Long-term comparison of trace organics removal performances between conventional and membrane activated sludge processes

The removal of trace organic compounds through membrane bioreactors (MBR) compared with a conventional wastewater treatment plant (WWTP) in a long-term study was investigated. Two MBR pilot plants were operated in parallel to a full-scale WWTP fed with the same municipal raw wastewater. Polar compounds (phenazone-type pharmaceuticals, their metabolites, and carbamazepine) and less polar estrogenic steroids (estradiol, estrone, and ethinylestradiol) were quantified. The removal rate of phenazone, propyphenazone, and formylaminoantipyrine by the conventional WWTP was less than 15%. Significantly higher removal rates (60 to 70%) started to be clearly monitored in the pilot plants after approximately 5 months. Higher removal rates coincided with higher temperatures in the summer. The conventional WWTP removed, on average, more than 90% of the natural steroids estrone and estradiol and approximately 80% of the synthetic ethinylestradiol. Approximately 99% of estradiol and estrone and approximately 95% of ethinylestradiol was eliminated by the MBR processes.