Effects of chemical and biological membrane filtration pre-treatment processes on NOM characteristics
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Date
2019-11
Authors
Vojdani, Zahra
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Abstract
Membrane filtration is commonly applied to reduce dissolved organic carbon (DOC) concentration to control trihalomethanes (THMs) formation; however, the high levels of DOC in the Canadian Prairies water sources can cause severe membrane fouling. Integrated biological and reverse osmosis membrane (IBROM) process is an RO membrane treatment unit utilizing primarily biological filtration pre-treatment. IBROM process claims to remove biodegradable DOC (BDOC), which allegedly should result in reduced fouling of the RO membranes. In this study, several pre-treatment methods, such as coagulation (with alum, polyaluminum chloride (PACl), aluminum chlorohydrate (ACH) and ferric chloride) and oxidation (with KMnO4 and H2O2/UV) were evaluated for removal of DOC, BDOC, and THMs formation potential (THMFP). Moreover, BDOC change was measured in the biofiltration process using filters in the IBROM system. High-organic raw water source supplying the community of Herbert (Saskatchewan, Canada) was used in the experiments (DOC =17.5-22.7 mg/L and BDOC= 5.7-7.5 mg/L). The IBROM filters reduced DOC by 11% and increased the BDOC by 7%. Although the coagulation with PACl achieved the highest DOC and BDOC reduction (up to 57% and 58%, respectively), the coagulated water had the highest THMFP. H2O2/UV oxidation reduced the DOC only slightly by 10%, but the corresponding increase of BDOC and reduction of THMFP was very high (43% and 72%, respectively). Similar observations were made regarding oxidation with KMnO4. Overall, the waters with a higher concentration of BDOC had lower THMFP.
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Keywords
Biodegradable dissolved organic carbon (BDOC), Integrated Biological and Reverse Osmosis membrane (IBROM), Membrane pre-treatment, Natural organic matter (NOM), Trihalomethanes (THMs)