INDUSTRIAL WATER AND WASTE WATER MANAGEMENT

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Code No: R4101A R10 Set No. 1 IV B.Tech I Semester Regular Examinations, December 2013

INDUSTRIAL WATER AND WASTE WATER MANAGEMENT

*********SCHEME OF VALUATION *******1.a What are the various treatment options available for boiler water treatment?

Ans: Safe and reliable operation of boiler is achieved through proper external treatment and

proper internal treatment.

External treatment: is the reduction or removal of impurities from water outside

the boiler. In general, external treatment is used when the amount of one or more of the

feed water impurities is too high to be tolerated by the boiler system in question. There

are many types of external treatment (softening, evaporation, deaeration, membrane

contractors etc.) which can be used to tailor make feed-water for a particular system.

Water is sometimes pretreated by evaporation to produce relatively pure vapor, which is

then condensed and used for boiler feed purposes. Certain natural and synthetic

materials have the ability to remove mineral ions from water in exchange for others. For

example, in passing water through a simple cation exchange softener all of calcium and

magnesium ions are removed and replaced with sodium ions. Since simple cation

exchange does not reduce the total solids of the water supply, it is sometimes used in

conjunction with precipitation type softening. One of the most common and efficient

combination treatments is the hot lime-zeolite process. This involves pretreatment of the

water with lime to reduce hardness, alkalinity and in some cases silica, and subsequent

treatment with a cation exchange softener. This system of treatment accomplishes

several functions: softening, alkalinity and silica reduction, some oxygen reduction, and

removal of suspended matter and turbidity.

4M

Internal treatment: is the conditioning of impurities within the boiler system.

During the conditioning process, specific doses of conditioning products are added to the

water. The commonly used products include: Phosphates-dispersants-reacting with the

alkalinity of boiler water, these products neutralize the hardness of water by forming

tricalcium phosphate, and insoluble compound that can be disposed and blow down on a

continuous basis or periodically through the bottom of the boiler.Natural and synthetic

dispersants (Anti-scaling agents): increase the dispersive properties of the conditioning

4M


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products. They can be: Natural polymers: lignosulphonates, tannins Synthetic polymers:

polyacrilates, maleic acrylate copolymer, maleic styrene copolymer, polystyrene

sulphonates etc. Sequestering agents: such as inorganic phosphates, which act as

inhibitors and implement a threshold effect.Oxygen scavengers: sodium sulphite,

tannis, hydrazine, hydroquinone/progallol-based derivatives, hydroxylamine

derivatives, hydroxylamine derivatives, ascorbic acid derivatives, etc. These scavengers,

catalyzed or not, reduce the oxides and dissolved oxygen. Most also passivate metal

surfaces. The choice of product and the dose required will depend on whether a

deaerating heater is used.Anti-foaming or anti-priming agents: mixture of surface-

active agents that modify the surface tension of a liquid, remove foam and prevent the

carryover of fine water particles in the steam.

1. b) What are the quality requirements of process water for Brewery industry [introduction-1M + any 3 kinds of water &their requirements 2M x 3=6M

Ans Very often water is considered a utility in a brewery. As water is an important

constituent of beer, though, making up more than 90% of the product, it is worth looking

at water from a raw material perspective. Historically the characteristics of different beer

styles were influenced by the composition of the water used in their manufacture

1M

Filtered water/ washing water

The minimum requirement for water used in a brewery should be that it conformsto potable water standards Filtered water of a suitable standard should be used for

cleaning. If water is not heated, there is no risk of scaling. There are limitations, though,

in the levels of chloride acceptable in filtered water. The chloride level should not

exceed 100 ppm to avoid corrosion of stainless steel.

Service water/ process water

This quality of water should be used whenever the water is heated but not used in

the brewing process It is important that hardness in this water is limited to prevent

scaling, which can, for example, lead to the blockage of spray nozzles in the bottle

washer. It is also important that the chloride content is limited to about 50 ppm. This is

to avoid corrosion of stainless steel. Furthermore, service water has to be free of

microbiological contamination.

6M


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Brewing water

As mentioned earlier, more than 90% of beer is water. Therefore it is of utmost

importance that the quality of the brew water is high. A very important ion in brew water

is calcium. During mashing it reacts with the phosphate buffer from the malt,

influencing the pH level. In order for the enzymes to work properly, a pH of 5.2±5.4 is

optimal.

Dilution water

It is important that the calcium content of dilution water is not higher than the

calcium content of the concentrated beer to be diluted, in order to avoid oxalateprecipitation. There are also strict requirements regarding oxygen content, which should

mainly be less than 20 ppb. The microbiological composition of the dilution water is

very important as this water is not necessarily boiled. Treatment with a proper

disinfection system and a UV (ultraviolet) system prior to use is indispensable

Boiler water For the boiler house it is necessary that the feed water is of

adequate quality and free of hardness. It is important that the feed water contains HCO3

at a level of less than 50 ppm Boiler feed water must also be thoroughly deaerated to

achieve an oxygen content ideally of less than 20 ppb. It should also be conditioned

properly with caustic to adjust the pH, with phosphate for hardness scaling prevention

and with sodium bisulphite for oxygen scavenging.


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2 Explain the various strength reduction techniques. [introduction-1M + 7 reduction techniques 2M x 7=14M] 1M

Waste Strength reduction is the second major objective for an industrial plant

concerned with waste treatment. The strength of wastes may be reduced by:

1.Process Changes2.Equipment Modifications

3.Segregation of Wastes

4.Equilization of Wastes

5.By-Product Recovery

6.Proportioning of Wastes and

7.Monitoring Waste Streams

Process Changes:

In reducing the strength of wastes through process changes, the sanitary engineer is

concerned with wastes that are most troublesome from a pollution standpoint.

Equipment Modification: Changes in equipment can effect a reduction in the

strength of the waste, usually by reducing the amounts of contaminants entering the

waste stream. An outstanding example of waste strength reduction occurred in the dairy

industry. The new cans were constructed with smooth necks so that they could be

drained faster and more completely. This prevented a large amount of milk waste from

entering streams and sewage plants.

Segregation of Wastes: Segregation of Wastes reduces the strength and/or the

difficulty of treating the final waste from an industrial plant. It usually results in two

wastes: one strong and small in volume and the other weaker with almost the same

volume as the original un-segregated waste. The small- volume strong waste can then be

handled with methods specific to the problem it presents. In terms of volume reduction

alone, segregation of cooling waters and storm waters from process waste will mean a

saving in the size of the final treatment plant. Equalization of Wastes: Plants, which have many products, from a diversity of

processes, prefer to equalize their wastes. This requires holding wastes for a certain

period of time, depending on the time taken for the repetitive process in the plant. For

example, if a manufactured item requires a series of operations that take eight hours, the


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2. Dispersion due to Currents: Self-purification of stream largely depends upon

currents, (as rapids, whirlpools, waterfalls and turbulent flow) which will readily

disperse the wastewater in the stream, preventing local accumulation of pollutants. High

velocity accelerates reaeration and reduces the concentration of pollutants. High velocity

improves reaeration, reduces the time of recovery, though length of stream affected by

the wastewater is increased.

3. Sedimentation: If the stream velocity is lesser than the scour velocity of

particles, sedimentation will take place, which will have two effects. (i) The suspended

solids, which contribute largely the oxygen demand, will be removed by settling and

hence water quality of the downstream is improved. (ii) Due to settled solids, Anaerobic

decomposition may take place.

4. Temperature: At low temperature, the activities of bacteria is low and hence

rate of decomposition will also be slow, though DO will be more because of increased

solubility of oxygen in water. At high temperatures, the self-purification takes lesser

time, though the quantity of DO will be less.

5. Sunlight: Sunlight helps photosynthesis of certain aquatic plants (as algae) to

absorb carbon dioxide and give out oxygen, thus accelerating self-purification. Sunlight

acts as a disinfectant.

3. b b) What are the problems in disposal of industrial wastes into lakes? [7]Water movement in lakes is slower than in streams, so reaeration is more of a

problem in lakes than streams. Because of the slow movement of water in a lake,

sediments, and pollutants bound to sediments, tend to settle out of the water column

rather than being transported downstream.Water pollution affects the health of the

waterway, the health of the organisms living in and around the waterway, and,

eventually, the health of humans. The effects of water pollution can range from aquatic

deformities to contaminated fish to "dead" lakes.Heavy metals such as mercury and lead, and human-made organic chemicals

such as pesticides, biomagnify as they move up the food chain, resulting in tumors and

death for predatory animals, such as lake trout, herring gulls, and even humans.

Toxic pollutants can also alter the genetic makeup of an organism, resulting in


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either death or extreme deformities.

Human health issues

Persistent Organic Pollutants, or POPs, such as dioxin, PCBs and DDT, are

chemical substances that persist in the environment and bioaccumulate through the food

web; therefore, POPs can also cause sickness and disease in humans, who are at the end

of the food chain. People who regularly consume a lot of fish will have larger levels of

toxic chemicals in their bodies than those who only eat fish occasionally. While

scientists are still studying the effects of high chemical levels in humans, studies have

suggested that toxic chemicals can lead to reproductive problems, cancer and

neurological disorders.

People who are most at risk of health problems due to contaminated fish

consumption are those with weakened immune systems, including children, pregnant

women and the elderly. Other human health issues related to water pollution include

drinking water contamination and skin infection, caused by bacterial contamination.

Eutrophication

Nutrient loading (more nutrients than the waterbody can handle) stimulates excessive

plant growth, which in turn decreases the amount of oxygen in the water and eventually

kills off certain species of animal life. Other pollution-tolerant species, such as worms

and carp, grow more rapidly; thus, the ecological balance of the lake is significantlyaltered.

4. a a) Discuss the quality of water from ion exchange treatment? [7]Ans Ion exchange is a reversible reaction in which a charged ion in solution is

exchanged for a similarly charged ion electrostatically attached to an immobile solid

particle. The largest application of ion exchange in water treatment is for softening,

where calcium, magnesium and other polyvalent cations are exchanged for sodium. It is

used both in industrial and domestic systems. Ion exchange is also used to remove

specific contaminants such as arsenic, barium, nitrate, and radium.

In common practice the raw water is passed through a bed of resin. The resin is the

made by polymerization of organic compounds into a porous matrix. When the bed

becomes saturated with the exchanged ion, it is shut down and regenerated by passing a

concentrated solution of sodium back through the bed.


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Ion exchange units that replace calcium and magnesium ions from water are known as

water softeners. They may also remove varying amounts of other inorganic pollutants

such as metals, but they will not remove organic chemicals, pathogens, particles, or

radon gas. Water softener units work most efficiently with particulate-free water. Ion

exchange systems effectively remove ions, but they do not effectively remove most

organics or microorganisms. Microorganisms can attach to the resins, providing a

culture media for rapid bacterial growth and subsequent pyrogen generation.

4. b Explain the technique of Ultra-filtration. Discuss its applications in industrialwater treatment. [8]

[3M]Ultrafiltration (UF) is a variety of membrane filtration in which forces like

pressure or concentration gradients leads to a separation through a semipermeable

membrane. Suspended solids and solutes of high molecular weight are retained in the

retentate, while water and low molecular weight solutes pass through the membrane in

the permeate. This separation process is used in industry and research for purifying and

concentrating macromolecular (103 - 106 Da) solutions, especially protein solutions.

Applications: [5M]

UF can be used for the removal of particulates and macromolecules from

raw water to produce potable water

UF is used extensively in the dairy industry; particularly in the processing of

cheese whey to obtain whey protein concentrate (WPC) and lactose-rich

permeate.

Filtration of effluent from paper pulp mill

Cheese manufacture, see ultrafiltered milk

Removal of pathogens from milk

Process and waste water treatment

Enzyme recovery

Fruit juice concentration and clarificationDialysis and other blood treatments

Desalting and solvent-exchange of proteins (via diafiltration)

Laboratory grade manufacturing

5. a What are the effects of wastewater from Textile industries? [7]Ans The environmental issues associated with residual dye content or residual colour in


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treated textile effluents are always a concern.

Dye concentrations in watercourses higher of 1 mg/L caused by the direct

discharges of textile effluents, treated or not, can give rise to public compliant. High

concentrations of textile dyes in water bodies stop the reoxygenation capacity of the

receiving water and cutoff sunlight, thereby upsetting biological activity in aquatic life

and also the photosynthesis process of aquatic plants or algae.

The colour in watercourses is accepted as an aesthetic problem rather than an eco-

toxic hazard. Therefore, the public seems to accept blue, green or brown colour of rivers

but the ‘non-natural’ colour as red and purple usually cause most concern.

The polluting effects of dyes against aquatic environment can be also the result of

toxic effects due to their long time presence in environment , accumulation in sediments

but especially in fishes or other aquatic life forms, decomposition of pollutants in

carcinogenic or mutagenic compounds but also low aerobic biodegradability.

Due to their synthetic nature and structure mainly aromatic, the most of dyes are

non-biodegradable, having carcinogenic action or causing allergies, dermatitis, skin

irritation or different tissular changes. Moreover, various azo dyes, mainly aromatic

compounds, show both acute and chronic toxicity.

High potential health risk is caused by adsorption of azo dyes and their breakdown

products (toxic amines) through the gastrointestinal tract, skin, lungs, and also formationof hemoglobin adducts and disturbance of blood formation. Several azo dyes cause

damage of DNA that can lead to the genesis of malignant tumors.

Electron-donating substituents in ortho and para position can increase the

carcinogenic potential.

5. b b) What are the various treatment alternatives for Paper and Pulp industries? [8]

Ans Pulp and paper industry is considered as one of the most polluter industry in the

world. The production process consists two mainsteps: pulping and bleaching. Pulping is

the initial stage and the source of the most pollutant of this industry. Bleaching is the last

step of the process, which aims to whiten and brighten the pulp. The wastewaters

generated from production processes of this industry include high concentration of

chemicals such as sodium hydroxide, sodium carbonate, sodium sulfide, bisulfites,

elemental chlorine or chlorine dioxide, calcium oxide, hydrochloric acid. The major


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problems of the wastewaters are high organic content (20-110 kg COD/air dried ton

paper), dark brown coloration, adsorbable organic halide (AOX), toxic pollutants, etc.

Physicochemical and biological treatment technologies are used extensively for

the pulp and paper mills. Sedimentation, floatation, coagulation and precipitation,

adsorption, chemical oxidation and membrane filtration were carried out. Biological

treatment both aerobic and anaerobic technologies are preferred for treatment of pulp

and paper mills because of wastewater composition consisting of high organic

compounds and economical aspects. Additionally, some fungi species are used to

remove color and AOX from the effluents.

6. a What are the special characteristics of wastewater from Fertilizer Plants? [7]

Ans Waste streams consist of spills and leakages, cooling waters, product washing

water, condensate stripping, vacuum condenser water, scrubbing water, boiler blow

downs, and phosphoric acid production pond water discharges. Storm water runoff is

also regulated. Depending on the subcategory, the wastewater constituents may include

the conventional pollutants BOD5, pH, and TSS; and ammonia, fluoride, nitrate,

organic nitrogen, and total phosphorus. In some cases, aluminum, potassium, and

sulfur may be present. Treatment processes may include neutralization with lime and

sedimentation in retention ponds to remove TSS, phosphorus, and fluoride; and air

stripping, biological nitrification & de-nitrification, ion exchange, or breakpoint

chlorination to remove ammonia.

6. b What are the various treatment alternatives for Distillery Wastes? [8]


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Ans The 295 distilleries in India produce 2.7 billion litres of alcohol and generating 40

billion litres of wastewater annually. The wastewater from distilleries, major portion of

which is spentwash, is nearly 15 times the total alcohol production. This massive

quantity, approximately 40 billion litres of effluent, if disposed untreated can cause

considerable stress on the water courses leading to widespread damage to aquatic life.

• For recovery from the treatment of distillery spentwash, depending on the

availability and cost of land in a particular area, simple treatment in

anaerobic lagoon to generate biogas followed by treatment in aerated

lagoon or oxidation ditch may be considered.

• Where the availability of land is a severe constraint, evaporation and

incineration of distillery spent wash to recover potash

• Anaerobic digestion of spent wash in a closed digester followed by its

treatment under an activated sludge process, especially in an oxidation

ditch to reduce costs, might be adopted as the most cost-effective system

for the distilleries which are located away from sugar factories.

Moreover, the treated effluent can be conveniently used for irrigation of

cane fields or other crop lands, subsequently.

• Biogas generated from the distillery effluents, can be effectively utilized

in production plant boilers thus saving about 50 to 60 percent fuel/steam.The treated effluent having almost all the potash retained in it may be

utilised for irrigation purposes.

• The utilisation of the distillery effluent in agricultural fields will not only

enrich these further with essential plant nutrients like nitrogen,

phosphorous and potash but also compensate the expenditure on

fertilizers for crop growth.

• Similarly spentwash utilization in bioearth composting, where adequate

land is available, being a simple process and not involving any heavy

machinery is also one of the cost effective methods of disposal.

7. a a) Explain the manufacturing process and origin of wastewater from Sugar mills? [7]

Generally, water is used in the sugar factory for spraying water on the crushed


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cane i.e. imbibition for

the purpose of

extraction of remaining

juice after first

extraction. Water is

also being used for

cooling bearings, juice

heaters, condensers and

for good house keeping

etc. The wastewater

produced from the

factory includes the

wastewater from mill

house, clarification house, lime house, sulphur house and floo; washings. The quantity

of wastewater discharged from all the units of mill including boiling house discharge,

spray pond overflow is around 800 - 1400 m3/ day. The source of wastewater generation

in manufacturing process is shown in Fig

Cane Wash Water: This is generated when the cane is washed before crushing. C

me washing is carried out only if it is mechanically harvested. The suspended solids .ontent in cane wash water is high.

Mill House Wastewater:Wastes from the mill house include the water used as

spla-hes to extract maximum amount of juice and those used to cool the roller bearings.

The mill house waste is large in volume and contains high BOD due to the presence of

sugar juice and oil from the machineries.

Boiler House Wastewater:The periodic blow of the boiler produces another

intermittent v aste discharge. this waste is high in suspended solids, low in BOD and

usually alkaline.

Leakages And Spillages:Additional waste originates due to the leakages and

spillages of; rice, syrup and molasses in different sections and also due to the handling

of molasses The periodical washings of the floor also contribute a great volume and are

discharged intermittently, which is having very high BOD.


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7.b b) What are the various treatment alternatives for Steel Mill Wastes? [8]

Treatment of coal washer waste:

The major pollutants of the coal washery waste is the suspended solid. As, such

this waste is usually treated in a clarifier with or without “coagulant”.

The “ froth floatation" is also suggested as a very efficient method of treatment

for the removal of ultra fine coal particles.

Treatment of Blast furnace waste:

1. As observed from the above characteristics of the waste can be treated in a

clariflocculator even with out the addition of coagulants.(Sedimentation with

coagulation). However, the flocculation time can be reduced to a great extent when

certain coagulants like alum or lime is added.

2. The efficiency of the clari-flocculator can be increased alternative by a judicious

mixing of this waste with me other wastes of the steel plant.

Treatment of Roll Milling Waste:

The effluent from the scale pits still contains considerable amounts of fine scale,

oil and grease and requires secondary treatment.

The above effluent contains about 170 mg/t to 440 mg/1 of suspended solids,

and can be treated well in the clari-flocculator using either NaOH or the oxygen plant

waste as coagulant.. The iron content of the clarifier sludge is as high as 46%. As such, the sludge is

thickened, dewatered using vacuum filters and then sent to the sintering plant. So mat it

can be fed back to blast furnace. (Thickening can accomplish almost complete removal

of oil and grease from the sludge and thus prepares it for dewatering and caking in

vacuum filters).

Treatment of Pickling Waste:

Treatment of this waste includes neutralization, using lime.

The ferrous sulphate recovery

The process of electrolysis of spent liquor is gaining importance in the matter of

regeneration of acid and recovering of iron.

Treatment of coke oven waste: the recovery of phenol by extraction methods.

The chemical oxidation of ammonical liquor with potassium permanganate,


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sodium dichromate, chlorine, ozone, etc., to recover the phenol.

using trickling filter, activated, .sludge, .process. and..waste .stabilization pond

maintain optimum pH, and temperature, proper loading of this Phenolic substrate to the

reactor may result in the desirable reduction.

The biological treatment of the coke oven effluent can be carried out

economically in a three-stage process, with isolated or cultured bacteria, appropriate in

each stage.

8. a a) What are the advantages of common effluent treatment plants? [7]

• Saving in Capital and operating cost of treatment plant. Combined treatment is

always cheaper than small scattered treatment units.

• Availability of land which is difficult to be ensured by all individual units in the

event they go for individual treatment plants. This is particularly important in

case of existing old industries which simply do not have any space.

• Contribution of nutrient and diluting potential, making the complex industrial

waste more amenable to degradation.

• The neutralization and equalisation of heterogeneous waste makes its treatment

techno-economically viable.

• Professional and trained staff can be made available for operation of CETP

which is not possible in case of individual plants.• Disposal of treated wastewater & sludge becomes more organised.

• Reduced burden of various regulatory authorities in ensuring pollution control

requirement.

8. b b) List the groups of industries for which common effluent treatment plants are

highly advantageous. [8]

• Drug & Chemicals

• Textile, Distillery, Pharmaceutical, Chemicals

• Dye & Dye Intermediate, Textile, Pharmaceutical, Pesticides, Pigments

• Chemical, Plastic, Pharmaceuticals, Paper, Garments, Engineering

• Dyeing & Printing ,Textile units, Tannery

• Chemicals, Dyes & Dye Intermediate


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• Dyes & dye Intermediates, Pharmaceuticals, Chemicals, Drugs & Drug

Intermediates

• Chemicals, Pharmaceuticals, Dyes & dye Intermediates, Paint & Textiles

• Sugar mills, distilleries, fertilizer, food processing, domestic sewage

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INDUSTRIAL WATER AND WASTE WATER MANAGEMENT