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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
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)
1 disinfection by products a historical perspective2
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-)
1 disinfection by products a historical perspective3
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.
1 disinfection by products a historical perspective4
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)
1 disinfection by products a historical perspective5
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
1 disinfection by products a historical perspective6
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
1 disinfection by products a historical perspective7
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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