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Proposed mechanisms for the increase and decrease in trichloroacetic acid formation potentials (TCAAFPs) of anthropogenic compounds after biodegradation. a Decrease in TCAAFPs of catechol and phenol. b Increase in TCAAFP of hydroquinone. c Decrease in TCAAFPs of paracetamol and 4-aminophenol
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During drinking water treatment processes, anthropogenic compounds act as important precursors of disinfection by-products such as haloacetic acids (HAAs). Several transformations in these precursors occur prior to the disinfection stage, such as partial biodegradation. We hypothesized that this partial biodegradation of anthropogenic compounds pot...
Citations
... The yield of TCAA increased linearly in the first 2 h (6.65 (μg/mg) •h − 1 ), then gradually stabilized after 24 h. The maximum yield of TCAA was 23.28 μg/mg at 48 h, which was about 42 times that of DCAA, and might be attributed to an excess of chlorine [83]. ...
As a globally important artificial sweetener, sucralose (SUC) is a persistent emerging contaminant in global aquatic environments. This research comprehensively track the fate and transport of SUC throughout an urban water cycle; to perform laboratory experiments to determine chlorinated disinfection by-products (DBPs) of SUC sebsequent to advanced oxidation with ozone; and to perform a risk evaluation of SUC related DBPs.; The results demonstrated that SUC was consistently present throughout the urban water cycle, including consumer's tap water. The inluent to the municipal wastewater treatment plant contained 1033.4-2626.3 ng/L SUC, and as expected for this non-biodegradable artificial sweetener, the concentration in the effluent was slightly reduced to 917.6-2031.2 ng/L. The concentration of SUC varied in surface waters with a peak value of 2070.0 ng/L. In finished drinking water 288.1–505.3 ng/L SUC was found, and values of 177.7–409.7 ng/L were present in the distribution system. Up to 16.3% of SUC concentration discharged as municipal wastewater was delivered to residents in their drinking water. While conventional treatment little removed SUC, the mean removal efficiency of SUC with ozonation followed by activated carbon filtration was 39.6% at a full-scale drinking water treatment plant. The fate and transformation of SUC in drinking water treated by ozonation and chlorination were investigated in laboratory experiments. Ozonation partially degraded SUC; however, intermediates reacted with chlorine to generate DBPs, including trichloromethane (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA). Peak 7-days potential formation of TCM, DCAA and TCAA were 0.016, 0.51 and 23.34 μg/mg SUC, respectively. DBP yields increased with increasing chlorine dosage, chlorination time, temperature, and solution pH. The presence of ammonia nitrogen in water facilitated dichloroacetonitrile (DCAN) production up to 0.78 μg/mg SUC, while simultaneously reducing the yield of TCM, DCAA and TCAA. Human exposure analysis revealed that carcinogenic risks of DBPs caused only by SUC ozonation were in the range of 1.86 × 10⁻¹²-6.12 × 10⁻⁹, while non-carcinogenic risks were in the range of 6.0 × 10⁻⁹-4.37 × 10⁻⁶. The pervasive occurrence of SUC in an urban water cycle, couple to its resistance to biological and chemical treatment, confirms that SUC is a persistent contaminant in the aquatic system, including tap water.
Wildfires can release pyrogenic dissolved organic matter (pyDOM) into the forest watershed, which may pose challenges for water treatment operations downstream due to the formation of disinfection by-products (DBPs). In this study, we systematically assessed the physio-chemical properties of pyDOM (e.g., electron-donating and -accepting capacities; EDC and EAC) and their contributions to DBP formation under different disinfection scenarios using (1) ten lab samples produced from various feedstocks and pyrolysis temperatures, and (2) pre- and post-fire field samples with different burning severities. A comprehensive suite of DBPs-four trihalomethanes (THMs), nine haloacetic acids (HAAs), and seven N-nitrosamines-were included. The formations of THM and HAA showed an up to 5.7- and 8.9-fold decrease as the pyrolysis temperature increased, while the formation of N-nitrosamines exhibited an up to 6.6-fold increase for the laboratory-derived pyDOM. These results were supported by field pyDOM samples, where the post-fire samples consistently showed a higher level of N-nitrosamine formation (i.e., up to 5.3-fold), but lower THMs and HAAs compared to the pre-fire samples. To mimic environmental reducing conditions, two field samples were further reduced electrochemically and compared with Suwannee River natural organic matter (SRNOM) to evaluate their DBP formation. We found increased DBP formation in pyDOM samples following electrochemical reduction but not for SRNOM, which showed increased N-nitrosamines but decreased THMs and HAAs post-electrochemical reduction. Furthermore, this study reported for the first time the formation of two previously overlooked N-nitrosamines (i.e., nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA)) in both laboratory and field pyDOM samples, raising concerns for drinking water safety given their higher toxicity as compared to the regulated counterparts. Results from this study provide new insights for DBP mitigation during post-fire recovery, which are particularly relevant to communities that rely on forest watersheds as their drinking water sources.
The occurrence of disinfection byproducts (DBPs) is related both to drinking water treatment (DWT) processes and to raw water’s characteristics. Emerging pollutants typically occur in low concentrations and are not removed by conventional DWT processes. Emerging DBPs appear within the DWT or in the distribution system due to the combination of disinfection agents (especially chlorine) with precursors as: natural organic matter (NOM), algal organic matter (AOM), anthropogenic contaminants (pesticides, pharmaceuticals, detergents etc.), brominated and iodinated compounds.
This study has as main goal a consistent analysis of the major problems caused by emerging DBPs to drinking water supplies. It presents a comprehensive review of the research efforts related to emerging DBPs considering three viewpoints: 1. an overview of their classification, legislative framework, methods of analysis, disinfection operational conditions and removal processes; 2. their occurrence, fate, health effects and impacts; 3. the analysis of the advanced DWT processes that might be used for the removal and control of precursors and DBPs, with a focus on pilot and full-scale installations. All presented case studies considered pollutants removed, process conditions and efficiencies, and a critical assessment of processes based on membranes, advanced oxidation and adsorption on activated carbon or other materials. The main challenges of the control and removal of emerging DBPs are their low concentrations and the technical and economic sustainability of their application at full-scale, which need to be carefully adapted to local boundary conditions.
