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1. Disinfection By-Products: A Historical Perspective. Effect of Early Analytical Methodology for Analyzing Trihalomethanes (THMs) Concentrating processes? Carbon adsorption method (CAM) – granular activated carbon (GAC) – solvent (chloroform or heating) Liquid-liquid extraction (LLE)

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1. Disinfection By-Products: A Historical Perspective

  • Effect of Early Analytical Methodology for Analyzing Trihalomethanes (THMs)

    • Concentrating processes?

      • Carbon adsorption method (CAM) – granular activated carbon (GAC) – solvent (chloroform or heating)

      • Liquid-liquid extraction (LLE)

    • Headspace analysis method (Rook, 1971,1972,1997)

      • Heated at 60oC for 12 hours  gas adsorbed on a small amount of activated silica

    • Purge-and-trap method (Bellar and Lichtenberg, 1974)


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1. Disinfection By-Products: A Historical Perspective

  • Influence of Early Studies and Surveys

    • Rook (1974): a strong relationship between source water color and chloroform levels

    • USEPA (Nov., 1974): Nationwide survey of source and finished waters (80 locations) – Started in Jan, 1975, one used ozone

      • All 79 locations – THMs found in their tap water

      • Chloramination produced lower concentrations of THMs

      • In most cases, the most abundant THM present was chloroform

      • In some locations, other THMs were higher

    • THM Formation Reaction?

      • Precursor

      • Temperature

      • Disinfectant

      • pH

      • Bromide ion (Br-)


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1. Disinfection By-Products: A Historical Perspective

  • Chlorine + Precursors  THMs

  • Control of THMs:

    • Remove the THMs

    • Remove the precursors (alum coagulation)

    • Change disinfectants

  • Increase in Bromide Ion  Increase in Brominated THMs

  • THM Formation Potential (THMFP)

    • In any given sample, a small percentage of the carbon present in the organic matter participated in the THM formation

    • The percentage influenced by the pH, temp., reaction time, chlorine residual, and bromide ion conc.


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1. Disinfection By-Products: A Historical Perspective

  • Development of the THM Rule

    • National Cancer Institute (NCI, 1976): chloroform – suspected human carcinogen

    • Maximum Contaminant Level (MCL): Federal Register (1978) – proposed MCL for TTHM as 0.10 mg/L

    • Final Rule (1979)

    • Modified THM Rule (1983)


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1. Disinfection By-Products: A Historical Perspective

  • Development of the DBP Rule

    • The Search for Additional DBPs

      • Individual compounds

        • Derivatization  GC/MS analysis

        • Identification of haloacetic acids (HAAs): Christman (1979)

        • Finding of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX): Hemming et al. (1986)

        • THMs, HAAs, haloacetonitriles (HANs), haloaldehydes, haloketones (HKs), chlororophenols, chloropicrin (trichloronitromethane), cyanogen chloride (CNCl): Krasner et al. (1989); Stevens et al. (1990)

      • A group parameter

        • Total organic chlorine (TOCl): adsorb the TOCl on powdered activated chlorine, pyrolyzing the activated carbon, and measuring the chloride ion in condensed combustion vapors – dissolved organic halogen (DOX); Standard Method 5320; total organic halogen (TOX)

        • Many of the chlorination by-products are still unknown


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1. Disinfection By-Products: A Historical Perspective

  • Development of the DBP Rule

    • Effect of the THM Rule on Water Quality

      • After the THM rule became effective in 1979  40 to 50 percent lessening in TTHM concentrations

        • Modification of their point(s) of chlorine application

        • Change of chlorine doses

        • Adoption of the use of chloramines

      • Chlroamination  decrease in TTHM conc., but increase in CNCl levels

      • Ozonation  formation of bromate ion (BrO3-), when bromide ion-containing water is treated with ozone


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1. Disinfection By-Products: A Historical Perspective

  • Related USEPA Regulations

    • Surface Water Treatment Rule (SWTR) (1987 prop. – 1989 prom.): control of pathogenic microorganisms

      • Giardia lamblia

      • Sufficient concentration of disinfectant + sufficient contact time (C  T)

    • Enhanced SWTR (ESWTR)

      • Giardia + Cryptosporidium

    • Total Coliform Rule (1987; 1989)

    • Lead and Copper Rule (1991)

      • Supply of noncorrosive water: pH increase

    • Ground Disinfection Rule (1992)


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