Reducing disinfection byproduct precursors and chlorine consuming substances by a special integration of biofiltration and ozonation: A pilot study

• Published in: Journal of water process engineering 2020-10, Vol.37, p.101419, Article 101419
• Main Authors: Nguyen, Phuoc Dan, Le, Thanh Do Quang, Nguyen, Nhat Huy, Tran, Kim Thach, Nguyen, Minh Tri, Huynh, Khanh An
• Format: Article
• Language: English
• Subjects: Biofiltration; Chlorine consuming substances; Disinfection by-products (DBPs); Dissolved organic carbon (DOC); Ozonation; Trihalomethane formation potential (THMFP)
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2020.101419

•Tricking filtration (TF) was unconventionally placed before low dose ozonation.•Returning of ozonated water to the TF doubled the DOC removal in Saigon river water.•A pilot system having TF-ozone and BAC removed > 70 % of THMFP in the wet season. Saigon river is the primary water supply source for Ho Chi Minh City, Vietnam. Currently, the formation of harmful disinfectant by-products (DBPs) in the piped water is elevating due to the increase in both organic matter pollution in Saigon river and chloride usage at water treatment plants (WTPs). To provide safe drinking water, the WTPs should upgrade their existing conventional surface water treatment technology to reduce DBP precursors and chlorine consuming substances efficiently. In this study, the long-term performance of a pilot system, including a biofiltration-ozonation unit and a biological activated carbon (BAC) filter in removing these compounds was evaluated. Different from other studies, a tricking filter (TF) was placed before a low-dose ozone contactor for water pretreatment. By partially returning the ozonated water to the TF, the removal of dissolved organic carbon (DOC), which contains DBP precursors, in the TF-ozonation unit was doubled. Over two months operated with highly fluctuated river water quality in the rainy season, the pilot systems stably removed 50 % of DOC, 71 % of trihalomethane formation potential (THMFP), 71 % of Fe2+, and 74 % of N-NH4+. The TF-ozonation unit was effective in removing DOC, THMFP, and NH4+, while the BAC filter was more effective in removing Fe2+. If implemented, this system can replace the pre-chlorination process accounting for 74 % of daily chlorine consumption at Tan Hiep WTP. The obtained results indicate that retrofitting WTPs with the tested processes can provide safe drinking water for Ho Chi Minh City residents in the future.