Impact of Soil Filtration on Metals, Nutrients, and Estrogenic Activity of Reclaimed Water.

This study examined the impact of soil filtration on water quality for reclaimed water from two municipal wastewater treatment processes with two soils (forest and farm). Soils were watered for 16 wk. Nutrients (NO-N, NH-N, and PO), electrical conductivity, hardness, pH, total metals, and estrogenic activity in source and effluents were measured. Results were evaluated in reference to current regulations in Washington State. Both reclaimed waters met standards for unrestricted agricultural use but did not meet current state regulations for ecological use. Metal concentrations in reclaimed waters were generally similar to the control (tap water). Both source and soil filtered water met Washington State stream water criteria for chronic exposure for As but exceeded groundwater standards. Concentrations of Cd, Pb, Ag, and Zn in the effluents were similar or slightly elevated to reclaimed source water for both soils and water types. Soil filtration improved water quality to levels within Washington State regulatory limits for ecological use for Cd, Cu, and Zn but decreased water quality for Pb for both soil and reclaimed water types. Phosphate concentrations were reduced by soil filtration, but NO concentrations were increased for both soils and all water types above source water concentrations. The estrogenic activity of the sand-filtered water decreased to near detection limits in the forest soil and by >200% in the farm soil. The degradation in water quality (increased NO, As, and Mn) after soil filtration observed in this study would likely occur with any water type, including rainwater.