Fate of Chlorination Byproducts and Nitrogen Species during Effluent Recharge and Soil Aquifer Treatment (SAT)

A pilot-scale study was conducted under field conditions to determine the potential role of soil aquifer treatment (SAT) in renovating wastewater effluent to potable water quality. Instrumented test basins were used to evaluate water quality transformations through the upper vadose zone during effluent recharge. Samples of either chlorinated secondary or reclaimed (tertiary) effluent were obtained from suction samplers situated in two separate test basins at depths of up to 6.1 m (20 ft). Samples were characterized according to dissolved organic carbon (DOC), a measurement of dissolved organic matter, and total organic halide (TOX), a measurement of chlorination byproducts. Average DOC and TOX removals were 50% and 40%, respectively, for secondary source water; slightly higher removals were observed for tertiary source water. Performance was found to be affected by operational factors; variations in DOC and TOX removal were observed within a wetting cycle as well as from cycle to cycle. Significant nitrification occurred during drying cycles between flooding cycles, resulting in an initial wave of high nitrate in the percolating water.