Influence of spent filter backwash water recycling on pesticide removal in a conventional drinking water treatment process
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Date
2018
Authors
Li, W.
Liang, X.
Duan, J.
Beecham, S.
Mulcahy, D.
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Environmental Science: Water Research and Technology, 2018; 4(7):1-11
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The effects of recycling spent filter backwash water (SFBW) on the removal of 14 organic pesticides were examined in a simulated conventional drinking water treatment process. The experimental results indicate that, the concentrations of these pesticides in the aqueous phase of SFBW remained unchanged although turbidity of the SFBW was increased greatly relative to the raw water during filter backwashing. With recycling of the SFBW, the concentration of pesticides in the blended influent raw water varied according to both the pesticide type and the recycling ratios. For the species difficult to remove, such as cyanazine and atrazine as well as carbaryl, even at high recycling ratios of SFBW the influent concentrations of the pesticides were almost the same. However, for those species that could be removed effectively, such as tolclofos-methyl and profenofos and chlorpyrifos, the influent concentrations decreased evidently with increasing recycling ratios. In addition, the mixing process of SFBW with raw water didn’t cause any noticeable pesticide release back into the solutions from the adsorbed surfaces of the clay particles in raw water or flocs in the SFBW. Moreover, the removal efficiencies of these pesticides under different recycling scenarios indicate that the SFBW recycling had no negative influence on the pesticide removal. Finally, this study shows that, with SFBW recycling, the pesticide concentrations in filtered water were slightly lower than those without recycling and decreased evidently for hydrophobic pesticides as the recycling ratio increased.
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Copyright 2018 the authors.
Access Condition Notes: Accepted manuscript available after 1 July 2019