Biological Treatment of Pollutants and Wastes

Abstract

Sewage is composed not only of the waste matter flushed from toilets, but also of the waste collected from all other drains in homes and other buildings. A sewer system brings all the tub, sink, and toilet drains together into larger pipelines and sewers. The final mixture from the collection system is called raw sewage or raw wastewater. Raw sewage contains about 1 part of waste in 1000 parts of water (i.e., 0.1% waste to 99.9% water). The raw sewage output in developed countries is on the order of 600--800 liters per person per day. This means that a community of 100,000 persons will produce 60--80 million liters of wastewater everyday. With storm water, raw sewage is diluted but the pollutants are nevertheless enough to darken the water and give it a foul smell.