Low Cost Soil-Based Biological Treatment for Water Reclamation

Abstract

Water reclamation is a strategy of moving toward sustainable management of freshwater and environmental protection. Treated wastewater has been widely recognized as a potential source of water for landscape and agricultural irrigation, industrial cooling, surface replenishment, groundwater recharge, portable and non-portable use for the past decades. However, concerns about pathogenic organisms and trace organic contaminants in reclaimed water remaine. Low-cost treatment methods show promise in reducing these contaminants in wastewater, but more investigation of these technologies is still needed to improve the efficiency for renewable and sustainable water reclamation. This study presents the soil based filter as a treatment means to remove bacteria in agricultural and domestic effluents for water reclamation. An improved soil filter by ferric oxide based materials integrated with native soil protozoa bacterivory was efficient to eliminate E. coli in swine wastewater. Under anaerobic environment, the microbial iron reduction (MIR) process was very efficient in inactivating E. coli cells. The ferrous production in MIR process was identified as a mechanism for E. coli inactivation under the anaerobic condition. Inactivated bacterial cells were used by the MIR community as an electron donor to drive the MIR process. The anaerobic-aerobic two-stage slow sand filter was a robust system for water reclamation. High removal efficiencies of carbon substrates, trace organic compounds, and microbial contaminants were obtained in this study. The iron oxide coated sand and MIR biofilm provided adsorptive surfaces to retain bacterial cells passing through the filter media. The integration of anaerobic iron coated sand filter and aerobic sand filtration removed not only ferrous production but also improved the overall performance of the treatment system in removing bacteria. This dissertation has shown that the filters packed by iron-rich porous media provided technical and economic feasibilities to remove microbial contaminants in water reclamation. This knowledge could further improve our understanding of the fate and transport of fecal bacteria in the subsurface and sedimentary environments. Future work can be explored for the removal of pathogens enhanced by the mechanisms discovered in this study in engineering processes, such as storm water bio-retention facilities, aquifer artificial recharge, and low-cost soil based water reclamation.