Look Mom, No Backwash Pumps! - Evaluation of a New Type of Membrane for Water Reuse

The West Basin Municipal Water District (California) supplies many industrial customers in Southern California with recycled water from several water recycling treatment facilities and pipelines. One such facility, the Juanita Millender-McDonald Carson Regional Water Recycling Plant, converts supplied Title 22 recycled water into 5.0 MGD of low-pressure boiler-feed and 0.7 MGD of cooling tower make-up water at a local petrochemical refinery. The existing treatment process uses pressurized microfiltration (MF) followed by reverse osmosis (RO). This paper documents a three-month onsite testing of a new type of pressurized MF system that claimed to be 1) more water efficient, 2) less mechanically complex, and 3) more energy efficient. The purported claims are based on an innovative air-assisted backwashing system that reduces the need for backwash water and eliminates the need for dedicated backwash pumps. The testing determined that the new membrane system was able to treat the Title 22 water to a comparable quality as the existing MF system without the need for the backwash pump, therefore the claim of treatment using a less mechanically complex system was verified. However, the claim for being more water efficient could not be substantiated as the pilot-tested system's overall water efficiency was no different than the existing MF system. The claim of greater energy efficiency could not be verified due to incomplete data.