Experimental evaluation of intermittent aeration of a hollow fibre membrane bioreactor

Intermittent membrane aeration provides a substantially improved energy efficiency in hollow fibre-based immersed membrane bioreactors (HF iMBRs). The benefits of intermittent aeration have been assessed with respect to sustaining a target flux and/or limiting the fouling rate to a sustainable level based on a small plant using full-scale HF modules. Results show that for the same specific aeration demand per unit of permeate produced (SAD_p), fouling rates were significantly lower for 10 s filtration, 30 s relaxation (“10:30” intermittent aeration) compared to 10:10 and continuous aeration. At a net flux (J_net) of 23.3 litres m⁻² h⁻¹ (LMH), a SAD_p of 4.6 was found sufficient to sustain operation, this value being up to 75% and 50% lower compared to continuous and 10:10 aeration respectively. This empirical data was compared with heuristic data from 5 large scale HF iMBR plants, which revealed that 10:30 aeration can sustain a relatively high flux (up to 25.3 LMH) under dry weather conditions in warm climates, with the recorded SAD_p ranging from 5.3–10.9.