SEPTICITY IN SEWERS - CAUSES, CONSEQUENCES AND CONTAINMENT

This paper reviews research and development on the causes, consequence s and methods of controlling septicity in sewers. It draws on informat ion given in 57 published papers on the subject. Explanations are give n on the deviation of equations used to predict critical conditions in sewers and rising mains. The consequences of septicity, including tox icity, corrosion and odour nuisance, are described and discussed. Prev ention is always recommended over cure, but where this cannot be achie ved the methods of controlling septicity generally rely on maintaining an adequate supply of oxygen (dissolved or chemically available) to o xidize previously formed sulphide. Other options to cure the effects o f septicity include minimizing the emission of hydrogen sulphide into the atmosphere, deodorizing vented air, and the use of protective coat ings or corrosion-resistant pipes.