Geochemical transformations during artificial groundwater recharge: Soil-water interactions of inorganic constituents

Six soils from two vadose-zone injection wells were used in conjunction wit h three types of recharge waters (microfiltered reclaimed wastewater; rever se osmosis-treated reclaimed wastewater and membrane-filtered Colorado Rive r water) to evaluate soil-water chemical processes that may alter water qua lity during recharge of these waters. Batch studies (soil-water slurries; 3 0-day contact time) and Bow-through column studies (upflow mode columns; si milar to 100 pore volumes over 30 to 100 days) showed that F, Ba and As wer e leached in appreciable concentrations, whereas leaching of B, Cr, Pb and Se was minimal. In the column study, concentrations often peaked during the first few days of operation (a "washout" phenomenon) and then declined. Pr ecipitation and dissolution reactions may be important from a standpoint of sustained infiltration rates. (C) 1998 Elsevier Science Ltd. All rights re served.