Non-ionic surfactant biodegradation in lab-scale activated sludge

The biodegradation of a non-ionic surfactant was evaluated by the evolution of the microbial activity and the determination of the soluble surfactant present in the effluent. Two lab-activated sludge reactors/systems were fed with synthetic sewage, one of which received in addition different concentrations - 5 and 10 mg/L - of nonylphenol ethoxylates (NPEO). The parameters employed in this assay were: control parameters (COD and SS) and activity microbial parameters (specific oxygen uptake rate and dehydrogenase activity). The removal of NPEO and the production of secondary metabolites were monitored. Solid-phase extraction and HPLC with fluorescence detection were employed for sample preparation and analysis. The results suggest that the microbial activity was not inhibited when 5 mg/L of NPEO was added. Nevertheless, an important inhibition of the general metabolism was observed for 10 mg/L of NPEO.