Thursday, January 19, 2017

Self-purification of water bodies

Self-purification of natural water bodies
Self-purification of natural water bodies is a combination of physical, chemical and biological processes working simultaneously. The amount of dissolved oxygen in water is commonly used to indicate river health. The maximum value of dissolved oxygen in water at 0℃ is 14.6 mg/L and at 25 ℃ is 8.24 mg/L. Oxygen demanding wastes (organic wastes) reduce the dissolved oxygen and increasing temperature also reduces the solubility of oxygen in water.
The factors affecting self purification of water are:
  1. Dilution
  2. Current
  3. Sunlight
  4. Temperature
  5. Rate of oxidation
  6. Reduction
  7. Sedimentation
  8. Hydrography
Dilution: If sufficient water is available in the receiving water body, the dissolved oxygen level might not reach the critical level due to availability of dissolved oxygen before discharge.

Current: The presence of currents in the receiving stream increases the dissolved oxygen in the receiving water body due to turbulence. Strong currents also prevent deposition of solids. Low currents encourage deposition of solids in wastewater resulting in decompoosition and reduction in dissolved oxygen.

Sunlight: Sunlight has a bleaching and stabilizing effect on bacteria. It helps aquatic plants and algae to absorb carbondioxide and release oxygen by a process called photosynthesis. The release of oxygen into water helps in self-purification through oxidation.

Temperature: The quantity of dissolved oxygen available in stream water is higher at colder temperatures. However, the activity of microorganisms is higher at high temperature. Hence, self-purification is carried out quickly in summers than in winters.

Rate of oxidation: Depletion of dissolved oxygen occurs mainly due to oxidation of organic matter. This rate is faster at higher temperature and lower at lower temperature.

Reduction: Reduction occurs due to hydrolysis of organic matter settled at the bottom either chemically or biologically. Anaerobic bacteria helps splitting the composition of sewage into liquids and gases thus paving the way for their ultimate stabilization.

Sedimentation: The settleable solids, if present in effluents settle at the bed of the river, near the outfall, thus helping in self-purification process.

Hydrography: Hydrography affects the velocity and surface expanse of the water body. High velocity and large surface expanse cause turbulence and rapid aeration.

Effects of industrial wastes on streams, land and human health

  • Streams  
    • Organic wastes in industrial wastewaters deplete the oxygen content of receiving streams
    • Discharge from fertilizer industry contains toxic components such as metals, nitrates and ammonia are responsible for causing metabolic impairment in aquatic organisms and may be fatal at higher concentrations.
    • Heavy metals such as Zn, Cu, Cr and Pb binds with certain proteins in fish and disrupt membrane integrity, cellular metabolism and ion-transport that causes harm to the maintenance of homeostasis
    • Inorganic substances like carbonates, chlorides, nitrates and phosphates make the water unfit for further use and encourage the growth of undesirable aquatic plants leading to eutrophication and its associated problems
    • Acids and / or alkalies cause damage to aquatic life and seriously hinder the operation of sewage treatment plants
    • Toxic substances like cyanides, sulphides, acetylene, alcohol, etc damage aquatic life, adversely affect treatment processes and endanger safety of workers
    • Colour producing substances are aesthetically objectionable
    • Oil, grease and other floating substances cause receiving streams to appear unsightly in addition to interfering with self-purification capacity of streams
  • Land
    • Industrial wastewater containing heavy metals when disposed on land has an adverse effect on plant growth and leads to accumulation in the food chain
    • Industrial wastes with high BOD and COD has an adverse effect on soil health by causing immobilization of plant nutrients
    • Direct use of industrial waste for irrigation less yield and decreased soil microbial activity
    • Indiscriminate disposal of industrial effluents may cause soil to develop anaerobic conditions and disrupt the physicochemical properties of soil
    • Disposal of industrial effluents on land may lead to problems like salinity, alkalinity and or toxicity
    • Metals present in industrial wastewater affect the growth and metabolism of plants irrigated by such water.
    • Reduction in soil fertility and crop yield
  • Human health 
    •  Industrial wastewater contains several toxic organic and inorganic substances that harm human health causing deformed limbs, birth defects, carcinogenic, mutagenic and teratogenic effects
    • The discharge of metals from industrial wastes is listed below:
      • High concentrations of Aluminum (Al) can lead to memory damage and convulsions. It is also linked to Alzheimers disease
      • Cadmium (Cd) is carcinogenic, embryotoxic, teratogenic and mutagenic. It might cause hyperglycemia, reduced immunopotency and anemia as it interferes with iron metabolism. Cd in the body also causes damage to kidney and liver while also causing deformation of bone structures.
      • Hexavalent chromium (Cr(VI)) is extremely toxic and has toxicity equivalent to cyanides. It causes skin ulcer, convulsions, kidney and liver damage. It causes genetic damage to cells in mammals and intensive exposure to chromium compounds causes lung cancer in human beings.
      • High concentration of Iron leads to production of free radicals which are responsible for degenerative diseases and ageing.
      • Lead accumulates in kidney, liver, bone and brain leading to encephalopathy in children
      • Mercury causes brain damage, heart, lung and kidney disease in humans. At very low concentrations it can permanently damage human nervous system. Methyl mercury (MeHg+ or CH3Hg+) is an organometallic cation is toxic and persistent. It crosses the placental barriers and leads to foetal brain damage
      • High exposure to Nickel (Ni) can lead to cancer
      • Excessive concentrations of Zinc can lead to muscular pain and intestinal haemorrage.
      • High concentrations of fluoride causes dental and skeletal fluorosis, deformation of ligaments and bending of spinal cord.
      • High concentrations of nitrate can cause methemoglobinemia in infants and cancer.
      • High concentration of Potassium nervous and digestive disorders, kidney, heart disease, coronary artery disease, hypertension, diabetes, pre existing hyperkalemia. Infants may experience renal reserve and immature kidney function.
      • Excessive sulphate concentration may cause laxative effect and affect the alimentary canal

Wednesday, January 18, 2017



Q1. List the effects of industrial waste on human health
Q2. What are the characteristics of industrial wastewater


 Q1. Draw the manufacturing process of a pulp & paper industry with the sources and characteristics of the   wastewater generated
 Q2. Describe the wastewater characteristics of wastewater from a cement industry


Q1. Describe the dispersion of air pollutants
Q2. List the effects of air pollutants on human health


Q1. Draw and label the various equipment used to control SPM
Q2. Describe briefly gas control by adsorption


Q1. List the objectives and capabilities of EIA
Q2. Describe briefly the issues involved in rehabilitation of affected people due to a development project

Characteristics of Industrial wastes

Characteristics of industrial wastes

The characteristics of industrial wastes vary greatly upon
  • Type of industry
  • Manufacturing process adopted and
  • Raw materials used
Industrial pollutants may contain:
  • Conventional pollutants like
    • Biological Oxygen Demand (BOD)
    • Total Suspended Solids (TSS)
    • pH
    • Fecal coliforms
    • Fats, Oils and Grease (FOG)
  • Toxic pollutants like
    • Metals and metalloids (As, Cd, Cr, Cu, Pb, Hg, Ni, Ag, Z)
    • Toxic organics 
      • Volatile organics
        •  1,1,1-trichloroethane
        • Benzene
        • Ethylbenzene
        • Methylene chloride
        • Toluene
        • Trichloroethylene, etc
      • Pesticides
      • Polychlorinated biphenyls (PCB)
      • Semi-volatile organics
        • di-n-butyl pthalate
        • Naphthalene
        • p-chloro-m-cresol
        • Phenols, etc 
    • Non conventional pollutants like ammonia, phosphate, etc

Friday, January 6, 2017


Assignment questions

Types of Industries

Characteristics of Industrial wastes

Effects of industrial wastes on streams, land and human health

Environmental legislation related to industrial effluents and hazardous wastes

Self-purification of water bodies

Streeter-phelps equation

Manufacturing processes & wastewater characteristics and treatment of wastes from

Sources, classification and effects of air pollutants

Meteorology of air pollutants

Wind rose diagrams

Lapse rates, atmospheric stability and dispersion of air pollutants

Stack height calculation

Ambient air quality monitoring

Stack sampling and analysis of air pollutants

Air quality standards

Methods of air pollution control - zoning, source correction,

Control of SPM by equipment (gravitation, centrifugation, filtration, scrubbing, electrostatic precipitation)

Selection of proper equipment

Gaseous pollutant control by absorption, condensation and combustion

Need for EIA

Objectives of EIA

Capabilities and limitations of EIA

Methods of EIA

Baseline data collection required for EIA

Evaluation of Impacts

Prediction of impacts

Preparation of EMP

Preparation of EIAs of road project, industry and dam

Issues related to rehabilitation and resettlement of displaced communities


Types of Industries

An industry broadly refers to any form of economic activity that  has the purpose of making money.
Based on the water (prevention and control of pollution) act, 1974 and the air (prevention and control of pollution) act, 1981 the CPCB has classified the industrial sectors under red, orange, green and white categories.
This categorisation is based on the relative pollution potential of industrial wastes while the grouping of industries is based on :
  • use of raw materials
  • manufacturing process adopted and
  • pollutants likely to be generated
Based on relative pollution index, the industrial sectors have been classified as follows:
Industries having pollution index score:
  • 60 and above are cartegorised as RED
  • 41 to 59 are cartegorised as ORANGE
  • 21 to 40 are cartegorised as GREEN
  • including and upto 20 are cartegorised as WHITE
 Pollution index is a function of:
  • Air pollutants
  • Water pollutants
  • Hazardous wastes generated and
  • Consumption of resources
The Pollution Index (PI) of any industrial sector varies from 0 to 100 with increasing value indicating increasing degree of pollution load.
The following industries are classified under RED category:
  • Isolated storage of hazardous chemicals
  • Integrated automobile manufacturing facilities
  • Industries engaged in recycling / reprocessing / recovery / reuse of hazardous waste (Eg: spent cleared metal catalyst containing Cu, Zn, Ni, Cd, As, V, Co)
  • Manufacture of lubricating oils, grease and petroleum based products)
  • Industrial Carbon including electrodes and graphite blocks, activated carbon, carbon black
  • Lead acid battery manufacturing
  • Phosphate rock processing plant
  • Power generation plant (Except wind and solar renewable power plants and mini hydel power plant of capacity < 25MW)
  • Processes involving chlorinated hydrocarbons
  • Fibre glass production and processing (excluding moulding) 
  • Manufacture and bulk storage of fire crackers
  • Industries engaged in dismantling and recycling components of waste electrical and electronic assemblies
  • Milk and dairy processes (integrated)
  • Pulp and paper industries
  • Petrochemical industry
  • Manufacture of explosives, detonators and fuses
  • Manufacture of paints, varnishes, pigments and intermediates
  • Manufacture of organic chemicals
  • Asbestos and asbestos based industries
  • Cement industry
  • Mining and ore benefaction
  • Nuclear power plant
  • Textile processing
  • Chlor Alkali
  • Ship breaking industry
  • Oil and gas extraction
  • Process involving metal surface treatment
  • Tanneries
  • Thermal power plant
  • Slaughter houses
  • Aluminium smelter or copper smelter or zinc smelter
  • Processing of Iron and steel from ore
  • Pharmaceutical industry
  • Distillery
 The following industries are classified under ORANGE category:
  • Dismantling of wagons and coaches
  • Bakery and confectionery units with capacity > 1 TPD
  • Manufacture of coated electrodes
  • CD, floppy, cassette and reel manufacturing
  • Food processing industries
  • Jute processing without dyeing
  • Manufacture of silica gel
  • Manufacture of toothpaste, toothpowder, talcum powder and other cosmetic items
  • Etching of glass sheet using hydrofluoric acid
  • Saree printing by wooden blocks
  • Manufacture of synthetic detergents and soaps
  • Manufacture of thermometer
  • Cotton spinning and weaving 
  • Dry mechanical processes like alimirah and grill manufacturing
  • Aluminium and copper extraction from scrap using oil fired furnace
  • Automobile servicing, repairing and painting
  • Manufacture of ayurvedic and homeopathic medicines
  • Building of construction project > 20,000 Sq. m built-up area
  • Brick fields, ceramics and refractories
  • Coal washeries
  • Dairy and dairy products (small scale)
  • D.G. set of capacity between 1 MVA and 5 MVA
  • Dry coal and mineral processing involving ore sintering, pelletisation, grinding and pulverisation
  • Fermentation industry including manufacture of yeast, beer and distillation of extra neutral alcohol
  • Ferrous and non-ferrous metal extraction involving different furnaces through melting, refining, reprocessing, casting and alloy-making
  •  Fertilizer formulation / granulation / blending only
  • Fish, poultry and cattle feed
  • Fish processing and packaging (excluding chilling)
  • Forging of ferrous and non-ferrous metals using oil & gas fired furnaces
  • Formulation of camphor and naphthalene tablets from respective powders
  • Glass, ceramics, earthen potteries and tile manufacturing using oil and gas fired kilns and coating on glasses using cerium fluoride and magnesium fluoride
  • Gravure printing, digital printing on flex vinyl
  • Hotels with > 20 rooms but less than 100 rooms
  • Ice cream manufacturing units
  • Industries engaged in recycling / reprocessing / recovery / reuse of paint and ink sludge / residues
  • Industries engaged in recycling / reprocessing / recovery / reuse of Brass, Copper dross, copper oxide mill scale, copper reverts, cake & residues, waste copper and copper alloys in dispersable form, slug from copper processing for further processing or refining, insulated copper wire, jelly filled copper cables, zinc dross, zinc slag, zinc alloy residues in dispersable form
  • Industry or processes involving foundry operations
  • Lime manufacturing
  • Manufacturing liquid floor cleaner (black phenyl, liquid soap, glycerol mono-stearate)
  • Manufacturing of glass
  • Manufacturing of iodised salt from crude salt
  • Manufacturing mirrors from sheet glass
  • Manufacturing mosquito repellant coil
  • Manufacturing starch
  • Mechanised laundry using oil fired boiler
  • Modular wooden furniture from particle board
  • New highway construction project
  • Non alcoholic beverage & bottling of alcoholic and non alcoholic products
  • Paint & varnish (mixing and blending only)
  • Plyboard manufacturing with oil fired boiler
  • IMFL by blending
  • Manufacturing printing ink
  • Printing press
  • Reprocessing of used plastic including PVC
  • Rolling mill (Hot and cold)
  • Spray painting, paint baking and paint shipping
  • Manufacturing steel and steel products
  • Stone crushers
  • Surgical and medical products
  • Teflon based productscycling / reprocessing / recovery / reuse of 
  • Manufacture and repair of transformers
  • Vulcanisation of tyres and tubes
  • Manufacturing of vegetable oil and hydrogenated oils including solvent extraction and refinery
  • Wire drawing and wire netting
  • Dry cell battery and assembling and charging of a lead acid battery battery on a micro scale
  • Synthetic resins
  • Cashew nut and coffee seed processing
  • Parboiled rice mills
  • Foam manufacturing
  • Industries engaged in recycling / reprocessing / recovery and reuse of used oil and waste oil
  • Producer gas plant using up drift coal gasification
Following industries are classified under GREEN category
  • Aluminium utensils from processing only
  • Ayurvedic and homeopathic medicines (without boiler)
  • Bakery / Confectionery / sweet products with production capacity < 1 TPD
  • Biomass briquettes without using toxic hazardous products
  • Blending of resins and powder additives by physical mixing
  • Cardboard or corrugated box and paper products without using boilers
  • Manufacture of wooden furniture by carpentry
  • Cement products without use of asbestos / boilers or steam curing
  • Ceramic colour manufacturing by mixing and blending only
  • Chilling plant, cold storage and ice making
  • Small scale spinning and weaving of cotton
  • Dal mills
  • Digital printing on PVC cloth
  • Flour mills (dry process)
  • Glue from starch
  • Gold and silver smithy
  • Lubricating oil, grease or petroleum based products (by blending at normal temperature)
  • Manufacture of pasted verneer
  • Manufacture of packing material from non-asbestos fibre
  • Power looms without dye and washing
  • Ready mix concrete
  • Reprocessing waste cotton
  • Saw mills
  • Soap manufacturing without steam
  • Spice grinding
  • Steel furniture without spray painting
  • Distilled water without boiler
  • Hotels with 20 rooms without boiler
  • Mineralised water
  •  Manufacturing tamarind powder
  • Cutting, sizing and polishing of marble stone
  • Export, transport and disposal of flyash
  • Seasoning of wood in steam heated chambers
  • Formulation of synthetic detergents
  • Processing of tea with boiler
Following industries are classified under WHITE category
  • Assembling, repair and servicing of air conditioners and air coolers
  • Assembly of bicycles, baby carriages and other small non motorizing vehicles
  • Hydraulic press of waste paper
  • Manufacture of biopesticides and biofertilizers
  • Blending and packaging of tea
  • Manufacture of chalk from plaster of paris without boilers
  • Manufacture of cotton and woolen hosiers (Dry process only)
  • Diesel pump repairing and servicing (Complete dry mechanical process)
  • Electric lamp and CFL manufacturing by assembly only
  • Assembly electrical and electronic items (Completely dry process)
  • Engineering and fabrication units (Dry process only)
  • Flavored beetel nut production / grinding (completely dry mechanical operation)
  • Manufacture of fly ash bricks
  • Making glass ampules and vials from glass tubes
  • Glass putty and sealant by mixing machine
  • Decorticating groundnut
  • Handloom carpet weaving without dyeing and bleaching
  • Manufacture of coir items from coconut husk
  • Manufacture of shoe brush and wire brush
  • Manufacture of organic manure by manual mixing
  • Manufacture of paper pins and clips
  • Repair of electric motors and generators by dry mechanical process
  • Manufacture of cotton and plastic ropes
  • Manufacture of scientific and mathematical instruments
  • Manufacture of solar module for non conventional energy apparatus
  • Power generation using photovoltaic cells, wind power and mini hydel power < 250MW
  • Assembly of surgical and medical products