Online Backwash Optimization of Membrane Filtration for Produced Water Treatment.

In the offshore oil and gas sector, produced water is discharged into the sea, but increasing environmental concerns and stricter governmental regulations require new technologies to be considered. Membrane filtration is a promising technology to improve separation, but fouling of the membranes causes a significant reduction in flow capacity. To reduce fouling, optimization of the backwashing parameters is given much attention. Comprehensive and time-consuming experiments are used to model the effect of backwashing, but most methods neglect time varying features present in the offshore produced water treatment train. In this paper, a backwashing scheduling algorithm is proposed, which dynamically selects the filtration and backwashing durations to maximize the average net permeate production. The proposed algorithm is tested on a lab-scaled pilot plant, where it was able to adapt as irreversible fouling accumulated and the OiW concentration changed. The paper concludes that the removal rate of oil fouling was observed to be dependent on the rate at which the backwashing pressure could be established. As the proposed method online adapts to the current conditions, it can improve the filtration capacity compared to cases with constant backwashing and filtration durations throughout the lifetime of the facilities.