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Composition of Sewage
It contains 99.9% water. Solids which barely comprise 0.1 % are partly organic and partly inorganic or partly in suspension and partly in solution. Offensive nature of the sewage is mainly due to the organic matter which it contains. In addition, sewage is charged with numerous living organisms derived from faeces, some of which may be agents to diseases. It is estimated that one gram of faeces may contain about 1000 million E.coli, 10-100 million of faecal streptococci and 1-10 million spores of Clostridium perfringens besides several other pathogens.