|Nora Han defends her final MSEE Technical report|
|January 11, 2005|
Nora Han's final oral defense of her MSEE Technical report will be held Wednesday, January 12 at 9:00AM in 1304 McGavran-Greenberg. Full details are as follows:
MSENV Technical Report Final Oral Defense
Nora J. Han
Compliance with the Stage 2 Disinfection By-Products Rule for Eleven Water Utilities in North Carolina
Tuesday, January 11th, 2005 1304 McGavran-Greenberg 9:00 AM
Eleven water utilities in North Carolina were examined to assess their potential compliance with the impending Stage 2 Disinfection By-Products (DBP) Rule. The Stage 2 Rule will require that all utilities meet the 80 5g/L maximum contaminant level (MCL) for four trihalomethanes (THM4) and the 60 5g/L MCL for five haloacetic acids (HAA5) on a locational running annual average (LRAA) basis. This represents a major departure from past DBP regulation for which compliance was based on a system-wide running annual average (RAA). Additionally, while compliance has previously been based on DBP levels for samples collected primarily at locations with average distribution system residence times, the Stage 2 Rule will base compliance on DBP levels collected at locations with maximum THM4 and HAA5 concentrations.
To assess potential compliance with the proposed Rule, it was necessary to estimate maximum THM4 and HAA5 concentrations in the distribution systems for each utility using historical data which included quarterly THM4 and HAA5 values. The approach taken was to use the USEPA Water Treatment Plant (WTP) Model and available data to extrapolate to the most remote locations in the distribution system to estimate DBP levels at these locations from which LRAAs could be calculated. In addition, because historic quarterly THM4 and HAA5 measurements could be taken as much as five months apart, the WTP Model was utilized to predict monthly DBP values from which LRAAs were calculated.
The results show that several of the utilities may have difficulties complying with the new Rule with regard to one or both of the MCLs for THM4 and HAA5. In addition, significant variations in LRAA concentrations were observed for the eleven utilities evaluated. These variations could be due to a number of factors (e.g. changes in source water quality, changes in treatment practices). A site-by-site analysis of raw water quality and treatment process trains was beyond the scope of this study but should be conducted by the individual utilities to better prepare them for the forthcoming Stage 2 DBP Rule.
Committee: Advisor: Dr. Philip C. Singer Readers: Dr. Francis A. DiGiano Dr. Howard S. WeinbergFor further information please contact Rebecca Riggsbee Lloyd by email at Rebecca_Lloyd@unc.edu