The total quantity of water available on earth does not vary much; it only goes through a gigantic cycle of conversions into gaseous form by evaporation and coming down again to the earth as rainfall. A part of it sinks to the soil pores and constitutes the ground water. Another part runs off as surface water in the rivers.

    Water pollution is a departure from its normal state, since this widely distributed substance is such a good solvent that it is never found naturally in a completely pure state. Even in the most unpolluted geographical areas, rainwater contains dissolved carbondioxide, oxygen and nitrogen and may also carry in suspension dust or other particles picked up from the atmosphere. Surface and well water usually contains dissolved compounds of metals like sodium, magnesium, calcium and iron. Even drinking water is not pure in a chemical sense. Even after the removal of suspended solids and destruction of harmful bacteria, many substances still remain in solution to give water the characteristic taste by which it is recognised.

    The World Health Organisation has estimated that 80 per cent of all sickness and disease is caused by polluted water, its unavailability and inadequate sanitation. Around 25 million children under five die each year from water-associated diseases, one-third of these deaths being from diarrohea alone.

    Due to indiscriminate discharge of domestic sewage and industrial wastes into rivers and streams everywhere, water is increasingly becoming polluted. It is a problem that merits people’s attention. When people put the environment first, development will be lasting.

    The signs of water pollution are obvious to even the most casual observer. Drinking water tastes bad. Masses of aquatic weeds are growing unchecked in many water bodies. Rivers, lakes and ocean beaches emit disgusting odors. Fish are decreasing in numbers and the meat of some of them is tainted. Oil can be seen floating on the surface of water bodies or deposited as scum on beaches. The origin of these problems must be attributed to many sources and types of pollution. These include plant nutrients, synthetic organic compounds (fuels, plastics, fibres, elastomers, solvents, detergents, paints, pesticides, food additives and pharmaceuticals), petroleum hydrocarbons, inorganic chemicals and mineral substances, sediments, radioactive substances and thermal pollution.

    The Central Pollution Control Board through its network of about 500 water quality monitoring stations on Indian rivers and their tributaries has identified 39 polluted river stretches requiring action programmes for upgrading water quality. Moreover, minor surface water drainage channels, receive untreated domestic sewage and industrial wastes and have virtually turned into open sewers. Indiscriminate disposal of municipal solid wastes and hazardous industrial sullage on land severely contaminates ground water reserves. Pumping of industrial wastewater into ground water to get rid of wastes is also being reported. Pollution of ground water is very difficult to be ckecked.

    The fact that ground water is commonly available and easily procurable has made it vulnerable to over-exploitation. Indiscriminate boring and extraction and over-exploitation of ground water in some areas has caused a disturbance of the state of equilibrium of the reservoir. This has resulted in lowering of water table, decreased pressure in aquifers and changes in the speed and direction of flow of water which could disturb the hydrological cycle in the region, triggering several negative environmental impacts. Because of domestic and industrial pollution, many areas have been affected, from natural pollutants like - high nitrate, high fluoride, high arsenic, high iron which are highly toxic.

    The pathogens most frequently transmitted through water are responsible for infections of the intestinal tract, i.e., typhoid and paratyphoid fevers, dysentery and cholera, and those causing polio and jaundice. Historically, the prevention of water-borne diseases was the primary reason for water pollution control. The responsible organisms present in the faeces or urine of infected persons ultimately get discharged into a water body and contaminate water supply leading to an outbreak of disease.

    Controlling water pollution is quite a complex and expensive exercise than thought few decades ago. This does not mean, however, that the millions of rupees spent on this purpose has been wasted. On the contrary, muchmore deterioration in water quality would have occurred otherwise. In the years ahead, the scope of the anti-pollution struggle is being broadened.

    Cleaning wastewater effluent is an important aspect of water pollution control efforts. The primary treatment includes screening, grit removal and sedimentation.

    The secondary or biological treatment consists of a trickling filter, activated sludge process or extended aeration process like aerated lagoons or oxidation ditches. A natural self-purification process using algae-bacterial symbiosis is referred to as stabilization pond. More recently, a device known as Rotating Biological Contactor has been developed as a low-cost wastewater treatment system.

    Tertiary or advance treatment includes the removal of suspended solids, dissolved organic compounds and dissolved inorganic plant nutrients and minerals. Microstraining, precipitation, adsorption, electrodialysis, reverse osmosis and chlorination are some of the processes in this category. A dissolved air floatation unit has been developed for removal of some of the suspended and dissolved impurities in water.

    The project is funded by the World Bank and the Netherlands Government . The project covers Gujarat, Madhya Pradesh, Maharashtra, Orissa, Andhra Pradesh, Tamil Nadu, Karnataka and Kerala. The beneficiaries are Central and State government organisations - Central Water Commission (CWC), Central Water and Power Research Station (CWPRS), Central Ground Water Board (CGWB), State Surface Water Department (SSWD), State Ground Water Department (SGWD), State Ground Water Survey and Investigation (SGWSI), Ground Water Survey and Development Agency (GSDA) and Water Resources Department (WRD) under the Ministry of Water Resources, Government of India. The objectives of the project are to develop a comprehensive, easily accessible and user-friendly data bases covering all aspects of hydrological cycle including surface and ground water in terms of quantity, quality and climatic measurements, particularly of rainfall, through a network of a total of about 299 laboratories. This would assist in the development of more reliable and specifically intensive data on water resources and making information available for planning and management of water resources. The goal is to be achieved by improving institutional and organisational arrangements, technical capabilities and physical facilities available for collection, processing and exchange of hydrological, hydro-geological and hydro-meteorological data.