A series of soil column tests and field experiments were designed to evaluate microbial removal of trace organics during rapid infiltration recharge of ground water. Field experiments demonstrated that operation of rapid infiltration systems using either primary or secondary wastewater can contribute trace organics to associated ground waters although concentrations of individual compounds can be reduced by the treatment process. Most of the removal occurred in the upper meter of the soil. Soil column tests demonstrated that trace organic removal from either primary or secondary wastewater was minimal when non-acclimated soil was conditioned by continuous flooding to eliminate adsorption as a removal mechanism. Batch tests indicated that most of the removal occurred in the wastewater prior to infiltration. Conversely, column tests using acclimated soil from an operational system demonstrated good removal of trace organics. Increased concentrations of target compounds in the feed did not always result in corresponding increases in the column effluent. Microbial adaptation was evident for some compounds. Other compounds appeared to exhibit a minimum concentration below which biodegradation did not proceed. Microbial activity was confirmed as a fate mechanism for several target compounds using radiolabels. In direct correlation with field results, the induction of anaerobiosis in the soil columns resulted in increased fractional breakthrough of trace organics
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