AWWA ACE95260

The USEPA proposed an Information Collection Rule (ICR) as an outcome of the reg-neg process, which addresses studies to develop this information so that more informed decisions regarding technology implementation and cost can be generated in future rule making. These studies must be performed by a subset of utilities through evaluation of either GAC, membranes, or both. Specifically, systems that serve more than 100,000 people and whose source is a surface water with an influent total organic carbon (TOC) concentration greater than 4.0 mg/L, and systems that serve more than 50,000 people and whose source is a groundwater with finished TOC greater than 2.0 mg/L will be affected by this portion of the ICR. The rapid small scale column test (RSSCT) has been proposed as a bench scale method to address the performance of GAC. The objectives of the DBP precursor removal studies are to generate representative process performance data to be used for the development of treatment cost estimates at different levels of organic DBP control. The two appropriate candidate technologies to be investigated are GAC adsorption and membrane separation processes. Both processes have been shown to be effective for the removal of DBP precursors. The treatment studies can be conducted with bench scale or pilot scale systems using effluent from the treatment processes already in place that remove DBP precursors. Empty bed contact times (EBCT) of both 10 and 20 minutes must be investigated in the GAC studies. For bench scale GAC systems, four RSSCT runs must be investigated in the GAC studies. For bench scale GAC systems, four RSSCT runs must capture seasonal variability. In addition to TOC, UV absorbance (UV 254) and the formation of THM, haloacetic acids (HAA) and total organic halide (TOX) under simulated distributed system (SDS) conditions are to be measured. Only a few systems will have to implement advanced treatment processes to meet proposed Stage 1 D/DBP Rule requirements, although GAC with an EBCT of 10 minutes will be designated as one best available technology. However, during the regulatory negotiation it was anticipated that many systems will have more difficulty in meeting potential Stage 2 D/DBP Rule requirements and consequently may require implementation of advanced precursor removal techniques such as GAC or membranes. In order to evaluate the potential national impact of lower MCLs as required under Stage 2, it is necessary to develop a more robust database relating advanced treatment to DBP control. The objectives of this paper are to: review the design and previous use of the RSSCT as a predictive tool of field scale control of NOM and DBP formation; present results from a new RSSCT study; and evaluate the results in terms of regulatory implications and costs.