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Technical, economic and environmental assessment of coagulation/filtration tertiary treatment processes in full-scale wastewater treatment plants

Wang, Dan, Guo, Fang, Wu, Yihui, Li, Zhiping, Wu, Guangxue
Journal of cleaner production 2018 v.170 pp. 1185-1194
chemical reduction, chlorides, coagulation, economic costs, electric energy consumption, energy conservation, environmental assessment, environmental impact, eutrophication, filtration, greenhouse gases, phosphorus, regression analysis, total suspended solids, wastewater treatment, China
The technical performance, economic cost and environmental impact of six full-scale tertiary coagulation/filtration processes located in Kunming, China were evaluated. All tertiary treatment processes removed total phosphorus (TP) and total suspended solids (TSS) efficiently, with the removal percentages of 55.0%–80.0% and 50.0%–74.0%, respectively. Polyaluminium chloride (PAC) consumption for TP and TSS removal in the six tertiary treatment processes were quite different, with chemical dosages of 7.9–38.5 g PAC/g TP removed and 0.3–1.7 g PAC/g TSS removed, respectively. The multiple linear regression analysis showed that the PAC dosage closed to the optimal value benefited TP and TSS removal, and this also reduced the economic cost. For environmental impacts, the main source of greenhouse gas was electricity consumption and the coagulation/filtration process had positive effect on reducing eutrophication. The comprehensive assessment including technical, economic and environmental aspects was characterized by the composite cost index. The composite cost index showed that the tertiary treatment process of micro-flocculation with D type/cloth media filtration achieved the best comprehensive performance, while D type filter had great potential for energy saving and chemical reduction.