Pollution in water resources
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This document discusses various aspects of water pollution including types of pollutants, sources, impacts, and control methods. The main types of pollutants are pathogens, organic wastes, nutrients, heavy metals, and toxic chemicals from industrial, agricultural, and domestic activities. These pollutants contaminate surface and groundwater, causing health issues and environmental degradation. Control of pollution requires reducing waste at the source, treating wastewater, and improved land management practices.
Pollution in water resources
- 1. 1 POLLUTION IN WATER RESOURCES By PROF. A. BALASUBRAMANIAN Centre for Advanced Studies in Earth Science University of Mysore Mysore-6
- 2. 2 Introduction: Water is essential for all life. It is mainly required for the survival of human population, agriculture, expanding urbanization, increasing industrialization and other causes. Water is needed for food, habitat, energy, recreation and tourism. Earth has enormous amount of water.
- 3. 3 The world’s fresh water resources can be classified into l. Surface water resources and 2. Groundwater resources. The Surface water resources are available in dams and reservoirs, lakes, ponds, tanks and rivers. The groundwater resources are tapped through bore-wells and dug-wells. Innumerable number of hand-pumps help a major population of the world in tapping groundwater.
- 4. 4 When the water is good, it can be used by all. When it is polluted, it becomes unsuitable for any purpose. Even a small amount of pollutant while mixing with the water resources will contaminate the whole resource.
- 5. 5 In this report, the following aspects of water pollution are discussed: 1. Types of water pollutants 2. Sources of water pollution 3. Groundwater contamination 4. Impacts of water pollution 5. Control of water pollution.
- 6. 6 1. Types of water pollutants Water pollution is the unwanted modification of the properties of water. This modification make the water useless or dangerous for further consumption. The modifications may be with reference to its physical, chemical and biological properties.
- 7. 7 Pollution in water resources may begin as water moves through the air, soil, rock and land. Soil erosion adds silt as a pollutant. The use of chemical fertilizers, pesticides, or other materials on watersheds is an additional factor contributing to water pollution.
- 8. 8 The runoff from septic tanks and the outflow of manures from livestock feedlots along the watersheds are the sources of organic pollutants. Industries located along waterways downstream contribute a number of chemical pollutants, some of which are toxic if present in any concentration. Finally, cities and towns contribute their loads of sewage and other urban wastes.
- 9. 9 The types of pollutants degrading the quality of water are: a. Inorganic salts and sediments b. Plant nutrients and fertilizers c. Organisms and organic matter d. Oxygen demanding wastes e. Acids and detergents f. Thermal wastes g. Oil h. Radioactive and toxic substances i. Heavy metals.
- 10. 10 Let us see the details of these pollutants. 1) The disease causing agents or pathogens causing water pollution are bacteria, viruses, protozoa, and parasites. These come from raw sewage and animal wastes. They may be responsible for about 80% of the diseases in the developing countries. It is measured by the amount of colliform bacteria present in water samples.
- 11. 11 2) Next comes the Oxygen demanding organic wastes. These can be decomposed by aerobic bacteria. These pollutants can cause a reduction in the dissolved oxygen, suffocating oxygen- consuming organisms (fish). It is measured as biological oxygen demand (BOD) in waters.
- 12. 12 3) Water-soluble inorganic chemicals, including acids, salts, and metals also form a major group of pollutants. These substances make the water unfit for consumption and use for irrigation. They also can harm organisms and cause material corrosion. 4) The next category of pollutants come from Inorganic plant nutrients. These are the (nitrates and phosphates used in fertilizers.
- 13. 13 They Cause excessive algal and plant growth that lower oxygen levels when they decompose in water bodies. 5) The Organic chemicals, including oil, gasoline, plastics, pesticides, solvents and detergents form a major category of pollutants in water resource. They pose serious health risks to humans and other organisms in the environment.
- 14. 14 6) Next comes the Water-soluble radioactive isotopes: These (and many other chemicals) substances often bioaccumulate in fish and other organisms at the top of the food chain and can cause serious environmental effects. 7) Sediment or suspended matter (particulates) from soil and other solids. Disrupt photosynthesis and transports large amounts of other, adsorbed pollutants.
- 15. 15 Also silt up lakes, rivers, and reservoirs, increasing flood risk. 8) Thermal pollution is originated from the cooling of industrial processes using water and from power plants. It lowers the solubility of oxygen and makes the organisms more susceptible to other pollution types.
- 16. 16 9) The Genetic pollution may be caused by the introduction of non-native or exotic species in to a new environment and create a menace to water resources through interactions. All of the different pollutant type can be discharged from point (specific location) or nonpoint (no single location; large area) sources.
- 17. 17 Point-source pollution is usually easier to identify, monitor, measure, and control. Most water pollution in many countries comes from nonpoint sources. Little has been done to control it. The pollutants released from the industries can be classified into organic and inorganic types. The inorganic sources can be divided into metals, salts, acids and bases.
- 18. 18 Metals are found in low concentration near the sources of pollution. Sometimes they may be adsorbed into the minerals, in soils and rocks. Metals can travel to longer distances along with the groundwater. The synthetic organics include thousands of chemicals. The behaviour of each chemical differs in the soil or groundwater environment.
- 19. 19 Sometimes, they may be highly toxic. A notable example of organic substance is the hydrocarbon. The organics from food processing and paper industries cause much pollution to soil and subsequently to groundwater.
- 20. 20 2. Sources of water pollution: Water resources may be polluted due to natural and man-made activities. The sources of natural degradation includes the (i) dissolution of more salts by the water, while moving through rocks,
- 21. 21 (ii) accumulation of impurities over leaves, barks, etc which mix with water subsequently and (iii) the intrusion of seawater along the coastal areas. As water moves through the hydrological cycle, its quality changes in response to the differences in the environment.
- 22. 22 Sources of man-made pollution Humans carryout a lot of activities during the consumption of water, and conservation of this resource. There are Four major categories of activities affecting water resources. They are: 1. Agricultural, 2. Industrial 3. Domestic and 4. Radiological activities.
- 23. 23 Based on the nature of pollutants released, the sources can be classified into five categories. 1. Sources designed to discharge substances, directly. 2. Sources designed to store, treat or dispose them. 3. Sources retaining the substances during transportation or transmission.
- 24. 24 4. Sources releasing pollutants due to other activities. 5. Sources which are naturally occurring and deteriorating the water quality. More than 200 chemical constituents have been identified in groundwater, out of which many of them are derived from environmental pollution.
- 25. 25 The quality of groundwater is affected by waste disposal and land use. A major source is the storage of waste materials in excavations, pits or mines. These pollute the surface water resources at the first instance. The water soluble substances may infiltrate and contaminate the ground water. Groundwater contamination is a local phenomena.
- 26. 26 The extent of pollution varies depending upon the nature of the geological environment. Agricultural Practices are the major sources of water pollution. The use of chemical fertilizers and pesticides, dumping of animal wastes, and crop wastes are the major activities which can affect the groundwater quality.
- 27. 27 These materials are point or local sources. The chemicals applied to the agricultural fields may be compounds of nitrogen, phosphorus and potassium of commercial fertilizers. In order to increase the crop yield, people use more and more fertilizers. This practice has created the nutrient pollution of surface and groundwater.
- 28. 28 Nitrogen Compounds play a dominant role. The pollution problem comes due to the mobility of nitrate nitrogen. The nitrogen applied to lands are available in the following forms: Urea Anhydrous ammonia Ammonium sulphate Ammonium nitrate Ammonium carbonate Ammonium chloride & calcium nitrate.
- 29. 29 The rate of application of these fertilizers is dependent upon the requirement per unit area of the crop. Mostly plants use nitrogen in the nitrate form. These organic compounds are not very mobile in soils which leads to pollution of water. During nitrification process, Nitrate is leached. It is mobile in soils and also groundwater.
- 30. 30 Next comes the role of phosphorus compounds: Phosphorous compounds occur in organic form and most of these become fixed in the soil. The inorganic forms used are: Iron and aluminium phosphates in acid soils and calcium phosphates in alkaline soils.
- 31. 31 The organic forms consist of n-acyitol- phosphates, nucleic acids and phospholipids. These are converted into an insoluble form and fixed in the soil. Later, they are carried away by the surface water and get polluted. Animal wastes are another sources of water pollution. Large quantities of animal wastes are generated due to the increase in the number of livestock and poultry operations.
- 32. 32 The solid organic matter generated from such operations is a source of nitrogen and phosphorus. These two compounds can pollute the water resources. When the wastes are applied to a land , they are leached into the groundwater systems and deteriorate the quality of water. Industrial pollution is an everlasting issue of the environment.
- 33. 33 Pollution of water by the industries, is one of the most serious problems in the world. Most of the industrial operations use a large quantity of water. They let out this water as sewage or effluent with diluted waste products or chemicals. When such waters are returned to the surface or groundwater source, they contaminate and make them, unfit for any use.
- 34. 34 This is characterized by a tremendous variety of organic and inorganic chemicals. The source of them may be local or point. There are major sources of industrial pollution to groundwater contamination. They are 1. the wastes generated by industries, 2. the Leaks and 3. the accidents occurring in industrial operation.
- 35. 35 The chemical components released from wastes and sewage are considered as environmental toxins. They include residuals of biodegradation, organic and inorganic substances. They are: Phenolic compounds, Chlorinated hydro carbons, Pesticides, Chlorinated biphenyls, Detergent residues, Petroleum products and Heavy metals.
- 36. 36 While concentrating to produce more products, many industries generate more residues or wastes. These are of no further usage and hence they are disposed of as wastes. They are of liquid or solid types. Liquid wastes include dangerous acids or organic complexes.
- 37. 37 These are discharged into surface ponds, reservoirs, pits, lagoons, basins and sometimes into some rivers. Mostly they percolate downward and mix with the groundwater systems. Solid wastes form another problem in industries. They are normally dumped on open areas, grounds as landfills.
- 38. 38 These are subjected to leaching and groundwater pollution. Leaks in pipelines and storage tanks play a major role in water pollution. Industries store chemicals and transport fuels regularly through tank and pipelines. They are normally be avoided at certain places. Most of the petrol bunks use underground tanks, which are significant sources of pollution due to leaks.
- 39. 39 Pipelines for collection, distribution or transportation of liquids are another source of pollution. Mostly they use petroleum products, natural gas and water. The oil spills will contaminate the water resources. Accidental spills associated with t he breakage of pipelines in industries is a serious threat.
- 40. 40 Before taking any alternative measure they infiltrate and mix with the groundwater resources. 3. Groundwater Contamination: The pollutants left by the industries on open grounds will infiltrate, with rain water, into the ground. They move through the top soil layer and unsaturated zone towards the saturated zone below.
- 41. 41 During this transport, they may be adsorbed onto the subsurface materials or may be subjected to chemical reactions or biological degradations. Pollutant transport and its fate within the groundwater zone can be considered in terms of 1. the hydrodynamic processes, 2. the abiotic processes and 3. the biotic processes .
- 42. 42 The hydrodynamic processes involved in this transport mechanism are : 1. Advection and 2. Dispersion. Advection is the process in which the contaminant moves with the velocity of groundwater flow. It is also referred to as convection.
- 43. 43 Dispersion refers to the spreading of a solute in the water saturated geologic media. This spreading results in the dilution of pollutant. The major abiotic processes involved in pollutant transport are 1. Adsorption / desorption of solutes on the materials, 2. Ion-exchange reactions, 3. Ion-pairing or complexation reactions, 4. Hydrolysis,
- 44. 44 5. Solution - precipitation reactions, 6. Acid -base reactions and 7. Oxidation - reduclion reactions . The major characteristics of chemicals which influence these processes are 1. Solubility, 2. Equilibrium vapour pressure and 3. Partition coefficient.
- 45. 45 Disposal of Municipal Waste Water is a major concern. In most of the towns and municipalities, the waste water is discharged over land adjacent to the city limits. The extent of groundwater pollution in these zones is mainly depending upon the following factors: 1. Amount of material discharged;
- 46. 46 2. Degree of previous treatment given to that sewage, 3. Local hydrologic conditions including the groundwater flow directions, 4. Local geological conditions, 5. The method of application . The ultimate effect on groundwater quality will be more severe.
- 47. 47 4. Impacts of Water Pollution: Water polluted with human or animal wastes can spread a lot of water borne diseases like typhoid fever, cholera, dysentery, and other diseases. In community water supplies, these are disinfected with chlorine to kill disease-causing germs.
- 48. 48 However, disinfection does not remove chemicals and metals, such as polychlorinated biphenyls (PCB's), chloroform, arsenic, lead, and mercury. The careless release of these toxic wastes, primarily in waste dumps, is seriously threatening ground water supplies. PCB's, chloroform, and pesticides have been found in drinking water supplies in many countries.
- 49. 49 Scientists are concerned that drinking water with even small quantities of these substances over many years may have harmful effects. Pollution prevents people from using and enjoying water for recreation. For example, odours and floating debris make boating and swimming unpleasant, and the risk of disease makes polluted water unsafe.
- 50. 50 Oil spilled from ships or from offshore oil wells may float to shore. The oil can cause serious pollution and kill water birds, shellfish, and other wildlife. In addition, water pollution affects fishing, both commercially and for sport. Fish have been killed by oil or by a lack of oxygen in the water. Industrial wastes, particularly PCB's, also harm fish.
- 51. 51 Water pollution also upsets various processes that occur naturally in water. These processes, which use the oxygen dissolved in water, help to make wastes harmless. Too many nutrients in surface water bodies may lead to a process called eutrophication.
- 52. 52 Many nutrients result from the natural disintegration of rocks and from mineralization of organic matter. But additional nutrients come from fertilizers draining off farmland, or from detergents or other parts of sewage. All the nutrients fertilize microscopic algae (simple plantlike organisms), as well as such plants as pondweeds and duckweeds.
- 53. 53 More algae and plants grow as a result of the additional nutrients. As more grow, more also die. In extreme cases, a river or lake may become so eutrophic that all the oxygen dissolved in the water is consumed during part of the day. Thermal pollution can also reduce the amount of oxygen that dissolves in water. In addition, the high temperature of the water can kill some kinds of plants and fish.
- 54. 54 5. Control of Water Pollution Industrial Pollution The key element to control this is the waste and water management. The following methods could reduce the problems: 1. Reduction in the volume and concentration of waste water. This can be achieved by improving the practices, i.e. by changes in industrial processes.
- 55. 55 2. Waste water recycling or reuse. 3. Treatment of waste water, to remove toxic materials. 4. Dispose the wastes over suitable locations, using suitable structures. 5. Leaks can be prevented through proper design and maintenance facilities. 6. Polluted groundwater can be pumped out. 7. Biological or chemical agents can be added ta speed biodegradation which can stop the mobility of pollutants.
- 56. 56 Agricultural Pollution The agricultural waste disposal methods are many. They can be grouped into two catogories, as 1. disposed on land directly and 2. after the separation of slurry-solids. The second variety of materials are normally 1. Spread over the land, 2. Soaked away into the ground, 3. Purified and 4. Discharged into a public sewer.
- 57. 57 To reduce the percolation of fertilizers, several methods are followed. l. Apply only necessary quantity of fertilizer at the appropriate time and place. 2. Rotate the crops. 3. Contouring of land to control loss of soil and water. There are two categories for classifying the Control of water pollution by pesticides.
- 58. 58 They are: 1. Use a substitute for chemical pesticides and 2 . Use chemical pesticides with greater efficiency. The methods may be : l. Follow the non-chemical pest control methods . (This involves a change in the method of cultivation and harvest so that the pest can not survive).
- 59. 59 2. Crop rotation is an ancient and effective method of pest con 3. Involve or introduce the predators to fight against the pests. However, this method is not reliable. 4. Use crops which are highly resistant to diseases, insects and nematodes. 5. Use a very little pesticide and a more effective pesticide.
- 60. 60 Natural Control Of Groundwater Pollution: There are four natural controls involved in the prevention of groundwater contamination. They are: 1. The physical and chemical characteristics of the earth material through which the liquid wastes flow .
- 61. 61 2. The natural processes that tend to remove or degrade the contaminant from the point of entry to the point of exit (Eg. : Filtration, absorption, ion-exchange, dispersion, oxidation, microbial degradation and dilution). 3. The hydraulics of the flow system. This is nothing but the nature of groundwater flow in transporting the solute (contaminant ). 4. The nature, physical, chemical and biological characteristics of the contaminant.
- 62. 62 The other methods of control include: a) Sewage treatment: The most efficient sewage treatment plants use three separate processes--primary treatment, secondary treatment, and tertiary treatment. But few sewage treatment plants use all three processes. As a result, most treated sewage still contains nutrients, which may cause eutrophication, and chemicals.
- 63. 63 b) Pretreatment of wastes. Industries can reduce pollution by treating wastes to remove harmful chemicals before dumping the wastes into water. Industrial wastes can also be reduced by using manufacturing processes that recover and reuse polluting chemicals.
- 64. 64 c) Maintaining the Drinking water standards. Most countries have standards designed to limit the amount of harmful bacteria, chemicals, and metals in drinking water. In addition, there may be rules to limit the amount of chloroform and other related organic chemicals called trihalomethanes (THM) in the drinking water of large cities.
- 65. 65 These chemicals are formed at treatment plants when chlorine is added to drinking water to kill disease-causing bacteria. Extended exposure to high levels of THM's, especially chloroform, is thought to increase the risk of cancer. Water pollution is one of our most serious environmental problems.
- 66. 66 Polluted water may look clean or dirty, but it all contains germs, chemicals, or other materials that can cause inconvenience, illness, or death. Impurities must be removed before such water can be used safely for drinking, cooking, washing, or laundering. Even some industries must clean the water before it can be used in their manufacturing processes.
- 67. 67 Water pollution has become a serious problem in most countries, particularly Canada, China, India, Japan, Russia, and the United States. Governments have passed laws limiting the amount and kinds of waste that can be dumped into water. Governments, industries, cities, and towns have spent vast sums of money on research and water treatment plants to reduce pollution.
- 68. 68 But there are still serious problems. Several large cities release a huge volume of untreated sewage into their harbours or coastal waters. By the year 2020, industrialized countries will probably produce twice as much sewage as they did in 1990. Much of the sewage goes through treatment plants that remove solids and such dissolved substances as nitrogen and phosphorus.
- 69. 69 Some of it passes through septic tanks before filtering through leaching fields into the land. The remaining sewage goes untreated directly into waterways or the ocean. Cholera, typhoid fever, dysentery, polio, infectious hepatitis, contract disease when drink, swim, or bath all are the ill effects of water pollution.
- 70. 70 Presence of coliform bacteria is an indicator of pollution in waters. More than 2 in 100 ml is unsafe to drink. Synthesized persistent organics Resist decomposition by bacteria, sun, air, or water. DDT and PCBs (polychloinated biphenyls) are examples.
- 71. 71 SEPTIC TANKS Used by rural and suburban homes to process all household waste is a typical issue. ALTERNATIVE METHODS are to be evolved for controlling these pollutions. WATER POLLUTION LEGISLATION has brought out many water quality standards and pollution controlling mechanisms.
- 72. 72 It is our duty to drastically reduce or eliminate the chemical pollutants from drinking water which might cause serious human illness. The Human Uses of Water has increased about 500% since 1950. It will double again by 2025 at which point we will be using essentially 100% of all reasonably accessible fresh water in the whole world.