Criticality of Flux and Aeration for a Hollow Fiber Membrane Bioreactor

A three-element microfiltration (MF) hollow fiber (HF) membrane module has been evaluated for treating municipal wastewater by an immersed membrane bioreactor (iMBR) based on a pilot-scale plant. The flux-step method, classically used to identify the critical flux, was compared with an aeration-step method conducted at the identified critical flux of 14.5lm-2h-1. It was found that the permeability of the central element was found to be higher, since the air stream imparted to the end elements was dissipated because there is no channel formed by the proximity of the neighboring elements. The aeration-step trials revealed the critical specific aeration demand for both intermittent and continuous aeration regimes to be lower than that applied to the critical flux-step experiments. This implies that the operating conditions identified for critical flux-step experiment are over conservative, corroborating results from previous reports, and that aeration stepping presents a more representative method for identifying sustainable operating conditions.