Removal of Trihalomethane Precursors by Nanofiltration in Low-SUVA Drinking Water

Yael Dubowski,Roni Greenberg-Eitan,Menachem Rebhun

doi:10.3390/w10101370

Yael Dubowski, Roni Greenberg-Eitan + Show 1 more

Open Access

https://doi.org/10.3390/w10101370

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Journal: Water	Publication Date: Sep 30, 2018
Citations: 7	License type: CC BY 4.0

Affiliation: Technion – Israel Institute of Technology

Abstract

Trihalomethanes (THMs) are prevalent disinfection by-products. High THM formation is usually associated with natural organic matter with high molecular weight and aromatic characteristics, which is efficiently removed by nanofiltration (NF). In the Sea of Galilee and the Israeli National Water Carrier (NWC), water shows high THM formation potential, although it mainly contains low molecular weight and hydrophilic organic matter with low aromaticity. In the present study, NF removal abilities were tested on treated NWC water using three different spiral wound membranes (NF90, NF270, and DL). Rejections and fluxes were tested as a function of pressure, water recovery, and membrane type. Feed and permeate dissolved organic carbon (DOC), UVA254, total THM formation (THMF), and total THM formation potential (THMFP), as well as alkalinity, conductivity, hardness, Ca2+, Mg2+, and Cl− were measured to evaluate rejection and THM formation reduction. The results demonstrated that NF can efficiently remove natural organic matter (NOM) and reduce THM formation, even in this challenging type of water. At low water recovery, membranes showed average rejection of about 70–85% for THMFP and THM. Upon elevating recovery, average THM and THMFP rejection decreased to 55–70%, with THM content still well below regulation limits. Of the membranes tested, the higher permeability of NF270 appears to make it economically favorable for the applications tested in this work.

Highlights

Chemical disinfection of drinking water is a common treatment against pathogens, but often generates disinfection by-products (DBPs) that may pose a health risk, such as trihalomethanes (THMs), haloacetonitriles, haloacetic acids, and other chemical compounds
dissolved organic carbon (DOC) rejection measurements in a dead-end filtration setting suggest that most of the natural organic matter (NOM) in the National Water Carrier (NWC) water is smaller than 500 Da, whereas only ~2% of it is >5000 Da
These results are in agreement with previous studies on NOM size distribution in Lake Kinneret and in NWC water conducted over 20 years ago [25]

Summary

Introduction

Chemical disinfection of drinking water is a common treatment against pathogens, but often generates disinfection by-products (DBPs) that may pose a health risk, such as trihalomethanes (THMs), haloacetonitriles, haloacetic acids, and other chemical compounds. The most common class of DBPs in chlorinated drinking water are THMs, which include chloroform (CHCl3 ), bromodichloromethane (CHBrCl2 ), dibromochloromethane (CHBr2 Cl), and bromoform (CHBr3 ) [1,2]. THMs are suspected genotoxic and carcinogenic compounds [3] and their concentrations are regulated in many countries (often the only regulated DBPs). THMs are formed in a complex set of reactions between the chlorine disinfectant and natural organic matter (NOM). Aromatic NOM with high molecular weight (e.g., humic acids) is considered more reactive towards THM formation [5,6]. An appealing approach to reduce THM formation is by removal of their organic precursors (which are usually easier to remove than small and stable molecules like THMs)

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