chapter ii water pollution

Environmental Science and Engineering-GE 2021

Unit-IIEnvironmental Pollution

Dr VNagarajan

UNIT II ENVIRONMENTAL POLLUTION

Definition ndash causes effects and control measures of (a) Air pollution (b) Water pollution (c) Soil pollution (d) Marine pollution (e) Noise pollution (f) Thermal pollution (g) Nuclear hazards Soil waste management causes effects and control measures of municipal solid wastes ndash role of an individual in prevention of pollution ndash pollution case studies ndash disaster management floodsearthquake cyclone and landslides

Field study of local polluted site ndash Urban Rural Industrial Agricultural

WATER POLLUTIONbull Water pollution can be defined as alteration in physical chemical or

biological characteristics of water making it unsuitable for designated use in its natural state

1 Physical Characteristics (ie respond to the senses of sight touch taste or smell )a Suspended Solids

bull SS consists of Inorganic solids (clay silt and other soil constituents) (OR) Organic (plant fibres bacteria algae cells etc) (OR) immiscible liquids (oil and grease)

bull Suspended matter has the following impacts on water qualityo Aesthetically displeasingo Biological degradation of organic matter may result in the form of

harmful byproductso It provides adsorption for harmful chemical or biological organisms

which may affect adversely the flora and fauna of the streamo Settled matter at the bottom suffocate the organisms inhibiting the

bottom of aquatic habitatso Affect the photosynthesis (light) and results in loss of food

production

WATER POLLUTION2 Turbidity ( Desirable = 5 Permissible = 10 NTU)

bull It is a measure of the extent to which light is either absorbed or scattered by suspended matter in water

bull Contributed bybull Erosion of colloidal material such as clay silt rock fragments and metal

oxides in soil contribute turbidity in surface waterbull Household and industrial wastewaterbull Stable colloids such as soaps detergents and emulsifying agents

bull Turbidity has the following impacts on water qualityo Causes undesirable taste odor and harmful to biological organisms

due to colloidal matter presenceo Impart brown or other color and interfere photosynthesiso Results in sedimentary deposits affecting flora and fauna in stream

process

3 Colour ( Desirable = 5 Permissible = 25 HU) bull Pure water is colourlessbull Apparent colour (SS) True colour (DS- remain even after removal of SS) bull Tanning humic acid- yellowish brown Iron oxides- reddish manganese

oxide- brown or blackish color

WATER POLLUTIONbull It has the following impacts on water quality

o Not aesthetically acceptableo High coloured water unsuitable for industrial use

4 Taste and Odour (agreeable and unobjectionable)bull Many substances (minerals metals and salts from soil products from

biological reactions and constituents of wastewater) with which water comes into contact in nature or during human use may impart perceptible taste and odour

bull It has the following impacts on water qualityo Not acceptable by consumers

5 Temperaturebull Most important parameter for natural surface water systemsbull It has the following impacts on water quality

o Affects biological activity(cold-slow hot-increases)o Affects DO level in water as T is a function of DOo Toxicity of chemical pollutants increases as T increaseso Viscosity of water increases with T

WATER POLLUTION1 Chemical characteristicsbull Universal solvent and chemical parameters are related to the solvent

capabilities of waterbull TDS alkalinity hardness fluorides metals organics and nutrients are main

chemical parametersbull TDS as DS ( Desirable = 500 mgl Permissible = 2000 mgl)

o Constitutes mainly chlorides ( Desirable = 250 Permissible = 1000 mgl) and sulphates ( Desirable = 200 Permissible = 400 mgl)

o Readily dissoluble salts are sometimes added to reduce its tendency to dissolve pipes and plumbing

o Impacts on water quality areo Results in aesthetically displeasing color odor and tasteo Some chemical salts are toxic

bull Alkalinity ( Desirable = 200 mgl Permissible = 600 mgl) o Measure of ability of water to neutralize acidso Most common constituents are bicarbonates carbonates and

hydroxideso Impacts on water quality are

o Imparts bitter tasteo Corrosion of pipes

WATER POLLUTIONbull Total Hardness (as CaCO₃ - Desirable = 300 mgl Permissible = 600 mgl)

o Property of water on account of which it consumes soap without forming lather freely

o Temporary (Carbonate) H ndash due to the presence of carbonates and bicarbonates of Ca

o Permanent (Non Carbonate) H ndash due to the presence of chlorides sulphates and nitrates of Ca and Mg

o Impacts on water quality areo Scaling problems in Boilero Beneficial to the human cardiovascular systems

bull Fluoride(Desirable = 10 mgl Permissible = 15 mgl) o Geographic regionso Impacts on water quality are

o F in desirable limit help to prevent dental cavities in children o High F causes Fluorosiso High F also results in bone fluorosis and skeleton abnormalities

bull Metals o Sources dissolution from natural deposits and discharge of domestic industrial

or agricultural wastewatero Heavy metals

WATER POLLUTIONo Impacts on water quality are

o Undesirable and even toxic in health aspects o High conc of metals affects plants and animals also

bull Organicso From natural sources or result from human activitieso Biodegradable (fats starches proteins alcohols acids aldehydes and

esters) and Non Biodegradable organics (organic pesticides hydrocarbons ie benzene products)

o Impacts of Biodegradable organics on water quality areo Causes undesirable odour colour and tasteo Depletes DO level resulting anaerobic conditions

o Impacts of Non-Biodegradable organics on water quality areo Pesticides ( Desirable = Absent Permissible =0001 mgl)are toxic

and cause problem in food chain systemso Pesticides contaminates surface water streams alsoo Damage caused mostly irreversible

bull Nutrients(Carbon Nitrogen and Phosphorous)o Essential element for plant animal and aquatic species growth and

reproduction activities


o Nitrate (as NO₃ Desirable = 45 mgl Permissible = 100 mgl) poisoning causes serious health problem to animal and human beings

o High conc of phosphate is threat to water quality

3 Biological characteristicsbull Pathogens( capable of infecting or transmitting disease to human)bull Water borne pathogens are bacteria viruses protozoa helminths or

parasite wormsbull High conc of E-coli indicates faeceal contaminationbull The methods to estimate the bacterial quality of water are

Standard Plate Count Test Most Probable Number Membrane Filter Technique

WATER POLLUTION

Causes Sources of Water Pollution

bull Point sources are specific sites (single location) near water which directly discharge effluents into them Major point sources of water pollution are industries power plants underground coal mines offshore oil wells etc

bull The discharge from non-point sources is not at any particular site rather these sources are scattered which individually or collectively pollute water

bull Surface run-off from agricultural fields overflowing small drains rain water sweeping roads and fields atmospheric deposition etc are the non-point sources of water pollution

WATER POLLUTION Ground water pollution bull Ground water forms about 62 of the total water available on planet earth and is

about 30 times more than surface water (streams lakes and estuaries)bull Ground water seems to be less prone to pollution as the soil mantle through which

water passes helps to retain various contaminants due to its cation exchange capacitybull However potential sources of ground water pollution are Septic tanks industry

(textile chemical tanneries) deep well injection mining etcbull Ground water pollution with arsenic fluoride and nitrate are posing serious health

hazards

Surface water pollutionbull The major sources of surface water pollution are

1 Sewage Pouring the drains and sewers in fresh water bodies causes water pollution The problem is severe in cities

2 Industrial effluents Industrial wastes containing toxic chemicals acids alkalis metallic salts phenols cyanides ammonia radioactive substances etc are sources of water pollution They also cause thermal (heat) pollution of water

3 Synthetic detergents Synthetic detergents used in washing and cleaning produce foam and pollute water

WATER POLLUTION4 Agrochemicals Agrochemicals like fertilizers (containing nitrates and phosphates)

and pesticides (insecticides fungicides herbicides etc) washed by rain-water and surface run-off pollute water

5 Oil Oil spillage into sea-water during drilling and shipment pollute it6 Waste heat Waste heat from industrial discharges increases the temperature of

water bodies and affects distribution and survival of sensitive species

Effects of Water Pollutionbull Toxic Compounds

o Pollutants such as heavy metals pesticides cyanides and many other organic and inorganic compounds are harmful to aquatic organisms

o The demand of DO increases with addition of biodegradable organic matter which is expressed as biological oxygen demand (BOD)

o BOD is defined as the amount of DO required to aerobically decompose biodegradable organic matter of a given volume of water over a period of 5 days at 20degC

o More BOD values of any water sample are associated with poor water quality

WATER POLLUTIONo The non-biodegradable toxic compounds biomagnify in the food chain and cause

toxic effects at various levels of food chain o Some of these substances like pesticides methyl mercury etc move into the bodies

of organisms from the medium in which these organisms live o Substances like DDT are not water soluble and have affinity for body lipids These

substances tend to accumulate in the organismrsquos body This process is called bioaccumulation

o The concentration of these toxic substances builds up at successive levels of food chain This process is called biomagnification

o Following is the example of biomagnification of DDT in aquatic food chain

WATER POLLUTIONHeavy Metal toxicity

o Some heavy metals like lead mercury and cadmium cause various types of diseases

o Mercury dumped into water is transformed into water soluble methyl mercury by bacterial action

o Methyl mercury accumulates in fish In 1953 people in Japan suffered from numbness of body parts vision and hearing problems and abnormal mental behaviour This disease called Minamata disease occurred due to consumption of methyl mercury contaminated fish caught from Minamata bay in Japan The disease claimed 50 lives and permanently paralysed over 700 persons

o Pollution by another heavy metal cadmium had caused the disease called Itai-itai in the people of Japan The disease was caused by cadmium contaminated rice The rice fields were irrigated with effluents of zinc smelters and drainage water from mines In this disease bones liver kidney lungs pancreas and thyroid are affected

o Arsenic pollution of ground water in Bangladesh and West Bengal is causing various types of abnormalities

o Nitrate when present in excess in drinking water causes blue baby syndrome or methaemoglobinemia The disease develops when a part of haemoglobin is converted into non-functional oxidized form

WATER POLLUTIONControl of Pollution

I Control of Pollution from Point sources It is easy to reduce water pollution from point sources by legislation For controlling water pollution from point sources treatment of wastewater is

essential before being discharged Parameters which are considered for reduction in such water are Total

solids biological oxygen demand (BOD) chemical oxygen demand (COD) nitrates and phosphates oil and grease toxic metals etc

Wastewater should be properly treated by primary and secondary treatments to reduce the BOD COD levels up to the permissible levels for discharge

Advanced treatment for removal of nitrates and phosphates will prevent eutrophication

Before the discharge of wastewater it should be disinfected to kill the disease-causing organisms like bacteria

Proper chlorination should be done to prevent the formation of chlorinated hydrocarbons or disinfection should be done by ozone or ultraviolet radiations


II Control of Pollution from Non-Point sourcesHowever due to absence of defined strategies it becomes difficult to prevent water

pollution from non-point sources

The following methods have to be followed in reducing water pollution from non-point sources

i Judicious use of agrochemicals like pesticides and fertilizers which will reduce their surface run-off and leaching Avoid use of these on sloped lands

ii Use of nitrogen fixing plants to supplement the use of fertilizers

iii Adopting integrated pest management to reduce reliance on pesticides

iv Prevent run-off of manure Divert such run-off to basin for settlement The nutrient rich water can be used as fertilizer in the fields

v Separate drainage of sewage and rain water should be provided to prevent overflow of sewage with rainwater

vi Planting trees would reduce pollution by sediments and will also prevent soil erosion


II Treatment of water and wastewater


Treatment of water and wastewater Drinking water supplied to the user should conform to the

IS10500 1991

Domestic wastewater sewage effluent discharged after treatment conform the norms prescribed by the SPCB

Industrial effluent after treatment shall comply with the discharge norms prescribed by the CPCBSPCB

SlNo Parameter Tolerance Limit

1 pH 55-90

2 TSS 30 mgl

3 BOD 20 mgl


Treatment of water and wastewaterThe types of treatment required for different sources are given in the following table


Treatment of water and wastewaterClassification of Treatment MethodsThe individual treatment methods are usually classified as

1048766 Physical unit operations

1048766 Chemical unit processes

1048766 Biological unit processes

Physical Unit Operations Treatment methods in which the application of physical forces predominates are known as physical unit operations

Most of these methods are based on physical forces eg screening mixing flocculation sedimentation flotation and filtration

Chemical Unit Processes Treatment methods in which removal or conversion or contaminant is brought by addition of chemicals or by other chemical reaction are known as chemical unit processes for example pH correction precipitation gas transfer adsorption and disinfection


Classification of Treatment Methods

Biological Unit Processes Treatment methods in which the removal of contaminants is brought about by biological activity are known as biological unit processes

This is primarily used to remove biodegradable organic substances from the wastewater either in colloidal or dissolved form

In the biological unit process organic matter is converted into gases that can escape to the atmosphere and into bacterial cells which can be removed by settling

Biological treatment is also used for nitrogen removal and for phosphorous and sulphate removal from the wastewater

The different treatment methods used in wastewater treatment plant are classified in three different categories as

bull Primary Treatment Refers to physical unit operations

bull Secondary Treatment Refers to chemical and biological unit processes

bull Tertiary Treatment Refers to combination of all three ie physical unit operations and chemical or biological unit processes

used after secondary treatment


Treatment of water and wastewaterThe layout of conventional water treatment plant is as follows


Treatment of water and wastewaterThe typical functions of each unit operations are given in the following table


Treatment SystemsPrimary Treatment (I) Screen- It is the first unit operation in wastewater treatment plant This is

used to remove larger particles of floating and suspended matter by coarse screening

The screen composed of parallel bars or rods is called a rack The screens are used to protect pumps valves pipelines and other

appurtenances from damage or clogging by rags and large objects


Treatment SystemsPrimary Treatment (ii) Equalization Tank To facilitate maintenance of uniform flow rate in the

treatment units for dampening the fluctuation in pollutant concentration in the

incoming wastewater to avoid shock loading on the treatment system


Treatment SystemsPrimary Treatment (II) Sedimentation Tank Settling Tank Clarifier Wastewater containing mainly lightweight organic matter is settled in

the primary sedimentation tank Rectangular PST


Circular PST Clarifier


Treatment SystemsSecondary Treatment Aeration systemBiological Treatment

Conventional biological treatment of wastewater under aerobic conditions includes activated sludge process (ASP) and Secondary settling tank clarifier

The ASP is developed in England in 1914 The activated sludge process consists of an aeration tank where

organic matter is stabilized by the action of bacteria under aeration and a secondary sedimentation tank (SST) is used where the biological cell mass is separated from the effluent and the settle sludge is recycled partly to the aeration tank

Recycling is necessary for activated sludge process The aeration conditions are achieved by the use of diffused or

mechanical aeration




Treatment SystemsAeration in ASPAeration units can be classified as1) Diffuser Air Units2) Mechanical Aeration Units (Floating and Fixed TypeAerators)3) Combined Mechanical and diffused air units


Treatment SystemsAeration in ASPAeration units can be classified as2) Mechanical Aeration Units

Oxidation Pond Low cost natural treatment system Biochemical oxidation of organic is done by bacteria Oxygen for bacteria is provided by atmospheric wind and

algae present in the pond Algae utilize the nutrients and CO2 (provided by the

bacteria) for photosynthesis and supplements the bacteria with oxygen (a product of photosynthesis)

This symbiotic relationship between the algae and bacteria is a major feature of OP

Depth of the OP must be minimal( lt 05m) to keep entire pond area in aerobic condition

If depth is more mechanical aerators can be provided( Aerated lagoon)

Constructed Wetlands(FWS and SF)

Advanced Treatment Technologies Filtration Types (remove 01 micron or larger particle)

Normal Dead End Rough screen sand filters multimedia filters Backwash Disposal of media and economy are the concerns

Cross flow filtration Rejected contaminants are continuously carried away form the

membrane surface Micro filtration ( 01 to 1 micron diameter) Ultra filtration - 20 to 500 angstroms dia - MWCO-5000 to 50000 excluded as rejects - removal of larger and colloidal species Nanofiltration (Loose RO) - 1 nanometer dia or 1 angstroms dia - Allows monovalent ions and rejects divalent and trivalent ions

Advanced Treatment Technologies Reverse Osmosis

MWCO-up to 200 excluded as rejects Industrial use Water purification and wastewater treatment

Advanced Treatment Technologies Filtration capabilities and application of RO depends upon several factors

Chemical composition of the influent Fluid Temperature Operating pressure Level of TDS hardness (scaling) organics (fouling) in the influent

Nature of Semipermeable materials Cellulose Acetate (CA)

Chlorine tolerant Non bacteria resistant Operating pH range 60 ndash 80 Good water production rate

CTA bull Chlorine tolerantbull Resistant to most bacteria bull Operating pH range 40 ndash 80bull Good water production ratebull Chlorinated water supply will extend membrane life

Thin Film Composite (TFC) bull Chlorine sensitive chlorine must be removed in the feed watereffluent

bull Bacteria resistant

bull Operating pH range 30 ndash 110

bull Highest water production rate and also highest salt rejection characteristics

bull Longest membrane life

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UNIT II ENVIRONMENTAL POLLUTION

Definition ndash causes effects and control measures of (a) Air pollution (b) Water pollution (c) Soil pollution (d) Marine pollution (e) Noise pollution (f) Thermal pollution (g) Nuclear hazards Soil waste management causes effects and control measures of municipal solid wastes ndash role of an individual in prevention of pollution ndash pollution case studies ndash disaster management floodsearthquake cyclone and landslides

Field study of local polluted site ndash Urban Rural Industrial Agricultural









production







process











































WATER POLLUTION









hazards

















































IS10500 1991




1 pH 55-90

2 TSS 30 mgl

3 BOD 20 mgl














































mechanical aeration






























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production







process











































WATER POLLUTION









hazards

















































IS10500 1991




1 pH 55-90

2 TSS 30 mgl

3 BOD 20 mgl














































mechanical aeration






























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process











































WATER POLLUTION









hazards

















































IS10500 1991




1 pH 55-90

2 TSS 30 mgl

3 BOD 20 mgl














































mechanical aeration






























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WATER POLLUTION









hazards

















































IS10500 1991




1 pH 55-90

2 TSS 30 mgl

3 BOD 20 mgl














































mechanical aeration






























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hazards

















































IS10500 1991




1 pH 55-90

2 TSS 30 mgl

3 BOD 20 mgl














































mechanical aeration






























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IS10500 1991




1 pH 55-90

2 TSS 30 mgl

3 BOD 20 mgl














































mechanical aeration






























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mechanical aeration






























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chapter ii water pollution

Documents