Method for Estimating the Toxicity of Chemicals to Activated Sludge. III. Effects of Commercial Detergents on Oxygen Uptake Rate.

Abstract

The inhibitory effects of twenty-five commercial detergents on the oxygen uptake rate (OUR) of activated sludge (AS) were investigated by the use of the oxygen electrode method. The commercial detergents are used for many application, such as laundry detergents (Sample No. 11-13), dish-washing detergents (Sample No. 21-25), household cleaners (Sample No. 31-39), fabric softeners (Sample No. 41-42), bleaching agents (Sample No. 51-54) and scouring cleansers (Sample No. 61-62). The IC50 values of the commercial detergents tested here were measured to be 670-2100, 720-2900, 660-22000, >25000, 1800-2300 and >2500 or >25000 mg/l, respectively, for No. 11-13, No. 21-25, No. 31-39, No. 41-42, No. 51-54 and No. 61-62. Surfactant is one of the major compounds in commercial detergents, and the IC50 values of the surfactants of LAS, SDS, AE, AOS, AES, AO, sodium palmitate, sodium laurate and sodium oleate were 250, 190, >2500, 150, 530, 100, >2500, 410 and >2500 mg/l, respectively. On the other hand, the builders such as sodium silicate, sodium carbonate, sodium sulfate, enzyme and fluorescent agents had little adverse effect on the OUR of AS. Therefore, it was revealed that the major inhibitory compounds in commercial detergents were not builders but surfactants.