Potential for in situ chemical oxidation of acid extractable organics in oil sands process affected groundwater

• The persistent oxidants, Na2S2O8 and KMnO4, oxidize AEOs found in OSPW.
• Na2S2O8 and KMnO4 oxidized 100% and 90% of 2-oxygen NAs in 110 d (22 °C), respectively.
• Na2S2O8 oxidation yields complete mineralization. KMnO4 mainly transforms AEOs.
• Initial oxidation produced different distributions of NAs by the two oxidants.
• Although testing was inconclusive, oxidation appears to reduce Microtox toxicity.

The process of bitumen extraction from oil sands in Alberta, Canada leads to an accumulation of toxic acid-extractable organics (AEOs) in oil sands process water (OSPW). Infiltration of OSPW from tailings ponds and from their retaining sand dykes and subsequent transport towards surface water has occurred. Given the apparent lack of significant natural attenuation of AEOs in groundwater, remediation may be required. This laboratory study evaluates the potential use of unactivated persulfate and permanganate as in situ oxidation agents for remediation of AEOs in groundwater. Naphthenic acids (NAs; CnH2n+zO2), which are a component of the acutely toxic AEOs, were degraded by both oxidants in OSPW samples. Permanganate oxidation yielded some residual dissolved organic carbon (DOC) whereas persulfate mineralized the AEO compounds with less residual DOC. Acid-extractable organics from oxidized OSPW had essentially no Microtox toxicity.