Use of engineered nanoparticles (NPs) in consumer products is resulting in NPs entering drinking water sources. Subsequent NP breakthrough into treated drinking water is a potential exposure route and human health threat.
Objectives:This study investigated the breakthrough of common NPs, silver, titanium dioxide (TiO2), and zinc oxide (ZnO), into finished drinking water following conventional and advanced treatment.
Methods:NPs were spiked into five experimental waters: groundwater, surface water, synthetic freshwater, synthetic freshwater with natural organic matter, and tertiary wastewater effluent. Bench scale coagulation/flocculation/sedimentation simulated conventional treatment, and microfiltration (MF) and ultrafiltration (UF) simulated advanced treatment.
Breakthrough of NPs into treated water was monitored by turbidity removal and inductively coupled plasma – mass spectrometry (ICP-MS).
Results:Conventional treatment resulted in 2-20%, 3-8%, and 48-99% of silver, TiO2, and ZnO NPs or their dissolved ions remaining in finished water, respectively. Breakthrough following MF was 1-45% for silver, 0-44% for TiO2, and 36-83% for ZnO. With UF, NP breakthrough was 0-2%, 0-4%, and 2-96% for silver, TiO2, and ZnO, respectively. Variability was dependent on NP stability with less breakthrough of aggregated NPs compared to stable NPs and dissolved NP ions.
Conclusions:Although a majority of aggregated or stable NPs were removed by simulated conventional and advanced treatment, NP metals were detectable in finished water. As environmental NP concentrations increase, we need to consider NPs as emerging drinking water contaminants, and determine appropriate drinking water treatment processes to fully remove NPs in an effort to reduce their potential harmful health outcomes.
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