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R AP/ECE Jhansirani.R AP/ECEDefinition : Definition 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. Jhansirani.R AP/ECETypes and Sources of Water Pollution: Types and Sources of Water Pollution Water is an essential commodity for survival. We need water for drinking, cooking, bathing, washing, irrigation and for industrial operations . Water has the property to dissolve many substances in it. Therefore it can easily get polluted. Pollution of water can be caused by Jhansirani.R AP/ECE Point sources Nonpoint sources Pg. 535Point sources: Point sources These are specified sites near water which directly discharge effluents into them Major point sources are: Industries Power plants Underground coal mines Offshore oil wells etc. Jhansirani.R AP/ECENon-point sources: Non-point sources The discharge from non-point sources is not at any particular site rather, these sources are scattered, which individually or collectively pollute water Ex: Surface run-off from agricultural fields Overflowing small drains Rain water sweeping roads & fields Atmospheric deposition etc., Jhansirani.R AP/ECEPoint and Nonpoint Sources: Point and Nonpoint Sources Jhansirani.R AP/ECE NONPOINT SOURCES Urban streets Suburban development Wastewater treatment plant Rural homes Cropland Factory Animal feedlot POINT SOURCESGround water pollution: Ground water pollution Ground water forms about 6.2% of the total water available on planet earth and is about 30 times more than surface water (i.e. streams, lakes and estuaries). Main responsible for ground water pollution is Septic tanks, Industry (textile, chemical, and tanneries), Deep well injection, Mining etc., Ground water pollution with arsenic, fluoride and nitrate are posing serious health hazards. Jhansirani.R AP/ECEGroundwater Pollution: Causes: Groundwater Pollution: Causes Jhansirani.R AP/ECE Coal strip mine runoff Pumping well Waste lagoon Accidental spills Groundwater flow Confined aquifer Discharge Leakage from faulty casing Hazardous waste injection well Pesticides Gasoline station Buried gasoline and solvent tank Sewer Cesspool septic tank De-icing road salt Unconfined freshwater aquifer Confined freshwater aquifer Water pumping well Landfill Fig. 20-11Surface water pollution: Surface water pollution The major sources of surface water pollution are: 1 . Sewage : Emptying drains & sewers 2. Industrial effluents : Toxic chemicals, acids, salts 3. Synthetic detergents : In washing & cleaning 4. Agrochemicals: Fertilizers, insecticides etc., 5. Oil : oil spill in sea water 6. Waste heat : from industrial discharge Jhansirani.R AP/ECESurface water pollution: causes: Surface water pollution: causes Jhansirani.R AP/ECEEffects of Water pollution: Effects of Water pollution Jhansirani.R AP/ECE Effects of various types of water pollutants: Bacteria, Viruses, Protozoa, Parasitic worms Oxygen demanding wastes Nitrogen and Phosphorus Compounds (Nutrients) Pathogens Toxic CompoundsOxygen demanding wastes: Oxygen demanding wastes Organic matter which reaches water bodies is decomposed by micro-organisms present in water. For this degradation oxygen dissolved in water is consumed. Dissolved oxygen (DO) is the amount of oxygen dissolved in a given quantity of water at a particular temperature and atmospheric pressure Amount of DO depends on: Aeration, photosynthetic activity in water, respiration of animals and plants and ambient temperature. Jhansirani.R AP/ECEOxygen demanding wastes: Oxygen demanding wastes The saturation value of DO varies from 8-15 mg/L. Active fish species requires 5-8 mg/L of DO Less desirable species like carp can survive at 3 mg/L of DO Lower DO may be harmful to animals especially fish population Oxygen depletion helps in release of phosphates from bottom sediments and causes eutrophication. Jhansirani.R AP/ECENitrogen & phosphorus compounds (nutrients): Nitrogen & phosphorus compounds (nutrients) 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 Under anaerobic conditions foul smelling gases are produced Excess growth or decomposition of plant material will change the concentration of CO2 which will further change pH of water Changes in pH, oxygen and temperature will change many physic-chemical characteristics of water. Jhansirani.R AP/ECEPathogens : Pathogens Many waste water especially sewage contain many pathogenic and non pathogenic micro-organisms and many viruses. Water borne diseases like cholera, dysentery, typhoid, jaundice etc., are spread by water contaminated with sewage. Jhansirani.R AP/ECEToxic compounds : Toxic compounds Pollutants such as heavy metals, pesticides, cyanides and many other organic and inorganic compounds are harmful to aquatic organisms The demand of DO increases with addition of biodegradable organic matter which is expressed as biological oxygen demand (BOD) 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 20◦c Jhansirani.R AP/ECEToxic compounds : Toxic compounds More BOD values of any water sample are associated with poor water quality The non biodegradable toxic compounds biomagnify in the food chain and causes toxic effects at various levels of food chain DDT is not water soluble and gets accumulated in the organisms body. This process is called bioaccumulation The concentration of these toxic substances builds up at successive levels of food chain. This process is called Biomagnification Jhansirani.R AP/ECEPowerPoint Presentation: Rainbow smelt 1.04 ppm Zooplankton 0.123 ppm Phytoplankton 0.0025 ppm Water 0.000002 ppm Herring gull 124 ppm Lake trout 4.83 ppm Herring gull eggs 124 ppm Biological MagnificationEffects of Water pollution: Effects of Water pollution Toxic substances polluting the water ultimately affect human health Heavy metals like lead, mercury, cadmium causes various types of diseases Mercury in water is transformed into methyl mercury Minamata disease is occurred due to consumption of methyl mercury contaminated fish Disease called Itai-Itai was caused by cadmium contaminated rice. Jhansirani.R AP/ECEEffects of Water pollution: Effects of Water pollution Arsenic pollution of ground water is causing various types of abnormalities Nitrate when present excess in drinking water causes blue baby syndrome Nitrate in stomach partly gets changed into nitrites which can produce cancer in stomach Fluoride in drinking water causes defects in teeth and bones called fluorosis Pesticides in drinking water causes health problems DDT, aldrin, dieldrin etc., have been banned. Jhansirani.R AP/ECEControl of water pollution: Control of water pollution It is easy to reduce water pollution from point sources by legislation. However it is difficult to prevent water pollution from non-point sources, The following points may help to reduce water pollution from non-point sources. 1. Judicious use of agrochemicals like pesticides and fertilizers which will reduce their surface run-off and leaching. Avoid use of these on sloped lands. Jhansirani.R AP/ECEControl of water pollution: Control of water pollution 2. Use of nitrogen fixing plants to supplement the use of fertilizers. 3. Adopting integrated pest management to reduce reliance on pesticides. 4. 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. 5. Separate drainage of sewage and rain water should be provided. 6. Plantation of trees would reduce pollution and will also prevent soil erosion. Jhansirani.R AP/ECEControl of water pollution: Control of water pollution Controlling water pollution from point source Treatment of waste water is essential before being discharged Parameters like total solids, BOD, COD, nitrates & phosphates, oil & grease, toxic metals etc., to be considered for reduction in waters Waste water should be properly treated by primary and secondary treatments to reduce the BOD,COD levels Jhansirani.R AP/ECEWaste water treatment: Waste water treatment The type of treatment of water depends upon its characteristics and the desired quality of water after treatment. Thus waste water treatment plants are primary, secondary or advanced treatment. The purpose of waste water treatment is to remove/reduce organic and inorganic substances, nutrients, toxic substances, kill pathogenic organisms,… Treatment of water thus aims at reduction of BOD, COD, eutrophication etc., and prevent biomagnifications, prevent diseases due to pathogenic organisms in waste water. Jhansirani.R AP/ECESteps involved in waste water treatment: Steps involved in waste water treatment Primary treatment Secondary treatment Trickling filters Activated sludge process Rotating biological contractor (RBC) Advanced sewage treatment Upflow anaerobic sludge blanket (UASB) reactor Jhansirani.R AP/ECEReducing Water Pollution through Sewage Treatment: Reducing Water Pollution through Sewage Treatment Jhansirani.R AP/ECEPrimary treatment : Primary treatment It’s a physical process for removal of debris, large particles with the help of screen The waste water after screening is passed through grit chamber where sand, grit and other solids settle down Water is then passed through the sedimentation tank or clarifier where most of the suspended solids settle down due to gravity For better removal of suspended solids, chemically treated polymers are used 35% of BOD & 60% of suspended solids are removed in primary treatment. Jhansirani.R AP/ECESecondary treatment: Secondary treatment It’s a biological process which involves microorganisms It removes up to 90% of BOD & 90% of suspended solids Biodegradable oxygen demanding wastes are stabilized Various approaches in secondary treatment are Trickling filters, Activated sludge process, Rotating biological contactor Jhansirani.R AP/ECETrickling filters: Trickling filters It consist of a bed of crushed stones/pebbles covered with slime which consists of aerobic bacteria, algae, fungi, protozoa, worms & insect larvae Sewage is degraded by the aerobic bacteria when it passes through the bed and is collected at the bottom of the filter It helps in better removal of organic matter and also keeps the filter moist when the flow rate is slow Jhansirani.R AP/ECEActivated sludge process: Activated sludge process The effluent from the primary clarifier goes to aeration tank. Aeration tank also receives microorganisms from the secondary settling tank known as activated sludge. Oxygen is pumped into aeration tank for maintaining aerobic conditions After few hours of agitation, the waste water goes to secondary settling tank where solids settle at the bottom The sludge is produced, dewatered and disposed off. Sludge can be used for landfills or disposed off in ocean or used in croplands, pastures, etc., Jhansirani.R AP/ECEActivated sludge process: Activated sludge process Jhansirani.R AP/ECERotating biological contactor (RBC): Rotating biological contactor (RBC) It consist of circular plastic discs which are arranged on a rotating shaft Circular discs have microorganisms grown on them The discs are contained in a wastewater holding tank About 40% area of the discs is submerged in the tank The disc rotates in and out of water as the RBC rotates The microorganisms present on the discs absorb organic matter when they are in water and obtain the required oxygen when the discs are out of water Thus a high degree of organic matter removal is achieved Jhansirani.R AP/ECERotating biological contactor (RBC): Rotating biological contactor (RBC) Jhansirani.R AP/ECEAdvanced sewage treatment : Advanced sewage treatment After primary & secondary treatment many undesirable substances still remain in the effluent Advanced water treatment involves the removal of such substances The materials to be removed in such treatment may include nitrates and phosphates, color, bacteria, viruses, pesticides, toxic metals, etc., Chlorination of water is generally done to kill harmful bacteria & viruses However chlorine can produce cancer causing chlorinated hydrocarbons by reacting with organic matter Jhansirani.R AP/ECEAdvanced sewage treatment : Advanced sewage treatment Other, but costly methods of disinfection are the use of ultraviolet light and ozone treatment The sludge produced after such treatment is used as a fertilizer in the fields However, there are chances of toxic metals and other untreated substances to build up in the food chain or leach to the groundwater. Jhansirani.R AP/ECEUp flow anaerobic sludge blanket (UASB) Reactor: Up flow anaerobic sludge blanket (UASB) Reactor Anaerobic treatment is gaining importance as a method of wastewater treatment due to its effectiveness in treating wastewater and economic advantages USAB process consists of 4 stages * Hydrolysis * Acidogenesis * Acetogenesis * Methanogenesis Jhansirani.R AP/ECEUSAB Reactor: USAB Reactor A dense blanket of granular anaerobic biomass is used to convert organic compounds that are passed through the sludge blanket continuously Biogas produced is collected at the top of the reactor Wastewater to be treated is fed into the reactor at the bottom As the influent flows through the loops and enters the reactor chamber, hydrolysis occurs The above mentioned 4 processes convert the influent into H2, CO2, CH4, Acetate, new cell-matter etc., COD removal up to 80% is achieved Methane and CO2 produced are separated from the reactor Jhansirani.R AP/ECEPowerPoint Presentation: Jhansirani.R AP/ECEPowerPoint Presentation: What Can You Do? Water Pollution • Fertilize garden and yard plants with manure or compost instead of commercial inorganic fertilizer. • Minimize your use of pesticides. • Do not apply fertilizer or pesticides near a body of water. • Grow or buy organic foods. • Do not drink bottled water unless tests show that your tap water is contaminated. Merely refill and reuse plastic bottles with tap water. • Compost your food wastes. • Do not use water fresheners in toilets. • Do not flush unwanted medicines down the toilet. • Do not pour pesticides, paints, solvents, oil, antifreeze, or other products containing harmful chemicals down the drain or onto the ground.PowerPoint Presentation: Jhansirani.R AP/ECE You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.