Fate and transport of organo-chlorine compounds within the vadose zone during artificial recharge of chlorinated effluent

Abstract

The effectiveness of soil aquifer treatment (SAT) to renovate both tertiary (Site 1) and secondary (Site 2) wastewater was investigated using two small recharge basins. Suction lysimeters collected soil water samples at various depths within the vadose zone from 0.5 to 20.0 feet. Total organic halide (TOX) and dissolved organic carbon (DOC) were evaluated to determine SAT efficiency in removing TOX and DOC found in the source waters. Approximately 77% of the TOX was removed from the tertiary wastewater during percolation through the vadose zone at Site 1, while the secondary source water underwent a maximum reduction of approximately 55% at Site 2. At Site 1 there was mobilization of in-situ humic materials causing increases in DOC concentrations at depth. These decreased with time and after 83 hours DOC concentrations at 20 feet were 51% of inflow concentration. At Site 2 DOC removal ranged from 44 to 73% at a depth of 15 feet for three flooding events. Discrepancies between the two locations are thought to reflect lithologic differences and dissimilarities in hydraulic loading rates.