Persulfate Oxidation Coupled with Biodegradation by Pseudomonas fluorescens Enhances Naphthenic Acid Remediation and Toxicity Reduction

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.

Mild Photocatalysis Removes Microbial Inhibition and Enables Effective Biological Treatment of Naphthenic Acids

“…The pseudo-first-order constant of the raw non-photocatalytically pre-treated sample agrees with previous reports. Meanwhile, the 1 and 2 d pre-treatment times exhibited a significant enhancement in pseudo-first-order kinetic constants that superseded enhancements seen for electro-oxidation pre-treatments with graphite anodes (1.4–4.1-fold improvements), ozonation, and persulfate oxidation (no improvement). ,− Since initial concentrations do not influence the biological degradation kinetics for NAs, the kinetic enhancements correspond to the increased O o ( o > 2) fractionation (Figure S.4) and, therefore, biodegradability …”

“…Advanced oxidation processes (AOPs), such as ozone, persulfate oxidation, and electro-oxidation, have been explored as pre-treatments for NA biodegradation. − Each AOP enhanced the biological uptake of NAs by oxidizing and breaking them down into simpler, biodegradable forms. However, mineralization was never attained in each case when applied at their optimal dosage.…”

Remediation of oil sands naphthenic acids by activated persulfate oxidation and biodegradation

“…Persulfate was primarily responsible for Merichem NA reduction while bacteria degraded the by-products, improving chemical oxygen demand (COD) removal up to 6.7× in the coupled system compared to persulfate oxidation alone. Comparing the persulfate concentrations tested (100, 250, 500 and 1,000 mg/L), the highest microbial density was observed in bottles containing 250 mg/L of persulfate (Balaberda & Ulrich 2021). It is likely that at this concentration the persulfate provided more bioavailable carbon sources for the bacteria, while increasing the concentration further led to declining microbial density due to increased oxidative stress.…”

“…Oxidation of NAFCs via activated persulfate has been investigated using various activation methods such as UV (Fang et al 2018(Fang et al , 2019(Fang et al , 2020Liang et al 2011), heat (Xu et al 2016(Xu et al , 2018(Xu et al , 2019, and iron (Aher et al 2017;Drzewicz et al 2012). The potential for combining persulfate oxidation with subsequent biological treatment has recently been examined (Balaberda & Ulrich 2021;Ganiyu et al 2022). Solar activated persulfate oxidation followed by biofiltration showed 60% overall mineralisation of dissolved organic carbon (DOC) and removal of toxicity (Ganiyu et al 2022).…”

“…Coupling unactivated (21°C) or activated (30°C) persulfate with biodegradation for the remediation of commercially produced Merichem NAs was previously studied by our lab (Balaberda & Ulrich 2021).…”