Complex odor control based on ozonation/GAC advanced treatment: optimization and application in one full-scale water treatment plant

Abstract

BackgroundTaste and odor problem in drinking water is one major concern for consumers and water supply. Exploring the odor characteristics and the major odor causing compounds in the source water is the base for odor control in drinking water treatment plant (WTP). In this study, focusing on a newly constructed reservoir with Huangpu River as the source water, the occurrence of typical odorants and their variations were first identified. Correspondingly, the removal behavior in an ozone/GAC advanced treatment process was investigated.ResultsThe results indicated that 2-methylisoborneol (2-MIB), geosmin (GSM), and bis (2-chloroisopropyl) ether (BCIE) have major contribution to the musty/earthy and chemical/septic odors in the source water, respectively. Pre-ozonation alone (1 mg L−1) showed limited removal for 2-MIB and BCIE, at less than 30% and 20%, respectively, while combining with coagulation, sedimentation, and sand filtration, the removals were improved to higher than 50%. After post-ozonation, the desired removal was achieved at a 1.5 mg L−1 dosage with all the odorants decreased below the corresponding odor threshold concentrations (OTCs) in the effluents. Furthermore, at a 1 mg L−1 post-ozone addition, by combining with subsequent GAC process, the odor problem was solved as well.ConclusionTo resolve the odor problem in the drinking water, the concentrations of the odorants at less than their OTCs need to be achieved. As 2-MIB and BCIE have low reactivity towards direct ozonation, a subsequent GAC is needed with a moderate dosage of post-ozonation (1 mg L−1). Thus, for the odor problem in the source water, the suggested operation is: 1 mg L−1 of pre-ozonation in combination with coagulation, sedimentation, and sand filtration, followed by a 1 mg L−1 dosage of post-ozonation and finished by a GAC process.