Existing criteria for soil filter design are based largely on particle retention principles, often involving comparison of particle size distributions of filter and the base soils, and do not account for filter clogging associated with the transport of colloid-sized fine particles. This research addresses the need for a comprehensive understanding and methodology development for design of filters incorporating physicochemical and biological mechanisms. Recent advances in filtration and biofilm theories will be exploited in the proposed research to develop design nomograms from fundamental principles. Specifically, the goals of the projects are: 1) to systematically perform an experimental evaluation of the role of physicochemical and biological characteristics of pore fluid suspension on soil filter clogging, 2) to develop and validate a mathematical model that quantitatively predicts the extent of soil clogging in terms of physicochemical and biological characteristics of the filter media and the pore fluid suspension, and 3) to use the model in a design mode and generate easily usable nomograms for designing soil filters. The experimental investigation will include two stages. In the first stage, biological activity will be suppressed and the effect of physicochemical characteristics such as the filter medium properties (particle and pore size distributions, void ratios) and the pore fluid composition (measured in terms of ionic strength/pH) will be assessed systematically. In the second stage, bacterial strains will be introduced and the effects of substrate concentrations and dissolved oxygen on biomass growth will be assessed. The filter medium in the experiments will be thoroughly characterized at the end of testing to determine the extent of particulate and biological clogging. The influent and effluent will be monitored continuously during the experiments. All information for model development and validation will be generated from the experiments. Finally, the study will take advantage of ongoing failure investigation on the Won-Ju landfill leachate collection system in Korea. The mutual collaboration with the Korean team will provide the field perspective necessary for validation of the research and the developed design tools.
