Influence of sedimentation with pre-coagulation on ultrafiltration membrane fouling performance

Baiwen Ma; Yanyan Ding; Bodong Wang; Zenglu Qi; Yaohui Bai; Ruiping Liu; Huijuan Liu; Jiuhui Qu

doi:10.1016/j.scitotenv.2019.134671

Influence of sedimentation with pre-coagulation on ultrafiltration membrane fouling performance

Sci Total Environ. 2020 Mar 15:708:134671. doi: 10.1016/j.scitotenv.2019.134671. Epub 2019 Nov 22.

Authors

Baiwen Ma¹, Yanyan Ding², Bodong Wang³, Zenglu Qi⁴, Yaohui Bai⁵, Ruiping Liu⁴, Huijuan Liu⁶, Jiuhui Qu⁴

Affiliations

¹ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
² Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
³ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
⁴ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
⁵ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: yhbai@rcees.ac.cn.
⁶ School of Environment, State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, China; Research Center for Water Quality and Ecology, Tsinghua University, Beijing 100084, China.

PMID: 31796291
DOI: 10.1016/j.scitotenv.2019.134671

Abstract

Coagulation plays an important role in effectively alleviating ultrafiltration (UF) membrane fouling due to the existence of flocs. In comparison to traditional filtration, direct filtration (no sedimentation tank) is generally considered to result in less membrane fouling due to the looser cake layer formed on the membrane surface. However, cake layer characteristics are easily influenced by operating conditions (e.g., sedimentation time, temperature), resulting in different fouling loads and the still very limited knowledge about the fouling behavior. Here, a detailed investigation of UF membrane performance was carried out to analyze the differences between traditional filtration and direct filtration. The results showed that a critical settling time indeed existed when flocs gradually settled, leading to severe membrane fouling induced by a dense and thick cake layer. Therefore, the traditional filtration performed worse when the settling time was shorter than the critical time, while it performed better when the settling time was longer. In comparison to room temperature water, the proportion of membrane fouling caused by the cake layer increased at low water temperature due to the contracted membrane pore size, and the cake layer thickness became the main fouling load. The longer the settling time, the fewer pollutants reached the membrane surface, the thinner the cake layer, and the lower the potential for membrane fouling. Thus, traditional filtration performed better than direct filtration, and the critical settling time was not obvious. Although solution pH played an important role in floc properties, the fouling load was influenced little and traditional filtration still performed better. This work shows that the cake layer properties/fouling loads vary with the settling time during the coagulation-UF process, and this finding is of great significance to the improvement of membrane technology in drinking water plants.

Keywords: Direct filtration; Fouling behavior; Sedimentation; Traditional filtration; Ultrafiltration.