AWWA WQTC60736

In 2002, the Disinfectants/Disinfection Byproducts (D/DBP) Rule affected surface watertreatment plants serving at least 10,000 people. The rule required staff at conventional treatmentplants to begin monitoring for total organic carbon (TOC). Staff at smaller plants also startedmonitoring 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 conventionaltreatment processes. Because these monitoring and removal requirements are a vital part ofregulations affecting numerous water suppliers across the nation, TOC is now used as theprimary surrogate for the determination of precursors to disinfection byproduct formation. Thesesame 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 datacollected during the first two years of the D/DBP Rule, and fewer still have compared treatmentplant TOC data to TTHM and HAA5 data collected from the distribution system.In Pennsylvania, compliance data for TOC, TTHM and HAA5 is available from 73surface water systems using a total of 85 conventional filtration plants, covering the first twoyears of monitoring under the D/DBP Rule. The data was gathered from a regulatory reportingdatabase housed at the Pennsylvania Department of Environmental Protection. This compliancedata was then compiled and analyzed to examine the relationships between TOC concentrationsat the plants and TTHM/HAA5 formation in the distribution system. In addition, an analysis wascompleted on 8 plants with the highest and lowest finished water TOC concentrations out of the73 systems in Pennsylvania. Finally, three plants in southeastern Pennsylvania were examinedmore closely to study the effects of enhanced coagulation on the levels of TTHM and HAA5 inthe finished water.When comparing data from the 73 water systems, the authors observed no apparentcorrelation between either raw or finished water TOC and TTHM concentrations over much ofthe range of TOC values examined in this study. In addition, they found no apparent correlationbetween TOC and HAA5 over the entire range of TOC values. Examining data from the 8 plantswith the highest and lowest average TOC concentrations in the finished water showed no grouprelationship with TTHM or HAA5 levels in the distribution system. Of the three treatment plantsstudied in detail, all were able to improve TOC removal through the plant as a result of enhancedcoagulation. Enhanced coagulation processes reduced TTHM levels but not HAA5 levels.Overall, this study found no universal relationship that can be used to predict disinfectionbyproduct formation in the distribution system based on TOC values in the source water orfinished water. While such a relationship may be possible at an individual water system, therelationship would have to be established empirically on a system-by-system basis. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/15/2004

Number of Pages:

20

File Size:

1 file , 1.1 MB