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1. Disinfection By-Products: A Historical Perspective PowerPoint Presentation
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1. Disinfection By-Products: A Historical Perspective

1. Disinfection By-Products: A Historical Perspective

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1. Disinfection By-Products: A Historical Perspective

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  1. 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)

  2. 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-)

  3. 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.

  4. 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)

  5. 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

  6. 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

  7. 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)