ETC/SPWSTAC Research |
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TITLE: DBP REMOVAL BY AERATION AUTHORS: Stephanie Sherant, Hardin Yeuell, Yuefeng Xie* SUMMARY: Trihalomethanes (THMs) are a group of disinfection byproducts (DBPs) regulated in drinking water because of potential health risks. Many consecutive systems are experiencing high levels of THMs due to longer reactions time between chlorine and natural organic matter in their distribution systems. Many technologies, including enhanced coagulation and alternative disinfectants, are effective in controlling THMs in parent systems. However, most of the consecutive systems can not use these technologies because these systems receive treated water from parent systems and do not employ additional treatment processes except adding chlorine. Aeration, or air stripping, has been shown to be effective in removing volatile organic compounds. This study will explore the use of aeration in water storage tanks for THM removal in consecutive systems. A pilot study was conducted using an aeration column in Environmental Engineering Laboratories at Penn State Harrisburg. The initial concentrations, 200¦Ìg/L for each THM, 150¦Ìg/L and 100¦Ìg/L for chloroform (CF), were used. THM samples were collected at 2, 5, 10, 20, 60, 120, 180, and 240 minutes. Pilot study results indicated a removal of up to 88% of CF, 89% bromodichloromethane (BDCM), 70% dibromochloromethane (DBCM), and 40% bromoform (BF) in 60 minutes, and up to 94% CF, 99% BDCM, 96% DBCM, and 82% BF in 240 minutes or 4 hours. A larger scale study has been conducted in a swimming pool. We are in the process to analyze the data. A full scale study will also be conducted in a storage tank in a consecutive system. The results indicated aeration could be a potential technology for THM removal in consecutive systems. This technology could also be used in other water systems to control THMs in hot spots in their distribution systems. PDF: Abstract, Presentation
TITLE: DISINFECTION BYPRODUCT COMPLIANCE FOR CONSECUTIVE SYSTEMS IN PENNSYLVANIA AUTHORS: Hardin Yeuell, Yuefeng Xie* SUMMARY: An objective of the U.S. EPA's Stage 2 Disinfectants/Disinfection Byproducts Rule is to provide more equitable protection to the public through more consistent regulation of consecutive systems. A consecutive system is a public water system that receives some or all of its finished water from one or more other water systems. This study evaluates current DPB levels within forty-nine (49) consecutive systems in Pennsylvania and their thirty (30) respective wholesalers. For the three and half (3?) years of study data, THM levels for the wholesalers averaged 45 ¦Ìg/L. The THM average for the consecutive systems was 56 ¦Ìg/L (a 25% increase). For THM and HAA MCL compliance calculations, the Stage 2 Rule replaces the running annual average (RAA) method with a locational running annual average (LRAA) method. Nine (9) of the forty-nine consecutive systems (18%) had recent THM LRAA values in excess of the Stage 2 THM MCL (80 ¦Ìg/L). Two (2) other consecutive systems had a THM LRAA just below the MCL. Because most consecutive systems are small systems (89%), serving less than 10,000 people, only single location is monitored; thus, the RAA and LRAA calculations are identical. Accordingly, the Stage 2 Rule change from an RAA to a LRAA calculation will have minimal affect on Pennsylvania consecutive systems state-wide. This study also indicates that THMs (vs. HAAs) pose a more substantial problem for consecutive systems in Pennsylvania . PDF: Abstract, Presentation
TITLE: MBR PROCESS FOR DBP PRECURSOR REMOVAL AUTHORS: Hao L. Tang, John M. Regan, Yuefeng Xie* SUMMARY: Natural Organic Matter (NOM) can react with disinfectants and form disinfection byproducts (DBPs). Because of the potential adverse health influence of DBPs, the removal of DBP precursors is required by U.S. Environmental Protection Agency. Membrane bioreactor (MBR) process is an emerging technology that can achieve exceptional effluent quality. The objective of this research is to investigate the removal of DBP precursors by MBR in drinking water treatment. A laboratory-scale MBR was set up to investigate the removal of DBP precursors from a reservoir water, which had relatively high concentration of organic matter and was difficult to treat using conventional drinking water treatment processes. The MBR had an effective volume of 1.8L and consisted of a hollow fiber membrane module, which had pore size of 0.4¦Ìm. DBP precursors in both MBR influent and effluent were evaluated based on the formation potential test. The results showed that the HAA precursors from the reservoir water could be removed by the MBR process while the THM precursors were not removed. The operational conditions (hydraulic retention time (HRT) and concentration of mixed liquor suspended solids (MLSS)) of the MBR could affect the removal efficiency for DBP precursors. The results of this study also indicated that a shorter HRT and higher MLSS concentration could enhance the removal of HAA precursors. A challenge in this study is to maintain the concentration of MLSS in the MBR system. The addition of new sludge temporarily raised the DBP precursors' level and increased TOC of the MBR effluent. Future studies will be focused on optimizing the operational conditions of the MBR system. |