Investigation on the behaviour of selected pharmaceuticals in the groundwater after infiltration of treated wastewater.

In a rural arid area without suitable receiving water the treated wastewater of a low loaded municipal wastewater treatment plant with full nutrient removal and additional post treatment steps is infiltrated into the unsaturated soil for groundwater recharge. Groundwater probes at increasing distances from the infiltration point have been sampled every two months over a period of 14 months. Beside conventional parameters (nutrients, carbon, and bacterial counts) samples were analysed for pharmaceutically active substances. Depending on and corresponding to their chemical structure and their fate during wastewater treatment, the selected substances showed different behaviour in the saturated zone of the groundwater. The antiepileptic Carbamazepine behaves very conservative and only is removed negligible even after long flow times within the subsurface zone. For other substances like the tranquilizer Diazepam or the analgesics Diclofenac a partial elimination during the different steps of wastewater treatment can be observed. Further degradation could be observed during the subsequent subsurface passage. In correlation with flow time additional removal of these substances from the aqueous phase can be observed. The musk substances Galaxolide and Tonalide were removed to some extend but not as good as the previous mentioned compounds.