Inorganic and organic substances in sewage waters

Inorganic substances present in sewage waters are essential constituents of drinking and service water, and they are also substances originating from 

Chlorides usually originate from urine. Seven to nine grams of chlorides are produced per capita per day. Higher content of chlorides can be caused by wastes from neutralization stations, recovery plants for water treatment by ion exchangers, or washings from streets after the use of sodium chloride in winter. Concentration of (borides in sewage waters is usually expressed in tens of mg 1 .  

Phosphorus compounds in sewage waters, assuming that they are not already present in drinking and service waters, come from urine, faeces and synthetic detergents. 

Other forms of organically bounded nitrogen also readily undergo mineralization, therefore, the quantitative representation of individual forms depends to a considerable degree upon the time factor. 

As regards organic nitrogen-free acids which volatilize with water vapour, acetic acid in particular occurs in sewage waters, followed by propionic, butyric, valeric, formic and caproic acids. Non-volatile acids are lactic, citric, glutaric, oxylic and other acids. These adds occur in concentrations of tenths or even units of mg 1 (expressed in the terms of carbon). 

---