WATER-QUALITY CHANGES DURING SOIL AQUIFER TREATMENT OF TERTIARY EFFLUENT

This paper summarizes the results of field studies in Tucson, Arizona, to estimate the soil aquifer treatment (SAT) effectiveness of a 5.7-ha (14-acre) water spreading facility, the Sweetwater Underground Storage and Recovery Facility. Groundwater samples collected from the facility during 1989 to 1990 were analyzed for pathogens. A specific basin was selected during the 1990 to 1991, 1991 to 1992, and 1992 to 1993 recharge seasons for sampling source water (tertiary effluent), pore-liquid samples from the vadose zone, and groundwater during recharge. These samples were analyzed for the nitrogen species, dissolved organic carbon (DOG), and total organic halide (TOX). The results showed that the site provides effective SAT. Enteroviruses were completely removed during travel in the 37-m (120-ft) thick vadose zone. No Giardia were detected in any of the groundwater samples. The DOC and TOX were reduced by 92% and 85%, respectively. After leaching of indigenous nitrogen from the vadose zone, total nitrogen was reduced by approximately 47% during recharge. Near-surface anaerobic conditions promote denitrification.