After bench-and pilot-scale studies demonstrated the effectiveness of a novel biological treatment process for removing oxidants from concentrate waste streams, an electrodialysis reversal pilot plant was used to remove perchlorate, arsenic, and total dissolved solids from groundwater. The resulting concentrate stream was blended with scalped municipal wastewater and treated in a fixed-bed (FXB) bioreactor through a process called BIOBROx TM . The data showed that an empty bed contact time of 10 min and a 0.6 blend ratio of wastewater flow to total flow sustained perchlorate removal to below the methodreporting limit (4 µg/L) in the FXB bioreactor. Testing also showed that the system was robust with respect to process upsets and temperature variations. Ongoing full-scale testing is designed to optimize the process so that BIOBROx effluent can be used directly for reuse applications after disinfection.

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A disadvantage of using separation-based oxidant (i.e., perchlorate, nitrate, bromate) treatment technologies (e.g. ion exchange or membranes) is that they produce an oxidant-laden concentrate that must be disposed or further treated. "Conventional" biological processes can be used to treat oxidant residuals but typically require a dedicated deoxygenation step, inoculation with exogenous salt-tolerant bacteria, long residence times due to high solution salinities, and the addition of a costly exogenous substrate such as ethanol. This paper describes the development of a novel approach for treating oxidant-laden residuals by blending them with scalped municipal wastewater followed by treatment in a fixed-bed (FXB) bioreactor. A six-month pilot study investigating the application of this treatment concept to perchlorate-laden electrodialysis reversal (EDR) concentrate demonstrated that perchlorate removal to below detection can be achieved and sustained in a FXB bioreactor using blend ratios around 0.5 (wastewater:EDR concentrate) and empty-bed contact times (EBCTs) as low as 10 minutes, that the process is robust with respect to system upsets, and that granular activated carbon (GAC) with an effective size of approximately 2 mm was optimal as a biogrowth support medium.

Pilot studies were performed to evaluate the use of a fixed-bed bioreactor process for removing nitrate from RO by-pass water at the Arlington Desalter facility in Riverside, California. Testing showed that the process efficiently removed nitrate while also meeting other treatment objectives such as removing perchlorate and turbidity. The process was robust with respect to various fluctuations in water quality and operational conditions. Design parameters developed during pilot testing are now being used to design the first centralized, potable biodenitrification facility in the United States (to the authors' knowledge).

A disadvantage of using separation-based oxidant (i.e., perchlorate, nitrate, bromate) treatment technologies (e.g. ion exchange or membranes) is that they produce an oxidant-laden concentrate that must be disposed or further treated. "Conventional" biological processes can be used to treat oxidant residuals but typically require a dedicated deoxygenation step, inoculation with exogenous salt-tolerant bacteria, long residence times due to high solution salinities, and the addition of a costly exogenous substrate such as ethanol. This paper describes the development of a novel approach for treating oxidant-laden residuals by blending them with scalped municipal wastewater followed by treatment in a fixed-bed (FXB) bioreactor. A six-month pilot study investigating the application of this treatment concept to perchlorate-laden electrodialysis reversal (EDR) concentrate demonstrated that perchlorate removal to below detection can be achieved and sustained in a FXB bioreactor using blend ratios around 0.5 (wastewater:EDR concentrate) and empty-bed contact times (EBCTs) as low as 10 minutes, that the process is robust with respect to system upsets, and that granular activated carbon (GAC) with an effective size of approximately 2 mm was optimal as a biogrowth support medium.