Need More Water? Get it From the Brine

Utilities are turning to groundwater replenishment with recycled water to build resilient water resources. Producing a suitable recycled water quality for such replenishment may include use of reverse osmosis (RO) to meet regulatory needs. RO, however, produces a concentrate stream that must be managed and disposed of in an environmentally acceptable manner. Alternatively, at typically 15 to 20 percent of the feed flow, RO concentrate can be considered a potential source of water, particularly in water-scarce regions. The Orange County Water District (OCWD) in Southern California, well known for its Groundwater Replenishment System (GWRS), has earmarked nearly every drop of available municipal wastewater for reuse. This leaves the RO concentrate as a future potential source. Following pilot testing to establish performance criteria, a study was undertaken to determine the possible site footprint needs and cost estimates for two concentrate treatment approaches—closed circuit RO (CCRO) and forward osmosis (FO).