Exploring impacts of water-extractable organic matter on pre-ozonation followed by nanofiltration process: Insights from pH variations on DBPs formation

Muhammad Saboor Siddique; Hongbo Lu; Xuejun Xiong; Hasan Fareed; Nigel Graham; Wenzheng Yu

doi:10.1016/j.scitotenv.2023.162695

Exploring impacts of water-extractable organic matter on pre-ozonation followed by nanofiltration process: Insights from pH variations on DBPs formation

Sci Total Environ. 2023 Jun 10:876:162695. doi: 10.1016/j.scitotenv.2023.162695. Epub 2023 Mar 8.

Authors

Muhammad Saboor Siddique¹, Hongbo Lu², Xuejun Xiong³, Hasan Fareed⁴, Nigel Graham⁵, Wenzheng Yu⁶

Affiliations

¹ State Key Laboratory of Environmental Aquatic Chemistry, Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People's Republic of China; University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
² Power China Huadong Engineering Corporation Limited, Hangzhou, Zhejiang 311122, People's Republic of China. Electronic address: lu_hb2@hdec.com.
³ State Key Laboratory of Environmental Aquatic Chemistry, Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People's Republic of China.
⁴ School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
⁵ Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. Electronic address: n.graham@imperial.ac.uk.
⁶ State Key Laboratory of Environmental Aquatic Chemistry, Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People's Republic of China. Electronic address: wzyu@rcees.ac.cn.

PMID: 36898544
DOI: 10.1016/j.scitotenv.2023.162695

Abstract

This study investigated the influence of pH (4-10) on the treatment of water-extractable organic matter (WEOM), and the associated disinfection by-products (DBPs) formation potential (FP), during the pre-ozonation/nanofiltration treatment process. At alkaline pH (9-10), a rapid decline in water flux (> 50 %) and higher membrane rejection was observed, as a consequence of the increased electrostatic repulsion forces between the membrane surface and organic species. Parallel factor analysis (PARAFAC) modeling and size exclusion chromatography (SEC) provides detailed insights into the WEOM compositional behavior at different pH levels. Ozonation at higher pH significantly reduced the apparent molecular weight (MW) of WEOM in the 4000-7000 Da range by transforming the large MW (humic-like) substances into small hydrophilic fractions. Fluorescence components C1 (humic-like) and C2 (fulvic-like) exhibited a predominant increase/decrease in concentration for all pH conditions during pre-ozonation and nanofiltration treatment process, however, the C3 (protein-like) component was found highly associated with the reversible and irreversible membrane foulants. The ratio C1/C2 provided a strong correlation with the formation of total trihalomethanes (THMs) (R² = 0.9277) and total haloacetic acids (HAAs) (R² = 0.5796). The formation potential of THMs increased, and HAAs decreased, with the increase of feed water pH. Ozonation markedly reduced the formation of THMs by up to 40 % at higher pH levels, but increased the formation of brominated-HAAs by shifting the formation potential of DBPs towards brominated precursors.

Keywords: Chlorination; Haloacetic acids; Nanofiltration; Ozonation; Surface water treatment; Trihalomethanes.