Knowledge-based control module for start-up of flat sheet MBRs

In start-up periods low MLSS concentration may lead to fouling phenomena and uncommon frequency of chemical cleanings using membrane bioreactors. A knowledge-based control module for the optimisation of start-up procedures in membrane bioreactors is presented and validated in this paper. The main objective of the control module is to accelerate the growth of MLSS and the achievement of the design flux while minimising the fouling phenomenon during start-up periods. The module was validated in a pilot-scale membrane bioreactor with the University of Cape Town configuration and submerged flat sheet microfiltration membranes. The knowledge of the control system was represented as a decision tree before being implemented. A fully satisfactory start-up, both for the filtration and the biological phase, was obtained in 20 days, saving time and preserving the membrane integrity.

► Automatic control module to accelerate the growth of mixed liquor suspended solids.
► Minimising the fouling phenomenon during start-up periods.
► Validated in a 2.2 m3 pilot-scale MBR with submerged flat sheet microfiltration membranes.
► The knowledge of the control system is represented as a decision tree.
► A fully satisfactory start-up was obtained, saving time and preserving the membrane integrity.