(608h) Novel Eductor-Based MBR with Enhanced Mass Transfer and Fouling Resistance for the Treatment of Domestic Wastewater

A patented aeration device based on mixing eductors was introduced into a flatsheet membrane bioreactor (MBR) for treating domestic wastewater. The device promotes enhanced aeration for a given pumping rate and thus can simultaneously aerate and mix the MBR reactor.

The eductor equipped MBR was studied in comparison with a conventional fine diffuser for the treatment of domestic wastewater at MLSS levels of 5-10 g/L. The eductor showed a high rate of oxygen transfer both in clean and wastewater compared to the diffuser (K_La of 18.49 and 5.6/h respectively for the eductor and the diffuser in clean water and K_La of 16.81/h and 4.17/h respectively for the eductor and the diffuser in wastewater. The α value with the eductor (0.91) was found to be more than the diffuser (0.75). The DO profile of the MBR tank was found to be homogeneous with the eductor up to a depth of 19 cm (mean DO=6.8±0.34 mg/L) whereas with the diffuser it was observed to be 5.52±0.92 mg/L.

Higher recirculation rates through the eductor resulted in a higher mixing/turbulance inside the MBR tank and thus significantly alleviated membrane fouling compared to the diffuser in terms of transmembrane pressure. The difference between the eductor and diffuser becames smaller at high fluxes due to local hydrodynamic effects. The effects were still noticeable at high MLSS loadings.

In terms of nutrient removal, the eductor-based reactor performed better than the diffuser in removing organic carbon and about the same in removing ammonia.

Overall the eductor offers a promising approach to enhancing efficiencies of MBR operating on domestic wastewater.