Occurrence of selected surfactants in untreated and treated sewage

Several surfactants were monitored in treated and untreated sewage in nine municipal wastewater treatment plants (WWTPs) in western Austria. The nine sampled WWTPs cover a wide variety referring to size and applied treatment technology. The investigation focused on linear alkylbenzene sulphonate (LAS), quaternary ammonia compounds (QAC), nonylphenol (NP), octylphenol (OP), nonylphenolmono- (NP1EO) and -diethoxylates (NP2EO). Whereas LAS, NP, OP and NP1,2EO were analysed separately in the liquid phase and in the solid phase, the QACs were measured in the total sample. Total influent concentrations of LAS varied between 2.4 mg l−1 up to 6.7 mg l−1 whereas total effluent concentrations were in the lower μg l−1 range (11–50 μg l−1). Whichever the type of treatment, a clear removal during treatment was observed. Solid liquid distribution coefficients Kd were calculated for untreated sewage. The calculated Kd values varied between 1300 and 3900 l kg−1. OP was of minor importance with total influent concentrations below 1 μg l−1. NP and NP1,2EO were present in all analysed influents in concentrations between 1 and 35 μg l−1. Effluent concentrations were notably lower than the measured influent concentrations. Kd values for NP varied between 500 and 6600 l kg−1, for NP1EO between 800 and 2700 l kg−1 and for NP2EO between 100 and 1800 l kg−1. From the QACs several alkyl benzyl (BAC), dialkyl (DDAC) and trialkyl (ATAC) ammonium chlorides with varying alkyl chain lengths were analysed. Highest total concentrations in the influents to the WWTPs were observed for the BAC-C12 and the ATAC-C16 homologues. Effluent concentrations were notably lower compared to influent concentrations, indicating removal by adsorption and/or biodegradation. The influence of the removal by adsorption increased with increasing alkyl chain length.