Abstract
Small drinking water treatment systems (serving <10,000 population) in rural communities frequently encounter multiple challenges in water quality and federal regulatory compliance, especially the disinfection byproduct (DBP) regulations, due to source water variations, limited resources, and aging infrastructures. Unlike most studies on the DBP control using synthetic water in laboratory settings, this research aimed to identify the major water quality issues confronting small systems in the state of Missouri (MO), the United States of America (USA). Three small systems were selected based on source water and geographic locations. Water samples were collected quarterly from each major treatment process during the period of May 2012 to March 2013 and analyzed to identify the treatment effectiveness and potential water quality issues in each small system. Results of water quality characterization showed that the major water quality issue in the selected small systems was the low efficiency of dissolved organic carbon (DOC) removal, especially the DOC species that are considered as the DBP precursors. Most collected water samples had a higher trihalomethane formation potential (THMFP) than the United States Environmental Protection Agency (USEPA) maximum contaminant limit (MCL) (80 μg/L). Based on the analysis of the treatment efficiency in each system, several strategies for water quality improvement were recommended, and a few of which have been implemented in the small systems, leading to improved drinking water quality and compliance with the USEPA DBP regulations. This study would provide a valuable aid to small system operators and local water authority in context of water quality improvement and the regulatory compliance.
Highlights
Drinking water treatment operation typically consists of a series of processes, including aeration, coagulation-flocculation-sedimentation, activated carbon treatment, and chlorination
Disinfection with various oxidants, such as chlorine, has widely been used for reducing the incidence of waterborne diseases caused by bacteria and viruses since the beginning of the 20th century [1,2]; the disinfectants applied deactivate waterborne microorganisms, and react with substances other than pathogens present in the source water, i.e., natural organic matter (NOM) or dissolved organic carbon (DOC), which leads to the formation of numerous disinfection
Among the toxic disinfection byproduct (DBP), trihalomethanes (THMs), a group of halogenated organic compounds including chloroform (CHCl3 ), dibromochloromethane (CHBr2 Cl), bromodichloromethane (CHBrCl2 ), and bromoform (CHBr3 ), were first detected as a result of water chlorination in 1974 [11]. As they are often the dominant DBPs, THMs were regulated by the United States Environmental Protection Agency (USEPA) in 1979 with maximum contaminant level (MCL) of 100 μg/L for total THMs (TTHM) [12]
Summary
Drinking water treatment operation typically consists of a series of processes, including aeration, coagulation-flocculation-sedimentation, activated carbon treatment, and chlorination. Among the toxic DBPs, trihalomethanes (THMs), a group of halogenated organic compounds including chloroform (CHCl3 ), dibromochloromethane (CHBr2 Cl), bromodichloromethane (CHBrCl2 ), and bromoform (CHBr3 ), were first detected as a result of water chlorination in 1974 [11]. As they are often the dominant DBPs, THMs were regulated by the United States Environmental Protection Agency (USEPA) in 1979 with maximum contaminant level (MCL) of 100 μg/L for total THMs (TTHM) [12]. The implementation of Stage 2 DBPR required all drinking water treatment plants in compliance with the MCL of
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