(647b) Self-Generated RO Concentrate Pulse Backwash of Ultrafiltration Module in an Integrated Seawater Desalination UF-RO Pilot Plant

The effect of self-generated RO concentrate pulse backwash was evaluated in a novel integrated UF-RO seawater desalination pilot plant (with RO permeate production of up to 45.2 m³/day at 35% feed water recovery). Direct usage of RO concentrate to backwash the UF module was further enhanced with pulse backwash (PBW) generated using bladder-type hydraulic accumulators. The accumulators were charged directly from the RO concentrate stream within a period of 30-40 s. Experimental and theoretical model analysis of the hydraulic accumulator operation (i.e., both pressure and flux time profiles), validated via a series of field experiments, demonstrated the ability to discharge the pulse over a short period along with continuous UF backwash (directly from the RO brine stream). This combined backwash strategy enabled peak UF backwash flux up to 4.2 - 4.6 times higher than the normal UF filtration flux. Along with the above backwash approach, the study successfully demonstrated automated control of the frequency and intensity of the PBW system in seawater field study. Given the rapid accumulator charging and discharge periods, UF backwash was feasible with multiple consecutive backwash pulses that was more effective than with a single pulse. Field testing of UF PBW with adaptive triggering of UF backwash and variable PBW instances per filtration/backwash cycle enabled highly effective UF operation over a wide range of water quality conditions and without the need for chemical cleaning. The results also showed that the UF system was capable of providing consistently high quality RO feed and the RO system operation was stable without deterioration in performance even during severe fouling conditions that have occurred during stormy weather.