Water Environment Federation (WEF)

Efficient Biodestruction of Wastewater-Blended, Oxidant-Laden Residual Streams

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.

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