In partnership with academic researchers from multiple university institutions, the District began a field-scale study of alternative methods for water treatment using engineered wetlands in 2013 to reduce the levels of nitrate in the Santa Ana River. At the time, nitrate from a variety of sources, including agricultural and dairy runoff as well as treated effluent from upstream water treatment plants, contributed to high levels.

Working together as the Engineering Research Center (ERC) for Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt), the National Science Foundation-supported group represents Stanford University, UC-Berkeley, Colorado School of Mines, and New Mexico State University. OCWD is a member of ReNUWIt's Industrial/Practitioner Advisory Board. The project is in its second of a three-year study.

Compared to the traditional methods currently used at the District's Prado Wetlands facility, new alternatives have the potential to treat a wider variety of water quality contaminants and to require less vegetation maintenance. Wetlands test cells for the study went into initial operation in late 2013 at Prado. The project has been designated as the Prado Open Water Unit Process (POWUP) Wetland Monitoring & Research Program.

The alternative treatment process involves the use of non-vegetated, shallow-depth, open-water wetlands. The system relies upon sunlight for photochemical treatment, as well as the establishment of a biologically active periphyton community on the wetland bottom. Periphyton is comprised of a complex community of algae, bacteria, other microbes, and plant matter. Testing at Prado will also allow for direct comparison of the alternative alongside the District's exiting wetlands treatment.

District staff and the ReNUWIt team proceeded to collaborate on the design of a series of open-water test cells at Prado. Subsequently, during regularly-planned wetlands pond cleaning, grading, and maintenance activities in 2013, District staff reconfigured one wetland pond into three individual test cells, each approximately 800 feet in length by 100 feet in width.

The three cells began receiving water in November 2013 and background water quality testing began while the periphyton layer developed. District staff will operate the system, assist with onsite water quality sample collection, and provide some laboratory analysis. The ReNUWIt team will provide additional laboratory analysis, data review and management, operational guidelines, and is designing a suite of online sensors that will allow for remote water quality and flow monitoring.

Results from the first year of sampling indicate that transformation of some compounds is occurring as expected. However, the removal of photosensitive compounds is not as effective as expected, largely due to floating and suspended algae in the cells inhibiting the penetration of UV light. The remedy was to modify a portion of the system to convey water directly to a narrow channel that will supply water directly to the inlet of each treatment cell, reducing the opportunity for duckweed and other algae to propagate.

The second year of sampling began in January with initial results that indicate modifications to the conveyance system are having positive results.