Reduction of pathogens and (antibiotic-resistant) bacteria in advanced sewage treatment by membrane bioreactor systems and retention soil filters

Sewage treatment plants (STPs) are important punctual sources of antimicrobial resistance spread, including antibiotic-resistant bacteria (ARB) [1]. Thus, an advanced wastewater treatment gained importance in order to decrease microbial load from the discharge of STPs, which enter freshwater systems.

In this study, two STPs with membrane bioreactor systems (MBRs) as advanced technologies in the activated sludge process were examined for their reduction performance for hygienically relevant pathogens and ARB. A retention soil filter (RSF) was tested at another STP as an additional treatment stage after conventional wastewater treatment. The reduction of ESBL (extended spectrum β-lactamase)-producing bacteria and VRE (vancomycin-resistant enterococci) as well as accompanying pathogens are in focus of this study. The MBRs and the RSF are running each on municipal STPs in Germany, operated by the Erftverband. Somatic coliphages, Clostridium (perfringens), E. coli, intestinal enterococci, target species of ESBL-producing bacteria (E. coli, Klebsiella spp., Enterococcus spp., Citrobacter spp., Pseudomonas (aeruginosa), Acinetobacter (baumannii)) and VRE were analyzed by cultural detection.

The purification performances of the tested species in the STPs with MBRs showed a reduction of 1-2 log10 units of colony-forming units (CFU/100 mL) higher than STPs with conventional wastewater treatment (Fig. 1 A). The RSF showed a reduction performance for e.g. ESBL-E. coli and E. coli of 1.2 and 3.4 log10 units (CFU/100 mL; mean values). ARB could only be detected in rare cases (Fig. 1 B). In total, both RSF and MBRs showed high potential in reduction of ARB and other hygienically relevant parameter. Thus, the treatment techniques offer benefits in reducing pathogens and preventing the dissemination of resistance into the environment.

Sib, E., Lenz-Plet, F., Barabasch, V., Klanke, U., Savin, M., Hembach, N., Schallenberg, A., Kehl, K., Albert, C. and Gajdiss, C. Bacteria isolated from hospital, municipal and slaughterhouse wastewaters show characteristic, different resistance profiles. Science of The Total Environment, 2020, 746, 140894, doi:10.1016/j.scitotenv.2020.140894.