Pilot Study of Membrane Hydraulic Performance In MBR

Membrane hydraulic performance was studied with a flat-sheet membrane bioreactor (MBR) pilot plant. Flat sheet MBRs are normally operated with a filtration and relaxation cycle and continuous scouring aeration. An in-situ method was introduced to determine the critical flux, which involves step-flux permeations performed with relaxation phases. The critical fluxes, determined by the method under different food to microorganism (F/M) ratios, different temperatures, and with/without alum addition, were compared. Under a constant sub-critical (below critical) flux operation, no long-term transmembrane pressure (TMP) increase was observed for a short period of time (a couple of days). Under a constant peak flux (above the critical flux) operation, the long-term TMP progression was found to be closely related to the TMP profile within one filtration cycle when the mixed liquor properties stayed the same. Finally, a TMP jump was observed after a long period of operation. A typical TMP profile during this jump phase and some operating parameters that can postpone the TMP jump were identified.