In 2002, the Disinfectants/Disinfection Byproducts (D/DBP) Rule affected surface water
treatment plants serving at least 10,000 people. The rule required staff at conventional treatment
plants to begin monitoring for total organic carbon (TOC). Staff at smaller plants also started
monitoring for disinfection byproducts, TOC and other parameters in the first quarter of 2004.
Additionally, the D/DBP Rule contains provisions for TOC removal through the conventional
treatment processes. Because these monitoring and removal requirements are a vital part of
regulations affecting numerous water suppliers across the nation, TOC is now used as the
primary surrogate for the determination of precursors to disinfection byproduct formation. These
same water suppliers must comply with maximum contaminant levels for total trihalomethanes
(TTHM) and haloacetic acids (HAA5), both of which are implicated as having long-term,
adverse health consequences. Up until now, few large-scale studies have analyzed the data
collected during the first two years of the D/DBP Rule, and fewer still have compared treatment
plant TOC data to TTHM and HAA5 data collected from the distribution system.
In Pennsylvania, compliance data for TOC, TTHM and HAA5 is available from 73
surface water systems using a total of 85 conventional filtration plants, covering the first two
years of monitoring under the D/DBP Rule. The data was gathered from a regulatory reporting
database housed at the Pennsylvania Department of Environmental Protection. This compliance
data was then compiled and analyzed to examine the relationships between TOC concentrations
at the plants and TTHM/HAA5 formation in the distribution system. In addition, an analysis was
completed on 8 plants with the highest and lowest finished water TOC concentrations out of the
73 systems in Pennsylvania. Finally, three plants in southeastern Pennsylvania were examined
more closely to study the effects of enhanced coagulation on the levels of TTHM and HAA5 in
the finished water.
When comparing data from the 73 water systems, the authors observed no apparent
correlation between either raw or finished water TOC and TTHM concentrations over much of
the range of TOC values examined in this study. In addition, they found no apparent correlation
between TOC and HAA5 over the entire range of TOC values. Examining data from the 8 plants
with the highest and lowest average TOC concentrations in the finished water showed no group
relationship with TTHM or HAA5 levels in the distribution system. Of the three treatment plants
studied in detail, all were able to improve TOC removal through the plant as a result of enhanced
coagulation. Enhanced coagulation processes reduced TTHM levels but not HAA5 levels.
Overall, this study found no universal relationship that can be used to predict disinfection
byproduct formation in the distribution system based on TOC values in the source water or
finished water. While such a relationship may be possible at an individual water system, the
relationship would have to be established empirically on a system-by-system basis. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 20 |
| Published : | 11/15/2004 |
