Simulation of groundwater recharge with advanced treated wastewater

Although the quality of the effluents of domestic wastewater treatment plants in Germany is better than in the past, there are still problems using it for groundwater recharge. The problems are caused by substances, which are not or only poorly degradable in the wastewater treatment facility. They can be described by the parameters dissolved organic carbon (DOG) and adsorbable organic halogens (AOX). In a laboratory plant for the simulation of groundwater recharge with advanced treated domestic effluent, various soils were used to differentiate between sorption and biodegradation. Using aquifer material, DOC-reduction by biodegradation was 23% under aerobic conditions, and 35% under anaerobic conditions. Under aerobic conditions AOX was degraded by 16% and under anaerobic conditions by 22%, based on a special cometabolism. Further examinations showed that 60 - 80% of the remaining DOC was not adsorbable by activated carbon used in drinking water facilities. The AOX in the effluent could be reduced by an activated carbon treatment (PAC) down to 23 μg/L, compared with 48 μg/L in the standard biological treatment. The subgroups AOCl, AOBr and AOI show a different behaviour, with the worst elimination of AOI under aerobic conditions. Nevertheless, after optimization of the modern treatment technologies, this reuse concept for wastewater could be realized in the Berlin region in a near future.