Demonstration Testing of Microfiltration for Microbial Reduction for Ocean Discharge

Following more than one year of successful pilot testing of non-biological treatment of primary effluent by microfiltration, as part of the new integrated membrane-anaerobic stabilization (IMANS™) system for wastewater treatment and water reclamation, a larger scale demonstration project was undertaken. The pilot scale work showed that a high quality effluent suitable for ocean discharge could be produced with microfiltation of primary effluent in a non-biological mode. Major concerns for the Orange County Sanitation District (OCSD) include management of peak flows and quality of the discharge effluent from two large treatment plants. Plants 1 and 2 currently treat 90 and 150 mgd, respectively. While the District has two ocean outfalls to discharge treated wastewater, the shorter of the two is not currently in regular use because it discharges closer to the shoreline and requires a significantly higher quality effluent. Regular use of the “short” ocean outfall could save the District millions of dollars by delaying the need to build another deep-water outfall. To meet the needs for higher quality effluent, non-biological microfiltration of primary effluent is one alternative that the District is now considering. In addition, the use of microfiltration gives the District the opportunity to consider the full IMANS™ concept for reclamation in future.Nine months of continuous operation of a larger, demonstration scale (200 gpm) microfiltration plant treating enhanced primary treated wastewater has confirmed the positive results and cost estimates resulting from the pilot plant work. Excellent solids and bacterial removals were achieved, with negligible evidence of long-term (irreversible) fouling of the membranes. Operation of the demonstration plant has been extended to a second phase.