Flux-step method for the assessment of operational conditions in a submerged membrane bioreactor.

A flux-step method was used for monitoring the pressure variation in a solids separation membrane at different operating conditions. A submerged membrane bioreactor pilot plant, used during the short-term tests, was used to purify actual restaurant wastewater. The influence of membrane backwash and relaxation on the variation of pressure variation was also evaluated. In order to reduce the deposition of irreversible fouling, the authors modified the literature-supported filtration to backwash cycling with filtration and relaxation cycling. The trials maintained a constant filtration to relaxation ratio that was in line with optimal filtration to backwashing ratios found in the literature. The relaxation cycling between two constant flux-steps effectively counteracted membrane fouling and the excessive decrease in average pressure, and it results in a lower waste of energy and water than a backwashing strategy.