Effects of aeration intensity and sludge return rate on microbial structure change and pharmaceutical removal performance of the novel solar-powered two-stage inclined-plate-membrane bioreactor system for the treatment of real building wastewater.

The solar-powered two-stage inclined plate-membrane bioreactor (STIP-MBR), utilized energy from an off-grid hybrid solar system, was developed for treatment of pharmaceuticals from the high-rise building wastewater with energy-savings. The aim of this work was to investigate the effects of aeration intensity in terms of aerobic and microaerobic conditions, and sludge return rates (100 % and 200 %) on the microbial structure changes and the removal performances of the targeted pharmaceuticals (Ciprofloxacin (CIP), Caffeine (CAF) and Sulfamethoxazole (SMX)). It was found that the removal performances of all target pharmaceuticals could be enhanced by increasing the aeration intensity. Both biodegradation and adsorption were the main mechanisms for pharmaceutical removal. In addition, increasing the sludge turn rate could enhance the adsorption of CIP and CAF and the biodegradation of SMX in the system. Higher aeration tended to reduce bio-cake and sludge foulants, but it increased pore blockage of the membrane compared to the microaerobic conditions. The microbial community associated with the removal of organics, nutrients and targeted pharmaceuticals inside the STIP-MBR system was systematically revealed. Overall, the STIP-MBR systems could achieve a complete reduction in energy consumption of 388.5 kWh (equivalent to 7 kWh/m) in treating the real building wastewater.