Methods to assess groundwater under direct influence of surface water and bank filtration performance

The Surface Water Treatment Rule requires the public water supplies derived from "ground water under the direct influence of surface water" (GWUDI) to receive the same treatment as waters derived directly from surface-water sources. In order to assess GWUDI, a microscopic particulate analysis (MPA) has been used as a primary tool. The objectives of this research are to find the limitations of the existing MPA and find solutions to overcome these limitations with providing a new method.;During the study, the list of indicators was revised to include other indicator surrogates that are pathogens of concern or could be a good representative of pathogens. The EnviroChek filter was evaluated as an alternative to replace existing Yarn filter and resulted in better recovery of all indicators of interest. The die-off experiments proved that a sequential elution in Laureth-12 and Glycine buffers leads to better recoveries than the existing MPA buffer.;The new protocol was applied in full-scale field studies, and it yielded better recoveries of target microorganisms than the existing protocol. Application of the new MPA resulted in the detection of Cryptosporidium and Giardia in samples which were negative for these pathogens by existing MPA. Aerobic spore concentrations in river bank filtration well water closely followed the trend of risk scores.;Results of pilot-scale indicator transport experiments were in qualitative agreement with colloid filtration theory which predicts a minimum deposition rate for colloids in the intermediate size range around 1 to 2 mum. The results also indicated that microbes might have transported over longer distances under high flow and low ionic strength conditions. The side-by-side evaluation of transport properties of aerobic spores and Cryptosporidium indicated a conservative transport behavior of aerobic spores compared to Cryptosporidium.;The new method developed in this research is faster to perform and it consistently yielded better recovery efficiencies for a broad range of microbial indicators. The result of this research suggests modifying the current risk table by including aerobic spores (conservative indicator of larger pathogens and well correlated with the MPA risk score) and Cryptosporidium oocysts (pathogen of interest) in the new MPA risk scoring table.