Biodegradation of nonionic surfactants containing propylene oxide

Insertion of oxypropylene groups into the polyoxyethylene chain of fatty and oxo alcohol ethoxylates decreased the rate and extent of biodegradation. The magnitude of the effects was proportional to the PO‐block size and the extent of branching in the alcohol. Data are presented from a series of PO‐containing nonionic surfactants in semi‐continuous activated sludge reactors over test periods of up to 12 weeks. Bioassays performed on effluents from the SCAS units showed little or no toxicity due to residual degradation metabolities towardPimephales promelas andDaphnia pulex and a stimulatory effect onSelenastrum capricornutum growth rate.