Effect of thiosulfate and of sulfide on biochemical oxidation of surface-active substances

The process of biological clean-up of viscose fiber wastewater was studied to determine the effect of thiosulfate and sulfide on the biodegradation of surface active substances (SAS). The studies were carried out in laboratory aeration tanks operating under a contact regime by one- and two-stage schemes, using model viscose manufacture wastewater containing SAS, thiosulfate, and sulfide. The aeration tanks operated with an activated sludge which had been adapted to SAS for 15- 20 days. The kinetics of biodegradation were reported. Both sulfide and thiosulfate have a negative effect on the SAS removal efficiency, with the efficiency of the two-stage scheme higher than the one-stage scheme. The effect of thiosulfate was also determined in treating actual wastewater and the inhibiting effect was similar.