AWWA WQTC62363

A disadvantage of using separation-based perchlorate treatment technologies (e.g. ion exchange or membranes) is that they produce a perchlorate-laden concentrate that must be disposed or further treated. "Conventional" biological processes can be used to treat perchlorate 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. A novel approach for treating perchlorate residuals is to blend them with scalped municipal wastewater followed by treatment in a fixed-bed (FXB) bioreactor. The municipal wastewater decreases the bulk dissolved oxygen (DO) concentration (DO inhibits perchlorate degradation), decreases solution salinity (salinity decreases biodegradation kinetics), and provides the requisite substrate and bacteria. This paper discusses a six-month pilot study investigating the application of this treatment concept to perchlorate-laden electrodialysis reversal (EDR ) concentrate. The study demonstrated that: perchlorate removal to below detection (~4 g/L) 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; 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.