Water pollution 02.pptx..................

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1. Water pollution Water Pollution; Water  pollution can be defined as alteration in physical , chemical , or biological characteristics of water which makes unsuitable for use. Sources of water pollution. Major point source of water pollution are industries, power plants , under ground coal mines . The discharge from non-point sources is surface runoff from agricultural fields, overflowing small drains, rain water sweeping roads and fields atmospheric deposition etc. 2.  Ground Water Pollution There  are a number of potential sources of ground water pollution. Septic tanks, industry, deep well injection , mining etc. are mainly responsible for groud water pollution. Ground water pollution with arsenic, fluoride, nitrate are posing serious health hazard. Surface water pollution The major sources of surface water pollution are: Sewage : Kitchen waste and toilet waste when discharges in water bodies causes water pollutions. Industrial Effluents : Industrial wastes containing toxic chemicals , acids, alkalis, metallic salts , phenols , radio active substances etc are sources of water pollutions. Detergents : Detergents containing phosphates pollute water.

2. Surface water Pollution Agrochemicals  : Agrochemicals like fertilizers (containing nitrate and phosphates) and pesticides (insecticides, herbicides, fungicides etc ) washed by rain water and surface runoff pollute water. Oil : Oil spillage into sea water during drilling and shipment pollute it. Waste heat : Waste heat from industrial discharges increases temperature of water bodies and affects distribution and survival of sensitive species. 4.  Effects of water  pollution Oxygen demanding wastes : Organic matter which reaches water bodies is decomposed by micro organisms present in water by using oxygen dissolved in water. As a result depletion of oxygen takes place which become harmful to animals especially fish population . Oxygen demanding wastes are two types Biochemical Oxygen demand (BOD) : The amount of oxygen required by microorganisms to oxidize organic matter in presence of oxygen is known as BOD. BOD5 : BOD5 is the total amount of oxygen consumed by microorganisms during the first 5 days of biodegradation at 20oC. Chemical Oxygen demand : The amount of oxygen required for oxidation of organic matter using strong chemical oxidant such as K2Cr2O7 is known as COD. 5.  Effects of water  pollution Nitrogen And Phosphorus Compounds Addition of compounds containing Nitrogen and phosphorus helps in the growth of algae and other plants which when die and decay consume oxygen of water. Pathogens sewage contains pathogenic and non pathogenic micro organism and virus. Water-borne diseases like cholera, dysentery, typhoid, jaundice etc are spread by water contaminated with sewage. Toxic Compounds Pollutants such as heavy metals, pesticides, many other organic and inorganic compounds are harmful to aquatic organisms . The non-biodegradable toxic compounds bio magnify in the food chain and cause toxic effects at various levels of food chain.

3. .  Effects of water  pollution Bioaccumulation : Toxic substances such as heavy metals and pesticides are present in soluble and suspended form in water, soil or food. These substances move into the bodies of organisms from the medium in which these organisms' live. These substances tend to accumulate in the organism’s body. This process is called bioaccumulation. Biomagnification : The concentration of toxic substances increases at successive higher tropic levels of a food chain. This process is known as biomagnification. Example: In aquatic ecosystem phytoplankton and bacteria consume toxic elements which may be consumed by the next tropic level such as such as small fish or zooplankton. When these organisms are consumed by the next tropic level, these toxic substances are further concentrated and it goes onto successive tropic levels. Thus , there is a magnification of toxic substances in higher tropic levels. 7.  Biomagnification The biomagnification of  DDT in aquatic food chain: Birds 10.00 Needle fish 1.0 Minnows 0.1 Zooplankton 0.01 Water 0.000001 8.  Pollution case studies Toxic  substances like heavy metals lead, cadmium and mercury causes various types of diseases.  ‘Minamata’ diseases occur due to consumption of methyl mercury contaminated fish cut from Minamata bay in Japan. Many people suffered from numbers of body parts, vision and hearing problems and abnormal mental behaviour .  Another disease called ‘ Itai-Itai ’ caused by cadmium contaminated rice . In this disease bones , liver, kidney, lungs, thyroid are affected. • Excess of fluoride in drinking water causes defects in teeth and bones called fluorosis. • Excess nitrate present in drinking water causes methaemoglobinemia . • Arsenic pollution of ground water in Bangladesh and West Bengal causes various types of diseases.

4. Eutrophication Eutrophication is a  natural process that occurs to all lakes over time as an enrichment of plant nutrients such as nitrogen in the form of nitrate (NO3) and phosphorus in the form of phosphate (PO4) in water. Types of Eutrophication i ) Natural Eutrophication : The proceess of lake aging characterised by nutrient enrichment is called natural eutrophication. ii) Cultural Eutrophication : This process is occurred by human activities which are responsible for addition of 80% nitrogen and 75% phosphorus to lake and streams 10.  Causes of Eutrophication    Natural run–off of nutrients from the soil and the weathering of rocks  Runoff from erosion  Runoff of manure from farms containing nitrates, phosphates and ammonia  Discharge of detergents containing phosphates  Discharge of partially treated or untreated sewage containing nitrates and phosphates Effects of Eutrophication  Increase in plant and animal biomass  Increase in turbidity of water  Depletion of concentration of dissolved oxygen  Increase in bacterial population which uses more and more oxygen for respiration 11.  Control of Eutrophication    Sewage and detergent wastes should be discharged in lakes.  Algae blooms should be removed  Algae growth should be controlled  Recycling of nutrients can be checked through harvest 12.  Control of water  pollution 1. Judicious use of agrochemicals like pesticides and fertilizers which will reduce their surface-runoff and leaching. 2. Use of nitrogen fixing plants to supplement the use of fertilizers. 3. Planting trees would reduce pollution by sediments and will also prevent soil erosion . 4. Prevent run-off of manure. 5. For controlling water pollution treatment of waste water is essential before discharging . 6. Waste water should be properly treated by primary and secondary treatments to reduce BOD, COD levels up to the permissible levels for discharge.

5. Waste water treatment The  aim of waste water treatment is removing the pollutants from water before discharging it into a water body . After the treatment of wastewater it can be reused or discharged into a receiving waterbody. The wastewater treatment processes are usually classified as 1. Primary treatment 2. Secondary treatment 3. Tertiary treatment 14.  Flow chart of  waste water treatment Waste Water influent Screening Grit removal Aeration Sedimentation Equalization & Neutralization PrimaryTreatment 15.  Waste Water Treatment Primary  clarifier Activated sludge/Aerated lagoon/Trickling filter Aerobic or anaerobic process Secondary clarifier Coagulation Carbon adsorption Secondarytreatment Chemical oxidation/disinfection Ion exchange Discharge to water body Tertiarytreatment