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Wastewater soil absorption systems (WSAS) have the potential to achieve high treatment efficiencies, yet the understanding and predictability of performance with respect to removal of virus and other pathogens remains limited. As part of a long-term program of research to elucidate the fundamental relationships between performance and WSAS process design and environmental conditions, research has been completed to evaluate virus and microbial purification using multicomponent surrogate and tracer addition. The primary goal of this research was to quantify the removal of virus and bacteria through the use of microbial surrogates and conservative tracers during controlled experiments with 3-D lysimeters in the laboratory and testing of mature WSAS under field conditions. The surrogates and tracers employed to date have included two viruses (MS-2 and PRD-1 bacteriophages), one bacterium (ice-nucleating active (INA) Pseudomonas), and one conservative tracer (bromide ion). In addition, efforts have been made to determine the relationship between virus and fecal coliforms in soil samples below a WSAS, and the correlation between E. coli. concentrations measured in percolating soil solution as compared to those estimated from analyses of soil solids samples. The results of the research completed to date have revealed that episodic breakthrough of virus and bacteria does occur in WSAS, particularly during early operation, but that a 3-log removal of virus and near complete removal of fecal bacteria can reasonably be expected in WSAS with 60 to 90 cm of sandy medium. Additionally, results from the research indicate that fecal coliforms may be indicative of virus in soil media directly beneath WSAS receiving STE and the concentrations of fecal coliforms in percolating soil solution may be conservatively estimated from analysis of soil solids. Further laboratory and field research is continuing.