industrial pollution and control

Subject : Industrial Pollution and Control [Theory] Branch: Metallurgy

Semester: 5th

Faculty: Mr. Vikram Singh Nanda Code: 338512 (38)

Department of Metallurgy, OPJIT, Punjipathara, Raigarh [C.G]

Class Lecture Notes of Unit-2

[Water Pollution – Source, Effect, Control]

Subject: Industrial Pollution and Control

[Theory - 338512 (38)]

Branch: Metallurgical Engineering Semester: 5th

Faculty: Mr. Vikram Singh Nanda

Water Pollution:

� Sources, Effects, Measurement, Water Quality, BOD, Eutrophication etc

� Water Pollution caused by various industries and in selected process industries

Water Pollution in Integrated Steel Plants

� Water Pollution in Electroplating Industry

� Water Pollution in Metal Finishing Industries

� Water Pollution in NF Industries – Aluminium and Glass Manufacturing!

� Waste Water Treatment Technology

Pollution in Physical, Chemical & Biological Processes.


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INTRODUCTION:

The pressure of increasing population, growth of industries, urbanization,

energy intensive life style, loss of forest cover, lack of environmental

awareness, lack of implementation of environmental rules and regulations and

environment improvement plans, untreated effluent discharge from industries

and municipalities, use of non-biodegradable pesticides/fungicides/

herbicides/insecticides, use of chemical fertilizers instead of organic manures,

etc are causing water pollution. The pollutants from industrial discharge and

sewage besides finding their way to surface water reservoirs and rivers are also

percolating into ground to pollute ground water sources.

The polluted water may have undesirable colour, odour, taste, turbidity, organic

matter contents, harmful chemical contents, toxic and heavy metals, pesticides,

oily matters, industrial waste products, radioactivity, high Total Dissolved

Solids (TDS), acids, alkalies, domestic sewage content, virus, bacteria,

protozoa, rotifers, worms, etc. The organic content may be biodegradable or

non-biodegradable. Pollution of surface waters (rivers, lakes, ponds), ground

waters, sea water are all harmful for human and animal health. Pollution of the

drinking water and that of food chain is by far the most worry-some aspect.

In order to avoid ill effects of water pollution on the human and animal health

and agriculture, standards/rules/guidelines have been devised for discharge of

effluents from industries and municipalities, quality of drinking water, irrigation

water, criteria for aquatic life in fresh water by various authorities including

central pollution control board (India), World Health Organization (WHO),

World Bank, Indian Standard Institution, Indian Council of Medical Research,

etc.

Alarming level of lead (Pb) and arsenic (As) has been found in the sediments as

well as waters of Damodar, Safi, Ganga, Adjai rivers in Jharkhand, and West

Bengal. High level of contamination by heavy metals, chemicals, organic

matter, nitrates, coliforms, human and animal excreta, pesticides, etc is found in

various rivers in India including Ganga, Yamuna, Gomti, Ramganga, Hindon,

Chambal, Godavari, Krishna, Sabarmati, Subernrekha, Cauvery, etc specially

near big cities and industries.

Many areas have arsenic and fluoride in underground waters. Arsenic in many

districts of West Bengal and UP is very high. Fluoride content in underground

water of many districts in Tamil Nadu, Orissa, Andhra Pradesh, Gujarat,

Rajasthan and UP is high while it is also high in some places in Jammu &

Kashmir, Punjab, Haryana, Delhi, Bihar, Madhya Pradesh, and Maharashtra.

The source of fluoride is generally underground rocks.


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What are the sources of water pollution?

Water Pollutants may enter usable or drinking water via: single or point

sources where pollutants have been discharged into the environment through

pipes (effluent), sewers, smokestacks [A large tall chimney through which

combustion gases and smoke can be evacuated] or ditches [extraction of natural

water from mines] from specific sites. Non-point sources where pollutants,

such as agrichemicals, smoke from forest fires, transportation vehicles, or they

can enter water bodies over large areas via groundwater and runoff.

There are many causes for water pollution but two general categories exist:

direct and indirect contaminant sources. Direct sources [or point sources]

include effluent outfalls from factories, refineries, and waste treatment plants

etc that emit fluids of varying quality directly into urban water supplies. In the

United States and other countries, these practices are regulated, although this

doesn't mean that pollutants can't be found in these waters.

Indirect sources [or non-point sources] include contaminants that enter the

water supply from soils/groundwater systems and from the atmosphere via rain

water. Soils and ground waters contain the residue of human agricultural

practices (fertilizers, pesticides, etc..) and improperly disposed of industrial

wastes. Atmospheric contaminants are also derived from human practices (such

as gaseous emissions from automobiles, factories and even bakeries).

Contaminants can be broadly classified into organic, inorganic, radioactive and

acid/base.

LIST OF SOURCES OF WATER POLLUTION:

• Pollution from Domestic waste

• Pollution from Sewage

• Pollution from Automobile Workshop

• Pollution from Hotels and Restaurant

• Pollution from Slaughter Houses

• Pollution from Solid waste disposal site

• Dumping of Solid Wastes

• Dumping of Earth Construction Debris

• Encroachment [Development of an area not previously occupied]

• Deforestation in the Catchment Areas [Natural Water collecting area]

• Agricultural activities

• Sand and stone mining/quarrying


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The effects of water pollution: Some forms of water pollution simply alter the

physical state of the water, such as its temperature, pH, or turbidity

[cloudiness], but others involve the addition of potentially harmful substances.

They include poisonous drinking water, poisonous food animals (due to these

organisms having bio-accumulated toxins from the environment over their life

spans), unbalanced river and lake ecosystems that can no longer support full

biological diversity, deforestation from acid rain, and many other effects.

Thermal pollution is the unnatural heating of water which changes the ambient

temperature. Heated water is produced during industrial processes, specifically

thermal power production, and the released water is cooled in local waterways.

In warmer waters the decomposition of organic waste occurs faster, depleting

the Dissolved oxygen in water; this affects the aquatics organisms’ ability to

Metabolize and may compromise sensitive species.

Acid rain (or more correctly termed acid deposition) can fall on the Earth as

rain, snow or sleet [mixture of rain and snow], as well as dry, sulfate-containing

particles that settle out in the air. It is a world-wide problem because of the

widespread use of coal for heating and electricity and the continued use of fossil

fuels for transportation. Normal rainfall has a pH between 5.2 and 5.6 where

acid rain is more acidic than normal rainfall. Acid rain produces forests with

sickly, stunted trees and lakes that are so acid that they cannot support fish. It

also releases heavy metals (for example, cadmium and mercury) into the food

chain.

Ocean Acidity: The Ocean acts as a CO2 sink, absorbing much of the CO2

produced by the burning of fossil fuels. CO2 reacting with water forms

carbonic acid through the chemical reaction: CO2 + H2O � H2CO3.

An increase in carbonic acid levels is causing the pH of the oceans to fall. This

has major implications for marine life. The pH is a logarithmic scale, so even a

small pH change represents a large change in H+. Thus a pH of 5 is 100 x more

acidic than a pH of 7.

Effect of Ocean Acidification: Because the oceans are naturally alkaline

[having a pH greater than 7 i.e Basic], acidification will not produce acid

waters. Shells will not dissolve but organisms will find it more difficult to gain

the CO32-

ions needed to make shells. Shell making organisms are able to use

CO32-

but cannot use HCO3-

. Acidification lowers the amount of CO32-

available.

Chemical Pollutants: Organic chemicals are carbon based chemicals like

detergents, pesticides, tree and brush debris, and food wastes. Inorganic


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chemicals are not carbon based, like phosphorous and nitrogen based chemicals

and can include acids, salts, and heavy metals. Most organic water pollutants

are synthetic, carbon based, chemicals created for human activities. These

include pesticides, solvents, industrial chemicals, and plastics. Some organic

compounds enter water sources directly or through seepage from landfills,

through agrichemical runoff, or by leaching into groundwater. Inorganic

chemical pollutants include mercury, lead, road salt, and acid drainage. Most

are toxic to aquatic organisms and their presence may make water unsuitable for

drinking and other uses. Inorganic chemicals enter water sources from industrial

plants, mines, irrigation runoff, oil drilling, and municipal storm drainage.

Inorganic Plant Nutrients: Fertilizer runoff from agricultural and residential

land contributes inorganic plant nutrients, particularly nitrogen and phosphorus,

to water bodies. This nutrient enrichment accelerates the natural process of

eutrophication, and causes algal blooms and prolific aquatic weed growth.

High nitrate levels caused by inorganic fertilizers are also toxic in drinking

water, particularly for infants, small children, and pregnant women.

Eutrophication: It is the Biological process. Eutrophication is a term

describing the enrichment of water with nutrients especially nitrates and

phosphates. It often results in excessive growth of weed and algae. In other

words, eutrophication is Excessive nutrients in a lake or other body of water,

usually caused by runoff of nutrients (animal waste, fertilizers, sewage) from

the land, which causes a dense growth of plant life; excessive plant and algal

growth depletes the supply of oxygen, leading to the death of animal life inside

water.

Microorganisms decompose the organic matter in the polluted water and their

activity increases the Consumption of dissolved oxygen [DO] in water. This

reduces the amount of dissolved oxygen available to other aquatic organisms /

animals in water and may subsequently cause their death.

BOD: Biochemical or Biological oxygen demand is a measure of the polluting

capacity of effluent [waste water] where decomposition of organic matter

results in oxygen depletion. Organic matter decays as bacterial activity

increases. BOD is measured as the weight (mg) of oxygen used by one litre of

sample effluent stored in darkness at 20oC for five days [also called BOD5].

When the BOD is high and dissolved oxygen becomes depleted, decomposition

becomes anaerobic [Living or active in the absence of free oxygen]. Anaerobic

microorganisms produce compounds with unpleasant odours, leading to a

further deterioration in water quality.


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Sewage Pollution

Raw or partially treated sewage is a common water pollutant. Sewage pollution

results from the disposal of household and industrial wastes into rivers, lakes,

and seas. Sewage includes all waste water that has been used by a household or

industry. It does not include storm water from road and property runoff, which

is usually diverted directly into waterways. In some cities, sewerage and storm

water systems may be partly combined, and sewage may overflow into storm

water during high rainfall. Most communities apply some treatment to raw

sewage prior to discharge from point sources, but even treated sewage can be

high in nutrients.

Sewage is a source of pathogens (disease-causing agents). During floods,

human waste may mix with drinking water and increase the risk of water-borne

diseases such as cholera.

Processing of Sewage Water: Sewage usually undergoes several levels of

treatment (purification):

• Pre-treatment removes any large objects, such as tree limbs, leaves,

condoms, & tampons, with screens.

• Primary treatment uses mechanical processes, such as screening and

settling, to remove suspended sand and silt. This forms the primary

sludge.

• Secondary treatment uses microorganisms to decompose the suspended

organic material in the waste water aeration tank. The bacteria-laden

solids settle out as sewage sludge.

• Disinfection (usually by chlorination but ozone and UV light can also be

used) kills any bacteria and other pathogens before the waste water is

discharged.

• Tertiary treatment using biological, chemical, and physical processes is

required to remove nitrogen, phosphorus, heavy metals, and synthetic

organic compounds.

Detecting Water Pollution

The extent of water pollution can be determined in many ways:

• The nutrient loading can be assessed by measuring the BOD (the

Biochemical (or Biological) Oxygen Demand).

• Electronic probes and chemical tests can identify the absolute levels of

various inorganic pollutants (nitrates, phosphates, and heavy metals).


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Measuring Water Quality

The following measurements are routinely made by agencies involved in

water quality monitoring:

• Dissolved oxygen, carbon dioxide, and temperature (in the field)

• Clarity or turbidity (in the field or the laboratory)

• Conductivity, pH, colour, nutrients (nitrogen and phosphorus), major

ions (magnesium, calcium, sodium, potassium, chloride, bicarbonate, and

sulphate), organic carbon, and fecal [stool] bacteria (coliforms and

giardia).

Water Pollution caused by various Industries:

Effluents and solid wastes from various industries and municipalities,

indiscriminate use of toxic chemicals, indiscriminate use of pesticides,

insecticides and fungicides, leaching of soils, wastes and rocks are the

principal causes of water pollution. Objectionable level of pollution of

water due to oils and oily substances may be found mainly in surface

waters near the industries using heavy quantities of lubricating oils,

greases, and liquid fuels, or refineries, big oil storages, etc. Ground water

may also be polluted due to soaking of oil in the ground or by

indiscriminate disposal of oil sludge. The heaviest polluting source for

surface water is sewage from cities.

CARCINOGENS IN WASTE WATER

Wastes from certain industries or leakages of certain materials in

handling, processing, etc may have substances which can cause cancer in

humans or animals. These carcinogenic substances may find their way in

waste waters which may pollute the source of waters for general use.

Many of the heavy and toxic metals like nickel, chromium, radioactive

substances, certain dyes, inks, resins, fumigants, gasoline additives,

nitrophenyl, naphthyamines, benzidine, azo compounds, some of the

pesticides like D.D.T. etc are carcinogens. Smoke from combustion of

certain organic materials may contain carcinogens which may eventually

find their way to pollute waters, besides polluting air. Prevention from

exposure, removal of such compounds or breaking down of such

compounds should be attempted.

POLLUTION BY E-WASTE

India generated about 1050 tonnes of electronic scrap per year as

reported in April 2005 which increased to 146,000 tonnes of e-waste per

year as reported in May 2007. This would go on increasing year by year.


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A study by U.S. environmental protection agency shows that e-waste

forms about 1% of municipal solid waste in USA. California alone

discards 6000 computers daily. They have estimated that about 70% of

heavy metals found in the land fills there, come from electronic discards

which may contaminate ground waters. When e-waste is incinerated with

other wastes it leads to hazardous emission-containing ‘Dioxins’. The

commonly found metals in e-waste like copper are catalyst for ‘Dioxin’

formation.

----x----x------x-----x-----x-----x-----x---------x---x----x----x-----x---x-

Various Water Pollutants:


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Pollution in Electroplating Industry Electroplating is a plating process in which metal ions in an electrolyte

solution are moved by an electric field to coat an metal-electrode [cathode].

Electroplating is primarily used for depositing a thin layer of material to bring a

desired property to a surface e.g., abrasion and wear resistance, corrosion

protection, lubricity [the property of reducing friction], aesthetic qualities [on

decorative pieces], etc. The process used in electroplating is called electro-

deposition.

Electroplating is the deposition of a metallic coating onto the surface of an

object [Cathode] by putting a negative charge onto the object and immersing it

into an electrolyte solution which contains a salt of the metal to be deposited. A

power supply supplies a direct current to the anode, oxidizing the metal atoms

that comprise it and allowing them to dissolve in the solution. At the cathode,

the dissolved metal ions in the electrolyte solution are reduced at the interface

between the solution and the cathode, such that they "plate out" onto the

cathode. The rate at which the anode is dissolved is equal to the rate at which

the cathode is plated, vis-a-vis the current flowing through the circuit. In this

manner, the ions in the electrolyte bath are continuously refilled by the anode.

Fig Electroplating of a metal (cathode) with nickel in a NiCl2 solution bath

Electroplating Industry Description and Practices Electroplating involves the deposition of a thin protective layer (usually

metallic) onto a prepared surface of metal, using electrochemical processes. The

process involves pre-treatment (cleaning, degreasing, and other preparation

steps), plating, rinsing, passivating, and drying.


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Fig: Basic Steps of Electroplating Process

Identify Base Metal

Clean

Acid Descale & Activate

Pre-Plate(If required)

Final Plate

Post Treatments(As Specified)

Rinse

Rinse

Rinse

Rinse

Rinse

Dry & Package

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 2R

Step 3R

Step 4R

Step 5R

Step 6R

Basic Electroplating Procedure

For Example: Steel,

Cooper , Brass

For Example:

Degrease, Soak, &

Electroclean

For Example:

Hydrochloric, Sulfuric,

or Fluoboric Acids.(Some cases Peroxide

Descale or Brite Dip

For Example:Cadmium, Chromium,

Copper, Gold, Lead,

Nickel. Silver, Solder, &

Tin

For Example:

Chromates, Lacquers,

& Seals

For Example: Box or

Hot Air Spin Dryers

For Example: Copper,Sulfamate Nickel, or

Nickel

If more than one is

specified Repeat Steps

4 & 4R as needed.


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The cleaning and pre-treatment stages involve a variety of solvents (often

chlorinated hydrocarbons, whose use is discouraged) and surface stripping

agents including caustic soda and a range of strong acids, depending on the

metal surface to be plated.

The use of halogenated hydrocarbons for degreasing purpose is not necessary

now a day, as water based systems are available and should be used. There are

following main types of plating electrolytic solutions: acid solutions, alkaline

solutions and complex agents such as cyanides. Electroplating and metal

finishing, both comes under “surface finishing” industries. In electroplating, we

add a layer of metal, while in metal finishing; we modify the surface layer of

metal by various processes.

Waste Characteristics in Electroplating Industry

Some or all of the substances used in electroplating (such as acidic solutions,

toxic metals, solvents, and cyanides) can be found in the wastewater, either via

rinsing of the final product or due to spillage and dumping of process baths.

The solvents and vapours from hot plating baths result in elevated levels of

volatile organic compounds (VOCs) and in some cases, volatile metal

compounds (when they contain chromates). Approximately 30 percent of the

solvents and degreasing agents used can be released as VOCs when baths are

not regenerated /or Improved / or redesigned.

The mixing of cyanide and acidic wastewaters can generate lethal hydrogen

cyanide gas and this must be avoided. The overall wastewater stream is usually

high in heavy metals (including cadmium, chrome, lead, copper, zinc, and

nickel), cyanides, fluorides, and oil and grease, all of which are process

dependent. Air emissions may contain toxic organics (such as trichloroethylene

and trichloroethane).

Cleaning or changing of process tanks and the treatment of wastewaters can

generate substantial quantities of wet sludge containing high levels of toxic

organics and/or metals.

Pollution Prevention and Control in Electroplating Industry

Plating involves different combinations of a wide variety of processes and there

are many opportunities to improve upon the traditional practices in the industry.

The following improvements should be implemented where possible:


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Changes in Process:

• Replace cadmium with high quality corrosion resistant zinc plating. If

Possible, Use cyanide-free systems for zinc plating. In those cases where

cadmium plating is necessary, use bright chloride, high alkaline baths or

other alternatives.

• Use trivalent chrome instead of hexavalent chrome: acceptance of the

change in finish needs to be promoted.

• Give preference to water-based surface cleaning agents, instead of

organic cleaning agents, some of which are considered toxic.

• Regenerate [improve or re-design] acids and other process ingredients,

whenever feasible.

Reduction in Drag-out and Wastage

• Minimize drag-out [by effective draining of bath solutions] from the

plated part by measures such as making drain holes in bucket type

pieces, if necessary.

• Maintain the density, viscosity, and temperature of the baths to minimize

drag-outs.

• Allow dripping time of at least 10 to 20 seconds before rinsing the part.

Minimizing Water Consumption in Rinsing Systems

It is possible to design rinsing systems to achieve 50-99% reduction of

traditional water usage.

• Agitation of rinse water or work pieces [via vibrations] to increase rinsing

efficiency.

• Multiple counter-current rinses of plated parts.

• Spray rinses (especially for barrel loads [cylindrical shape baths]).

Management of Process Solutions

• Recycle process baths after concentration and filtration. Used bath

solutions should be sent for recovery and regeneration of plating

chemicals, not discharged into wastewater treatment units.

• Recycle rinse waters (after filtration).

• Regularly analyze and regenerate process solutions to maximize useful

life.

• Clean racks between baths to minimize contamination.

• Cover degreasing baths containing chlorinated solvents when not in

operation to reduce losses.


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Why should my electroplating shop reduce air pollution? Why

should I be concerned about air pollution from my electroplating

shop? Explain Various Health Issues related to them?

Electroplating operations can produce emissions of toxic air pollutants,

including heavy metals and cyanide.

Degreasing and cleaning solutions can release toxic air pollutants and volatile

organic compounds (VOC). Chemicals in these substances can react in the air to

form ground-level ozone (smog), which has been linked to a number of

respiratory effects.

Plating processes generate heavy metals such as hexavalent chromium and

cadmium. While federal, state, local, and Tribal regulations limit the amount of

emissions from electroplating shops, dangerous releases of toxic air pollutants

can occur if an electroplating shop is not in compliance with regulations.

Cyanide has been a key component of plating solutions for years. It can impact

the nervous system, heart, and lungs.

People who are exposed to toxic air pollutant at sufficient concentrations, for

sufficient durations, may increase their chances of getting cancer or

experiencing other serious health effects, such as reproductive problems, birth

defects, and aggravated asthma. Pollution prevention safeguards the health of

your employees, customers, and families by using materials, processes, or

practices that reduce or eliminate air pollution at the source.

For example, covering containers of cleaning solvents prevents vapours from

affecting your employees. Pollution prevention practices also save money on

waste disposal, materials usage, and the cost of air pollution controls.

How can I reduce air pollution from my electroplating shop?

Substitute Materials

• Use cleaners such as water-based cleaners that have a lower toxic air

pollutant and VOC content.

• Use degreasing solvents with a lower toxic air pollutants and VOC

content.

• If you are a chromium electroplater, switch from hexavalent chromium

bearing solutions, which can cause cancer, to trivalent chromium ones,

which do not cause cancer.


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• Replace the cyanide in plating solutions with less toxic compounds like

zinc chloride and pyro-phosphate copper.

Lower Emissions at the Source

� Cover containers of cleaning solvents and used shop towels. This will

reduce emissions of toxic air pollutants and VOC as well as the amount

of solvent lost to evaporation. This reduces the amount of new solvent

purchased.

� Securely cover all containers to reduce the chance of spills when

transferring materials.

� Use funnels or pumps to avoid spills when dispensing materials.

� Install ventilation hoods over plating baths to help protect workers from

evaporative plating solutions.

Change Cleaning Procedures

� Mandate a “clean as you go” policy to reduce the amount of solvent

needed for removing heavy buildup.

� Mechanically clean parts with a wire brush or sandblasting equipment to

reduce solvent use.

� Use old solvent as a pre-wash or wipe for cleaning equipment or parts.

� Switch to a water-based cleaning system like ultrasonic cleaners, manual

parts washers, automatic spray equipment, steam cleaners, or baths with

agitation.

� Clean parts with hot water and detergent at high pressures in a

pressurized washer.

Recycle Materials

� Use an on-site distillation unit to clean dirty cleaning liquid. This makes

the solvent available for reuse in the production process. An on-site

distillation reduces the costs of both solvent disposal and fresh solvent

purchase.

� Use old solvent for cleaning very dirty parts.

� Reuse plating bath solution and rinse water.

� Reduce bath dumps by continuously filtering bath solutions.

Change Production Processes

� Review and streamline production processes to reduce overall cleaning

solvent and degreaser use. For example, evaluate your solvent quality,

consolidate parts washing processes, and service units only when

necessary. These steps can greatly reduce solvent waste.


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� Lower emissions of toxic air pollutants such as cyanide, chromium and

other heavy metals by using alternative electro-coating technologies like

thermal spray coating, vapor deposition, and chemical vapor deposition.

� Minimize chemical usage and its associated emissions by using the

lowest concentration of chemicals in the bath that will produce the

desired results.

� If possible, use mechanical scraping instead of a chemical solution to

remove undesired buildup on the metal.

� Change baths and rinses based on bath/rinse quality, not to meet an

arbitrary schedule.

Key Issues that should be addressed in electroplating industry:

The following summarizes the key production and control practices that will be

accepted with emission guidelines:

1. Use cyanide free systems.

2. Avoid cadmium plating.

3. Use trivalent chrome instead of hexavalent chrome.

4. Prefer water-based surface cleaning agents where feasible, instead of

organic cleaning agents, some of which are considered toxic.

5. Minimize drag-out.

6. Use counter-current rinsing systems and/or recycle rinse waters to the

process after treatment.

7. Regenerate and recycle process baths and rinse waters after treatment.

8. Recycle solvent collected from air pollution control systems.

9. Send used solvents for recovery.

10. Do not use ozone depleting substances.

11. Manage sludges as hazardous waste. Reuse sludges to the extent feasible,

provided toxics are not released to the environment


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Pollution in Metal Finishing Industry METAL FINISHING - INDUSTRY PROFILE

The Metal SURFACE finishing processes improve the surface of a basic

material by cleaning it, hardening or softening it, smoothing or roughening it,

depositing another metal on it by chemical exchange, electroplating another

metal or series of metals on it, converting its surface by chemical deposition,

coating it with organic materials, and oxidizing by electrolysis.

In other words, metal finishing includes both electroplating and coating

operations, as well as their supporting processes (polishing, cleaning,

degreasing, pickling, etching, etc.). The purpose of metal finishing is to prevent

corrosion and wear, change electrical properties [electrical conductivity],

enhance bonding for adhesives and coatings, and provide a decorative finish

[durability, aesthetic appearance] for metal products. Metal Finishing

Industries are either micro or small scale enterprises [MSEs].

Electroplating and other metal finishing operations use a wide variety of

processes to provide desired surface properties:

� Physical processes, such as buffing [Polish and make shiny], abrasive

blasting, grinding, tumbling [Roll over and over, back and forth], and

polishing.

� Chemical processes, such as degreasing, cleaning, pickling, etching,

coating, and electro-less plating [Plating without current but with the help

of Chemical catalyst in bath solution].

� Electrochemical processes, such as electroplating, anodizing, electro-

cleaning, and electro-polishing.

Physical processes involve the use of solid materials (abrasives). Chemical and

electrochemical processes involve the use of a wide variety of materials such as

acids, alkalis, cyanides, chromates, metal oxides, solvents, aldehydes,

surfactants, and other organic additives. These operations are typically

performed in baths (tanks) and are then followed by a rinsing cycle.

It is a common belief among those involved that the metal finishing industry is

the second most regulated sector, following the nuclear industry. The fact is the

metal finishing industry is regulated on a federal, state and local level under:

The Clean Water Act, The Clean Air Act, Resource Conservation and Recovery

Act (RCRA), Toxic Substances Control Act (TSCA).


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The metal finishing processes generate wastes, non-hazardous and hazardous, in

all physical states: liquid waste, solid waste, and air emissions. Therefore, the

metal finishing facilities have a high potential for multi-media contamination if

these wastes are released to the environment.

Adverse Environmental Impacts and Mitigation Opportunities in Metal Finishing Industries:

Several key environmental issues associated with metal finishing are listed

below:

� Use of hazardous chemicals

• Solid and hazardous wastes

� Air pollution

� Water use

� Wastewater

Use of Hazardous Chemicals

Metal finishing operations routinely use various hazardous chemicals, including

solvents for cleaning the metal parts, acids and bases for etching them, and

solutions of metal salts for plating the finish onto the desired form (substrate).

Most coating processes require the metal surface to be thoroughly cleaned

before-hand, because surface contaminants greatly diminish the quality of the

finished product. Both cleaning and plating processes generally occur in a

“bath”—that is, a tank in which parts are dipped into a solution of chemicals.

Preparing the surface of the metal for treatment involves the removal of greases,

soils and oxides. Cleaning agents used for this purpose include detergents,

solvents, acidic solutions and caustics. Finished metal parts are often further

coated with some combination of paint, lacquer or ceramic coating. These

coatings can themselves contain toxic solvents and heavy metals.

Chemicals used may include the following:

• Acids (sulphuric, hydrochloric, nitric, phosphoric)

• Toxic metals (cadmium, nickel, zinc, chromium, lead, copper) and

compounds which contain these metals

• Solvents (1,1,1-trichloroethane, methylene chloride, tetrachloroethylene,

methyl ethyl ketone [MEK], toluene, xylene)

• Cyanide compounds.

These chemicals may be toxic to humans and animals, cause cancer in both

humans and animals, easily catch fire, and/or persist in the environment for a

long time, entering the food supply.


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In particular, hexavalent chromium is highly toxic to humans, causing kidney

damage and increasing the risk of lung cancer in humans. It is also highly toxic

to aquatic animals at very small doses. Both workers and local communities are

at risk from exposure to these chemicals, particularly those that persist in

ground and surface water supplies for long times.

In general, cleaner production [CP] can reduce the environmental harm caused

by using hazardous chemicals and improve the financial performance of the

production process. Cleaner production [CP] options in this area are simple

techniques, including pre-cleaning, production/inventory planning, substituting

less hazardous chemicals and/or processes, and reusing or reclaiming “dirty”

chemicals.

Selected Mitigation Strategies:

Avoid keeping outdated chemicals. Chemicals may lose their effectiveness if

used past their expiration date, resulting in poor-quality products and wasted

bath solutions. Recently purchased chemicals should be used after older

chemicals (a “first in, first out” policy) in order to prevent accumulation of

expired stock. Creating an inventory control system will prevent waste by

ensuring that all chemicals are used in order of arrival in the storeroom.

Label all chemical containers with the name of the chemical, the date it arrived

at the storeroom, the name of the manufacturer/distributor, and any appropriate

hazard warnings. The manufacturer, and in some cases the distributor, may be

able to provide a Material Safety Data Sheet (MSDS), which includes necessary

warnings as well as details about proper safety equipment and procedures for

handling the chemical.

Conduct employee trainings in the proper handling of chemicals, the reasons

for using safer techniques, and emergency response. Trained employees will be

better able to operate baths at peak efficiency, minimize spills, and improve the

consistency of solutions.

Training can also minimize the number of “bad baths” in which the entire

solution must be changed out, which wastes time, materials and water, and may

require workers to reprocess of metal parts. Ensure that only trained employees

are responsible for mixing bath solutions and setting flow levels.


Semester: 5th



Reduce the need for chemicals.

Reduce the use of rust inhibitors (a toxic cleaning agent) by ordering metal parts

to be delivered only at the time that they are needed, and also by storing them

away from moisture if possible. This reduces the chances that they will rust.

Optimize solvent-handling procedures. There are a number of ways to reduce

the amount of solvents used throughout a facility; several require little or no

investment.

� Covering degreasing baths when they are not in use will reduce

evaporation of solvents; firms can spend less on solvents and lower the

risk of toxic exposures to workers.

� Alkali washes can be used instead of solvents in degreasing operations.

This way, wastes from alkaline cleaners can be chemically treated to

reduce toxicity and then discharged into the sewer, which minimizes

cleaning costs.

� Extend the life of cleaning solutions and reduce costs by filtering the

cleaning solutions to remove sludge build-up.

� Recycle solvents onsite. Use gravity to separate a solvent/sludge mixture

and reclaim the clear solvent for equipment cleaning. If reclaimed solvent

is pure enough, it can also be used for formulating primers and base coats

of paint.

Use process substitution to reduce hazards to workers, communities, and the

environment.

� Zinc alloy plating, such as zinc-nickel or zinc-cobalt, can be used to

provide corrosion protection instead of cadmium plating, which is highly

toxic and carcinogenic.

� Because cyanide is highly toxic to humans, use cyanide-free systems for

zinc plating when possible. Cyanide-free systems include zinc chloride

(acid) baths and zinc alkaline systems.

� Zinc chloride baths have higher operating efficiencies, offer energy

savings through improved bath conductivity, and result in better quality

of product because hydrogen embrittlement is reduced. (This is a type of

metal deterioration that reduces metal strength and ductility.) Zinc

chloride baths, however, require that traditional steel tanks be lined with

an acid-resistant material, such as hard rubber or polypropylene.

� Use non-fuming cleaners such as sulphuric acid and hydrogen peroxide

instead of chromic acid cleaner.

� Use trivalent chromium instead of hexavalent chromium, as it is less toxic

to humans and aquatic animals, creates less sludge, and is less viscous,

therefore causing less drag-out . Trivalent chromium also uses the same

equipment as hexavalent chromium, so it requires no infrastructure


Semester: 5th



changes. Unfortunately, trivalent chromium can only be used for a plating

thickness no greater than 0.003mm. Trivalent chrome baths may also

require additives to correct color differences.

Consider options to reduce drag-out. Drag-out is the residual solution that

adheres to a part when it is removed from a process bath. Drag-out reduces the

concentrations of chemicals in the plating bath, requiring more chemical inputs

to maintain operating conditions.

Air Pollution Vapour degreasing operations and hot plating baths generate

used solvents that emit volatile organic compounds (VOCs). VOCs can cause

serious health problems for workers, and they also contribute to air pollution in

the lower and upper reaches of the atmosphere. Poor handling practices can

result in the loss of as much as 30 percent of solvents and degreasing agents.

This can be a significant cost, as these chemicals would otherwise be reused.

VOCs are also emitted during paint application, curing and drying. In general,

some sort of pollution control investment will be necessary to fully control air

emissions from metal finishing facilities. Cleaner production can help to reduce

air pollution by preventing solvents from escaping into the air (i.e., volatilizing)

and improving the efficiency of pollution control systems. These methods are

described in detail below.


�� Cover the degreasing unit during idle or down times to prevent solvent

from volatilizing.

�� Exhausts should be treated to reduce VOCs and heavy metals before

venting to the atmosphere. Carbon filters can both reduce VOC levels and

allow employees to recover solvent using steam stripping and distillation.

�� Use mist collection and scrubbing systems to control vapours and mists

from process baths.

�� Use non-caustic paint removers such as alkaline or non-phenolic strippers

to reduce phenol emissions.

Wastewater Problems Metal finishing, especially electroplating, generates large quantities of

wastewater, primarily from rinsing between process steps. Because of the

hazards to the community associated with the chemicals involved in metal

finishing operations, wastewater should always be treated before disposal into

ground or surface waters. Improperly treated wastewater can contaminate

drinking water and irrigation supplies, with long-term consequences for the

health of the local population, including employees.


Semester: 5th



Cleaner production [CP] can best help reduce impacts of wastewater by

reducing the toxicity of the wastewater at the source. Once options for reducing

source pollution are used, however, it will still be necessary to build or share

use of a wastewater treatment plant. In order to be effective, wastewater

treatment plants need to be properly designed for the types of wastes to be

treated and the volumes of wastes generated. Operating such plants can be

costly, although in areas where water is scarce or expensive, treating wastewater

may help pay for itself by permitting re-use of water in facility operations.


� A waste treatment plant should treat wastewater to destroy cyanide,

neutralize pH, and remove toxic metals.

� It must separate waste streams. If cyanide and acidic wastewaters mixes,

it can generate lethal hydrogen cyanide gas. Also, nickel solutions must

be separated from cyanide and ammonium solutions in order to allow

nickel to precipitate out of solution.

� Use a reducing agent such as a sulphide to reduce wastewater containing

hexavalent chromium, which is water-soluble, to trivalent chromium,

which is insoluble. Add lime to the wastewater to precipitate out the

chromium, and dispose of the solids in a sanitary landfill.

� Use sodium sulphides and iron sulphates to remove metal from rinse-

water instead of salts, phosphates, EDTA and/or ammonia.

� Sludge from water treatment operations must be treated before disposal in

order to control metals. Use electrolytic methods to recover metals from

the sludge when metal concentrations are high. Sludges should be

thickened, de-watered, and stabilized with lime before disposal in a

controlled landfill. Oxidize chromium acid wastes with sodium bisulphite

and sulphuric acid. Use magnesium oxide instead of caustic soda to adjust

pH.

Water Use Metal finishing requires water in almost every stage of the process. Many metal

finishing businesses have yet to grab major opportunities to reduce their water

use. Often, limited water resources in an area must satisfy the needs for public

drinking water, sanitation, irrigation, river transport and industrial needs.

Inefficient use of these resources for metal finishing can leave insufficient or

highly polluted waters in lakes, rivers and wetlands, degrading their ability to

perform crucial economic and ecological functions.


Semester: 5th



There are various cost-effective ways for metal finishing enterprises to reduce

their water use that could provide substantial savings.


• Ensure the proper design of rinse tanks in order to improve rinsing

efficiency, reduce water use, and reduce drag-out. Tanks should be the smallest

size necessary for all parts/products that will be used in them, in order to reduce

water usage. Using a static rinse tank before a running rinse tank will reduce

drag-out in the running rinse tank, using less water for the same degree of

cleanliness.

Carefully placing water inlets and outlets on opposite ends of the tank will

maximize water mixing in the tank, improving the effectiveness of the rinse.

Inlet flow baffles, diffusers, distributors or spray heads can also help control the

injection of freshwater into the rinsing tank and aid in mixing the water. Also,

adding air blowers, mechanical mixing, or pumping/filtration systems can

improve mixing by agitating tank water.

Mechanical agitation is preferable to air agitation, however, since air blowers

can introduce contaminants like oil into the bath.

• Consider alternatives to tank rinsing. Tank rinsing may not be the most

water-efficient solution for rinsing certain types of parts. Consider spray rinsing

instead of immersion for flat-surfaced parts. Ultrasonic rinsing works well for

cleaning parts with small crevices or irregular shapes.

• Employ a flow control technique. Effective flow control techniques are flow

restrictors AND flow cut-off valves. Flow restrictors ensure that excessive

water is not fed to the process line. Flow cut-off valves are simple mechanisms

that shut off water flow to rinse tanks when the process lines are not in use.

• Measure usage at individual production points. Install an inexpensive flow

meter or accumulator on the main water feed line (leading to the process line) or

on individual rinse tanks. Flow meters indirectly conserve water by allowing

careful monitoring of usage and can identify optimum water usage (or excessive

waste), leaks, and system failures.

• Change the mechanics of the rinsing process. Rinsing is more

effective when the parts are dipped into the rinsing tank multiple times

than when parts are dipped once and agitated while submerged.


Semester: 5th



Dipping parts twice in rinse baths is 16 times more effective at

reducing drag-out than dipping once.

• Re-use treated wastewater for minor rinsing steps, such as after

alkaline cleaners and acid pickling steps. Note: Caution should be

exercised in re-using wastewater that has been conventionally treated (via

hydroxide precipitation) as it can introduce high amounts of dissolved

solids into the plating line.


Semester: 5th



WHAT IS POLLUTION PREVENTION?

Pollution prevention (also known as “source reduction” and “waste

minimization”) is any action that reduces the production of wastes (at their

source) that may be otherwise released to the air, land, or water. There are two

general methods to achieve pollution prevention: (1) process changes and (2)

product changes.

The Pollution Prevention Act of 1990 established a clear national policy that

pollution should be prevented or reduced at the source whenever possible. The

Environmental Protection Agency (EPA) defines pollution prevention as "any

effort to reduce the quantity of industrial, hazardous, or toxic waste through

changes in the waste generation or production process at the source." This

includes all pollution, hazardous and non-hazardous, regulated and unregulated,

across all media and from all sources.

The Pollution Prevention and Best Management Practices (P2-BMPs) have been

developed to enable the metal finishing industries to achieve compliance with

all federal, state, and local environmental regulations, prevent the release of

chemicals to the environment, and develop a comprehensive Pollution

Prevention Program.

Each Pollution Prevention Program will identify ways in which a given facility

can reduce the use of hazardous materials and the subsequent generation of

hazardous and non-hazardous wastes. In addition the Program will also seek to

establish enhanced water and energy conservation practices.

Pollution Prevention & Best Management Practice For Metal Finishing

Facilities

The P2-BMPs promote the use of good housekeeping measures, development of

a preventive maintenance program, employee training in pollution prevention,

and other pollution prevention techniques recommended for metal finishing

operations. These techniques can be applied so as to maximize the use of

resources through source reduction, energy efficiency and water conservation,

waste tracking and reduction.

THE GOALS AND BENEFITS OF POLLUTION PREVENTION

The goal of a pollution prevention program is to minimize all waste produced.

Pollution prevention includes any action a company takes to reduce the amount

of waste created by a manufacturing process prior to recycling, treatment, or


Semester: 5th



disposal of the waste. To effectively accomplish this, the program must be an

ongoing, comprehensive assessment of the operations at a facility.

BENEFITS OF A POLLUTION PREVENTION PROGRAM

Both businesses and governments have strong incentives to reduce the toxicity

and sheer volume of the waste they generate. The cost of producing each unit

will decrease as pollution prevention measures lower operating costs. Therefore,

companies with an effective, ongoing pollution prevention plan will have a

significant competitive edge. The overall benefits of a pollution prevention

program, discussed in more detail below, include the following:

� Protecting human health and environmental quality

� Reducing operating costs

� Improving employee morale and participation

� Enhancing your company’s image in the community

� Reducing the potential for penalties and fines

Why Focus on Cleaner Production for Mitigation?

Cleaner production (CP) is a preventive business strategy designed to conserve

resources, mitigate risks to humans and the environment, and promote greater

overall efficiency through improved production techniques and technologies.

Cleaner production methods may include:

• substituting different materials

• modifying processes

• upgrading equipment

• redesigning products

In addition to environmental, health and safety benefits, many CP techniques

provide opportunities to substantially reduce operating costs and improve

product quality. MSEs [Micro and Small scale Enterprise] can profit from CP

through more efficient use of inputs and machinery, higher-quality goods that

command higher prices, and reduced waste disposal costs. Improved safety

measures can also help MSEs avoid costly accidents and worker absences.


Semester: 5th



Water Pollution in NF Industries – Please do Self Study !!

1. Environmental Guidelines for Aluminium Manufacturing


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2. Environmental Guidelines for Glass Manufacturing


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industrial pollution and control

Documents

water pollution source

water quality

industrial pollution

fresh water

irrigation water

sea water

polluted water

water reservoirs