Abstract
The effects of disinfectants on activated sludge were studied using pretreated swine feces as a waste water. The disinfectants used were sodium dichloroisocyanurate (SDIC), sodium hypochlorite (SHC) and formaldehyde (FA). The COD and transparency of the effluent, accumulation of MLSS and faunal characteristics of mircroorganisms (protozoa and metazoa) were investigated. The critical concentrations of SDIC, SHC and FA at which the effluent COD and transparency were deteriorated were 5, 1 and 25mg/l respectively, and those at which the accumulation of MLSS was reduced were 5, 5 and 100mg/l respectively. The concentrations of these disinfectants at which the microorganisms were adversely affected were 2.5, 1 and 10mg/l respectively. Carchesium, Trachelophyllum, Aspidisca, Vorticella and Aeolosoma were highly susceptible to these disinfectants. The results obtained indicated that FA is suited for the safest achievement of waste water treatment by the activated sludge process, and SDIC and SHC come next to FA in the order named. The results also suggested the necessity of controlling the concentrations of SDIC, SHC and FA not to exceed 5, 1 and 25mg/l/day respectively for preventing deterioration of the purification efficiency.
