Occurrence of phthalates in surface runoff, untreated and treated wastewater and fate during wastewater treatment

Abstract

Dimethyl phthalate, diethyl phthalate, dibuthyl phthalate, butylbenzyl phthalate, bis(2-ethylbenzyl) phthalate (DEHP) and dioctyl phthalate were analysed in raw and treated wastewater as well as in surface runoff samples from traffic roads. All six investigated phthalates have been detected in all raw sewage samples, in nearly all wastewater treatment plant (WWTP) effluent samples and in all road runoff samples, with DEHP being the most abundant compound. DEHP inflow concentrations ranged 3.4–34 μg L −1 and effluent concentrations 0.083–6.6 μg L −1. In two WWTPs the fate of the phthalates was assessed by performing mass balances. Overall removal efficiencies of approx 95% were calculated. Removal is attributed to biotransformation and adsorption and the relevance of the removal via adsorption to sludge increased with increasing molecular weight and increasing lipophilic character of the compound. Except DEHP phthalate concentrations were higher in treated effluent samples than in road runoff. The environmental quality standard (EQS) for DEHP in surface waters is exceeded only in a few effluent samples, whereas nearly all road runoff samples were higher than the EQS. An assessment based on pure concentrations is not feasible and a mass balance based approach is required. Nevertheless the observations highlight the relevance of stormwater emissions and direct emissions from separated sewer systems to surface waters in relation to emissions from WWTPs and the necessity to consider all potential influences in the assessment of the status of surface water bodies with reference to xenobiotics.