Selenium Treatment in Refinery Wastewater

Oxidation of Stripped sour water (SSW) followed by iron co-precipitation has been identified as one of the promising options to remove selenium because of its cost effectiveness as well as the successful application of iron co-precipitation in the refinery biotreater effluent. However, this removal is insufficient to achieve single digit ppb levels of selenium in the discharge in most instances. Therefore, this study focused on the additional selenium removal possible in a biotreater as a form of nutrient uptake and adsorptions to flocs.A laboratory bench scale biotreater system was operated to monitor uptake of selenium from SSW after being treated with oxidation and iron co-precipitation process. The results indicated that selenium uptake in the biomass was a percentage of the influent selenium, and not a fixed amount. Therefore, it is not recommended to rely on the biotreater itself for any additional selenium uptake of the already treated selenium streams.