Over the years progress of the society has become synonymous with environmental degradation. Our effort is to break this association and to prove that we may progress without the pollution. It is a proven fact that pollution prevention pays.

Sewage
Sewage is defined as untreated excrements from humans and other animals. Since the beginning of civilization, when man learnt to live in communities and to use water fir domestic purpose, sewage is being generated. Till recently it was not creating any major problems to aquatic resources because there was no extensive water use to generate enough sewage. Now a day's rapid development and urbanization is posing problems to water resources in two ways. The increasing need for water to meet the domestic requirement and the impact of resultant sewage discharge on the receiving waters have the cumulative effect on deteriorating the quality of receiving waters. The piped water supply is the most safe and convenient mode of drinking water supply to population. In our country this facility is lacking in the village, but most urban centers are being benefited by this. When water is easily available, it is quite natural that its use will increase. As far as volume is concerned, there is much difference between water use and its consumption, because more then 80% of water being used for domestic purposes comes out sewage.

Generation of Sewage
The major problems associated with organized water supply is the management and safe disposal of sewage. In the developed countries whole city sewage is collected through a sewerage system and goes to sewage treatment plant. In our country most of the cities and towns do not have any sewerage system. It is most common to find sewage flowing on roads and being collected in some low-lying areas. In the villages, this problem is not so common because it gets absorbed by soil itself. Many experts claim that our three fourth of surface water resources are polluted and 80% of pollution is created by sewage alone. The contribution of industrial effluents and agricultural waste in water pollution is only 20% Total sewage generation from urban centers of our country is about 20,000 million litres per day and total treatment capacity is only 3,000 million litres.


Health Hazards
Raw sewage present a significant public health hazard because humans and other animals infected with pathogens, i.e. disease causing bacteria, viruses other parasitic organisms, generally discharge large number of these organisms or their eggs in their fecal excrements. These may include pathogens for typhoid, paratyphoid, diarrhoeal diseases and cholera. When discharged into the environment these parasitic organisms may infect other individuals and cause the spread of disease. These organisms are also among the most important biotic factors holding natural population in check. It is a recognized fact that natural populations are essential to maintain the quality of water. The aquatic ecosystems are also affected because, raw sewage when discharged into surface waterways, deplete dissolved oxygen content of water. As a result animals suffocate and die. Water holds only minuets amount of dissolved oxygen as compared to the atmosphere or by photosynthesis is a slow process, therefore, loading an aquatic system with too much organic matter from sewage or other sources causes an excessive proliferation of decomposers. These organisms consume oxygen faster than it enters the system, thus depending the oxygen supply. Another environmental problem resulting from the discharge of sewage into waterways is eutrophication or algal blooms, that makes water unfit for consumption.

Value of Sewage
Handing and treatment of raw sewage involves three distinct phases; collection and removal of sewage from the immediate human removal of sewage from the immediate human proximity, suitable treatment and disposal or use of treated sewage. On an average a healthy person discharges 100 to 400 grams of fecal matter and 1 to 1.31 kilogram's of urine per day, which have nitrogen, phosphate and potassium in sufficient quantities in addition to organic matter. These all are essential for plant growth and applied as chemical fertilizers in agriculture for better cropyield. The process of reusing the treated sewage is known as recycling of water

As long as the receiving body is large, compared to input of sewage, and as long as the wastes are adequately mixed and diluted, the natural ecosystem can handle additional inputs without upsetting the natural environment. However, after critical point is reached, the dissolved oxygen depletes, the number of microorganisms goes beyond the limit and obnoxious odour accompanied by undesirable qualities make water unfit for aquatic ecosystem and human consumption including bathing.

Potential Uses
After treatment, sewage may be used for irrigation, aquaculture and some industrial purpose. Raw sludge, also produced in the process, if not further processed creates another pollution problem, because it is foul smelling and houses many pathogens. Upto some years back, it was only used for incineration, land filling or simply dumping anywhere as waste. Now it has been realised that it is not a waste at all, but a valuable resource. In era of energy crisis, it is viewed as an economic source of methane, a fuel. In our country, some treatment plants have got the facility of methane generation, but gas is not properly used and simply burnt in open space. Okhla Sewage Treatment Plant in Delhi, uses this gas for electricity generation which is used for the lighting its colony. The famous, Sulabh International of Patna, Bihar is using nightsoil and urine for streetlighting. At the Asian institute of Technology, Bangkok, it was found out that raw sludge mixed with water hyacinth and vegetable leaves is very much effective for biogas production. This composting method does not require any mechanical aerators; retain most of the valuable nutrients and compost piles. In addition to this, a considerable yield to Tilapia fish was obtained when the composted product was applied as feed to fish ponds.

Everyday Urban centers are just throwing away tonnes of essential plant nutrients like nitrogen, phosphorus and potassium in the form of sewage, thus creating a burden of our economy and pollution hazards in rivers, lakes and coast line. If we manage to put al the sewage for irrigation, it is assumed that about 24 thousand tonnes of phosphorus input as chemical fertilizers may be saved. The over supply of nutrient rich sludge and sewage is causing eutrophication and premature aging of recepient water bodies. The concentration of nitrogen, phosphate, potassium and organic matter in the cities having population of more than 50 thousand, is 645, 148, 282, and 5377 tonnes per day. It is very much unfortunate for our country that despite so much technological advanced we are unable to use this resource and as a result dumping about 1685 million rupees per year in our water courses. The value of water for irrigation is additional 490 million rupees.