Application of microfiltration–nanofiltration combined technology for drinking water advanced treatment in a large-scale engineering project

Abstract

Abstract By analyzing and comparing the pressurized-pot microfiltration (MF) system and the ultrafiltration membrane as the pretreatment technology of the nanofiltration (NF) system through pilot testing, the research demonstrates the feasibility of combined technology of NF with pressurized-pot MF for the practical application in engineering. The testing result indicates that the combined technology performs over 90% removal rate for organic substances and humus (UV254) and 70–80% removal rate for disinfection by-products including chloroform, bromoform and carbon tetrachloride. In addition, the combined technology also shows 70% minimum removal rate for pigments including chlorophyll and phycocyanobilin, 20–60% removal rate for water hardness, over 95% removal rate for sulfates which occupies the major part of bivalent salts, and 50–70% removal rate for odorous substances. Based on the pilot testing results, a new water purification process, which is sequentially combined by the conventional drinking water treatment technology, pressurized-pot MF and NF, is creatively applied in the large-scale engineering project of drinking water advanced treatment of Zhangjiagang Third Water Plant for the first time in China. The designed water-production amount of this project is 100 thousand tons per day, and the project is aimed at reforming and upgrading the drinking water treatment technology which is currently used in the Zhangjiagang Third Water Plant. The recovery rate of the NF system applied in the project is able to reach 90%, and the predicted electricity consumption of pressurized-pot MF system and NF system is, respectively, 0.003 and 0.197 kWh/ton of water. After accomplishing the project, Zhangjiagang Third Water Plant will be capable of supplying drinking water with higher quality and will simultaneously possess higher capability of replying to water contamination emergencies.