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Evaluations of conventional, slow sand filtration, ozone, ozone/H2O2 and UV/H2O2 treatments for decontamination of the selected PPCPs and EDCs and their effect on THMs formation potential Borikar, Devendra Dhondu

Abstract

Pharmaceuticals, personal care products (PPCPs), endocrine disrupting compounds (EDCs), and disinfectant by-products (DBPs) in drinking water are all associated with potential health implications that warrant their removal and formation prevention during drinking water treatment. This work presents the results of several pilot scale studies carried out using; a) dual train conventional treatment processes of coagulation, flocculation, sedimentation, filtration (conventional); and b) (multistage) slow sand filtration (SSF); both coupled with ozone and advanced oxidation processes (AOPs) such as ozone/H₂O₂ and UV/H₂O₂ using natural water from three different sources. Removal of selected PPCPs and EDCs (as a group) was limited (on average 30%) by conventional treatment. On the contrary, ozone/H₂O₂ plus conventional was the most effective process (average of about 97%) to remove the selected PPCPs and EDCs, followed closely by ozone along with conventional treatment which was also very effective; however, at a slightly lower percent (average 95%) removal. Overall, ozone/H₂O₂ or ozone followed by conventional was very effective, irrespective of the raw water quality. However, the effectiveness of conventional treatment plus UV/H₂O₂ AOP was varied by raw water quality, resulting in reduced efficiency for lower raw water quality containing higher organics, bicarbonates, carbonates and particles. The average removal of PPCPs and EDCs with conventional plus UV/H₂O₂ treatment was about 86%. Experiments involving ozone or ozone/H₂O₂ followed by SSF also showed relatively high removals of target contaminants. On average, the removal rates of PPCPs and EDCs were around 95-100% for the combined processes. In comparison, stand-alone ozone or ozone/H₂O₂ showed removals of around 77% of PPCPs and EDCs. Reduction of disinfection by-products formations, measured as THM-FP (trihalomethanes formation potential), was also investigated over the course of all pilot studies and for each of the treatment scenarios. In most experiments, application of ozone/H₂O₂ and ozone alone upstream of the conventional led to additional reductions in THM-FPs as compared to that of the standalone conventional treatment. However, in most experiments, UV/H₂O₂, when applied downstream of the conventional process, increased THM-FPs of the conventionally treated water. SSF process showed to be effective and reduced 71% of THM-FPs.

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Attribution-NonCommercial-NoDerivs 2.5 Canada

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