Abstract:

Historical mining practices have resulted in elevated selenium concentrations (160 µg/L) in local springs that are an expression of the local groundwater system. The current pilot water treatment system utilizes an ultrafiltration (UF) and reverse osmosis (RO) membrane process to concentrate selenium fourfold for biological selenium removal.

WesTech piloted the Electro-Biochemical Reactor (EBR) technology for selenium removal from reverse osmosis concentrate (ROC) waters. The EBR system uses an innovative approach to biotreatments by decoupling the electron provision from organic carbon metabolism. The electrons are provided to the bioreactor directly, using a low applied potential at milli-Amp current levels. The directly supplied electrons are readily available to the microbes in a consistent manner without the metabolic energy expenditure.

The six-month pilot demonstrated an average total selenium removal rate of 99.3%, reducing the ROC concentrations of 650 µg/L to less than 5 µg/L. The nutrient requirement was low, reducing operating expenses and limiting the excess biogrowth production often experienced with conventional bioreactors. The post-treatment requirement was greatly reduced because of the low bioreactor BOD levels, no residual selenite, low phosphorus, and low turbidity. The final system design produces no liquid waste streams.

This paper will describe the pilot system configuration, testwork program, granular results, and full-scale system design considerations.

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Elise Hotz