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 60 o C 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 (BrO 3 - ), 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)