Behavior of organic compounds during infiltration of river water to groundwater. Field studies

Abstract

The behavior of organic micropollutants during infiltration of river water to groundwater has been studied at two field sites in Switzerland. In agreement with predictions from model calculations, persistent organic chemicals exhibiting octanol/water partition coefficients smaller than about 5000 moved rapidly with the infiltrating river water to the groundwater. The biological processes responsible for the "elimination" of various micropollutants (e.g., alkylated and chlorinated benzenes) occurred predominantly within the first few meters of infiltration. Alkylated benzenes were "eliminated" at faster rates than 1,4-dichlorobenzene. Anaerobic conditions in the aquifer near the river hindered the biological transformation of 1,4-dichlorobenzene. Among the compounds that were found to be persistent under any conditions were chloroform, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene. With respect to such chemicals, bank filtration is ineffective as a first step in the treatment of river water for water supplies.