PREAMBLE (NOT PART OF THE STANDARD)

In order to promote public education and public safety, equal justice for all, a better informed citizenry, the rule of law, world trade and world peace, this legal document is hereby made available on a noncommercial basis, as it is the right of all humans to know and speak the laws that govern them.

END OF PREAMBLE (NOT PART OF THE STANDARD)

(Reaffirmed 2009)

IS : 9841 - 1981
(Reaffirmed 2005)

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

(Second Reprint FEBRUARY 1998)

UDC 628·543 (026) : 631·8

© Copyright 1981

BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

Gr 9

November 1981

i

Indian Standard

GUIDE FOR TREATMENT AND DISPOSAL OF
EFFLUENTS OF FERTILIZER INDUSTRY

Water Sectional Committee, CDC 26

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)

(Continued on page 41)

2

Indian Standard

GUIDE FOR TREATMENT AND DISPOSAL OF
EFFLUENTS OF FERTILIZER INDUSTRY

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.
3 When 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
5 process, 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
7 fluoride 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

Fig. 1 A Typical Effluent Treatment Scheme of Fertilizer Factory Producing Urea and Phosphatic Fertilizers

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
   21 waste 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
   24 nitritying 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
   26 Oxidation 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

Fig. 6 Ammoniacal Effluent Treatment By Algae Culture

Fig. 7 Ammonia and Urea Bearing Effluent Treatment By Thermal Urea Hydrolysis

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

Fig. 8 Oil Bearing Effluent Treatment

30 from 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).

Fig. 9 Chromate Bearing Effluent Treatment

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:

Reduction of chromate

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

31

Precipitation with lime

Cr₂(SO₄)₃ + 3Ca(OH)₂ → 2Cr (OH)₃ + 3CaSO₄

Fe₂(SO₄)₃ + 3Ca(OH)₂ → 2Fe (OH)₃ + 3CaSO₄

Lime 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:

Cr₂O₇ + 3SO₂ + 2H⁺ → 2Cr⁺⁺⁺ + 3SO₄^-- + H₂O

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.

Fig. 10 Cyanide Bearing Effluent Treatment

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:

NaCN + Cl₂ → CNCl + NaCl.

In the presence of caustic soda cyanogen chloride is converted into sodium cyanate as follows:

CNCl + 2 NaOH → NaCNO + H₂O + NaCl

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.

2NaCNO + 4NaOH + 3Cl₂ → 2CO₂ + 6NaCl + N₂ + 2H₂O

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
33 present 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).

Fig. 11 Fluoride and Phosphate Bearing Effluent Treatment

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:

H₂SiF₆ + 3CaCo₃ → 3CaF₂ + SiO₂+ 3CO₂+ H₂O

2H₃PO₄ + CaCO₃ → Ca (H₂PO₄)₂ + H₂O + CO₂

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
34 of 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:

H₂SiF₆ + 3Ca (OH)₂ → 3CaF₂ + SiO₂ + 4H₂O

3Ca (H₂PO₄)₂ + 7Ca (OH)₂ → 2Ca₅OH (PO₄)₃ + 12H₂O

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
35 will 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.

36 In 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
37 individual 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

(Clause 0.5)

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)

Secretary
Shri N. K. Sharma
Deputy Director (Chern), ISI

Waste Treatment Methods Subcommittee, CDC 26 : 1

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)

Panel for Fertilizer Industry Wastes, CDC 26 : 1 : 12

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

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44 45