Comparative Analysis of Contaminant of Emerging Concern Discharges from Common On-site Wastewater Treatment Systems

Though over 25% of the United States population employs decentralized on-site technologies for wastewater treatment, a comparative understanding of treatment efficacies of these systems remain less understood than those from centralized municipal wastewater treatment plants.  In fact, it is estimated that 10 to 20 percent of these systems malfunction annually, potentially releasing untreated wastewater to groundwater, which can degrade water quality and result in impacts on surface waters in regions experiencing high groundwater–surface water exchange.  Even less understood is a comparative understanding of contaminants of emerging concern (CECs) associated with these systems and subsequent mass loadings to the environment.  The objective of this study was to assess the occurrence and mass loadings of select CECs among several different wastewater treatment systems.  An additional objective was to evaluate the influences of seasons on the mass loadings among on-site aerobic treatment systems.  The studied CECs covered a variety of common pharmaceutical classes, including analgesic, anti-hypertension, antibiotic, psychostimulant metabolites, antihistamine, anti-seizure, benzodiazepine, anticoagulant, anti-inflammatory, antilipemic, caffeine, and the artificial sweetener sucralose, which appears to represent a robust tracer of anthropogenic activities.  An isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method that employed independent isotopically-labeled standards for quantitation of each compound was applied to quantitate target analytes for all samples.  ANOVA was performed to test differences of treatment type and season on environmental loadings of CECs and other routine water quality parameters.  Results showed that mass loadings of CECs from advanced aerobic on-site systems were reduced relative to septic systems.  The present study, which included CECs with varied physicochemical properties, provides an initial understanding of the range of potential mass loading among common on-site wastewater treatment systems to the environment.