Abstract
The aim of this study is to determine the impact upon dissolved organic matter (DOM) and removal of disinfection by-product (DBP) precursors of adding an ozone-biological activated carbon (O3-BAC) process after the conventional treatment process (CTP) using water from the Huangpu River in Shanghai, east China. Several metrics, including size fractionation, dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP), were employed to accomplish this goal. In the raw water collected from the Huangpu River, the low molecular weight (MW) molecules (MW <3 kDa) were absolutely dominant in DOM, accounting for more than 55% of total DOC, and the DOM resulted in a high THMFP level of 472.91 ± 4.63 µg/L after an excessive chlorination. The CTP reduced high MW molecules (MW >10 kDa) by 61% and the low MW molecules (MW <3 kDa) by only 8%. The O3-BAC presented an accumulated DOC removal efficiency of approximately 50%, in particular, showing a high degree of the removal effectiveness of low MW molecules. Samplings from the CTP, ozone and BAC were subjected to excessive chlorination to determine the THMFP, and the measured concentrations were 211.89 ± 4.58 µg/L, 169.52 ± 4.55 µg/L, and 124.42 ± 4.27 µg/L, respectively. Therefore, coupled with the THMFP removal rate of 74%, the addition of the O3-BAC process after an existing CTP improved the water quality of the effluent, particularly, in terms of the improved reduction in the precursors of DBPs.
Highlights
The presence of dissolved organic pollutants, xenobiotic compounds, in drinking water can cause a significant threat to human health, due to their chronic toxicity, persistence and bioaccumulation [1,2,3]
Hydrophobic organic pollutants and high molecular weight (MW) fractions can be efficiently removed through a conventional treatment process (CTP), which consists of multi-step unit processes of coagulation, sedimentation and sand filtration [5,6]
The total dissolved organic carbon (DOC) of the raw water collected from the Huangpu River ranged from 6.251 mg/L to 7.215 mg/L, with a mean value of 6.768 mg/L
Summary
The presence of dissolved organic pollutants, xenobiotic compounds, in drinking water can cause a significant threat to human health, due to their chronic toxicity, persistence and bioaccumulation [1,2,3]. The DOM in drinking water sources usually consists of a large range of different compounds, from largely aliphatic compounds to highly colored aromatics. Among these compounds, hydrophobic organic pollutants and high molecular weight (MW) fractions can be efficiently removed through a conventional treatment process (CTP), which consists of multi-step unit processes of coagulation, sedimentation and sand filtration [5,6]. Most of the DOM can produce precursors of disinfection by-products (DBPs) during the chlorination treatment of drinking water These DBPs are either carcinogenic or potentially carcinogenic, and their presence in drinking water is being increasingly regulated by water quality standards in many countries [7]. Increasing concerns have been focused on the reduction of the DOM levels and DPB generation during the treatment of drinking water, especially in the treatment of micro-polluted water sources [8]
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