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Investigation of Biofouling/reduced flow through a ZVI PRB (Mississippi)

A ZVI Permeable Reactive Barrier (PRB) showed reduced flow after only 2 years of operation with the flow being deflected around one end of the PRB. Removing a few inches of material from the up gradient face via a boring resulted in immediate flow increase, however, the flow slowed again within a year. These observations fit the theory that the front face was biofouled and would require antibiofouling measures no matter what restoration method was chosen.

A column study was designed with an academic laboratory to evaluate antifouling agents; moderate concentrations of ethanol worked well. Groundwater was pumped over the plugged face into the PRB and occasionally dosed with ethanol which also serves as an electron donor for a biobarrier installed down gradient to treat any CVOCs exiting the PRB. (Freedman et. al. 2022) Contaminant levels in the downgradient receptor stream have dropped below MCLs.

A 2nd biobarrier was installed to treat the low pH groundwater going around the end of the PRB and was bioaugmented by a low pH culture developed at Clemson. (Freedman et. al. 2022)