Abstract
High cyanobacteria-derived dissolved organic carbon (DOC) in source water can cause drinking water quality to deteriorate, producing bad taste, odor, toxins, and possibly elevated levels of disinfection byproduct (DBP) precursors. Conventional water treatment processes do not effectively remove algal organic substances. In this study, rapid-sand-filtration effluent from a water treatment plant on Kinmen Island, where serious cyanobacterial blooms occurred, was used to evaluate the DOC- and DBP-removal efficiency of ozonation and/or biofiltration. To simulate a small-scale water distribution system following water treatment, 24 h simulated distribution system (SDS) tests were conducted. The following DBPs were analyzed: trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and trichloronitromethane (TCNM). Applying biological activated-carbon filtration (BAC) on its own achieved the greatest reduction in SDS-DBPs. Ozonation alone caused adverse effects by promoting THM, HAA, and TCNM formation. Ozonation and BAC filtration yielded better DOC removal (51%) than BAC filtration alone (41%). Considering the cost of ozonation, we suggest that when treating high cyanobacterial organic matter in water destined for a small-scale water distribution system, BAC biofiltration alone could be an efficient, economical option for reducing DBP precursors. If DOC removal needs to be improved, preceding ozonation could be incorporated.
Highlights
Cyanobacterial blooms in source water can impact tap water quality and pose a serious health threat
Increases in the frequency and intensity of cyanobacteria blooms in source water have been linked to human population growth, climate change, and extreme weather events, implying that the treatment of water with excess cyanobacteria growth may become a serious challenge for water treatment facilities in the future
DOCRemoval concentration of the rapid sand filtration (RF) was high (6.69 mg C/L), and all the treatment processes tested in dissolved organic carbon (DOC) concentration of the RFparticularly was high (6.69 mg C/L), and all theBAC
Summary
Cyanobacterial blooms in source water can impact tap water quality and pose a serious health threat. Can cyanobacteria produce various toxins [1,2] and compounds responsible for taste and odor problems [3,4], they can generate algal organic matter (AOM), which has been identified as a precursor of various disinfection byproducts (DBPs) when chlorinated or chloraminated in water treatment processes [5,6,7,8]. The processing by conventional means of cyanobacteria-derived organic substances, including both intracellular and extracellular organic matter (IOM and EOM respectively), has been found to. Public Health 2018, 15, 2633; doi:10.3390/ijerph15122633 www.mdpi.com/journal/ijerph
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