Selenium and Nitrate Removal from Agricultural Drainage Project

Selenium and Nitrate Removal from Agricultural Drainage Project

This research project will develop and demonstrate an intermediate scale system to treat 200 gallons per minute of subsurface drainage water to remove selenium and nitrate, expanding upon the existing Algal Bacterial Selenium Removal (ABSR) facility. Subsurface drainage will be piped into a fully lined and covered treatment system. A carbonaceous substrate, such as agricultural molasses, will be introduced to create anaerobic conditions to induce heterotrophic bacterial growth. Bacterial action will reduce nitrates and selenate to selenite, which forms colloidal particals with the bacteria or silt. Ultimately, the selenite will be reduced to elemental selenium or to selenide, which combines with other heavy metals such as magnesium or iron to form heavy insoluble precipitates. Final treated liquid effluent will be returned to the Northside Drain, while the final slurry will be coagulated, clarified and filtered, applied to sand beds and ultimately dried. The sand beds will be covered by bird-proof netting and any drainage will be captured and removed. Dried sludge may have commercial uses or will be disposed of at the CWMI Kettleman Hills Facility.

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Fresno