San Diego City Council members approved the Water Purification Demonstration project’s final report and asked the city’s staff to develop a plan and timeline to implement a full-scale project within 90 days.
Implementation of an indirect potable reuse (IPR) program would provide a significant new local water supply, while reducing the amount of primary effluent discharged to the ocean, helping the City avoid a $1.5 billion upgrade of the Point Loma Wastewater Treatment Plant. According to the report, that savings could offset water purification expenses and cut the effective cost of purified water in half.
The two-year study included multiple workshops involving an Expert Panel and other stakeholders and the operation of a 1 MGD (3,785 m3/d) demonstration project at the North City Water Reclamation Facility (WRF) to demonstrate the robustness of the multi-barrier MF/RO and advanced oxidation arrangement to produce better-than-potable-quality water from tertiary effluent. As a result of the Study, the California Department of Public Health (CDPH) gave conditional approval to the proposed IPR concept, which would augment the natural and imported water flows into the San Vicente reservoir with repurified water advanced treated water.
An earlier 2006 Reuse Study developed a 16 MGD (16,560 m3/d) IPR project, while a more recent 2012 Recycled Water Study identified the opportunities to cost effectively produce up to 88 MGD (333,000 m3/d) of potable and non-potable reuse by diverting additional wastewater flows to both of the city’s existing WRFs and adding a third WRF on Harbor Drive, near a major wastewater pump station. The 2012 Study found that recycled water could cost effectively provide up to 40 percent of the city’s demand for raw water to feed their potable water treatment plants.
Although the approved Study only considered an IPR project, a stakeholder panel has already met to consider the possibility of direct potable reuse (DPR) as an alternative to the IPR project. Under a DPR arrangement, the purified effluent—which exceeds the potable water quality requirements—would be introduced into an existing raw water supply line that delivers raw water to an existing water treatment plant. This scheme would eliminate the need for a challenging 22-mile (33km) pipeline, and its $200 million price tag, that would convey the water to the San Vicente reservoir.
The implementation plan to be provided by the city staff is understood to include a plan for a DPR option, as well as a plan for taking legislative action to get the CDPH to move faster to establish DPR regulations.