Treatment of municipal wastewater by a pilot membrane bioreactor with powdered activated carbon dosage for agricultural water reuse

Due to climatic changes, droughts are expected in Germany, which increases the pressure to use alternative water resources. The study investigates the treatment of municipal wastewater for agricultural reuse by a membrane bioreactor (MBR) with powdered activated carbon (PAC) at three different dosages regarding standard parameters, membrane performance, microbiological parameters and 24 organic micropollutants (OMPs). The MBR was operated at 10 g/l total suspended solids, 13.6 l/(m²·h) net flux and 6.4 h hydraulic retention time without denitrification. The chemical oxygen demand was reduced by over 95% without PAC addition. The log removal values (LRV) of the MBR were 4.8 for total coliforms, 6.2 for E. coli, 5.3 for Clostridium perfringens (indicator for protozoa), 3.8 for human adenoviruses and 4.8 for somatic coliphages. The MBR reduced the cumulated concentration of the 24 analysed OMPs by 71% without PAC. The addition of PAC increased the elimination to 93%. However, 6 out of 24 OMPs could not be significantly eliminated by the MBR even with the greatest PAC addition. Overall, the MBR with integrated PAC dosing shows a high potential for agricultural water reuse due to a small footprint, the flexible use of PAC for enhanced OMP elimination and good retention of bacteria, protozoa and viruses.