UNIVERSITY OF PETROLEUM & ENERGY STUDIES Pesticides and Fertilizer Industry

Submitted By:Akhil Krishnan R: 0001Asith K.A:0009Kimi Garg:0017Sandeep Samisheety:0028

Submitted To:Pavan Kumar MandapakaDept of HSEUPES

INTRODUCTION

A pesticide is any substance or mixture of substances intended for:

preventing, destroying, repelling, or Mitigating any pest.

Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides, rodenticides, molluscicides and various other substances used to control pests.

Under United States law, a pesticide is also any substance or mixture of substances intended for use as a plant regulator, defoliant, or desiccant.

Man employs pesticides as powerful environmental contaminants in order to improve environmental quality for himself and his domesticated animals and plants. In agriculture, pesticides are used to increase the cost/benefit ratio in favor of the farmers.In developing countries where food supplies are marginal, pesticide use may represent the margin between survival and starvation.

In surveying the role of pesticides in environmental quality it must be considered that pests themselves generally affect adversely the quality of the environment. The spectrum ranges from a mosquito in the bedroom or a cockroach in the pantry to a plague of locusts or the tsetse flies. Therefore it must be recognized that the purposeful environmental contamination by pesticides generally provides environmental benefits substantially greater than the risk of environmental pollution.

Presently, India has about 675 pesticides industries manufacturing about 75000 tonnes of pesticides. The pesticides industry has been identified as one of the highly polluting industries needing pollution control on priority.

Many household products are pesticides. All of these common products are considered pesticides:

Cockroach sprays and baits; Insect repellents for personal use; Rat and other rodent poisons; Flea and tick sprays, powders, and pet collars; Kitchen, laundry, and bath disinfectants and sanitizers; Products that kill mold and mildew; Some lawn and garden products, such as weed killers; and Some swimming pool chemicals.

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TYPES OF PESTICIDES

Pesticides are often referred to according to the type of pest they control. Another way to think about pesticides is to consider those that are chemical pesticides or are derived from a common source or production method. Other categories include biopesticides, antimicrobials, and pest control devices.

Chemical Pesticides

Some examples of chemically-related pesticides follow. Other examples are available in sources such as Recognition and Management of Pesticide Poisonings.

Organophosphate Pesticides - These pesticides affect the nervous system by disrupting the enzyme that regulates acetylcholine, a neurotransmitter. Most organophosphates are insecticides. They were developed during the early 19th century, but their effects on insects, which are similar to their effects on humans, were discovered in 1932. Some are very poisonous (they were used in World War II as nerve agents). However, they usually are not persistent in the environment.

Carbamate Pesticides affect the nervous system by disupting an enzyme that regulates acetylcholine, a neurotransmitter. The enzyme effects are usually reversible. There are several subgroups within the carbamates.

Organochlorine Insecticides were commonly used in the past, but many have been removed from the market due to their health and environmental effects and their persistence (e.g. DDT and chlordane).

Pyrethroid Pesticides were developed as a synthetic version of the naturally occurring pesticide pyrethrin, which is found in chrysanthemums. They have been modified to increase their stability in the environment. Some synthetic pyrethroids are toxic to the nervous system.

Pesticides ManufacturePesticides include insecticides, fungicides, weedicides, rodenticides and plant growth

regulants. There are many formulations used in manufacturing of pesticides. They are:

Dusting Powders (DP):The basic pesticides are mixed with a mineral base, such as soapstone, lavigated clay and

hydrated calcium silicate (called inert).

Granules:The granule formulation consists of absorptive granular carrier (clay) containing solution

of basic pesticide adsorbed on the surface. Calcium silicate is used as adsorbent. The granules need no further dilution and have easier application, thereby reducing hazards to the operators.

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Emulsified Concentrates (EC):The Emulsified Concentrates have three components consisting of basic pesticide,

solvent and emulsifier. Sometimes a stabilizer is also used. These concentrates give emulsions when diluted with water.

Solvents used are aromex, butanol, cyclohexane and xylene. Emulsifiers used are polyoxyethylene, ether, alkyl aryl sulphonate. Stabilizers used are epichlorohydine, triethanolamine and urea.

Emulsifier, stabilizer (3rd stage)

Solvent Vessel Filter Packaging

(1st stage)

Basic pesticide (2nd stage)

Wastewater Generation in Pesticide Industry:The entire manufacturing process for a particular product is a combination of various unit

operations. The unit operations, where water is used and wastewater is generated, are to be identified so as to accurately identify the characteristics of wastewater generated.

In view of the wide variety of process technology options, the quantity of water used and waste water generation are widely varying from product to product and industry to industry. Hence it is difficult to summarize a specific limit for water use and wastewater generation as done for other industries.

However, the pesticides industries may realize that there is wide scope in reducing the quantities of water usage and wastewater generation which may effect in reduction in cost of treatment.

Environmental effects of pesticidesOver 98% of sprayed insecticides and 95% of herbicides reach a destination other than

their target species, including nontarget species, air, water, bottom sediments, and food.Pesticide contaminates land and water when it escapes from production sites and storage

tanks, when it runs off from fields, when it is discarded, when it is sprayed aerially, and when it is sprayed into water to kill algae.

The amount of pesticide that migrates from the intended application area is influenced by the particular chemical's properties: its propensity for binding to soil, its vapor pressure, its water solubility, and its resistance to being broken down over time.

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Some pesticides contribute to global warming and the depletion of the ozone layer.

AirPesticides can contribute to air pollution. Pesticides that are applied to crops can

volatilize and may be blown by winds into nearby areas, potentially posing a threat to wildlife.Droplets of sprayed pesticides or particles from pesticides applied as dusts may travel on the wind to other areas or pesticides may adhere to particles that blow in the wind, such as dust particles. Pesticides that are sprayed onto fields and used to fumigate soil can give off chemicals called volatile organic compounds, which can react with other chemicals and form a pollutant called ozone.

WaterThere are four major routes through which pesticides reach the water: it may drift outside

of the intended area when it is sprayed, it may percolate, or leach, through the soil, it may be carried to the water as runoff, or it may be spilled.

They may also be carried to water by eroding soil.Factors that affect a pesticide's ability to contaminate water include its water solubility, the distance from an application site to a body of water, weather, soil type, presence of a growing crop, and the method used to apply the chemical.

SoilMany of the chemicals used in pesticides are persistent soil contaminants, whose impact

may endure for decades and adversely affect soil conservation.The use of pesticides decreases the general biodiversity in the soil. Not using the

chemicals results in higher soil quality.

A smaller content of organic matter in the soil increases the amount of pesticide that will leave the area of application, because organic matter binds to and helps break down pesticides.

Plants

Nitrogen fixation, which is required for the growth of higher plants, is hindered by pesticides in soil. The insecticides DDT, methyl parathion, and especially pentachlorophenol have been shown to interfere with legume-rhizobium chemical signaling.

Aquatic life

Fish and other aquatic biota may be harmed by pesticide-contaminated water. Pesticide surface runoff into rivers and streams can be highly lethal to aquatic life, sometimes killing all the fish in a particular stream.

Application of herbicides to bodies of water can cause fish kills when the dead plants rot and use up the water's oxygen, suffocating the fish. Some herbicides, such as copper sulfite, that are applied to water to kill plants are toxic to fish and other water animals at concentrations similar to those used to kill the plants. Repeated exposure to sublethal doses of some pesticides can cause physiological and behavioral changes in fish that reduce populations, such as

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abandonment of nests and broods, decreased immunity to disease, and increased failure to avoid predators.

Application of herbicides to bodies of water can kill off plants on which fish depend for their habitat.

Pesticides can accumulate in bodies of water to levels that kill off zooplankton, the main source of food for young fish. Pesticides can kill off the insects on which some fish feed, causing the fish to travel farther in search of food and exposing them to greater risk from predators.

The faster a given pesticide breaks down in the environment, the less threat it poses to aquatic life. Insecticides are more toxic to aquatic life than herbicides and fungicides.

HumansPesticides can enter the human body through inhalation of aerosols, dust and vapor that

contain pesticides; through oral exposure by consuming food and water; and through dermal exposure by direct contact of pesticides with skin. Pesticides are sprayed onto food, especially fruits and vegetables, they secrete into soils and groundwater which can end up in drinking water and pesticide spray can drift and pollute the air.

The effects of pesticides on human health are more harmful based on the toxicity of the chemical and the length and magnitude of exposure. Farm workers and their families experience the greatest exposure to agricultural pesticides through direct contact with the chemicals. But every human contains a percentage of pesticides found in fat samples in their body. Children are most susceptible and sensitive to pesticides due to their small size and underdevelopment. The chemicals can bioaccumulate in the body over time.

Exposure to pesticides can range from mild skin irritation to birth defects, tumors, genetic changes, blood and nerve disorders, endocrine disruption, and even coma or death.

Wastewater Treatment:Existing Treatment Facilities:The flow diagrams of wastewater treatment adopted in some of the industries are shown

below

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Observations on Existing Treatment Systems: The problems associated with the present wastewater treatment options adopted by the

industries are as follows: A. Solar Evaporation System

The solar evaporation system has limitations based on quantity of effluent and climatic condition at the site. The effluent in the evaporation tanks if not a leachate-proof holding arrangement, may cause pollution by virtue of precolation, overflow and evaporation of toxic volatile matter into the atmosphere

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.

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B. Biological Treatment SystemThe characteristics and the quantity of wastewater in a pesticides industry are varying from products to products and also seasonally, daily, and hourly, whereas the ASP(Activated Sludge Plant) type of biological treatment system needs a relatively uniform rate of organic loading and without shock loads due to toxicity, non-uniform flows etc.

The wastewaters, unless properly segregated, bear high dissolved solids thus affecting the biological treatment.

Under extreme climatic conditions, biological treatment does not work efficiently as the microbes find difficulty in surviving.

Disposal of Wastewater:From the point of wastewater discharge various industries it is observed that wastewater

is disposed to On land for irrigation Public drain/sewer/nullah River/creek Sea Solar evaporation tanks(within factories limit)

Choosing the mode of disposal for treated effluent is very important in view of the toxic nature of effluent. The level of treatment required is to be decided based on the actual quality of the receiving body.

Wastewater Management:The conventionally adopted end-of-the-pipe treatment technology is not only ineffective

but is also costly. Also, in view of the effluent and the complexity of the pollution problem from the pesticides industries, it is required to manage the wastewater very effectively such that he waste is minimized, cost in treatment and risk due to pollution are lowered and the environment is protected. Various aspects for an effective wastewater management are:

Location of the plant Plant layout Waste minimization Reduction of Raw Material Losses Recycling and Reuse of Wastewater In-plant Control Treatment Control Waste Segregation and Pretreatment

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Effluent treatment Plant:

The treatment of liquid wastes can be achieved by employing physical, chemical, and biological methods. The common physical methods are flow equalization, oil and grease removal, sedimentation with or without coagulation, sludge removal, filtration and adsorption. Equalized and steady flows are very important for improved efficiency, reliability and control of treatment plant.

Most solids can be removed using simple sedimentation techniques with the solids recovered as slurry or sludge. Very fine solids and solids with densities close to the density of water pose special problems. In such case filtration or ultrafiltration may be required. Although, flocculation may be used, using alum salts or the addition of polyelectrolytes.

Oils and grease removalMany oils can be recovered from open water surfaces by skimming devices. Considered a

dependable and cheap way to remove oil, grease and other hydrocarbons from water, oil skimmers can sometimes achieve the desired level of water purity. At other times, skimming is also a cost-efficient method to remove most of the oil before using membrane filters and

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chemical processes. Skimmers will prevent filters from blinding prematurely and keep chemical costs down because there is less oil to process.

Hydraulic oils and the majority of oils that have degraded to any extent will also have a soluble or emulsified component that will require further treatment to eliminate. Dissolving or emulsifying oil using surfactants or solvents usually exacerbates the problem rather than solving it, producing wastewater that is more difficult to treat.

The chemical treatment includes neutralization, oxidation, detoxification etc. Neutralization is required to maintain a pH of 6.5-8.5.It is required for:

Corrosion control. Reaction control on many chemical treatment processes. Protection of system organisms, if direct discharge is employed. Protection of micro-organisms in biological treatment system.

Biological treatment:It includes aerobic treatment and anaerobic treatment. Some of the factors affect the biodegradability. These are:

Compounds in emulsified form are not readily available to micro-organisms. Eg: DDT

Aliphatic compounds are in general more degradable than aromatic. Halogen substitution to an aromatic compound renders it less degradable.

The biological methods used for pesticide containing wastewater include:

Trickling filters. Activated sludge process. Aerated lagoons. Stabilization ponds.

Activated sludge process:Activated sludge is a biochemical process for treating sewage and industrial wastewater

that uses air (or oxygen) and microorganisms to biologically oxidize organic pollutants, producing a waste sludge (or floc) containing the oxidized material. In general, an activated sludge process includes:

An aeration tank where air (or oxygen) is injected and thoroughly mixed into the wastewater.

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A settling tank (usually referred to as a "clarifier" or "settler") to allow the waste sludge to settle. Part of the waste sludge is recycled to the aeration tank and the remaining waste sludge is removed for further treatment and ultimate disposal.

Trickling filter process:A trickling filter consists of a bed of rocks, gravel, slag, peat moss, or plastic media over

which wastewater flows downward and contacts a layer (or film) of microbial slime covering the bed media. Aerobic conditions are maintained by forced air flowing through the bed or by natural convection of air.

The process involves adsorption of organic compounds in the wastewater by the microbial slime layer, diffusion of air into the slime layer to provide the oxygen required for the biochemical oxidation of the organic compounds. The end products include carbon dioxide gas, water and other products of the oxidation. As the slime layer thickens, it becomes difficult for the air to penetrate the layer and an inner anaerobic layer is formed.

The components of a complete trickling filter system are: fundamental components:

A bed of filter medium upon which a layer of microbial slime is promoted and developed. An enclosure or a container which houses the bed of filter medium. A system for distributing the flow of wastewater over the filter medium. A system for removing and disposing of any sludge from the treated effluent.

The treatment of sewage or other wastewater with trickling filters is among the oldest and most well characterized treatment technologies.

A trickling filter is also often called a trickle filter, trickling biofilter, biological filter or biological trickling filter.

Disposal of Treated Wastewater:

The treated wastewater may be for floor wash, gardening/irrigation purpose or disposed. The treated wastewater may be disposed to:

Public sewer. Inland surface water. Marine coastal water.

For any of these disposals, the treated wastewater should confirm to the CPCB. Firm should incorporate the Monitoring system to evaluate the performance of the pollution control systems. It must also evaluate the impact of the disposed wastewater on the receiving environment.

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Strategies for reducing agricultural pesticide contaminationSeveral strategies that have been suggested to reduce agricultural pesticide contamination

and its effects include comprehensive risk communication and education programs, the use of appropriate personal protective clothing, the discontinuation of calendar spraying, selection of disease-resistant hybrids, and the adoption of Integrated Pesticide Management (IPM).

IPM emphasizes non-chemical and cultural cultivation pest control strategies such as removal of diseased plant parts, crop rotation that may disrupt the life cycle of pests, and biological control such as the use of insect predators. While the need exists to prevent or reduce agricultural pesticide contamination and its effects world-wide, special attention needs to be paid to developing countries for several reasons.

Also, the adverse human health effects of pesticide poisoning are particularly high in many of these countries because of the low nutritional status, and the scarcity of heath care facilities especially in the rural areas where most of the agricultural activities occur.

Eliminating PesticidesDue to the toxic effect caused by the pesticides upon the environment some of them are

banned from normal use in India. They are as follows:

PESTICIDES RESTRICTED FOR USE IN INDIA

S.No. Name of Pesticides1. Aluminium Phosphide2. DDT3. Methyl Bromide4. Methyl Parathion5. Sodium Cyanide6. Methoxy Ethyl Mercuric Chloride (MEMC)7. Monocrotophos8. Endosulfan9. Fenitrothion10. Diazinon

Many alternatives are available to reduce the effects pesticides have on the environment. There are a variety of alternative pesticides such as manually removing weeds and pests from plants, applying heat, covering weeds with plastic and placing traps and lures to catch or move pests.

Pests can be prevented by removing pest breeding sites, maintaining healthy soils which breed healthy plants that are resistant to pests, planting native species that are naturally more resistant to native pests, and use biocontrol agents such as birds and other pest eating organisms.

FERTILISER MANUFACTURING INDUSTRY

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INTRODUCTION

India is one of the largest Nirtogen fertilizer producer in the world, which needs a variety of feedstocks like Lignite, Coal, Coke oven gas, Electrolysis of water, Natural gas, Associated gas, Naphtha, fuel oil etc. Considering the diversity of the resources the plants are located mostly at the point nearest to the feed stocks.

Fertilizers can be divided into three categories:

I. Nitrogenous fertilizers

II. Complex fertilizers like Nitrophosphates, Diammonium phosphate etc

III. Phosphatic fertilizers like single super phosphates and triple super phosphates

These fertilizers need a variety of raw materials and intermediates like natural gas ,fuel oils, carbon dioxide, nitric acid, sulphuric acids etc. Today about 52% of the fertilizer plants use natural gas as a raw material, 24% use Naphtha, 13% use fuel oil, 4%use coal, 6% use imported ammonia an 1% use other sources.

EMISSIONS FROM FERTILIZER INDUSTRY

Like any other chemical industry, fertilizer industry too produces some gaseous/liquid/solid effluents depending upon the technology adopted, feedstock used, location of the industry etc. The major air emissions are SO2, NOx, and Fluorine. Major liquid effluents are nitrogen and urea nitrogen, Fluorides and phosphates, Oil and grease, Chromates, Suspended solids. Solid wastes Generated are mainly Carbon sludge, hard coke, Lime sludge, Inerts generated in nitrophosphate plant, Fly-ash, Calcium carbonate, Chemical sludge from nitro ETP, Gypsum.

The disposal of wastes creates damages to underground water and endanger ecosystem. The industry faces a problem of utilization/disposal of waste generated in fertilizer production namely Phospho-gypsum, Hydrofluosilicic acid chromium sludge, waste catalyst etc. So there is a need for developing a suitable and acceptable technology or recycling/utilization of waste and for recovery of useful/ valuable material from waste. Environment management has been organized to focus attention on the efforts made by the fertilizer industry in this direction.

CONTROL OF GASEOUS EMISSIONS

Over the years, technology and methods used by industries are becoming more and more sophisticated which will help to decrease the emissions and improve the fuel consumption which will result in good environmental conditions. However there are some old industries which follows old and outdated methods and machine which does not help in optimization of emissions and its standards, along with fuel consumption. As said above major gaseous emissions are sulphates, nitrates and d fluorides

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CONTROL OF SULPHUR DIOXIDE EMISSION & SULPHURIC ACID MIST:

Sulphuric acis is produced by oxidation of sulphur to SO2 and then to SO3, which is absorbed to produce sulphuric acid. All plants use Vanadium catalyst to convert SO2 to SO3 according to contact process most of the new plants are having a conversion capacity of 99.5%-99.7%. During start up and shutdown catalysts beds will become cold which results in poor conversion factors and causes high emissions of SO2 which causes a threat to environment. A sulphuric acid plant with 6% SO2 feed working at 99.7% conversion efficiency will give out an emission of 197 ppm, when its efficiency decreases to 97% its concentration increases to nearly 2000 ppm, which is ten times of the earlier concentration so special control measures have to be made to reduce it during start up and shutdown

So sulphuric acid plants are equipped with either a start up heater to increase catalyst bed temperature to the required level or a start up scrubber – which is packed with towers of caustic soda to absorb the SO2 – in this case Sodium Sulphate or Sodium Bisulphate is formed depending on the PH of the scrubbing solution.

Acid mist consist of liquid droplets of sulphuric acids ranging from 10 - .07 microns. It causes a visible and persistent plume in the stack but also results in equipment corrosion. Mist is formed when water vapor in the air combines with SO3 in the convertor. To prevent this problem from happening different types of mist eliminators are used

I. Impaction type fibre bed mist eliminator

II. Mesh pad type mist eliminator

CONTROL OF PARTICULATE MATTER

UREA DUST:

Urea is produced by reacting NH3 and CO2 at elevated temperatures and pressure, which is further converted to solid form by prilling techniques. During this prilling process particulate matter is emitted solid urea is obtained in a prilling tower by cooling the solution with air to expel its water content. In a typical 1000 tpd plant around 200 – 500 mg/nm3 of urea dust will be formed in the process which has to be controlled else it would cause air pollution to a devasting extent.

Mostly wet scrubbers are used for particulate matter removal dust laden air rising through the prilling tower enters the annular duct. Air is drawn from this annular duct by a ring of liquid jets consisting of nozzles arranged in annular space which provides the energy required to overcome the pressure drop in the system. The liquid droplets acts as a spherical collector for the urea dust which ranges from 2- 200 microns. Urea solution is taken out when its concentration reaches almost 10-15% for further processing. Outlet concentration of urea will get reduced to 30-50% mg/nm3

CONTROL OF OXIDES OF NITROGEN:

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Nitric acid is commercially produced by reducing ammonia with air to produce nitrogen oxides which are then absorbed in water to yield the acid. Tail gas produced are mainly nitrogen, water vapor, and oxides of nitrogen is normaly preheated and expanded through a tuebine to recover energy, which is used to power the plant’s compressor. The NOx, content in the tail gas varies from 1000-3000 ppm of which approximately 60% is NO2 and the rest is NO.

Four types of processes which can be used to reduce or control emissions are

I. Catalytic reduction (selective and non-selective)

II. Extended absorption

III. Chemical absorption

IV. Absorption

CATALYTIC COMBUSTION

Non – Selective: - The oxides of nitrogen formed during the combustion of ammonia are absorbed in water to form nitric acid. The unabsorbed part of oxides of nitrogen and inerts are emitted to atmosphere which generally contains .2- .4% of NOx and 2-3% free oxygen. The exit gas is decolorized by mixing with a fuel gas like natural gas and the mixture is passed over a catalyst bed which converts the NO2 into NO rendering exit gas colorless. The remaining NO is converted in to N2 with the help of oxygen in tail gas ant fuel gas at temperature between 650-700C.

Selective: - in this method reduction of NOx in the gas system is done with slight excess of stochiometric quantities of ammonia over a mixed catalyst. Two catalysts are used in this reaction the first is based on precious metals mixed metallic oxides, noble or iron group or V2O5 on alumina which promotes NOx reduction and the second is platinum based which destroys or converts any ammonia fed to the system into harmless nitrogen.

EXTENDED ABSORPTION

The extended absorption process aims to continuing the process of absorption of the NOx in water beyond the level at which it normally ends .i.e 2000-3000 ppm NOx. The extended absorption is made possible by provision of large absorption columns.

CHEMICAL ABSORPTION

The tail gas should be scrubbed with a liquid containing caustic soda or urea. In case of caustic , it results in the formation of NaNO2 and NaNO3. There should be provision to reuse and recover the NaNO2/NaNO3 from the solution otherwise it could act as a source of pollution. Liquid

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scrubbing system is best adopted in combination with extended absorption. After cleaning the tail gas substantially in additional absorber, liquid scrubbing could be adopted to reduce the pollution levels.

ABSORPTION

The absorption of NOx on a fixed bed of solids has not been extensively commercialized as other processes. Normal absorption on activated carbon or molecular sieves is very efficient but the absorbers must be regenerated either by thermal desorption or by pressure reduction.

CONTROL OF FLUORINE EMISSIONS

Fluoropatite ores are used for the production of fertilizers such as single superphosphates, triple superphosphates or converted to wet phosphoric acid and there on to other fertilizers.fluorine content may differ in rocks according to its source from 1-5% and is released as Silicon tetrafluoride (SiF4) and Hydrogen Fluoride (HF). The fluorine emissions are controlled by scrubbing these gases in either Venturi scrubbers, packed towers, crossflow scrubbers or a spray chamber. Water is used as the scrubbing liquor which converts the HF and SiF4 to H2 SiF4. Efficient scrubbing system can operate upto 25% H2SiF4 but above this point the SiF4 vapour pressure rises steeply.

One of the commomly encountered problems is deposition of silica when concentration of phosphoric acid less than 50%. This leads to choking of scrubber nozzles. Hence nozzles have to be periodically cleaned and specially designed for this service.

LIQUID EFFLUENTS

Liquid effluents generated in a fertilizer plant vary in nature, quality and quantity depending upon various factors. The effluents generated in various sections of the plants are conveyed to the effluent treatment plant through segregated sewers as some of the effluents needs separate specific treatments before common treatment. Some common treatment and control measures are

PROCESS CONDENSATE STRIPPERS:-

These are generally used in ammonia plants. The condensate produced from the shift conversion, CO2 absorption and methanation sections of a typical ammonia plant contains high concentration of ammonia, methanol and CO2. A typical quantity of condensate for a plant producing 900tpd ammonia is around 50m3/hr.the condensate first flows to a CO2 flash vessel where most of the dissolved CO2 flashes away. From there this is ent to condensate stripper where mainly ammonia and methanol are stripped off in a distillation tower by means of stream at 4 kg/cm2 and at 180®C. the stripped condensate leaving the bottom of thr tower contains only 10 ppm of ammonia and is used back in the plant completely.

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PARAMETER CONCENTRATION NOT TO EXCEED mg/l(except PH)

pH

Ammonical nitrogen

Free ammonia

Total Kjeldahl Nitrogen (TKN)

Nitrate nitrogen

Cyanide (CN)

Vanadium

Arsenic

Hexavalent chromium

Total chromium

Suspended solids

Oil and grease

6.5 – 8

50+

4

100

10

0.2

0.2

0.2

0.1

2

100

10

Liquid effluent standard for nitrogenous and complex fertilizer industries

AIR STRIPPING FOLLOWED BY NITRIFICATION AND DENITRIFICATION:

It is used to remove ammonical nitrogen in fertilizer industry. Here principle dissociation of ammonium ions to free ammonia at PH of 10-11. The pH of the effluent is raised by the addition of alkali usually lime and the free ammonia is then stripped with air in a counter current stripping tower. This is followed by biological treatment by nitrification - denitrification. In this process, effluent is sent to the nitrification tank where residual ammonical nitrogen is converted to nitrates. The process destroys alkanity and lowers the PH which has to be adjusted by addition of Mg CO3. Aerators are provided in the nitrification tank for oxidation of ammonical nitrogen to nitrates. Effluent than goes to the denitrification tank where nitrates are anaerobicaly converted to nitrogen in the presence of carbon source like methanol or molasses. Sludge removal is done in the final clarifier where polyelectrolyte is added to improve the setting characteristics.

AIR STRIPPING WITH RECOVERY:

Air stripping invariably leads to contamination of the environment with the ammonia. For plant generating 100m3/hr of air /hr for stripping the ammonia and 14 tonnes per day of nitric acid or 11 tonnes per day of sulphuric acid for recovery. Use of (NH4)2SO4 and NH4NO3 has to be found within theplant or has to be marketed. The liquid effluent containing residual ammonical nitrogen (normally less than 250 mg/litre) can now be spent for biological treatment through nitrification. The nitrates can then be denitrified as explained.

HYDROLYSER STRIPPER

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Urea production in all plants is accompanied with a large amount of water , arounf 450 – 480 kg of effluent is generated for each metric tone of urea produced. A typical composition of effluent is 4-5% ammonia, 1.5-2% CO2 and .5-1% urea. This water is pumped to a distillation tower operating at 2.5 kg/cm2. The feed is preheated before it enters the tower. Since water contains urea after stripping of ammonia in the upper part of the tower, it is pumped into the hydrolyser where urea is decomposed into ammonia and carbon dioxide by means of saturated steam ata pressure of around 26 kg/cm2g.the vapors produced in the hydrolyser are sent to an overhead condenser, while the solution returns to the lower part of the tower where the remaining ammonia is stripped out by means of vapour produced in the reboiler which is fed by 4.5 kg/cm2 saturated steam.

CONTROL OF FLUORIDES AND PHOSPHATES

Fluorides and phosphates are normally removed by adding lime, this results in precipitation of fluoride as calcium fluoride and phosphates as mono and dicalcium phosphate/calcium hydro-xylapatite.

CONTROL REDUCTION OF CHROMATES

Chromates in the form of sodium chromate or dichromate are added as a corrosion inhibitor in circular cooling waters for heat exchange equipment. To maintain a certain level of total dissolved solids in the cooling water, a small quantity has to be discharged termed as blowdown. This blowdown contains 15-20mg/l of chromates in hexavalent form. Removal of this is achieved by lowering pH of the effluent to 2-3 and then reducing the hexavalent chromate to its trivalent form.this is then precipitated using lime and caustic soda as Cr(OH)3. As diposal of Cr(OH)3 is problematic due to some regulation some more alternatives are currently used for the safed diposal of the material.

SOLID WASTES

Waste is an unavoidable factor of an industry, it is more focused to use these waste in such a way that new value product can be made out of it, this not only help to dispose waste but also helps to generate profit for the company. Some methods to utilize these watses are

UTILIZATION OF CARBON SLUDGE IN BOILER AS FUEL:

The carbon slurry formed during the start up and shutdown is stored ina slurry pond, where settling of carbon takes place and overflow is treated for removal of ammonical nitrogen. The

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carbon which gets accumulated will get drained of which can be used as a fuel for boiler and has a calorific value of 8547 Kcal/kg.

UTILIZATION OF SPEND HARD COKE IN BOILERS:

The effluent coming from ammonia plant is expected to contain 200ppm of oil. To remove this oil from effluent, gravity separation is followed by hard coke adsorption facility. The oil soaked coke removed from effluent treatment plant is utilized in boiler which results in saving equivalent quantity of coal.

UTILIZATION OF LIME SLUDGE:

Lime sludge is generated while treating effluent for removal of ammonical nitrogen. During the reaction lime sludge is generated, which can be stored in brick lined pond from where it is supplied to customers which is ultimately used for manufacturing of sagol and neutralization. This lime sludge is also used for flooring, tiles and building materials.

UTILIZATION OF INERTS GENERATED IN AMMONIUM NITRO PHOSPHATE:

During digestion of rock phosphate some portion of rock phosphate remains as inert which is an unavoidable by product in ammonium nitro phosphate plant. It is used as filler material to manufacture 20:20:0 grades ANP.

UTILIZATION OF FLY-ASH:

Ash is produced as a result of burning of pulverized coal in fired boilers. The ash is conveyed to slurry dump and is converted into slurry and transported to ash pond through pipeline.

REUSE OF SOLID WASTES

FLY-ASH-CLAY BRICKS TECHNOLOGY:

Developed by CBRI roorkee for manufacture of Fly ash bricks. Fly-ash is mixed with black cotton soil 34% and burnt in bricks in kilns with same compressive strength of 80 kg/cm2 and of uniform shape, size and colour. Ash consumption

1. Higher cost compared to conventional bricks2. Process involved mixing of black cotton soil with flt-ash and was resulting usage of top

layer of fertile agriculture land3. Process involved firing in kiln which in turn involved use of fuel like coal4. Clay available in our area is coarser than fly-ash and has lumps which requires grinding

of clay5. Vast area of land required for obtaining earth6. Number of plants required to be established

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Other building materials with fly-ash:

a) Activated pozzolona: it is fy ash only in which lime reactivity index is increased by increasing its surface area and removal of unburnt carbon. It can be grinded with Portland cement clinker or blended uniformly with Portland cement to make Portland pozzolona cement

b) Portland pozzolona cement (PPC): it is prepared by either grinding cement clinker and fly-ash in the cement mill or by uniformly blending with Portland cement in blenders the percentage of fly ash shall not exceed 25.

c) Lime pozzolona: this is prepared by mixing 1 part of hydrated lime and 2 parts of flyash and can be used as masonary mortar,plater and flooring mass.

d) Fly-ash bricks: of all the other uses fly ash bricks are the most demanding material and it consumes almost 80% of fly-ash and rest are binding agent,lime,sand and other additives.

WASTE GYPSUM

Gypsum, CaSO4, is a major solid waste disposed from chemical and fertilizer industries. Gypsum is mainly used by sulphuric acid manufacturing industry in the form of phosphogypsum, byproduct of gypsum is used in manufacture of cements, partition blocks, sheets, and tiles, insulation boards and plater of paris. Besides these industries pharmaceuticals, textile, asbestos products, paints, etc also use gypsum byproducts.

MINIMAL NATIONAL STANDARD (MINAS)

It will cover all the fertilizer plant; the effluents of fertilser plants should be adequately treated to meet the stipulations of MINAS. The thus treated and after satisfying the MINAS limits may join the effluents of other product plants. It is applicable to all waste waters of the fertilizer plant.

All the industries shall meet MINAS irrespective of the mode and place of discharge of treated effluent. While evaluating MINAS the present status of presently operating industries and also the industries which are likely to come in near future are considered with special stress on the aspects of pollutions and control measures. The MINAS is based on the pollution control technology already practiced by some or other industries in the country. This ensures practicability of implementation and achievability of the MINAS limits.

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