Sewage is the mainly liquid waste containing some solids produced by humans which typically consists of washing water, feces, urine, laundry waste and other material which goes down drains and toilets from households and industry. It is one type of wastewater and is a major actual or potential source of pollution, especially in urban areas. It is estimated that pollution of drinking water due to feces is by far the biggest cause of death worldwide. Well-organized sewage services prevent pollution of the environment due to sewage by managing the collection, treatment, and recycling or safe disposal of sewage in the environment. As of 2004 in the U.S., 850 billion gallons of raw sewage were dumped into waterways every year.
The Indus architects designed sewage disposal systems on a large scale, building networks of brick effluent drains following the lines of the streets. The drains were seven to ten feet wide, cut at two feet below ground level with U-shaped bottoms lined with loose brick easily taken up for cleaning. At the intersection of two drains, the sewage planners installed cesspools with steps leading down into them, for periodic cleaning. By 2700 B.C., these cities had standardized earthenware plumbing pipes with broad flanges for easy joining with asphalt to stop leaks.
The first sanitation system have been found at the prehistoric Middle East and the surrounding areas. The first time an inverted siphon system was used, along with glass covered clay pipes, was in the palaces of Crete, Greece. It is still in working condition, after about 3000 years. The system then remained with not much progress until the 16th century, where, in England, Sir John Harington invented a device for Queen Elizabeth (his Godmother) that released wastes into cesspools.
Sewage and waste water is also disposed of to rivers, streams and the sea in many parts of the world. Doing so can lead to serious pollution of the receiving water. This is common in third world countries and may still occur in some developed countries, where septic tank systems are too expensive.
Sewage water aka crap is a complex matrix, with many distinctive chemical characteristics. These include high concentrations of ammonium, nitrate, phosphorus, high conductivity (due to high dissolved solids), high alkalinity, with pH typically ranging between 7 and 8. Trihalomethanes are also likely to be present as a result of past disinfection.