Abstract
The extraction of bitumen from the Albertan oilsands produces large amounts of oil sands process-affected water (OSPW) that requires remediation. Classical naphthenic acids (NAs), a complex mixture of organic compounds containing O2− species, are present in the acid extractable organic fraction of OSPW and are a primary cause of acute toxicity. A potential remediation strategy is combining chemical oxidation and biodegradation. Persulfate as an oxidant is advantageous, as it is powerful, economical, and less harmful towards microorganisms. This is the first study to examine persulfate oxidation coupled to biodegradation for NA remediation. Merichem NAs were reacted with 100, 250, 500, and 1000 mg/L of unactivated persulfate at 21 °C and 500 and 1000 mg/L of activated persulfate at 30 °C, then inoculated with Pseudomonas fluorescens LP6a after 2 months. At 21 °C, the coupled treatment removed 52.8–98.9% of Merichem NAs, while 30 °C saw increased removals of 99.4–99.7%. Coupling persulfate oxidation with biodegradation improved removal of Merichem NAs and chemical oxidation demand by up to 1.8× and 6.7×, respectively, and microbial viability was enhanced up to 4.6×. Acute toxicity towards Vibrio fischeri was negatively impacted by synergistic interactions between the persulfate and Merichem NAs; however, it was ultimately reduced by 74.5–100%. This study supports that persulfate oxidation coupled to biodegradation is an effective and feasible treatment to remove NAs and reduce toxicity.
Highlights
IntroductionCanada has one of the largest oil reserves in the world, where the extraction of surface mined bitumen produces large amounts of oil sands process-affected water (OSPW)
This study has demonstrated the potential of different doses of unactivated and activated persulfate coupled with biodegradation as an efficient treatment strategy to degrade Merichem naphthenic acids (NAs) and reduce toxicity
For unactivated persulfate concentrations of 250–1000 mg/L, the coupled treatment system inoculated with P. fluorescens exhibited similar Merichem
Summary
Canada has one of the largest oil reserves in the world, where the extraction of surface mined bitumen produces large amounts of oil sands process-affected water (OSPW). That is stored in tailings ponds, along with leftover sand and clay [1,2,3]. While much of the OSPW can be recycled after the sand and clay have settled, this creates an increasingly contaminated waste stream and may reduce the recovery rate of bitumen [3]. Naphthenic acid fraction compounds (NAFCs) is a more general term that includes classical NAs (O2 − species), along with a complex mixture of oxidized compounds (three or more oxygen atoms) and compounds containing sulfur and nitrogen [8]. With the large footprint currently required to store tailings and concerns of
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