Seasonal species composition, density and role of nematodes in activated-sludge effluent treatment works

The species composition, seasonal distribution and role of the nematode communities in two oxidation ditch activated-sludge effluent treatment works in Cumbria, U.K. were investigated for a 12 month period (1982/83). The Diplogasteridae, and Diplogasteritus nudicapitatus in particular, dominated the nematode community in the mixed liquor, with lesser numbers of the family Rhabditidae. No correlation was apparent between seasonal patterns of nematode species composition and densities and COD, ammonia, nitrate, nitrite, chloride or inorganic phosphate in the sewage; there was a correlation with BOD5. Maximum numbers occurred at suboptimal temperatures indicating that temperature is overriden by a combination of other factors related to sewage quality and loading. Total daily energy contributions by the nematodes indicate that their role in bacterial grazing and decomposition processes in activated sludge is negligible. This is attributable to the unstable nature of the mechanical environment and an unfavourable relationship between nematode doubling time and sewage retention times. © 1987.