The use of reverse osmosis (RO) to treat municipal wastewater for various reuse purposes has gained considerable momentum in recent years, with multiple facilities now exceeding 100 million gallon per day (mgd) in capacity. Early wastewater RO (WWRO) facilities, built 10 to 15 years ago, were generally designed with low RO fluxes to reduce the risk of organic fouling, while recoveries were generally designed between 80 and 85%. One such facility was the Leo J. Vander Lans Water Advanced Water Treatment Facility, owned by the Water Replenishment District of Southern California (WRD). This 3 mgd facility began operation in 2005, and was designed using a 2-stage RO configuration to achieve 85% recovery at a conservative flux of 10 gallons per square foot per day (gfd). While the plant has operated sustainably since start-up, challenges were experienced from the beginning with fouling of the RO membranes, resulting in several changes to plant operation and upstream treatment processes. Previous papers have discussed potential causes of this fouling and various remedies used to address it, however, the fouling remained a challenge until the plant expansion was completed in 2014, with RO cleaning frequency average every 1 to 2 months. The facility expansion increased the production to 8 mgd using a more aggressive design approach than the original facility. Pilot testing and demonstration testing conducted by CDM Smith for the cities of Los Angeles and San Diego had demonstrated that higher RO fluxes could actually reduce membrane fouling by improving hydraulics within the RO membranes and maintaining better crossflow on the membrane surface. A full-scale demonstration test was also conducted at the Vander Lans facility, demonstrating that the plant could be operated sustainably at a flux exceeding 12 gfd. The plant expansion incorporated this higher RO flux, along with an increased recovery to 93%, and the inclusion of interstage booster pumps to improve flow balance within the RO skids. Plant operation since the November 2014 start-up has demonstrated that the RO system is functioning better than ever. As of June 2016, the primary RO trains have not yet been cleaned, and the secondary RO skids, which take recovery from 85 to 93%, have been cleaned only twice.
This presentation is available to AMTA Members only.
- Gregory Wetterau, P.E., BCEE / Paul Fu / Bruce Chalmers / Alex E. Wesner, P.E.
- CDM Smith Inc. / WRD / Separation Processes, Inc.
- AMTA/AWWA Membrane Technology Conference, Long Beach, CA
- AMTA/AWWA Membrane Technology Conference
- Case Study, Optimization, Reverse Osmosis, Fouling, Reuse