Reduction of Nonionic Surfactant Toxicity following Secondary Treatment

Field and laboratory studies of biodegradability and toxicity of an alkyl ethoxylate nonionic surfactant were conducted to determine degradability of the surfactant by secondary wastewater treatment and the effects of the effluent on the benthic fauna of the receiving stream. No increase in surfactant levels in plant effluent or stream stations was observed during periods when influent was spiked at 4 and 14 mg/l. The acute toxicity is eliminated by secondary treatment and the degradation products of an initial 30 mg/l concentration are nontoxic to fathead minnows. Significant changes in benthic species composition and density of some macroinvertebrates occurred during the spiking program, but these resulted from the natural seasonal life cycles.