Biodegradation of organic compounds in OSPW with microbial community indigenous to MFT

Abstract

Tailings ponds contain significant amounts of organic contaminants that cannot be released to the environment without further treatment. The use of mature fine tailings (MFT) was proposed as a potential source of microorganisms for biological treatment to remove dissolved organic compounds from oil sands process-affected water (OSPW). In order to test the capacity of microorganisms indigenous to MFT for organic compounds removal in OSPW and determine whether they could be extracted from MFT to form biofilm on biofilm carriers, two groups of batch bioreactors were established (1) one treating acetic-acid-supplemented OSPW and (2) one treating high pressure oxidation (HiPOx)-treated OSPW. In addition, several bioreactors that contained no MFT but MFT-originated biofilm were set up to test the feasibility of using MFT-originated biofilm to biodegrade organic compounds. The bioreactors supplemented with acetic acid yielded a rapid depletion of sulfate and nitrate with partial removal of COD. The COD was reduced from 600 mg/L to a minimum residual COD of 200 mg/L. This is lower than the COD in the original OSPW before acetic acid addition, indicating possible co-metabolic biodegradation of recalcitrant organic compounds. HiPOx-treated OSPW contained larger amounts of sulfate and less readily biodegradable organic compounds compared to acetic-acid-supplemented OSPW. With longer reaction times, sulfate could be depleted and the residual COD could be further reduced to 150 mg/L. The bioreactors that contain MFT-extracted biofilms could remove 20% of the NAs from the acetic-acid-supplemented OSPW and 50% of the COD from the HiPOx-treated OSPW. Further confirmation was obtained from bioreactors using acclimatized biofilms, which could remove 30% of the NAs from the OSPW without HiPOx treatment. This study demonstrated the feasibility of seeding biofilm reactor with indigenous microorganisms from MFT. The results provide insights on biodegradation of toxic and recalcitrant organic compounds and help the design of continuous bioreactor for OSPW treatment.