Water pollution_Notes.pdf

CVL100: Environmental Science Prof Sovik Das Department of Civil Engineering, IIT Delhi Block-V, Room No.-305 Email: [email protected] 13 August 2024 1 st class 2 Water Pollutio...

CVL100: Environmental Science Prof Sovik Das Department of Civil Engineering, IIT Delhi Block-V, Room No.-305 Email: [email protected] 13 August 2024 1 st class 2 Water Pollution: Overview 3  Water Pollution Water pollution can be defined as an alteration in water's physical, chemical, and biological characteristics through natural or human activities, making it unsuitable for its designated use. Water pollution in the environment and its sources 4  Water pollution (cont..) During the Middle Ages, diseases such as cholera and typhoid fever broke out all across Europe. These epidemics were directly related to unsanitary conditions caused by human and animal wastes, and garbage. By the 1800s, people began to understand that unsanitary living conditions and water contamination contributed to disease epidemics. In the mid-1850s, Chicago built the first major sewage system in the United States to treat wastewater The World Economic Forum has identified water scarcity as one of the major global risks Two-third of the world’s population live in areas facing water scarcity for at least a month in a year and about 50% of this population lives in China and India Only 37% of wastewater produced in India is getting treated More than half of the Indian cities fall under water stress regions 5  Water pollution (cont..) Share of people without access to safe drinking water worldwide as on 2020 6 Sustainable development goals (SDG) of UN 17 sustainable development goals with interlinked objectives designed to serve as a "shared blueprint for peace and prosperity for people and the planet, now and into the future." 7  SDG 06 Clean water and sanitation Ensure availability and sustainable management of water and sanitation for all ✓ TARGET 6.1: Achieve universal and equitable access to safe and affordable drinking water for all ✓ TARGET 6.2: Achieve access to adequate and equitable sanitation and hygiene for all and end open defecation, paying special attention to the needs of women and girls and those in vulnerable situations ✓ TARGET 6.3: Improve water quality by reducing pollution, eliminating dumping and minimizing the release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally ✓ TARGET 6.6: Protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers, and lakes Water quality is addressed also under other SDGs such as the goals on health, poverty reduction, ecosystems, and sustainable consumption and production, recognizing the links between water quality and the key environmental, socioeconomic, and development issues (Goals 1, 3, 12, 15 and Targets 1.4, 3.3, 3.9, 12.4, 15.1). 8  Baseline water stress (Worldwide) India placed thirteenth among the world's 17 ‘extremely water-stressed’ countries, according to the Aqueduct Water Risk Atlas released by the World Resources Institute (WRI) Total annual water withdrawals (municipal, industrial, and agricultural) 9 expressed as a percent of the total annual available flow as on 2019 Baseline water stress (India) Orange and dark-orange areas in the map show highly or extremely highly water- stressed areas, meaning that more than 40 percent of the annually available surface water is used every year. Water stress in India as on 2019 10  Water quality impact Number of habitations affected in total by water quality problems in rural India as on 2009 11  Water pollution scenario in India RIVER GANGA ✓ Approximately 1 billion litres of raw, untreated sewage is dumped in Ganga regularly. ✓ Ganga contains 60,000 fecal coliform bacteria per 100 mL, which is a threat to human health. ✓ Ganga is considered to be the most polluted river in India. RIVER YAMUNA ✓ More than 57% of Delhi’s waste is thrown into the Yamuna river. ✓ Only 55% of Delhi’s residents are connected to a proper sewerage system. ✓ According to Centre for Science and Environment (CSE), around 80% of Yamuna’s pollution is due to raw sewage. 12 Data on polluted rivers in India as on 2022  Sources of Water Pollution POINT SOURCE POLLUTION A point source is a single, identifiable source of pollution, such as a pipe or a drain. Industrial wastes are commonly discharged to rivers and the sea in this way. Example includes pipe attached to a factory, oil spill from a tanker, effluents coming out from industries. NON-POINT SOURCE POLLUTION When the source of water pollution is not known or pollution does not come from single discrete source of pollution is known as non-point source pollution. It is very difficult to control and may come from different sources like pesticides, fertilizers industrial wastes etc. Point source and non-point source of water pollution in environment 13  Surface water pollution Surface water pollution occurs in three ways: naturally, accidentally, and intentionally. Naturally: Flooding or tsunamis, that pick up fertilizers, pesticides, debris, and other contaminants. Accidentally: Oil spills and agricultural runoff. Intentionally: Industries dumping waste directly into waterways 14 Surface water pollution in environment  Groundwater pollution A key source of water pollution that ends up in groundwater resources comes from agriculture. Fertilizers and pesticides applied to farmland are easily absorbed into the ground, or they can be transported as runoff during rainfall. Groundwater can also become contaminated when waste from landfills and septic systems leaches into the ground. Ground water pollution in environment 15  Thermal pollution Heat is also considered a type of water pollution, as it reduces the ability of water to hold dissolved oxygen (DO); as the temperature of water increases, the level of DO decreases. Thermal pollution also increases the rate of metabolism in fish and damages larvae and eggs in rivers. The main source of thermal pollution comes from power plants discharging cooling water into rivers. The raising of temperatures due to global warming is also thought to be a type of thermal water pollution Thermal pollution in the environment 16 Causes of Water Pollution 17  Agricultural runoff SOURCES - Farmland Irrigation, Rainfall Events, Livestock Operations, Overland Flow etc. Here are some ways in which agricultural runoff can cause water pollution: Runoff carries nitrogen and phosphorus from fertilizers, leading to nutrient pollution in water bodies. Rain and irrigation water can transport pesticides and herbicides into rivers and lakes, impacting aquatic ecosystems. Exposed soil from farming activities can be eroded by water, carrying sediment into water bodies. Runoff from areas with livestock can contain bacteria, nutrients, and pathogens, contributing to water pollution. Lack of vegetation cover to trap and filter runoff Agricultural runoff in environment allows pollutants to reach water bodies more easily. 18  Industrial discharge Sources: Liquid waste discharged directly into water bodies from industrial processes Rainwater carrying pollutants from industrial areas into nearby rivers and streams Unintended releases of chemicals or pollutants during industrial activities Industrial discharge in the environment 19  Deforestation Deforestation can contribute to water pollution through various mechanisms, and the impact is often indirect but significant. Here are some ways in which deforestation can be a cause of water pollution: Soil Erosion Runoff of Chemicals Loss of Riparian Zones (banks) Altered Water Flow Loss of Biodiversity Increased Risk of contamination 20  Municipal sewage Sources: Effluents released from sewage treatment facilities into water bodies Discharges occurring during heavy rainfall, when stormwater and untreated sewage mix and overflow into waterways Leaks, breaks, or blockages in municipal sewer lines leading to untreated sewage entering water sources Ill effects of released effluents from sewage treatment plants 21  Oil spills Sources - Shipping Accidents, Offshore Drilling, Pipeline Ruptures, Well Blowouts, Natural Seepage, Industrial Activities, etc. Here are some ways in which oil spills can cause water pollution: Oil spills release toxic substances, such as polycyclic aromatic hydrocarbons (PAHs), which are harmful to aquatic life and can contaminate water. Oil coats the surfaces of marine organisms, disrupting their natural functions, affecting respiration, and impairing their ability to feed. Microbes that break down oil consume oxygen, leading to reduced oxygen levels in the water, which can harm fish and other aquatic life. Oil from spills can wash ashore, affecting beaches and shorelines, and causing harm to coastal ecosystems. 22  Atmospheric deposition Sources: Airborne pollutants released by industries settling on water surfaces Pollutants from vehicle emissions depositing into water bodies through air Pesticides and fertilizers transported by air settling into rivers and lakes Schematic diagram of diffuse sources, distribution and atmospheric deposition of pollutants 23 2 nd class 24  Environmental impacts Bioaccumulation and Biomagnification Disruption of the food chain leading to loss of habitat, loss of biodiversity, altered habitats, effects on aquatic life, etc., 25 Biomagnification & Bioaccumulation 26  Effects on Aquatic Life High levels of pollution can lead to the decline or extinction of various aquatic species, disrupting the balance of ecosystems Pollutants such as organic matter or nutrients can stimulate the growth of microorganisms, leading to increased microbial activity that consumes oxygen. This depletes oxygen levels in the water, causing "dead zones" where aquatic life cannot survive. Toxic chemicals, heavy metals, or excessive nutrients can lead to fish kills, harming populations and affecting the food chain. Pollutants like heavy metals and certain chemicals can accumulate in the tissues of aquatic organisms, gradually reaching higher concentrations as they move up the food chain. This poses risks to predators, including humans. Sedimentation and pollution can degrade or destroy aquatic habitats, affecting the reproduction and survival of various species. Hormone-disrupting pollutants can interfere with the reproductive systems of aquatic organisms, leading to altered reproductive patterns and reduced reproductive success. 27  Effects on aquatic life (cont..) Exposure to certain pollutants may cause genetic mutations and physical abnormalities in aquatic organisms, affecting their health and viability. Changes in nutrient levels and the presence of pollutants can disrupt the intricate web of relationships within ecosystems, affecting the availability of food for various species. Pollutants can hinder the growth and development of aquatic organisms, particularly larvae and juveniles, leading to population declines. Aquatic organisms may exhibit altered behavior in response to pollution, affecting feeding habits, migration patterns, and overall ecosystem dynamics. Effect of water pollution on aquatic life 28  Human Health Implications Some of the chemicals present in water affecting human health are the presence of heavy metals such as Fluoride, Arsenic, Lead, Cadmium, Mercury, petrochemicals, chlorinated solvents, pesticides, and nitrates Fluoride in water is essential for protection against dental carries and weakening of the bones. Concentration below 0.5 mg/L causes dental carries and mottling of teeth but exposure to higher levels above 1 mg/L for 5- 6 years may lead to adverse effects on human health leading to a condition called fluorosis. Arsenic is a very toxic chemical that reaches the water naturally or from wastewater of tanneries, the ceramic industry, chemical factories, and from insecticides such as lead arsenate, effluents from fertilizers factories, and from fumes coming out from burning of coal and petroleum. Arsenic is highly dangerous for human health causing respiratory cancer, and arsenic skin lesions from contaminated drinking water. Long exposure leads to bladder and lung cancer. Lead is contaminated in the drinking water source from pipes, fittings, solder, and household plumbing systems. In human beings, it affects the blood, central nervous system, and the kidneys. Child and pregnant women are mostly prone to lead exposure. 29  Human Health Implications (cont..) Mercury is used in industries such as smelters, manufacturers of batteries, thermometers, pesticides, fungicides etc. The best-known example of Mercury pollution in the oceans took place in 1938 when a Japanese factory discharged a significant amount of mercury into Minamata Bay, by contaminating the fish stocks there. It took several years to show its effects. By that time, many local people had eaten the fish and around 2000 were poisoned, hundreds of people were left dead and disabled and the cause for death was named “Minamata disease” due to consumption of fish containing methyl mercury. It causes chromosomal changes and neurological damage to humans. Mercury shows biological magnification in aquatic ecosystems. Effects of mercury in drinking water Effects of arsenic in drinking water 30 Minamata disease 31  Water-related disease Category Transmission Disease examples Gastroenteritis, enteric Ingestion of water contaminated hepatitis, amoebic & bacillary by human or animal faeces or Water-borne dysentery, cholera, urine containing pathogenic leptospirosis, poliomyelitis, bacteria, viruses or parasites typhoid/paratyphoid fever Skin, ear or eye contact with Conjunctivitis, trachoma, Water-washed contaminated water & poor intestinal helminth infections, personal hygiene leprosy, scabies Water-aerosol Inhalation of water aerosol Legionellosis, phiesteria disease containing pathogen Parasitical worm infections Dracunculiasis, schistosomiasis, Water-based (parasites found in intermediate (tricho) bilharziasis organisms living in water) Water-related Dengue, lymphatic filariasis, Insect vectors breeding in water arthropod malaria, onchocerciacis, or biting near water vector trypanosomiasis, yellow fever 32  Human health implication (cont..) Death rates as the number of deaths per 100,000 individuals from unsafe water sources till 2019 33  Human health implication (cont..) The WHO reports that nearly 2 billion people around the world lack safe drinking water, of which 297 thousand are children aged under 5 years, are estimated to die each year from water pollution-related diseases, particularly infectious diarrhea. Deaths attributed to water, sanitation and hygiene (diarrhoea) in children aged under 5 years till 2004 34 Monitoring and Measurement Growth of water pollution monitoring network in India – CPCB 2009 35  Water quality parameters Reflection of how clean/polluted the sample of water is There are three types of water quality parameters physical, chemical and biological Biological Physical parameters Chemical parameters parameters Solids pH Bacteria Turbidity Alkalinity Virus Color Hardness Protozoa Temperature Dissolved ion Helminths Taste and odor Heavy metals Electrical Refractory conductivity organics Nutrients 36  Solids Solids retained by the filter Solids passing paper through the filter paper Solids in water can be in suspended, colloidal or in dissolved form Particle type Size range, µm Suspended 1 to 100 Colloidal 10-3 Dissolved 10-5 to 10-3 Interrelationships of solids found in water 37  Turbidity Turbidity is a measure of the extent to which light is either adsorbed or scattered by the suspended material in water Indirect measure of solids in water Commonly used in water treatment plants (WTP) to measure the quality of potable water Turbidity in surface waters is mostly due to the presence of colloidal particles Measured using turbidimeter and expressed as NTU (Nephelometry turbidity unit) Turbidity of different water samples 38  Alkalinity Measure of the ability of water to neutralize acids Most common constituents of alkalinity are bicarbonate (HCO3-), carbonate(CO32-) and hydroxide (OH-) Alkalinity is pH dependent Measured by titration Used as a process control variable in water and wastewater treatment The pH scale showing alkalinity of water 39  pH pH is a measure of how acidic or basic (alkaline) the water is. The term pH comes from the French: "puissance d'Hydrogène”, which means strength of the hydrogen. It is defined as the negative log of the hydrogen ion concentration. The pH scale is logarithmic and goes from 0 to 14. For each whole number increase (i.e. 1 to 2) the hydrogen ion concentration decreases ten fold and the water becomes less acidic. As the pH decreases, water becomes more acidic. As water becomes more basic, the pH increases. Many chemical reactions inside aquatic organisms (cellular metabolism) that are necessary for survival and growth of organisms require a narrow pH range. Changes in pH may alter the concentrations of other substances in water to a more toxic form 40  Hardness Defined as the concentration of multivalent metallic cations in solution In natural waters, hardness is caused by calcium and magnesium ions Hardness is classified as carbonate hardness and noncarbonate hardness depending on the anion with which it associates Carbonate hardness is equivalent to alkalinity Carbonate hardness precipitates readily as upon boiling Measured by titration and expressed as mg/L as CaCO3 Effect of hard water 41  Conductivity The conductivity of water is a measure of the ability of a solution to carry or conduct an electrical current. Since the electrical current is carried by ions in solution, the conductivity increases as the concentration of ions increases. The major positively charged ions are sodium, (Na+) calcium (Ca+2), potassium (K+) and magnesium (Mg+2). The major negatively charged ions are chloride (Cl-), sulfate (SO4-2), carbonate (CO3-2), and bicarbonate (HCO3-). Nitrates (NO-2) and phosphates (PO4-3) are minor contributors to conductivity, although they are very important biologically. The conductivity can be used to estimate the TDS value of water 42  Nutrients Nitrogen and phosphorus are the limiting nutrients in aquatic plant growth High amounts of nutrients in surface water leads to the excessive growth of algae which is known as Eutrophication eutrophication Nitrate contamination leads to methemoglobinemia or blue baby syndrome 43 Blue baby syndrome  Pathogens 1. BACTERIA Typhoid fever – salmonella typhi Paratyphoid fever – salmonella Paratyphi Cholera – vibrio cholerae Bacillary dysentery – shigella Dysentrial 2. PROTOZOA Amoebiasis Amoebic dysentery – entamoeba Histolytica Different types of pathogens and water-borne diseases associated with them 3. VIRUS Organisms capable of infecting or transmitting diseases to humans Polio Bacteria, viruses, protozoa, helminths Infectious hepatitis Most critical parameter in drinking water quality 4. HELMINTHS Swimmer’s itch 44 3 rd class 45 Organic content estimation 46  Estimation of organic content of the wastewater The organic matter present in the water body can be analyzed in laboratory by determining Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and by determination of Total Organic Carbon (TOC). The Total Organic Carbon (TOC) analyzer utilizes a catalytic oxidation combustion technique at high temperature (the temperature raises up to 720 ºC), to convert organic carbon into CO2. The CO2 generated by oxidation is measured with a sensor. 47  Biochemical Oxygen Demand (BOD) The BOD can be defined as the oxygen required for biochemical oxidation of organic matter present in the water under aerobic conditions. This test is based on the premise that all the biodegradable organic matter contained in a water sample will be oxidized to CO2 and H2O by microorganisms using molecular oxygen. The actual BOD will be less than theoretical oxygen demand due to incorporation of some of the carbon into newly synthesized bacterial cells. 48  Biochemical Oxygen Demand (BOD) During the BOD test the organic matter will be converted into stable end product such as CO2, sulphate (SO4), orthophosphate (PO4) and nitrate (NO3). The simple representation of carbonaceous BOD can be explained as below: This reaction continues till sufficient DO is available in the water. When DO is not available, anaerobic decomposition takes place (fermentative reduction). The reaction under anaerobic conditions is as under: 49  BOD profile For polluted water and wastewater, a typical value of K (base e, 20°C) is 0.23 per day and K (base 10, 20°C) is 0.10 per day. These values vary widely for the wastewater in the range from 0.05 to 0.3 per day for K (base 10) and 0.23 to 0.7 for K (base e). 50  BOD profile The ultimate BOD (Lo) is defined as the maximum BOD exerted by the wastewater. It is difficult to assign exact time to achieve ultimate BOD, and theoretically it takes infinite time. From the practical point of view, it can be said that when the BOD curve is approximately horizontal the ultimate BOD has been achieved. The time required to achieve the ultimate BOD depends upon the characteristics of the wastewater, i.e., chemical composition of the organic matter present in the wastewater and its biodegradable properties and temperature of incubation. The ultimate BOD best expresses the total concentration of degradable organic matter based on the total oxygen required to oxidize it. However, it does not indicate how rapidly oxygen will be depleted in the receiving water. 51  Formula for BOD estimation For non-seeded samples Note: The total volume is generally 300 mL for a BOD sample bottle For seeded samples 52  Numerical A test bottle containing only seeded dilution water has its DO level drop by 1.0 mg/L in a 5- day incubation. A 300 mL BOD bottle filled with 10 mL of wastewater and the rest seeded dilution water experiences a DO drop of 6.2 mg/L in the same time period. What would be five day BOD of the wastewater? 53 Solution 54  Temperature correction The biochemical reactions are temperature dependent and the activity of the microorganism increases with the increase in temperature up to certain value, and drop with decrease in temperature. Since, the oxygen utilization in BOD test is caused by microbial metabolism, the rate of utilization is similarly affected by the temperature. The standard temperature at which BOD is determined is usually 20°C; however, BOD can be converted to different temperatures. However, the water temperature may vary from place to place for the same river; hence, the BOD rate constant is adjusted to the temperature of receiving water using following relationship: 55 Temperature correction 56  Numerical The BOD of a sewage incubated for one day at 30°C has been found to be 100 mg/L. What will be the five day 20°C BOD? Assume K = 0.12 (base 10) at 20°C, and θ = 1.056. 57 Solution 58  Chemical Oxygen Demand (COD) In this test to determine the oxygen requirement of the wastewater, strong oxidizing agent ‘potassium dichromate’ is used. Acidic environment is provided to accelerate the reactions by addition of sulphuric acid. The reflux flasks (or closed reflux vials), used for the test, are heated to 150°C for two hours with silver sulphate as catalyst. When silver sulphate catalyst is used, the recovery of most organic compounds is greater than 92 percent. COD test measures virtually all oxidizable organic compounds whether biodegradable or not, except some aromatic compounds which resists dichromate oxidation. 59  Chemical Oxygen Demand (COD) The COD is proportional to BOD only for readily soluble organic matter in dissolved form e.g. sugars. No correlation between BOD and COD exists when: Organic matter is present in suspended form; under such situation filtered samples should be used. Complex wastewater containing refractory substances. For readily biodegradable waste, such as dairy COD = BODu/0.92 60 Correlation between BOD and COD 61  Chemical Oxygen Demand (COD) The COD is faster determination but does not give idea about the nature of organic matter whether biodegradable or biorefractory organic matter. Hence, determination of BOD is necessary for the wastewater to know the fraction of biodegradable organic matter. The BOD is not very useful test for routine plant control due to the requirement of long incubation period, hence requiring long time (5 days) to obtain results. 62  Theoretical Oxygen Demand (ThOD) Theoretical oxygen demand for the wastewater is calculated as oxygen required for oxidizing the organic matter to end products. For example, for glucose, the theoretical oxygen demand can be worked out as below: For most of the organic compounds (except aromatics resisting dichromate oxidation) COD is equal to ThOD. 63 4 th class 64 Self Purification of Natural Streams 65  Self Purification of Natural Streams The self purification of natural water systems is a complex process that often involves physical, chemical, and biological processes working simultaneously. The amount of Dissolved Oxygen (DO) in water is one of the most commonly used indicators of a river health. As DO drops below 4 or 5 mg/L the forms of life that can survive begin to be reduced. A minimum of about 2.0 mg/L of DO is required to maintain higher life forms. Oxygen demanding wastes remove DO; plants add DO during day but remove it at night; respiration of organisms removes oxygen. In summer, rising temperature reduces solubility of oxygen, while lower flows reduce the rate at which oxygen enters the water from atmosphere. 66 DO vs temperature 67  Factors Affecting Self Purification Dilution Current Temperature Sunlight Rate of oxidation 68 Oxygen sag curve 69  Oxygen Sag Analysis The oxygen sag or oxygen deficit in the stream at any point of time during self purification process is the difference between the saturation DO content and actual DO content at that time. The saturation DO value for fresh water depends upon the temperature and total dissolved salts present in it. The DO in the stream may not be at saturation level and there may be initial oxygen deficit ‘Do’. At this stage, when the effluent with initial BOD load Lo, is discharged in to stream, the DO content of the stream starts depleting and the oxygen deficit (D) increases. The variation of oxygen deficit (D) with the distance along the stream, and hence with the time of flow from the point of pollution is depicted by the ‘Oxygen Sag Curve’. The major point in sag analysis is point of minimum DO, i.e., maximum deficit. The maximum or critical deficit (Dc) occurs at the inflexion points of the oxygen sag curve. 70 Oxygen sag curve 71  Rate of reoxygenation Depth of water in the stream: more for shallow depth. Velocity of flow in the stream: less for stagnant water. Oxygen deficit below saturation DO: since solubility rate depends on difference between saturation concentration and existing concentration of DO. Temperature of water: solubility of oxygen is lower at higher temperature and also saturation concentration is less at higher temperature. 72  Streeter – Phelps analysis The analysis of oxygen sag curve can be easily done by superimposing the rates of deoxygenation and reoxygenation as suggested by the Streeter – Phelps analysis. Where, K or K’ = BOD reaction rate constant, Dt = DO deficit at any time t, R or R’ = Reoxygenation constant Do = Initial oxygen deficit at the point of waste discharge at time t = 0 t = time of travel in the stream from the point of discharge Lo = Ultimate BOD tc = time required to reach the critical point 73 Dc =critical DO  Numerical A river is having discharge of 20 m3/s receives wastewater discharge of 6 m3/s. The initial DO of the river water is 6.2 mg/L, and DO content in the wastewater is 0.7 mg/L. The five day BOD in the river is 2 mg/L, and the wastewater added to river has five day BOD of 100 mg/L. Consider saturation DO of 8.22 mg/L and deoxygenation and reoxygenation constant values of 0.1 and 0.3 per day (base 10), respectively. Find critical DO deficit, distance at which critical DO occurs and DO in the river water after one day. The average velocity of flow in the stream after mixing the wastewater is 0.18 m/s. 74  Solution River Wastewater 3 Q= 20 m /s Q= 6 m3/s DO = 6.2 mg/l DO = 0.7 mg/l BOD = 2 mg/l BOD = 100 mg/l Finally Q1  DO1 + Q2  DO2 DO = 4.93 mg/l DOm = Q1 + Q2 BOD = 24.62 mg/l Similarly BOD should be calculated Saturation DO = 8.22 mg/l K' = 0.1 d-1 R' = 0.3 d-1 u (velocity) = 0.18 m/s Lo = 36 mg/l Initial DO = 3.29 mg/l tc = 1.95 days Dc = 7.66 mg/l L (distance) = 30.29 km Distance = velocity X time t= 1 day (given) Distance = 15.55 km Distance = velocity X time (1 day) Dt = 6.92 mg/l 75  How to tackle water pollution Tackling water pollution is a complex task that requires coordinated efforts from individuals, communities, governments, and industries. Here are some strategies to address water pollution: Raise Awareness: Educate the public about the sources and impacts of water pollution. Promote water conservation practices to reduce overall water usage. Proper Waste Disposal: Encourage proper disposal of household and industrial waste. Implement and enforce strict regulations regarding the disposal of hazardous substances. Wastewater Treatment: Improve and upgrade wastewater treatment facilities to ensure they meet environmental standards. Implement advanced treatment technologies to remove pollutants from industrial and municipal wastewater. 76  How to tackle water pollution (cont..) Regulations and Enforcement: Strengthen and enforce water quality regulations. Implement penalties for individuals or industries that violate pollution control laws. Monitoring and Testing: Regularly monitor water quality in rivers, lakes, and other water bodies. Implement early warning systems to detect and respond to pollution incidents promptly. Protect Watersheds: Implement measures to protect and restore natural ecosystems, such as wetlands and forests, which play a crucial role in maintaining water quality. Establish buffer zones along water bodies to reduce runoff of pollutants. Promote Sustainable Agriculture: Encourage the use of environmentally friendly agricultural practices. Implement measures to reduce the runoff of pesticides and fertilizers into water bodies. 77  How to tackle water pollution (cont..) Community Involvement: Involve local communities in water pollution prevention efforts. Establish community-based monitoring programs. Research and Innovation: Invest in research and development of innovative technologies for pollution prevention and remediation. Support initiatives that focus on sustainable water management practices. International Cooperation: Collaborate with neighboring countries to address transboundary water pollution issues. Share knowledge and best practices on water pollution prevention and management. Corporate Responsibility: Encourage industries to adopt environmentally friendly production methods. Promote corporate responsibility and accountability for water pollution. Plastic Pollution Reduction: Implement measures to reduce plastic usage and improve waste management to prevent plastic pollution in water bodies. 78 Doubts or questions? 79