Centralized wastewater treatment plants (WWTPs) and decentralized wastewater treatment systems (DEWATS) differ in terms of the size of their sewersheds and the greater reliance on aerobic treatment in conventional centralized plants compared to primarily anaerobic treatment in typical DEWATS. Given that hundreds of new chemicals are approved annually, many of which are introduced to wastewater streams, the ubiquitous organic compounds found in WWTPs and DEWATS as well as their persistence and removal is of interest from public health and ecosystem health perspectives. Here, we utilize non-targeted analysis (NTA) with comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry (GC×GC/TOF-MS) to conduct a comprehensive evaluation of the common persistent and removed compounds found in two centralized WWTPs in the USA and South Africa and one DEWATS in South Africa that treat primarily residential wastewater. Overall, removal efficiencies of chemicals were similar between the treatment plants when they were compared for the number of chemical features detected in the influents and effluents of each treatment plant. However, the DEWATS treatment train, which has longer solids retention and hydraulic residence times than both of the centralized WWTPs and utilizes primarily anaerobic treatment processes, was able to remove additional compounds with low numbers of oxygen atoms. Of the 111 compounds tentatively identified in all three influents, 15 compounds were persistent in all replicates, including well-known emerging contaminants like triclosan and 7 other compounds not previously reported in effluents of WWTPs or water reuse systems. There were no significant differences among the physico-chemical properties of persistent and removed compounds, but significant differences were observed among molecular descriptors related to shape and bonds. These results have important implications for the treatment of trace organic chemicals in centralized and decentralized WWTPs and the monitoring of new compounds in WWTP effluent.

Ubiquitous trace organic chemicals in conventional aerobic and decentralized anaerobic wastewater treatment systems

ACS Spring Meeting 2021

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