Ion exchange brine management

• Main Author: Nguyen, Bao Lam
• Other Authors: Chong Tzyy Haur
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Civil engineering
• Online Access: https://hdl.handle.net/10356/157827
• Institution: Nanyang Technological University

The presence of natural organic matter (NOM) in the reservoir water can pose challenges for Singapore’s water treatment system as NOM leads to membrane fouling and reacts with chlorine disinfectant to form disinfection by-products, which are carcinogenic. Magnetic ion exchange (MIEX®), a patented technology from IXOM Watercare, is an effective pre-treatment before coagulation to enhance NOM removal, reduce membrane fouling and lower the level of disinfection by-products. MIEX® resins are coupled with Vibratory Shear Enhanced Processing (VSEP) based nanofiltration (NF) process to recover sodium chloride (NaCl) from the waste brine as resin regenerant. Research into treatment of MIEX® waste brine using pressure-driven membrane filtration has been focused on polymeric membranes. There is a lack of studies into ceramic membrane, despite its advantages over the polymeric counterparts, such as reduced fouling, longer life-span and higher fluxes. Thus, the performance of ceramic membrane and the treatment of ceramic permeate to achieve high-quality permeate for make-up brine deserve further studies. Additionally, most studies related to waste brine management only focus on salt recovery from the filtration permeate. There is insufficient research into the recovery of humic substances from the concentrated waste brine for agricultural purposes. NOM in the concentrated waste brine can be recovered by diafiltration. However, several questions regarding this process are yet to be answered, such as the optimum membrane for diafiltration, and the suitable dilution factor to lower the salinity in the final concentrate to satisfactory level. Based on the research gaps highlighted above, this study consists of 3 parts. The first part investigates the filtration performance of ceramic membrane as an alternative to VSEP to achieve high-quality permeate as make-up brine. The quality of the ceramic permeate was assessed to decide whether it should be filtered through tighter polymeric NF membrane. The second part examines the filtration performance of 4 different polymeric membranes to treat the concentrated waste brine to find the optimum one for diafiltration. The final part explores the diafiltration dilution factor to recover NOM and reduce the salinity in the final concentrate to satisfactory level. The results from part 1 show that ceramic NF filtration of MIEX® waste brine followed by tighter polymeric NF membrane can achieve high dissolved organic carbon (DOC) rejection of 99.7%, high sulphate removal (99.5%), and low NaCl rejection (-4.5-27.6%). For part 2, the Na+ rejection of the 4 polymeric NF membranes is too high (over 50% removal) for diafiltration. Thus, ceramic membrane was selected for diafiltration. Three runs of diafiltration achieves an overall DOC yield of 85.4%, reduce the Cl- by 99.9%, and Na+ by 76.1%.