent after the second stage reaction is transferred to a settler for the removal of fluoride and phosphate precipitates and the overflow water is discharged. The settled sludges arc removed periodically and dumped or used as fill for low lying areas.

4.3.10.1

Where by-product precipitated chalk from ammonium sulphate produced by Merseburg process is used for preliminary treatment, the chalk should have a minimum optimum ammonia level or preferably it should be free from ammonia.

4.3.11

Sewage Effluent—The waste water from toilets and other sanitar facilities in the factory area has high biochemical oxygen demand (BOD) and contains suspended solids. The sewage effluent is segregated from other industrial wastes and treated for removal of BOD and suspended solids. The volume of the effluent is normally comparatively low. The general practice is to treat these effluents in oxidation ponds or by aeration processes. However, depending on the level of BOD, these waste waters may be subjected to partial BOD removal by any conventional practice and discharged along with the other treated industrial waste water so that the BOD value of the final effluent does not go beyond specified limits.

4.4

Sampling and Analytical Control—In order to observe the performance of the diluent treatment units and also to control the plant operating system effectively, suitable instrumentation for recording pollutants and other physical characteristics (namely temperature, pressure, flow of effluents, quantity of treatment chemicals, etc) are required to be incorporated into the diluent treatment process design, so that input and output conditions of effluent treatment units can be assessed properly. Where suitable automatic continuous monitoring of pollutants in the effluents cannot be provided, regular sampling and analysis of the pollutants necessary for the control of operation arc to be conducted. In such a case, the frequency of sampling and analysis
35will depend on the process plant operating conditions but a minimum of two composite samples should be analysed daily. In the case of final effluent discharged beyond the factory boundary limit, a suitable arrangement for recording the volume and proper sampling of the final effluent is to be made. Installation of an automatic pollutant monitoring and recording system for final effluent of the factory is very advantageous and an endeavour should be made to install these instruments wherever possible. Similarly, a composite sample of the receiving water should also be analysed daily. In case some other industries are located on the upstream of the river and they also discharge some effluents to the same river, sampling and analysis of the receiving water should be done, both from the upstream and downstream of the effluent outfall. This will indicate the contribution to pollution by the fertilizer industry concerned.

4.5

Waste Utilization—Apart from the utilization of waste waters and reuse of treated effluents for conservation of water as well as for other purposes, recovery of usable products present in this waste water has gained importance in recent days. The main recoverable products from waste waters of fertilizer industries are ammonia, urea, carbon, fluoride, gypsum, phosphate, chalk, etc, depending on the product manufactured and the process adopted.

4.5.1

Ammonia—The processes commonly used for the recovery of ammonia from ammoniacal waste waters are steam stripping and ion exchange system. Steam stripping of ammonia is suitable for ammoniacal effluent containing high concentration of ammonia with comparatively low volume. The stripped ammonia gas is either absorbed in acid to form ammonium salts or condensed to form ammonia liquor which is recycled in the process itself. In the case of ammoniacal waste waters containing low concentration of ammonia, ammonia can be recovered using a cation exchange system regenerated with acid to produce ammonium salt solution. This process is more suitable where already a secondary ammonium salt manufacturing facility exists.

4.5.2

Urea—In spite of improvement in the design of the urea manufacturing process, substantial amount of urea along with ammonia finds its way into the waste waters of urea plant. The different methods of recovery of urea from these effluents are as follows:

1. Thermal hydrolysis of urea present in the condensate followed by stripping of the ammonia produced and recycling of the ammonia in the urea process itself;
2. Collecting of all spillages, leakages and overflows of urea bearing waste, concentrating and recycling them in the urea process; and
3. Scrubbing urea dust from prilling tower exhaust vapours and recovering this urea as per process mentioned in (b) above.

36In modern plants all or some of the above processes form an integral part of the urea plant itself and the effluent which comes out from urea plant contains practically a negligible quantity of urea. In older plants installation of the above facilities is difficult, as it requires large investment. Also, there are constraints in accommodating this additional load in the process, in any case installation of these facilities for the recovery of urea improves process efficiency by reducing the specific ammonia consumption. The cost of ammonia recovered bv this process is enough to pay back the capital invested in a short time.

4.5.3

Carbon—In the partial oxidation process of ammonia manufacture, the carbon formed in the process is normally thrown out as carbon slurry. This carbon can be recovered either by pelleting with a suitable petroleum distillate followed by further processing or by filtration and drying. The recovered carbon has very low particle diameter, large surface area, high covering power and adsorption capacity. It can be used as carbon black suitable for printing ink, rubber, battery and other industries. It can also be further processed into active carbon.

4.5.4

Flouride—The effluents from phosphoric acid plants contain varying concentration of fluoride which pollutes the water course seriously if not removed prior to its discharge. Fluoride is now recovered from the fluoride bearing diluents by treating them with lime to recover calcium fluoride, with aluminium salts to recover aluminium fluoride and with sodium salts to recover sodium fluoride. Various processes are available for the recovery of fluorides that serve as raw material for the manufacture of a wide range of fluoride chemicals.

4.5.5

Gypsum—Gypsum obtained as a byproduct during the production of phosphoric acid used to be dumped in low lying areas. This gypsum can be processed for various products like ammonium sulphate by Mersburg process, plaster boards, and building blocks; it can also be used for land reclamation and recovery of sulphur with simultaneous manufacture of cement.

4.5.6

Chalk—The chalk is obtained as a byproduct in ammonium sulphate production using Mersburg process utilising gypsum. This chalk is used as a raw material in the manufacture of cement. It is also used to a large extent in neutralizing acidic effluents in industry.

4.5.7

Phosphate—Substantial amounts of phosphates are present in waste waters of phosphatic industries; these are normally removed during the removal of fluorides. This phosphate can be used in phosphoric acid manufacture after blending with rich rock phosphate. The phosphate bearing sludge can also be used as low nutrient value cheap fertilizer in some cases.

4.6

Disposal—The final disposal of the treated effluents beyond the factory boundary limit is an important step. Normally, effluents originating from
37individual effluent treatment units are led to a mixing pond. The uncon taminated effluents which do not require any treatment also flow to this mixing pond. It is preferable to give sufficient detention time in this mixing pond for equalization and also to effect secondary settling of suspended matter. The overflow from this final mixing pond passes to the effluent drain leading to the receiving waters. It may be clearly understood that the treated effluents in the effluent drain conform to IS : 2490* and therefore cannot normally be used as raw water source. In case the drain passes through a locality where there is possibility of use of this water as raw water source by the inhabitants and cattle, suitable protection of the drain from the approach of the people and cattle with proper warnings has to be made. In some cases it is preferable to discharge the treated effluents through a pipeline to the receiving water. When all the characteristics of the individual effluent streams of the process plants are properly assessed, the effluents discharged from effluent treatment units also can be evaluated with respect to the extent of treatment necessary during the planning and designing stage of the effluent treatment plants. The final effluent characteristics can be predicted and made to comply with the requirements prescribed by the regulatory authorities.

APPENDIX A
REFERENCES

1. Alagarsamy (S R), Bhalerao (B B) and Rajagopalan (S), Treatment of wastes from fertilizer plants. Indian J. Environ. 15, 1 ; 1973; 52.
2. Austin (R J) and Vanse (E H). Chemical Coagulation of refinery waste water. Proc. of 6th Industrial Waste Conference. Purdue Univ. Feb. 1951; 272.
3. Baumann (R E). On removal of ammonia by air stripping—EPA Design seminar Kansas city, USA 1971.
4. Bennet (F W) and Spall (B C). A review of effluent problems in fertilizer manufacture Paper presented at the Seminar of the Fertilizer Society of London April 1976. *Tolerance limits for industrial effluents discharged into inland surface waters (first revision):
   Part I-1974 General limits (first revision)
   Part VIII-1976 Phosphatic fertilizer industry (first revision)
   Part IX-1977 Nitrogenous fertilizer industry (first revision).
   38
5. Bhattacharya (G S), Roy (G S), Banerjee (C D) and Dutta (B K), Removal of fluorides and phosphorous from phosphatic fertilizer factory wasted Paper presented in the seminar “Utilization and Disposal of Industrial Wastes”organised by 1.1. Ch. E (Calcutta) at Jadavpur University, Dec 1973.
6. Bhattacharya (G S), Roy (G S) and Dutta (B K). Investigation into the use of algae for removing ammonium nitrogen from nitrogenous industrial wastes Part I Technol 3 ; 3 ; 1966 ; 135. Part II Technol 5 ; 1 ; 1968 ; 31.
7. Bhattacharya (G S), Roy (G S) and Dutta (B K). Treatment and disposal of effluents of modern urea fertilizer factories. Technol 6 ; 1 ; 1969 : 62. Paper presented in seminar on “industrial waste” at I. I. T., Kanpur 1969.
8. Bhattacharya (G S), Sarkak (C D) and Dutta (B K). Phosphate pollution and its effects on water treatment. Proc. Sym. of water pollution control in Dec 1965 CHPERI—Nagpur (1966).
9. Bhattacharya (S K), Bhattacharya (G S) and Dutta (B K). Removal of nitrogen from nitrogenous effluent. Technol 10 ; 3 ; 4 ; 1973 ; 321.
10. Bingham (E C). Solutions for minimum pollution in nitrogen industry. UNIDO Expert Group meeting on minimizing pollution from fertilizer plants. Helsinki Aug. 1974.
11. Bingham (E C) and Chopra (R C). A unique closed cycle water system for an ammonium nitrate producer using Chem-seps continuous counter current ion exchange. Proc. of 32nd International Water Conference of the Engs Soc. of West Penn. Pittsburg, USA Nov 1971.
12. Bringmann (G). On nitrification and denitrification in sewage treatment. J. Water Poll Abstr. 37 ; 1964 ; 18.
13. Bringmann (G). On nitrification sewage treatment. J. Water Poll Abstr. 34 ; 1961 ; 310.
14. Chatterjee (D D), Srivastava (A C) and Dutta (B K). Hydrogen cyanide removal from weak aqueous potassium cyanide solution. Technol. 13 ; 4 ; 1976 ; 273.
15. Cook (N E) and Cooper (R M). Some aspects of pollution control at a large fertilizer complex. Ammonia Plant safety symposium of the 3rd joint meeting AICLE-IHIQ, Denver, Colorado, USA Aug-Sept 1970.
16. Culp (G L) and Culp (RL). On stripping of ammonia from effluents. Advanced waste water treatment. Van Nostrand, Reinhold. New York 1971.
17. Culp (R L). On air stripping of ammonia from effluents and water reclamation. J. Amer. Water wks Assn. 60 ; 1968 ; 84.
18. Das (A C), Khan (J A) and Dutta (B K). Removal of nitrogen from the fertilizer factory effluents by biochemical nitrification and denitrification. Technol 3 ; 4 ; 1966 ; 41. Spl issue of seminar on wastes and effluents in chemical industries.
19. De Lora (F Y) and Masia (A). Influence of effluent standards on the economics of alternate waste water treatment designs; UNIDO Expert Group meeting on minimizing pollution from fertilizer plants, Helsinki Aug 1974.
20. Dijksaka (F). Measures to minimize aqueous waste pollution from fertilizer plants situated in an integrated chemical complex. UNIDO Expert Group meeting on minimizing pollution from fertiliser plants, Helsinki Aug 1974. 39
21. Dutta (B K). Removal of ammonia from fertilizer plant effluents Paper presented in All India Symposium on Affluent Treatment organized by ICTD Bombay, May 1980.
22. Dutta (B K). Treatment of effluents with special emphasis on waste recycle. Chemical Age of India 30 ; 12 ; 1979 : 1107. Paper presented in All India Symposium on “Water Treatment” organised by ICTD, Bombay, Nov. 1979.
23. E. P. A. USA Federal Register 39 (68) April 8 (1974) : 40 (9) Jan 14 (1975) : 40 (121) Jun 22 (1975) ; 41 (11) Jan 16 (1976) ; 41 (98) May 19 (1976) ; 41 (138) July 16 (1976).
24. Esaki (M). Pollution control in modern ammonia and urea plants. Paper presented in FAI Seminar on Improving Productivity in Fertilizer Industry in New Delhi, Nov 1978.
25. Howl, Robert (H L). On processes for removal of cyanide from waste water. Proc. of the 18th industrial waste conference, Purdue University, April-May 1963.
26. Hug (A). Pollution from fertilizer plants in Bangladesh. UNIDO Expert Group meeting on minimizing pollution from fertilizer plants Helsinki, Aug. 1974.
27. Johnson (W K) and Schroepter (G J). Nitrogen removal by nitrification and denitrification. J. Water Poll. Contr. Fed. 43 ; 1971 ; 1845.
28. Liptak Bela (G). Removal of cyanide and chromium. Environmental Engineers Handbook vol 1. Water pollution. Chilton Book Co. USA p 1365-1382.
29. Mazumder (M M), Dutta (B K) and Chakraborty (K R). Carbon black from waste stream of petroleum oil gasification. Indian Patent No. 193573 (1966).
30. Pollution control in fertilizer industry Part 1. FAI Report Tech 4, 1979. Fertilizer Assoc, of India, New Delhi.
31. Prosad (R R) and Dutta (B K). A study of effluents of Sindri Fertilizer Factory. Technol 3 ; 4 ; 1966 ; 65 Spl. issue. Seminar on wastes and effluents in chemical industry.
32. Roy (G S), Bhattacharya (G S) and Dutta (B K), Treatment and disposal of effluents from fertilizer industries. Technol 7 ; 3 ; 1970 ; 193. Paper presented in seminar on “Water pollution and industrial waste treatment” in Bangalore, Dec 1969.
33. Srivastava (A C) and Dutta (B K). Ammonia recovery from coke oven industries by an ion exchange process, Technol 7 ; 4 ; 1970 ; 66 spl. issue on seminar on coal and coal chemicals. Nov. 1968.
34. The Water (Prevention & Control of Pollution) Act. 1974 Govt, of India.
35. Whalley (L). Modern technology for minimizing pollution from fertilizer plants. UNIDO Expert Group meeting on minimizing pollution from Fertilizer plants. Helsinki, Aug 1974.

40(Continued from page 2)

Members	Representing
Shri R. M. Shah	Tata Chemicals Ltd, Bombay
Shri R. K. Gandhi (Alternate)
Shri P R. Sheth	Excel Industries Ltd, Bombay
Shri S. P. Iyer (Alternate)
Dr V. Sreenivasa Murthy	Central Food Technological Research Institute (CSIR), Mysore
Shri M. S. Subba Rao (Alternate)
Shri S. B. Tagore	Department of Environmental Hygiene (Govt of Tamil Nadu), Madras
Dr (Smt) S. M. Vachha	Director of Health Services, Government of Maharashtra, Bombay
Dr Hari Bhagwan, Director (Chem)	Director General, ISI (Ex-officio Member)

Convener
Shri A. Raman	National Environmental Engineering Research Institute (CSIR), Nagpur
Members
Shri B. V. S. Gurunathrao (Alternate to Shri A. Raman)
Dr R. N. Chakrabarty	Universal Enviroscience Pvt Ltd, New Delhi
Chief Water Analyst, King Institute, Madras	Director of Public Health, Government of Tamil Nadu, Madras
Shri L. M. Choudhry	Haryana State Board for the Prevention & Control of Water Pollution, Chandigarh
Shri M. L. Prabhakar (Alternate)
Dr D. Choudhury	Indian Chemical Manufacturers’ Association, Calcutta
Shri V. K. Dikshit (Alternate)
Shri B. D. Deshmukh	Maharashtra Prevention of Water Pollution Board, Bombay
Director (C. S. & M. R. S)	Central Water Commission, New Delhi
Shri N. C. Rawal (Alternate)
Shri B. K. Dutta	Fertilizer (Planning & Development) India Ltd, Sindri
Shri G. S. Ray (Alternate)
Shri R. C. Dwivedi	Uttar Pradesh Water Pollution Prevention & Control Board, Lucknow
Shri S. P Saxena (Alternate)
Dr A. K. Gupta	Hindustan Fertilizer Corporation Ltd, Durgapur
Shri T. P. Chatterjee (Alternate)	41
Shri S. Gupta	Central Board for the Prevention and Control of Water Pollution, New Delhi
Dr H. S. Matharu (Alternate)
Shri R. V. Kadam	Paramount Pollution Control Pvt Ltd, Vadodara
Shri N. V. Vashi (Alternate)
Shri K. R. Krishnaswami	Madras Fertilizers Ltd, Madras
Shri V. N. Lambu	Ion Exchange, (India) Ltd, Bombay
Shri V. V. Joshi (Alternate)
Shri A. K. Majumdar	Geo Miller & Co Pvt Ltd, Calcutta
Shri U. C. Mankad (Alternate)
Shri S. V. Mani	Greaves Cotton & Co Ltd, Bombay
Shri S. R. Luthra (Alternate)
Shri V. S. More	Indian Oil Corporation Ltd (Refineries & Pipelines Division), New Delhi
Shri Paramjit Singh (Alternate)
Shri D. V. S. Murthy	M. P. State Prevention & Control ot water pollution Board, Bhopal
Dr G. K. Khare (Alternate)
Shri R. Natarajan	Hindustan Dorr-Oliver Ltd, Bombay
Shri Amit S. Desai (Alternate)
Dr V. Pachaiyappan	The Fertilizer Association of India, New Delhi
Dr R. N. Trivedi (Alternate)
Dr R. Pitchai	College of Engineering, Madras
Shri H. S. Puri	Punjab State Board for the Prevention & Control of Water Pollution, Patiala
Shri Qimat Rai (Alternate)
Shri John Raju	Steel Authority of India Ltd, New Delhi
Shri A. P. Sinha (Alternate)
Shri M. K Roy	Chief Inspectorate of Factories, Ranchi
Shri J. M. Tuli	Engineers India Ltd, New Delhi
Shri K. Rudrappa (Alternate)
Shri T. K. Vedaraman	Ministry of Works & Housing
Dr S. R. Shukla (Alternate)

Convener
Shri B. K. Dutta	The Fertilizer (Planning & Development) India Ltd, Sindri
Members
Shri G. S. Ray (Alternate to Shri B. K. Dutta)
Dr R. N. Chakrabarty	Universal Enviroscience Pvt Ltd, New Delhi
Dr S. K. Gupta (Alternate)
Shri P. P. Chandhna	National Fertilizers Ltd, New Delhi
Shri V. Charandas	Gujarat State Fertilizers Co Ltd, Vadodara
Shri M. D. Patel (Alternate)
Shri L. M. Choudhry	Haryana State Board for the Prevention & Contro of Water Pollution, Chandigarh
Shri M. L. Prabhakar (Alternate)42
Shri K. P. Dohare	Directorate General of Technical Development, New Delhi
Shri K. V. Sampath (Alternate)
Shri A. N. Dutta Choudhury	Board for Prevention & Control of Water Pollution, Assam, Gauhati
Shri B. K. Choudhury (Alternate)
Dr A. K. Gupta	Hindustan Fertilizer Corporation Ltd, Durgapur
Shri T. P. Chatterjee (Alternate)
Shri V. V. Joshi	Ion Exchange (India) Ltd, Bombay
Shri S. K. Bhattacharyya (Alternate)
Shri S. Mallick	Indian Explosives Ltd, Kanpur
Shri T. N. Mehrotra (Alternate)
Prof R. S. Mehta	Gujarat Water Pollution Control Board, Gandhi-nagar
Shri R. Natarajan	Hindustan Dorr-Oliver Ltd, Bombay
Shri A. G. Nene	Shriram Chemical Industries, New Delhi
Dr R. K. Niyogi	Hindustan Lever Ltd, Bombay
Shri S. K. Subbaroyan (Alternate)
Dr V. Pachaiyappan	The Fertilizer Association of India, New Delhi
Dr R. N. Trivedi (Alternate)
Shri D. Panigrahi	The Fertilizers & Chemicals, Travancore Ltd, Udyogamandal
Shri N. J. Joseph (Alternate I)
Shri K K. Jose (Alternate II)
Shri T. C Pitchappan	Madras Fertilizers Ltd, Madras
Shri K. R. Krishnaswami (Alternate)
Shri H. S. Puri	Punjab State Board for the Prevention & Control of Water Pollution, Patiala
Shri Qimat Rai (Alternate)
Shri K. Rudrappa	Engineers India Ltd, New Delhi
Shri A. D. Jalonkar (Alternate)
Dr K. L. Saxena	National Environmental  Engineering Research Institute (CSIR), Nagpur
Dr T. Chakraborty (Alternate)

43

BUREAU OF INDIAN STANDARDS

Headquarters:
Manak Bhavan, 9 Bahadur Shah Zafar Marg, NEW DELHI 110002
Telephones: 323 0131, 323 3375, 323 9402 Fax: 91 11 3234062, 91 11 3239399, 91 11 3239382
Telegrams: Manaksanstha (Common to all Offices)
Central Laboratory:		Telephone
Plot No. 20/9, Site IV, Sahibabad Industrial Area, Sahibabad 201010		8-77 00 32
Regional Offices:
Central:	Manak Bhavan, 9 Bahadur Shah Zafar Marg, NEW DELHI 110002	323 76 17
*Eastern:	1/14 CIT Scheme VII M, V.I.P. Road, Maniktola, CALCUTTA 700054	337 86 62
Northern:	SCO 335-336, Sector 34-A, CHANDIGARH 160022	60 38 43
Southern:	C.I.T. Campus, IV Cross Road, CHENNAI 600113	235 23 15
†Western:	Manakalaya, E9, Behind Marol Telephone Exchange, Andheri (East), MUMBAI 400093	832 92 95
Branch Offices::
‘Pushpak’, Nurmohamed Shaikh Marg, Khanpur, AHMEDABAD 380001		550 13 48
‡Peenya Industrial Area, 1st Stage, Bangalore-Tumkur Road, BANGALORE 560058		839 49 55
Gangotri Complex, 5th Floor, Bhadbhada Road, T.T. Nagar, BHOPAL 462003		55 40 21
Plot No. 62-63, Unit VI, Ganga Nagar, BHUBANESHWAR 751001		40 36 27
Kalaikathir Buildings, 670 Avinashi Road, COIMBATORE 641037		21 01 41
Plot No. 43, Sector 16 A, Mathura Road, FARIDABAD 121001		8-28 88 01
Savitri Complex, 116 G.T. Road, GHAZIABAD 201001		8-71 19 96
53/5 Ward No.29, R.G. Barua Road, 5th By-lane, GUWAHATI 781003		54 11 37
5-8-56C, L.N. Gupta Marg, Nampally Station Road, HYDERABAD 500001		20 10 83
E-52, Chitaranjan Marg, C-Scheme, JAIPUR 302001		37 29 25
117/418 B, Sarvodaya Nagar, KANPUR 208005		21 68 76
Seth Bhawan, 2nd Floor, Behind Leela Cinema, Naval Kishore Road, LUCKNOW 226001		23 89 23
NIT Building, Second Floor, Gokulpat Market, NAGPUR 440010		52 51 71
Patliputra Industrial Estate, PATNA 800013		26 23 05
Institution of Engineers (India) Building 1332 Shivaji Nagar, PUNE 411005		32 36 35
T.C. No. 14/1421, University P. O. Palayam, THIRUVANANTHAPURAM 695034		6 21 17
*Sales Office is at 5 Chowrtnghee Approach, P.O. Princep Street, CALCUTTA 700072		27 10 85
†Sales Office is at Novelty Chambers, Grant Road, MUMBAI 400007		309 65 28
‡Sales Office is at ‘F’ Block, Unity Building, Narashimaraja Square, BANGALORE 560002		222 39 71

4445

Pollution in Delhi far worse than in Beijing, Greenpeace India says

According to a startling claim made by Greenpeace India, pollution in Delhi is much worse than in Beijing and an average day in Delhi would be considered a very bad-air day in China’s capital.
The green NGO, which has collated data from various studies to give perspective about Beijing and Delhi in terms of parameters of pollution and mitigation plans, said Delhi’s air pollution is worst than that of the Chinese capital and called for stringent targets for industrial emissions and an action plan to protect citizens from air pollution.
Citing WHO’s 2014 report on air pollution across the globe, the NGO said that Delhiites are breathing the most polluted air in the world. The NGO said that while Beijing’s air quality has been making the headlines lately, there is strong evidence that New Delhi’s air is often worse than that of Beijing.
The examination of pollution figures collected and based on bad and good air quality days from Beijing and Delhi suggests that on an average, Delhi’s air is more laden with dangerous PM 2.5 (fine particulate matter than can penetrate deep into the lungs) than Beijing’s.
Observing that an average day in Delhi would be considered a very bad-air day in Beijing, Greenpeace India said despite the capital’s air pollution, there was hardly any emphasis on it in the Union Budget, and funding given to pollution control board was not enough to address a problem of this scale.
The NGO said Delhi also does not have Health Advisories or Action Plans in place which is contrary to Beijing which has a four-level alarm system to tackle heavy pollution episodes.
“There should be stringent targets for industrial emissions. We need an action plan similar to that of Beijing. It should include an emergency alert system that issues health advisories to public on heavy pollution days along with instructions for industries to cut down emissions.”
Greenpeace campaigner Aishwarya Madineni said, “Delhi had several bad-air days in 2014 for which no health advisories were issued. We have no emission standards for coal-fired power plants in India, a sector responsible for emitting 7,500 tons of PM 2.5 into the city.”
Noting that Delhi’s PM 2.5 levels are several times higher than those of Beijing as per the data submitted by Pollution Control Board to WHO, Madineni said despite this, the Environment Ministry continues to be in denial of the fact that we are taking worse care of our citizens than Beijing.
Greenpeace said that the government needs to wakeup and show that it cares for its citizens including children, the sick and elderly who are at most risk from Delhi’s toxic air.
It quoted a recent study published in the Economic and Political Weekly which indicated that 660 million people across India are exposed to unhealthy levels of PM 2.5 resulting in reduced life expectancy by 3.2 years on average.
PM2.5 is estimated to have been responsible for over three million premature deaths in 2010, it said.
Madineni said in the last couple of months, several studies including one from the Jawaharlal Nehru University have thrown light on the hazardous levels of PM 2.5 in Delhi possibly leading to as many as 47,800 premature deaths per one million population.
“The study has further acknowledged that Delhi’s air is full of cancer-causing particles,” it said.
The Central Pollution Control Board reported Delhi’s average PM 2.5 level in 2013 as 153 ng/m3, based on hourly measurements at six different stations which is 15 times the WHO guideline and 3.8 times the national standard while Delhi’s average is also 80 per cent higher than the average in Beijing, it noted. As per a recent study published in the Atmospheric Pollution Research Journal, an international journal on air pollution and atmospheric processes, the Nation Capital Region in Delhi faces the highest health risks from air pollution.

10 myths about fossil fuel divestment put to the sword

1. Divestment from fossil fuels will result in the end of modern civilisation

It is true that most of today’s energy, and many useful things such as plastics and fertilisers, come from fossil fuels. But the divestment campaign is not arguing for an end of all fossil fuel use starting tomorrow, with everyone heading back to caves to light a campfire. Instead it is arguing that the burning of fossil fuels at increasing rates is driving global warming, which is the actual threat to modern civilisation. Despite already having at least three times more proven reserves than the world’s governments agree can be safely burned, fossil fuel companies are spending huge sums exploring for more. Looked at in that way, pulling investments from companies committed to throwing more fuel on the climate change fire makes sense.

2. We all use fossil fuels everyday, so divestment is hypocritical

Again, no-one is arguing for an overnight end of all fossil fuel use. Instead, the 350.org group which is leading the divestment campaign calls for investors to commit to selling off their coal, oil and gas investments over five years. Fossil fuel burning will continue after that too, but the point is to reverse today’s upward trend of ever more carbon emissions into a downward trend of ever less carbon emissions. Furthermore, some of those backing a “divest-invest” strategy move money into the clean energy and energy efficiency sectors which have already begun driving the transition to a low-carbon world.

3. Divestment is not meaningful action – it’s just gesture politics

The dumping of a few fossil few stocks makes no immediate difference at all to the amount of carbon dioxide entering the atmosphere. But this entirely misses the point of divestment, which aims to remove the legitimacy of a fossil fuel industry whose current business model will lead to “severe, widespread and irreversible” impacts on people. Divestment works by stigmatising, as pointed out in a report from Oxford University: “The outcome of the stigmatisation process poses the most far-reaching threat to fossil fuel companies. Any direct impacts pale in comparison.”
The “gesture politics” criticism also ignores the political power of the fossil fuel industry, which spent over $400m (£265m) on lobbying and political donations in 2012 in the US alone. Undercutting that lobbying makes it easier for politicians to take action and the Oxford study showed that previous divestment campaigns – against apartheid South Africa, tobacco and Darfur – were all followed by restrictive new laws.
Those comparisons also highlight the moral dimension at the heart of the divestment campaign. Another dimension is warning investors that their fossil fuel assets may lose their value, if climate change is tackled. Lastly, backing divestment does not mean giving up putting direct pressure on politicians to act or any other climate change campaign.

A cardboard version of the Statue of Liberty stands in the ocean at the Gaviota Azul beach in Cancun, Mexico. Photograph: Stringer/Reuters

4. Divestment is pointless – it can’t bankrupt the coal, oil and gas companies

More organisations are divesting all the time, from Oslo city council to Stanford University to the Rockefeller Brothers Fund, but the sums are indeed relatively small when compared to the huge value of the fossil fuel companies. But the aim of divestment is not to bankrupt fossil fuel companies financially but to bankrupt them morally. This undermines their influence and helps create the political space for strong carbon-cutting policies – and that could have financial consequences.
Investors are already starting to question the future value of the fossil fuel companies’ assets and, for example, it is notable that no major bank is willing to fund the massive Galilee basin coal project in Australia. This myth can also be turned on its head by considering the risk of fossil fuel companies bankrupting their investors. Many authoritative voices, such as the heads of the World Bank, Jim Yong Kim, and the Bank of England, Mark Carney, have warned that many fossil fuel reserves could be left worthless by action on climate change. If the retreat from fossil fuels does not happen in a gradual and planned way investors could lose trillions of dollars as the “carbon bubble” bursts.

5. Divestment means stocks will be picked up cheaply by investors who don’t care about climate change at all

To sell a stock you have to have a buyer. But the amounts being divested are too small to flood the market and cut share prices, so they won’t be going cheap. Also, the buyers of the stock are taking on the risk that the fossil fuel stocks may tank in the future, if the world’s nations fulfil their pledge to keep global warming below 2C by sharply cutting carbon emissions. If these stocks are risky, then the public and value-based institutions primarily targeted by the divestment movement should not be holding them. The argument that owning a stock gives you influence over a company leads us neatly into the next divestment myth.

6. Shareholder engagement with fossil fuel companies is the best way to drive change

This argument would have merit if there was much evidence to support it. When, for example, the Guardian asked the Wellcome Trust to give instances where engagement had produced change, it could not. And as campaigner Bill McKibben has pointed out, engagement is unlikely to persuade a company to commit to eventually putting itself out of business. In fact some market regulators, such as in the US, do not allow this kind of engagement.
The leading environmentalist Jonathon Porritt spent years engaging with fossil fuel companies only to conclude recently that such efforts were futile. Nonetheless, serious engagement could drive some change and 2015 has seen both BP and Shell having to support such shareholder resolutions. But such resolutions need specific changes and deadlines to be effective. Whatever your view, remember this is not an either/or situation. Many campaigners view divestment as the stick and engagement as the carrot, with both aiming for the same ultimate goal.

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7. Divestment means investors will lose money

Many of those who have divested so far are philanthropic organisations, universities and faith groups who use their endowments to fund their good works. Selling out of fossil fuels would cut their income, say critics, as those companies have been very profitable investments over the last few decades.
The first response to this is money does not trump morality for many of these groups. But the second is that when it comes to investments, the past is no guide to the future. Coal stocks have plummeted in value in recent years, as has the oil price in recent months, meaning recently divested funds have actually avoided losses. Furthermore, a series of analyses have suggesteddivestment need not dent profits.
Of course, oil prices might rebound, possibly even coal prices. But such volatility is unwelcome for investors looking for steady incomes. And for long-term investors, major financial institutions including HSBC, Citi, Goldman Sachs and Standard and Poor’s have all warned of the risks posed by fossil fuel investments, particularly coal.
Perhaps the best response to this myth is that the proof of the pudding is in the eating: over 180 organisations have already asked themselves if divestment would help or hinder their missions and then gone ahead and done it. The most notable is the Rockefeller Brothers Fund, founded on a famous oil fortune. Valerie Rockefeller Wayne noted that funding companies that cause the problems being tackled by their programmes is pretty dumb: “We had investments that were undermining our grants.”

8. Fossil fuels are essential to ending world poverty

Fossil fuel supporters often argue that coal, oil and gas made the modern world and is vital to improving the lives of the world’s poorest citizens. It is an emotive argument. But the most recent report from the UN’s Intergovernmental Panel on Climate Change, written and reviewed by thousands of the world’s foremost experts and approved by 195 of the world’s nations, concluded the exact opposite. Climate change, driven by unchecked fossil fuel burning, “is a threat to sustainable development,” the IPCC concluded.
It warned that global warming is set to inflict severe and irreversible impacts on people and that “limiting its effects is necessary to achieve sustainable development and equity, including poverty eradication”. The IPCC went even further, stating that climate change impacts are projected “to prolong existing and create new poverty traps”.
That could not really be clearer. The challenge is to ensure poverty is ended by the large-scale deployment of clean technology, and shifting money out of fossil fuels by divesting could help that.

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9. Most fossil fuels are owned by state-controlled companies, not the publicly traded companies targeted by divestment

This is true. The International Energy Agency estimates that 74% of all coal, oil and gas reserves are owned by state-controlled companies. The most straightforward response to this is that divestment is just one of many ways of trying to curb carbon emissions and that international action at state level will of course be essential. But there are reasons why divestment could help. The listed fossil fuel companies have huge influence and undermining their power could embolden politicians in leading nations to deliver ambitious international climate action.
In any case, many of the biggest state-controlled companies float some of their stock, while also contracting the publicly traded companies to help extract their reserves. Furthermore, the state-controlled reserves tend to be the ones that are easiest and cheapest to extract and are therefore the most sensible to use in filling up the last of the atmosphere’s carbon budget, the trillion tonnes or so of carbon that scientists say is the limit before dangerous climate change kicks in. Last, the extreme and expensive hydrocarbons that really must stay in the ground – such as tar sands, the Arctic and ultra deep water reserves – are the near exclusive preserve of listed companies.

10. It’s none of your business how other people invest their money

First, some divestment campaigners target their own pensions funds – it is their money. But even if it is not, the impacts of fossil fuel investments are not limited to the stock owners themselves. The carbon emissions from fossil fuel burning are causing climate change that affects everyone on Earth. Furthermore, the “none of your business” argument would imply no divestment campaign was legitimate, meaning the harm caused by tobacco and apartheid South Africa would have gone on longer.

Standing tall for trees: meet the women who are changing forestry

Sure, women around the world have made great strides in the workplace – but many fields are still dominated by men, including one that is dear to our heart: forestry. In honor of International Women’s Day, join the Rainforest Alliance in celebrating three women, who are not only breaking down gender barriers, but also working to protect and conserve forests – sometimes risking their lives to do so.
Christine Korol, Toronto, Canada

“You do see a few women in the field here and there, but it’s really rare. It can be intimidating to be the only woman in the room – or in the field – but it’s also pretty amazing. When we go to do the audits we’re out in the bush, sometimes we literally go to the end of a road – it just ends there. I go to places [in Canada] that I’d never go to otherwise. Even if you were a crazy camper, you’d have no reason to go to these places. But I love being in the field. It’s touching when you go see a small private landowner and they’re so proud of their forests – they can practically tell you the story of every tree. And they are so passionate about managing their forests sustainably. We’ve worked with some of these people for 20 years and they’re still at it.”

Natalia Quevedo, Medellín, Colombia

“Ever since we began working with forestry operations, sustainability has been one of our principle goals, and it’s marvelous when we get clients who share that goal. Then we can join forces to ensure that everyone from managers to employees are immersed in sustainability. The employees take the concept of sustainability back to their families, and in that way we start to create a culture – not just a business culture but a local culture – that reinforces this idea through the social projects that we’ve established in different regions, where we’re also trying to reach children through the schools.”

Juana Payaba Cachique, Tres Islas, Peru
Cachique fought a tortuous – and eventually, successful – three-year legal battle to defend the forests of Madre de Dios from the ravages of gold mining. Cachique’s life was continually threatened throughout her legal battle, but she persevered, undeterred.

“The miners not only destroyed the communal territory, but also brought an increase in bars and introduced child prostitution to the area. They were destroying trees because they didn’t live here. It wasn’t their home, and they didn’t care about the land the way we did. As leaders, we have to think about the future and our children. We can’t think about ourselves.”

As part of that forward-thinking approach, Cachique has helped lead her community, along with five other indigenous groups in La Asociación Forestal Indigena de Madre de Dios (AFIMAD), to develop a sustainable forest management plan in collaboration with the Rainforest Alliance. The association has already conserved 76,000 acres (31,000 hectares)of land surrounding Madre de Dios (roughly three and a half times the size of the island of Manhattan in New York) through sustainable forest business development. By harvesting and processing non-timber products, such as Brazil nuts and palm fruit, the enterprises generate vital revenue that gives local communities the incentive to keep their forests intact.

http://www.theguardian.com/rainforest-alliance-partner-zone/2015/mar/09/women-gender-diversity-forestry-colombia-canada-peru

1.    Introduction
Fertilizer consumption in India is highly skewed with wide inter-state, inter- district and inter-crop variations.  The NPK ratio - a measure of balanced use of fertilizer - shows wide inter-state disparity. Though there has been an impressive growth in the consumption of fertilizers in post green revolution period, their reckless use has been one of the reasons for declining productivity in recent years. Investigations have revealed that one reason for the unbalanced fertilizer use is lack of adequate soil testing facilities that forced the farmers to rely on fertilizer dealers for advice on the fertilizer requirement.
2.    Constraints in functioning of existing Soil Testing Laboratories (STLs)
In spite of the proven benefits of the soil testing service for farmers, the service is suffering on financial, management and technical fronts. Receipt of large number of samples by each of the STLs makes it difficult for them to analyze and send the reports in time to the farmers. This may be one of the reasons for lack of required success in the programme, as time taken between collection of samples and receipt of recommendations by the farmers is too long. In other words, it can be stated that the huge network of STLs has not yet rendered the services of a watchdog for monitoring the soil health under major cropping systems in the country.

There is a need to organize soil testing laboratories at block level so that farmers need not travel far to get the soil tested and wait endlessly to get the results and recommendations.  Keeping this in view, a scheme is formulated to serve as guide to aspiring individuals / institutions in establishing a static soil testing laboratory offering services of soil and water testing, consultancy on problems like soil reclamation etc.
3.    Objectives:

The scheme has the following objectives:-
i.    Undertake soil testing and testing of irrigation water for quality
ii.    Provide recommendation on fertilizer application including bio-fertilizers.
iii.    Provide guidance on soil reclamation and related areas.
4.    Need for new Soil Testing Laboratories at Block Level:
The annual installed analyzing capacity of soil samples at STLs has also grown to 8.0 million samples with the annual growth rate of 11% during the last two decades. The analyzing capacity per 1000 ha of Gross Cultivated Area (GCA) has more than doubled during the last 20 years from 26 samples in 1980 to 56 samples in 2000. There is also a wide disparity in the analyzing capacity in terms of number of samples per STL across the regions. The annual analyzing capacity per STL has decreased in nineties in all the regions (except for north-east region) which may be due to the fact that the new STLs being set up are either mobile vans or are of less analyzing capacity (about 5.0 lakh samples per year). In all the regions, potential of STLs are not efficiently utilized and their utilization efficiency varies from 64% in northern region to as low as 16% in North-eastern region. The utilization efficiency of STLs has drastically reduced in all the regions. It has been reduced by more than 50% in eastern and north eastern region followed by 27% in northern region and about 11% both in southern and western regions during the last 10 years resulting in a net reduction of 20% (from 76% to 56%) at all India level. Since challenges ahead are to encourage precise and balanced fertilization in irrigated areas (northern & southern region) and ensure adequate fertilization in other area, especially dry land area of western & southern regions, there is a need for maintaining or improving soil fertility, correcting inherent soil nutrient deficiency and restoring productivity of the land that has been degraded by exploitative activities in the past. It also highlights that the need for intensive soil tests for developing specific nutrient management scenarios/strategies at more desegregated level is enormous in all the regions. Thus, it reveals that the creation or establishment of new STLs in the country at each block level is essential to cater to the needs of the farming community.
Though there is enormous scope for the project, lack of awareness among farmers on the importance of soil test based fertilizer use limit the commercial scope. A laboratory with a capacity to test 8000 samples per year will be adequate to cater to a few villages in one block. The scientist manning the unit could also engage in providing guidance in the areas of land reclamation, compost making, use of bio-fertilizer etc.
5.    Project requirements
5.1 Location
Such a unit has to be located in block head quarters.  The unit could also be housed in a laboratory of the Junior college to take advantage of the facilities and expertise available. Vocational course for S.S.C. students may also be run in those junior colleges on collection of soil samples for testing and laboratory analytical methodologies during summer months so that these students become expert trainees and they may be absorbed as soil health workers at block level to facilitate soil testing programme with fair degree of success.
5.2 Capacity of the Laboratory
Though it is possible to test 10000 -14000 samples in a year, the installed capacity is considered at a moderate level of 8000 samples annually and the capacity utilization is considered at 35%, 50%, 75%, and 80% in the first three years and fourth year onwards in that order.
5.3 Equipment
The equipments suggested for the laboratory are given in Annexure I.  These equipments can be used for finding out pH, electrical conductivity, available Nitrogen, Phosphorus, Potassium, Organic Carbon, available sulphur and calcareousness of soil etc.
5.4 Transport
As the Laboratory is static, there is need for transport to initially canvass for the work and collect samples.  As the awareness about the facility builds up in the villages, farmers would come to the laboratory with the soil samples for testing. The trainees of vocational course may be deputed and their services may be utilized for collection of representative soil samples as well as transfer of them to the nearest laboratory.
5.5 Raw Material
Glass ware and chemicals required are available with leading scientific equipment manufacturers and chemical suppliers.
5.6 Manpower
    One post graduate in agriculture with soil science specialization will man the laboratory supported by two semi-skilled persons for collection, preparation of samples and other laboratory/field related works.
    Financial aspects

    6.1 Benefits
    The laboratory is primarily used for soil testing as also for water testing. Testing fee of 150/- per soil sample (excluding micro-nutrients) and 150/- per water sample is considered in the model. The benefits in the first three years, and fourth year onwards would be 4.200 lakh, 1.536 lakh, 3.936 lakh and 4.416 lakh respectively.

    6.2  Project Cost
    The project cost comprises of 8.60 lakh towards capital cost and 4.104 lakh for operational cost in the first year.  The detailed operational cost has been furnished in Annexure II.  The operational cost in the second, third and fourth year onwards is 4.464 lakh, 5.064 lakh and 5.184 lakh respectively.

    6.3 Margin Money

    The margin money / down payment considered in the model is 15 % of the unit cost which works out to 190000.

    6.4 Bank Loan

    Bank loan of 85 - 95 % of the total cost shall be available from the financing institution. Bank loan considered in the model is 85%.  It works out to 1080000 in the model.

    6.5 Rate of interest

    Banks are free to decide the rate of interest within the overall RBI guidelines issued from time to time. However, the ultimate lending rate has been considered as 12 % for working out the bankability of the model project.

    6.6 Security

    Banks are guided by RBI guidelines issued from time to time in this regard.

    6.7 Financial analysis
    The techno economic parameters assumed in the model are given in Annexure III.  The cash flow statement and detailed financial analysis are shown in Annexures IV & V respectively.  The financial analysis indicates that the scheme is viable. The major financial indicators are given below:
    NPV :  2.98 lakh
    BCR : 1.12 : 1
    IRR  : 28.79 %

    6.7 Financial analysis 

The techno economic parameters assumed in the model are given in Annexure III.  The cash flow statement and detailed financial analysis are shown in Annexures IV & V respectively.  The financial analysis indicates that the scheme is viable. The major financial indicators are given below:
NPV :  2.98 lakh
BCR : 1.12 : 1
IRR  : 28.79 %
6.8 Repayment schedule 
Based on the cash flow the detailed repayment schedule has been worked out and furnished in Annexure VI.  The repayment period works out to six years.

A company’s financial statement is used to show a company’s performance over a certain period of time, generally every fiscal quarter. The financial statement really consists of three different statements: balance sheets, cash flow statements and income statements.
By being able to read a financial statement, you can determine where a company has made or lost money, where the money went and how the company stands financially. The financial statement gives shareholders an accounting of how their investment is performing.

Components of a Financial Statement

Balance Sheets

Represent the assets, liabilities and the net worth or shareholder equity of the company. Assets make up all the property the company owns, including bank accounts, real estate, machinery etc. An asset can also be intangible such as a trademark or patent.
Liabilities consist of the money the company owes others. This can include leases on real estate, loans, accounts payable to suppliers of material, tax liabilities or obligations to deliver product.  Liabilities also include employee payrolls and money borrowed from banks.
Shareholder equity represents the company’s net worth if it were liquidated and what each shareholder would receive after paying the creditors of the company.

Cash Flow Statements

Reports on the inflow and outflow of the company’s money. The cash flow statement is divided into financing activities, operating activities and investment activities. In combination, these three parts show the change in capital position the company had over a period of time.

Income Statements

Show how much revenue the company took in over a specified time period and how much money was spent to get that revenue. The income statement shows the company’s net earnings or losses on the bottom line and begins with all the cash the company took in at the top, and goes through all the expenses it took to make that money with the net figure on the bottom.
Knowing how to read a financial statement gives an investor or analyst a clear picture of the financial position of a business. Nevertheless, past performance does not generally guarantee future results; keep this in mind before investing in any company.

Thursday, March 12, 2015

Temperature
Mean Temperature	27 °C	-
Max Temperature	34 °C	-	- ()
Min Temperature	20 °C	-	- ()
Cooling Degree Days	16
Growing Degree Days	30 (Base 50)
Moisture
Dew Point	21 °C
Average Humidity	63
Maximum Humidity	85
Minimum Humidity	49
Precipitation
Precipitation	0.0 mm	-	- ()
Sea Level Pressure
Sea Level Pressure	1014.88 hPa
Wind
Wind Speed	1 km/h ()
Max Wind Speed	6 km/h
Max Gust Speed	-
Visibility	7.0 kilometers
Events

T = Trace of Precipitation, MM = Missing Value

Source: Averaged Metar Reports

Daily Weather History Graph

Hourly Weather History & Observations

Time (IST)	Temp.	Dew Point	Humidity	Pressure	Visibility	Wind Dir	Wind Speed	Gust Speed	Precip	Events	Conditions
2:30 AM	23 °C	20 °C	74%	1014 hPa	4 km	Calm	Calm	-	-		Clear
5:30 AM	22 °C	17 °C	68%	1014 hPa	4 km	Calm	Calm	-	-		Clear
8:30 AM	27 °C	20 °C	57%	1017 hPa	10 km	Calm	Calm	-	-		Clear
11:30 AM	34 °C	24 °C	50%	1017 hPa	10 km	ESE	5.6 km/h /	-	-		Clear
2:30 PM	34 °C	24 °C	49%	1014 hPa	10 km	ESE	5.6 km/h /	-	-		Clear
5:30 PM	30 °C	23 °C	55%	1013 hPa	10 km	Calm	Calm	-	-		Clear
8:30 PM	27 °C	22 °C	68%	1015 hPa	4 km	Calm	Calm	-	-		Clear
11:30 PM	24 °C	22 °C	85%	1015 hPa	4 km	Calm	Calm	-	-		Clear

Local Weather Report and Forecast For: Kakinada    Dated :Mar 12, 2015

	Past 24 Hours Weather Data Maximum Temp(oC) 34.0 Departure from Normal(oC) 0 Minimum Temp (oC) 20.5 Departure from Normal(oC) -2 24 Hours Rainfall (mm) NIL Todays Sunset (IST) 18:10 Tommorows Sunrise (IST) 06:11 Moonset (IST) 10:28 Moonrise (IST) 23:39
Today's Forecast:Sky condition would be partly cloudy. Maximum and minimum temperatures would be around 34 & 21 degrees celsius respectively.
Date Temperature ( o C ) Weather Forecast Minimum Maximum 13-Mar 22.0 36.0 Partly cloudy sky 14-Mar 23.0 35.0 Partly cloudy sky 15-Mar 23.0 35.0 Partly cloudy sky 16-Mar 23.0 35.0 Partly cloudy sky 17-Mar 23.0 34.0 Partly cloudy sky with Thundery development 18-Mar 23.0 34.0 Partly cloudy sky with Thundery development

Local Weather Report and Forecast For: Kakinada    Dated :Mar 13, 2015

T = Trace of Precipitation, MM = Missing Value

Source: Averaged Metar Reports

Time (IST)	Temp.	Dew Point	Humidity	Pressure	Visibility	Wind Dir	Wind Speed	Gust Speed	Precip	Events	Conditions
2:30 AM	23 °C	21 °C	87%	1013 hPa	4 km	Calm	Calm	-	-		Clear
5:30 AM	21 °C	18 °C	81%	1013 hPa	4 km	Calm	Calm	-	-		Clear
8:30 AM	26 °C	20 °C	65%	1015 hPa	10 km	Calm	Calm	-	-		Clear
11:30 AM	33 °C	21 °C	41%	1015 hPa	10 km	Calm	Calm	-	-		Clear
2:30 PM	35 °C	23 °C	40%	1013 hPa	10 km		3.7 km/h /	-	-		Clear
5:30 PM	32 °C	20 °C	37%	1013 hPa	10 km	SSW	5.6 km/h /	-	-		Clear
8:30 PM	26 °C	19 °C	60%	1015 hPa	4 km	Calm	Calm	-	-		Clear
11:30 PM	24 °C	20 °C	73%	1016 hPa	4 km	Calm	Calm	-	-		Clear

Monthly Weather History Graph

Local Weather Report and Forecast For: Kakinada    Dated :Mar 13, 2015

	Past 24 Hours Weather Data Maximum Temp(oC) 35.5 Departure from Normal(oC) 1 Minimum Temp (oC) 21.0 Departure from Normal(oC) -2 24 Hours Rainfall (mm) NIL Todays Sunset (IST) 18:11 Tommorows Sunrise (IST) 06:10 Moonset (IST) 12:11 Moonrise (IST) 00:33
Today's Forecast:Sky condition would be partly cloudy. Maximum and minimum temperatures would be around 35 & 21 degrees celsius respectively.
Date Temperature ( o C ) Weather Forecast Minimum Maximum 15-Mar 21.0 34.0 Partly cloudy sky 16-Mar 21.0 34.0 Partly cloudy sky 17-Mar 22.0 35.0 Partly cloudy sky with Thundery development 18-Mar 22.0 34.0 Partly cloudy sky with Thundery development 19-Mar 23.0 35.0 Partly cloudy sky with Thundery development 20-Mar 23.0 35.0 Partly cloudy sky with Thundery development

Degree Days - Handle with Care!

Degree days are a simplified form of historical weather data. They are commonly used in monitoring and targeting to model the relationship between energy consumption and outside air temperature.
Weather normalization of energy consumption is one of the most common such uses of degree days. In theory, weather normalization (or "weather correction") enables a like-for-like comparison of energy consumption from different periods or places with different weather conditions.
Weather normalization techniques are often based around regression analysis of past energy consumption data, a method that is frequently used with degree days to:

• Identify signs of waste from past energy-consumption data (often using CUSUM analysis).
• Assess recent energy performance by comparing recent consumption with a past-performance-based estimate of expected consumption. In particular, this process is often used to identify excess consumption (or overspend), and to quantify the savings from improvements in energy efficiency.

Although much of the theory behind these methods is sound, the results are usually a lot less accurate than many people realize. Such degree-day-based methods are central to many energy management programmes, and, as a result, important decisions are frequently based on figures that can be misleading to those who put too much faith in them.
This article looks at some of the problems associated with the common uses of degree days in monitoring and targeting, and suggests a few ways that those problems can be mitigated. Its aim is not to denigrate the degree-day-based methods that are widely accepted in the energy industry, but to highlight the major sources of inaccuracy, and to encourage the reader to ensure the validity of degree-day-calculated figures before using them as a foundation for decision making.
If you are looking for degree-day data (rather than an article about it), you might want to head over to another of our websites: Degree Days.net.

Contents

First, this article looks at the basics of degree-day theory (you might want to skip this if you already know the basics):

• Weather, energy consumption, and weather normalization basics
• An example demonstrating the motivation for weather normalization
• Introducing degree days - historical weather data made easy
• Heating degree days (HDD)
• Cooling degree days (CDD)
• Celsius or Fahrenheit
• Methods for using degree days in energy monitoring and targeting
• Simple ratio-based weather normalization of energy consumption
• Linear regression analysis of energy consumption
• Separating weather-dependent consumption from the "baseload"

Next, this article highlights problems with the ways in which degree days are commonly used, and then suggests ways in which those problems can be mitigated:

• Problems with common degree-day-based methods
• The base temperature problem
• The baseload energy problem
• The intermittent heating problem
• The meter reading problem
• The "ideal" temperature problem
• Suggestions for improvement: using degree days wisely
• Use the most appropriate degree-day data you can
• Ignore periods with an "ideal" outside temperature
• Get interval metering
• Get interval submetering
• Use a yearly timescale for comparisons of weather-normalized data
• Remember the level of accuracy
• Look at proportional differences before looking at absolute numbers
• Conclusions

Weather, energy consumption, and weather normalization basics

In heated or cooled buildings, energy consumption tends to depend on the outside air temperature:

• The colder the outside air temperature, the more energy it takes to heat a building to a comfortable temperature.
• The warmer the outside air temperature, the more energy it takes to cool an air conditioned building to a comfortable temperature.

"Weather normalization", or "weather correction", allows you to adjust your energy-consumption figures to factor out the variations in outside air temperature. In theory, you can then compare the normalized figures fairly.
Weather normalization is commonly used when analyzing changes in a building's energy consumption, and, when combined with other normalization techniques (such as normalizing for occupancy and building size), when comparing the energy consumption of different buildings.

An example demonstrating the motivation for weather normalization

Let's say you have several years' worth of energy consumption data for a building, and you want to compare the energy consumption in 2005 with that in 2006, to see if there was an improvement in energy efficiency.

Year	Total energy consumption (kWh)
2005	175,441
2006	164,312

The raw figures show that the building used less energy in 2006 than it did in 2005. However, let's say you know that a large proportion of the building's energy consumption went on heating, and you also know that 2006 was a warmer year than 2005. You would therefore expect less energy to have been used in 2006 than in 2005, as the warmer outside temperatures in 2006 meant that less energy was needed to heat the building.
So, less energy was used in 2006 than in 2005, but did energy efficiency improve, or was it just because 2006 had warmer weather?
This is where weather normalization can help. Provided you have the appropriate historical weather data (most probably heating degree days), you can calculate the weather-normalized energy consumption in 2005, and the weather-normalized energy consumption in 2006. These two figures can then, in theory, be compared on a like-for-like basis, enabling you to see whether or not there was an improvement in the building's energy efficiency.

Introducing degree days - historical weather data made easy

Degree days are essentially a simplification of historical weather data - outside air temperature data to be specific. Degree-day data is easy to get hold of, and very easy to work with. This makes degree days popular amongst energy consultants and energy managers, certainly when compared with other forms of past weather data such as hourly temperature readings.
Degree days can come in any timescale, but they typically come as weekly or monthly figures. You can sum them together to make figures covering a longer period (e.g. sum 12 consecutive monthly degree-day figures to make an annual degree-day total). This is useful if you are working with, say, quarterly or annual energy-consumption figures.
There are two main types of degree days: heating degree days (HDD) and cooling degree days (CDD). Both types can be Celsius based or Fahrenheit based.

Heating degree days (HDD)

Heating degree days (HDD) are used for calculations that relate to the heating of buildings. For example, HDD can be used to normalize the energy consumption of buildings with central heating.
Heating degree-day figures come with a "base temperature", and provide a measure of how much (in degrees), and for how long (in days), the outside temperature was below that base temperature. In the UK, the most readily available heating degree days come with a base temperature of 15.5°C; in the US, it's 65°F.
An example calculation: if the outside temperature was 2 degrees below the base temperature for 2 days, there would be a total of 4 heating degree days over that period (2 degrees * 2 days = 4 degree days). In reality, the process of calculating degree days is complicated by the fact that outside temperatures vary throughout the day. Fortunately, however, you can use degree days in your own calculations without worrying about how they were calculated originally!

Cooling degree days (CDD)

Cooling degree days (CDD) are used for calculations relating to the cooling of buildings. For example, CDD can be used to normalize the energy consumption of buildings with air conditioning.
Cooling degree-day figures also come with a base temperature, and provide a measure of how much, and for how long, the outside temperature was abovethat base temperature.
Although this article talks mainly about heating degree days, much of the information is also applicable to calculations involving cooling degree days.

Celsius or Fahrenheit

Celsius-based degree days are calculated using a base temperature that is measured in Celsius, and outside temperatures that are measured in Celsius.
In contrast, Fahrenheit-based degree days are calculated using a base temperature measured in Fahrenheit, and outside temperatures that are measured in Fahrenheit. Fahrenheit degree days are common in the US, where they typically come with a base temperature of 65°F (equivalent to 18°C). Since a temperature difference of 1°C is equivalent to a temperature difference of 1.8°F, Fahrenheit-based degree days are 1.8 times bigger than their equivalent Celsius-based degree days.
Although this article talks mainly about Celsius-based degree days, the theory and arguments presented are equally applicable to Fahrenheit-based figures and calculations.

Methods for using degree days in energy monitoring and targeting

Degree days are commonly used in monitoring and targeting of energy consumption. As an understanding of the popular methods is necessary for an understanding of the bulk of this article, they are briefly explained below:

Simple ratio-based weather normalization of energy consumption

Heating degree days are often used to normalize the energy consumption of a heated building so that, in theory, the normalized figures can be compared on a like-for-like basis. So, for the example given above, heating degree days would enable you to calculate normalized energy-consumption figures for 2005 and 2006 that, in theory, could be compared fairly.
The simplest way to normalize energy-consumption figures is to calculate the kWh per degree day for each kWh energy-consumption figure in question. Simply divide each kWh figure by the number of degree days in the period over which that energy was used. In theory, dividing by the degree days factors out the effect of outside air temperature, so you can compare the resulting kWh per degree day figures fairly.
The following figures continue the example explained above, using real degree days from the South Eastern region of the UK:

Year	Total energy consumption (kWh)	Total heating degree days	kWh per degree day	Normalized kWh
2005	175,441	2,075	84.55	171,383
2006	164,312	1,929	85.18	172,660

The last column in the table, normalized kWh, shows how you can multiply the kWh per degree day figures by a single "average year" degree-day value (in this case we used 2,027 degree days as the multiplier - an average-year value calculated from the last 10 years' worth of degree-day data from the South Eastern UK region). This gives you normalizedequivalents of your original kWh figures that you can, in theory, compare fairly.
The normalized figures from the example above indicate that energy efficiency was actually slightly worse in 2006 than in 2005.
NB Some people use 5-year-average degree days as the multiplier, some use 10- or 20-year-average degree days, and others use "standard degree days" (to normalize figures in such a way that they can be compared between regions). Provided you use just one multiplier (e.g. do not use "rolling" averages) it should not matter much what multiplier you use, as your figures will at least be proportionally comparable.

Linear regression analysis of energy consumption

Linear regression analysis is commonly used as a monitoring and targeting technique. Central to this is the assumption that energy consumption is caused by a "driving factor" (or "driver") - this could be the widgets produced by a production line, or, in the case of heating or cooling, the degree days. So, for a heated building, it is assumed that the energy consumption required to heat that building for any particular period is proportional to (or driven by) the number of heating degree days over that period.
Typically you would select a "baseline" set of energy consumption data: this would usually be weekly or monthly data from the past year or two. For each figure of energy consumption, you need a corresponding figure for the degree days (or whatever driving factor you are using) - you would then correlate these two sets of figures.
For example, the scatter plot below shows a years' worth of monthly degree days (x-axis) plotted against monthly kWh (y-axis). Specifically, the chart shows 15.5°C-base-temperature heating-degree-day figures from North West Scotland in 2006, and a very good correlation with the energy consumption data (an R² close to 1):
The "regression line" is the line of best fit through the points in the scatter chart. It is often known as the "trend line" or the "performance characteristic line".
Once you've established the formula of the regression line, you can use it to calculate the baseline, or expected, energy consumption from the degree days. So, each time you obtain a new figure for the degree days (typically each week or month), you can plug it into the regression-line formula to get the expected energy consumption. You can compare this figure with the actual energy consumption for the period, to determine whether more energy was used than expected.
There are a number of other techniques that revolve around the degree-day-based regression analysis described here. The proximity of the points around the regression line is often used as an indication of the accuracy of the heating control (the greater the scatter, the worse the control), and it is common for people to plot a CUSUM chart of the difference between actual and expected consumption. Estimating "baseload" energy consumption is another typical application:

Separating weather-dependent consumption from the "baseload"

It is very common for a single energy meter to measure both weather-dependent and non-weather-dependent energy consumption together. For example, a building with electric heating might have a single electricity meter measuring all its electricity consumption (heating, lighting, office equipment etc.).
In degree-day analysis, energy consumption that does not depend on the weather is often referred to as "baseload" energy consumption. It generally comes from energy uses that are not directly involved with heating or cooling the building; examples include electric lights, computer equipment, and industrial processes. For the purposes of degree-day-based calculations, it is usually assumed that a building's baseload energy consumption is constant throughout the year.
It is worth nothing that the term "baseload" is often used to describe the total kW power of all the equipment that is on constantly, including when the building is closed. However, the baseload energy that we are talking about here is a total of all the non-weather-dependent energy consumption (including energy consumption from equipment that is only used during occupied hours), and is usually expressed as an average daily, weekly, or monthly kWh value.
Anyway, baseload energy consumption complicates the simple ratio-based approach to weather normalization that was described above. You can only apply that method to energy consumption that is 100% degree-day dependent, so, if the raw energy-consumption figures contain baseload energy consumption as well as degree-day-dependent energy consumption, you need to subtract the baseload kWh from the raw figures before applying the ratio-based method. (You would typically add the baseload kWh back on to your normalized figures afterwards.)
There are two methods that are commonly used to calculate the baseload energy as a monthly kWh value:

• Linear regression analysis: when you plot monthly degree days (x-axis) against monthly energy consumption (y-axis), you can estimate the monthly baseload energy consumption from the point at which the regression line crosses the y-axis. For example, the scatter plot shown above (in the section introducing linear regression analysis) shows a baseload (y-axis intercept) of around 7,455 kWh per month.
• If the building's heating is switched off over the summer, you can estimate the monthly baseload by taking an average of the monthly energy consumption over that period.

The same methods can be also be used on a weekly basis, if weekly data is available.

Problems with common degree-day-based methods

We've given a brief overview of the motivation and methods that are commonly associated with degree days in energy monitoring and targeting, and we shall now move on to the substance supporting the main theme of this article:
When applied to real-world buildings, common degree-day-based methods suffer from a number of problems that can easily lead to inaccurate, misleading results.
To explain how significant inaccuracies occur, following is an explanation of several major problems with the ways in which degree days are commonly used:

The base temperature problem

In degree-day theory, the base temperature, or "balance point" of a building is the outside temperature above which the building does not require heating. Different buildings have different base temperatures.
In the UK, for example, the majority of energy professionals primarily use degree days with a base temperature of 15.5°C. This is partly because 15.5°C base-temperature degree days are the historical norm in the UK, and partly because, unlike degree days with other base temperatures, 15.5°C figures have always been readily and freely available.
Use of a 15.5°C base temperature is often justified with arguments along the lines of:

• Buildings are typically heated to a temperature of around 19°C.
• The heating system does not need to supply all the heat necessary to ensure that the building is heated to 19°C: some heat comes from other sources such as the people and equipment in the building. These sources contribute to an "average internal heat gain" that is typically worth around 3.5°C.
• If you subtract the typical average internal heat gain from the typical building temperature (19°C - 3.5°C) you get a base temperature of 15.5°C. This is effectively the temperature that the heating system needs to heat the building to, as the average internal heat gain supplies the difference. 15.5°C is therefore an appropriate base temperature for degree-day-based calculations relating to the energy consumption of the heating system.

The method of calculating an appropriate base temperature by subtracting the average internal heat gain from the building temperature is a sensible approximation. However, the figures used in the above arguments are where the problems lie:

• Different buildings are heated to different temperatures. Although it's often recommended that office buildings be heated to 19°C, in reality they are often several degrees warmer. Industrial buildings are often several degrees cooler.
• Average internal heat gain varies greatly from building to building. Clearly a crowded office packed with people and equipment will have a much higher average internal heat gain than a sparsely-filled office with a high ceiling. Clearly the internal heat gain from industrial processes depends greatly on the processes in question.

In reality, 15.5°C is rarely the most appropriate base temperature to use for degree-day-based calculations. This is important, as degree-day-based calculations can be greatly affected by the base temperature of the degree days used.
The base temperature with which degree days are most readily available actually varies from country to country. For example, the "default" base temperature in the UK is 15.5°C, whilst, in the US, it's 18°C (65°F). This alone is a pretty strong indication that the one-base-temperature-fits-all approach to degree-day-based calculations is inappropriate!
The following chart is based on 2006 heating degree day figures for North West Scotland. Figures for three different base temperatures (18.5°C, 15.5°C and 10.5°C) are displayed as percentages of the March value (March being the coldest month in 2006 for that region). The figures are displayed as percentages (as opposed to absolute degree-day values) so that they can be compared easily.
This chart makes it clear that the base temperature of degree days has a big effect on the proportional difference between the degree days of one month and the degree days of the next. This is critically important to realize if you are weather normalizing monthly energy-consumption figures - getting the base temperature just slightly out can easily lead to misleading results.
To complicate things further, the base temperature of most buildings actually varies throughout the year. It is affected by the sun (solar heat gain), the wind, and the patterns of occupancy, all of which typically vary throughout the year. Even the internal temperature of the building will typically vary unless the building's heating control system is working perfectly.
As this section has shown, it's important to pick an appropriate base temperature for degree-day-based calculations, and degree days in the most appropriate base temperature are unlikely to be those that are most readily available. As a building's base temperature typically varies throughout the year, even the most appropriate base temperature is usually only an approximation.

The baseload energy problem

Any baseload energy needs to be removed from energy-consumption figures before they can be weather normalized. This is fine in theory, but very difficult in practice.
As described above, linear regression is one way to calculate the baseload energy (plotting degree days on the x-axis against energy consumption on the y-axis, and taking the baseload energy from the point at which the regression line crosses the y-axis). However, the accuracy of this method is highly dependent on the degree days having an appropriate base temperature, which introduces all the base-temperature problems described above.
To illustrate the effect of base temperature on the baseload energy, the plot below extends the example correlation that was originally used to illustrate the method by adding a correlation of the same energy data with 18.5°C-base-temperature degree days. This is, in fact, made-up energy data (kWh and degree days don't correlate perfectly in the real world!), but the degree days are real, and show the striking effect of base temperature on the baseload energy calculated by this method.
The chart clearly shows that, although the 15.5°C and the 18.5°C base-temperature data both correlate very well with energy consumption, the 15.5°C data gives a baseload energy that is around 50% greater than that given by the "perfect" 18.5°C correlation. Choosing the the right base temperature clearly makes quite a difference to the baseload energy!
In reality, energy consumption will never give a "perfect" correlation with degree days of any base temperature, so, even if you do have degree days with a range of base temperatures available, you can never be certain that you are picking the appropriate base temperature just by looking at the correlations. And, since the y-axis intercept varies so significantly with the base temperature chosen, it will consequently be impossible to obtain the baseload energy accurately.
In fact, the whole concept of baseload energy is usually a pretty big approximation, as much of the energy consumption that typically contributes towards it depends on the time of year. For example: lighting energy consumption typically depends on the level of daylight, which varies seasonally and from day to day.
Baseload energy is certainly not suited to being wrapped up as a monthly kWh figure, as months are very different in calendar terms (this is explained further in our article on energy performance tracking). The simple fact that, in common 365-day years, March is over 10% longer than February makes it pretty clear that baseload energy consumption is unlikely to be constant from month to month.

The intermittent heating problem

Many buildings are only heated to full temperature intermittently, usually to fit around occupancy hours (e.g. 0900 to 1700, Monday to Friday). However, degree days cover a continuous time period: 24 hours a day, 7 days a week. This means that degree days are often not a perfect representation of the outside air temperatures that are most relevant to heating energy consumption.
Consider, for example, a building that is unheated overnight. The colder night-time temperatures do have a partialeffect on the day-time energy consumption, as a colder night will typically mean more energy is required to bring the building back up to temperature in the morning. (Thanks to the complicated way in which buildings retain heat/coolth, there is a time lag, typically of the order of hours not minutes, between changes in the temperature outside and their effect on the energy consumption inside.) However, whilst this effect is only partial, the cold night-time temperatures are fullyrepresented by degree days.
This problem is not only limited to day/night intermittent heating, as many buildings are also unheated through weekends, public holidays, and shutdown periods. When a particular weekend is uncommonly warm or cold, the degree-day total for that week or month will be affected accordingly, even though the outside temperature on that weekend is largely irrelevant to a building that is unheated on weekends.
With degree-day analysis of monthly figures, such intermittent heating also introduces a calendar mismatch: although monthly degree days cover the entire month, the proportion of days for which a building is heated typically depends on the calendar of the month in question. Consider the following example monthly figures for a building that is heated on weekdays only:

Month	Total no. days	No. unheated days (weekends)	No. heated days (weekdays)	Proportion of days that are heated
Feb 2007	28	8	20	71.43%
Mar 2007	31	9	22	70.97%
Apr 2007	30	9	21	70.00%
May 2007	31	8	23	74.19%

These example figures show that, for a building that is heated on weekdays only, the proportion of days that are heated varies quite considerably from month to month. This is a simple result of the way that the calendar works. Monthly totals of degree days do not take this calendar mismatch into account, giving another reason why they should not be expected to relate closely to monthly heating energy consumption (kWh). When bank holidays and shutdown periods are considered (as they should be), the effect of this calendar mismatch becomes more marked, and weekly degree-day analysis is also affected.

The meter reading problem

As mentioned previously, degree days typically come as weekly or monthly values. So, in order to compare or correlate energy consumption with degree days, you need meter readings that are taken at the start of each week or month. If you're taking those meter readings manually, you should take them at midnight, and often on weekends.
Of course, it is rarely convenient to take manual meter readings at midnight or on weekends, so it is common for such readings to be taken up to several days early or late. This can introduce a significant inaccuracy into degree-day-based calculations.
For example, the month of June 2006 ended at midnight on Friday 30th June. If, for convenience, the meter reading was taken at 0900 on Monday 3rd July, June's energy consumption would cover a period that was around 8% longer than it should be, and July's energy consumption would cover a period that was around 8% shorter than it should be. The degree-day figures would match the calendar months exactly, but the energy consumption data would not. It's not difficult to see that this would introduce a significant inaccuracy!

The "ideal" temperature problem

(This is as much a symptom of the base temperature problem and the intermittent heating problem as it is a problem in its own right.)
When the outside temperature is close to the base temperature of the building, the building will often require little or no heating. Degree-day-based calculations are particularly inaccurate under such circumstances:

• Results are particularly sensitive to the base temperature of the degree days used, and, as explained above, the base temperature is difficult to pin down precisely. It's important to estimate it well, but there's rarely a perfectly "correct" base temperature for any given building.
• Intermittent heating means that the temperature difference caused by lower night-time temperatures can often cause degree-day figures to indicate that heating is needed when, in fact, the higher daytime temperatures mean that it is not.

Matters are complicated further if the building has both heating and air conditioning. Under such conditions (an outside temperature close to the base temperature), a building will often require both heating and cooling to maintain a constant inside temperature over the course of a single day.
An energy-efficient building would usually sacrifice the maintenance of a constant temperature by ensuring that the temperature above which the air conditioning came on was a few degrees higher than the temperature below which the heating came on (a "comfort zone"). However, it is rare for real-world buildings to have perfect HVAC control. In fact, poor HVAC control can often result in a building being heated at the same time as it is being cooled - not very energy efficient at all!
Anyway, the upshot of all these complexities is that, when the outside temperature is close to the base temperature of the building, degree-day-based calculations are typically much less reliable. The inaccuracies introduced by the base temperature problem and the intermittent heating problem are exaggerated, making it difficult to place much confidence in results.

Suggestions for improvement: using degree days wisely

This article has highlighted several significant problems with the popular degree-day-based calculation methods. The greatest danger with these methods is that they are used without an awareness of their shortcomings - inaccurate figures that are thought of as accurate can easily lead to bad decision making.
Following are a few suggestions for how you can mitigate the problems highlighted above, and improve the accuracy of your results from degree-day-based calculations:

Use the most appropriate degree-day data you can

You should aim for data that is:

• From a weather station near to the building you are analyzing.
• Calculated accurately from good-quality temperature readings.
• In the timescale that is most appropriate for your analysis. For regression analysis, weekly data is often best for smoothing over the effects of weekend-related inaccuracies, but of course you need weekly energy-consumption data to match it. If you have irregular periods of consumption, you should sum daily degree days to match them.
• In the most appropriate base temperature for your building. The base temperature will almost certainly be different for heating than it is for cooling (cooling would usually have a higher base temperature). Internal heat gains will push both the heating and cooling base temperatures downwards. Intermittent heating will effectively push the heating base temperature down, and intermittent cooling will effectively push the cooling base temperature up. With experience, many people can estimate a building's base temperature(s) pretty well, but it's often a good idea to try a multi-base-temperature regression analysis to see what fits best.

When we originally wrote this article, it was very hard to get data that satisfied the above criteria. We consequently included Hitchin's Formula - a rather inaccurate and esoteric way to estimate degree days in any base temperature using mean temperature readings. However, since then we have set up the Degree Days.net website, which offers free heating and cooling degree days, in any base temperature, in daily, weekly, or monthly format, for locations worldwide. You can also now get weekly degree-day data for 77 UK weather stations from The Environmental Change Institute of Oxford University. Given that these sources make it much easier to get good data for locations worldwide, we decided that there wasn't much point in including Hitchin's Formula any more.

Ignore periods with an "ideal" outside temperature

The "ideal" temperature problem occurs when the outside temperature is such that the building requires minimal heating or cooling. Since the standard approaches to degree-day-based analysis are particularly inaccurate under such circumstances, it's often best to simply leave these periods out of your regression analysis.

Get interval metering

Interval metering has only become readily available in recent years, and much of the energy-management literature has yet to catch up. Analysis of the high-resolution detail contained within interval data such as half-hourly data can, in seconds, reveal patterns of energy wastage that could never be revealed by weekly or monthly regression analysis.
Other benefits aside, interval meter data can help in overcoming the degree-day problems that this article has highlighted. An interval meter can completely solve the problem of taking accurate meter readings at exactly the right times, as interval meters automatically take readings at the start and end of each week and month (in fact, they typically take readings every 15 or 30 minutes). Software such as Energy Lens can be very useful for splitting interval meter data into the weekly or monthly totals that are usually necessary for degree-day analysis.
Interval metering helps further if several interval meters are fitted:

Get interval submetering

Separate submetering can significantly reduce or even eliminate the baseload energy problem. If the heating energy consumption is metered separately, any baseload energy will be minimal, so there will be minimal potential for inaccuracies to be introduced by a fluctuating or poorly-estimated baseload. You should therefore be free to perform degree-day-based calculations on the heating energy consumption data without having to worry about inaccurate estimates of baseload energy.
Submetering can also give you greater confidence in your analysis of the non-heating energy consumption of the building. If the non-heating energy consumption is metered separately, it will be unlikely to be affected by variations in outside temperature, and you should be able to make more accurate comparisons of week-on-week and month-on-month energy performance, without need for degree-day normalization techniques.

Use a yearly timescale for comparisons of weather-normalized data

It is best to be sceptical when comparing weather-normalized figures from one week or month to the next, as inaccuracies caused by the base temperature problem, the baseload energy problem, and the intermittent heating problem are likely to be exaggerated by natural changes in those properties throughout the year.
However, provided the size and general operational patterns of the building do not change from one year to the next (energy-efficiency improvements aside), a comparison of yearly weather-normalized figures is less likely to suffer to the same extent, as the changes throughout any one year will usually be approximately repeated every year. Comparisons of year-on-year weather-normalized energy consumption are not infallible, but they should be less prone to the problems highlighted in this article than weekly or monthly comparisons.

Remember the level of accuracy

Remember that the figures calculated using degree-day-based methods are usually only approximate.
Plugging numbers into a formula will almost always give a result, but the accuracy of that result can only be trusted if the formula is sound and the numbers that went into it are accurate themselves. This is essentially the main problem with the common uses of degree days in monitoring and targeting: the calculations have no difficulty producing "results", but the combined effect of the problems highlighted in this article means that the overall accuracy of those results is often very low (despite the fact that they may appear with several figures after the decimal point).
After reading about the inaccuracies introduced by each of the problems that this article highlights, it should not be difficult to see how simple, justifiable changes to input parameters could easily turn a supposed 3.74% improvement in energy efficiency into a supposed 1.12% overspend (figures after the decimal point are shown here to highlight the misleading nature of numbers that appear more accurate than they really are).
Unless you have accounted for the problems highlighted in this article, figures that you calculate using standard degree-day-based methods will usually only be very approximate. There is no danger in using these methods to give you an indication of what may be happening with the energy consumption you are analyzing. However, before placing too much confidence in the figures, be sure to consider how different those figures might be if you had changed your approach to calculating them just slightly (e.g. by using degree days with a slightly different, but no less "correct", base temperature).

Look at proportional differences before looking at absolute numbers

The degree-day-based techniques described in this article are just as applicable to buildings with consumption figures in the millions of kWh as they are to buildings with consumption figures in the hundreds of kWh. However, the magnitude of the absolute numbers has no bearing on their accuracy - it's the proportional differences that matter.
For example: if you use regression analysis to calculate that, over the last month, a building consumed 2% more energy than expected (a relatively low proportional difference), that might be more likely to be a symptom of inaccuracies in the calculation than an indication of a real problem. And, if you have little confidence that a 2% difference means anything, it's irrelevant whether that 2% difference equates to 200 kWh or 2,000,000 kWh.
In contrast, a 20% proportional difference may well be high enough for you to consider it meaningful. If you have confidence in the proportional difference, you can also have confidence in the corresponding absolute numbers, and can confidently use them for deciding priorities and so on. The critical point is that only the proportional difference can enable you to judge whether the result of a calculation is likely to be meaningful, and, until you have judged that, the absolute numbers can only be a distraction.
By looking at the general accuracy of your calculation process (e.g. how many of the problems highlighted in this article apply), and by looking at the quality of your baseline correlation, you should be able to get a feel for the level of proportional difference that makes a figure worthy of your attention. It's only worth looking at the absolute numbers (e.g. excess kWh or cost) once you've determined from the proportional differences (e.g. percentage above expected) that they are likely to be meaningful (and not just a symptom of calculation inaccuracies).

Conclusions

Degree-day-based monitoring and targeting is a central part of many energy management programmes, but degree days are commonly used in ways that can easily lead to inaccurate, misleading results. If you are using the popular degree-day-based methods, it's important that you have an understanding of the sources of inaccuracy, and a sense for the reliability of the figures on which you base decisions. Otherwise you will frequently find yourself chasing excess consumption that doesn't really exist, and highlighting improvements that haven't really be made