BEHAVIOR OF ORGANIC MICROPOLLUTANTS DURING GROUNDWATER RECHARGE

Pilot plant studies were conducted to investigate the behaviour of org anic micropollutants (OM) during artificial ground water recharge of p retreated river Rhine water in the dune areas. The behaviour of the st udied OM was mostly affected by biological anaerobic processes. The ra te of these processes correlated with the redox potential, which was p rimarily controlled by the biologically unstabilised organic matter of the recharge aquifer. Under anaerobic conditions (E(h) similar to +15 0 mV) a substantial or complete transformation of a number of halogena ted C-1-C-3 aliphatics, nitro- and chloronitrobenzenes was found at te mperatures higher than 5 degrees C. At lower temperatures a lower degr ee of the degradation and the formation of some potentially hazardous reaction products (dichloromethane, bromochloromethane, chloroanilines ) has been observed. Furthermore the studies revealed a substantial re tardation of the transformation rate at low concentration levels of so me studied compounds (toluene, dichlorobenzenes, EDTA). Aerobic proces ses led to a significant elimination of brominated trihalomethanes, so me phenoxy pesticides and NTA.