Combined solar activated sulfate radical-based advanced oxidation processes (SR-AOPs) and biofiltration for the remediation of dissolved organics in oil sands produced water

Abstract

• Effective degradation of dissolved organics in produced water by solar activated SR-AOPs. • SO 4 •− , • OH and 1 O 2 reactive species were formed during solar activated SR-AOPs. • Better performance by solar activated peroxymonosulfate compared to persulfate. • Excellent mineralization of dissolved organic by post-treatment biofilm filtration. • Microbial profiling indicated presence of hydrocarbons and carboxylic acid degraders. This study reported for the first time the potential of sequential solar activated sulfate radical advanced oxidation processes (SR-AOPs) and fixed bed biofiltration for the enhanced remediation of dissolved organics in oil sands process water (OSPW). The effect of initial sulfate precursors namely persulfate (PS) and monopersulfate (PMS) was examined on the degradation of naphthenic acid (NA) surrogates and various classes of organics in real OSPW. Effluents from solar activated SR-AOPs treatment of OSPW at specific conditions were subjected to biofiltration for 45 days. Fast and complete degradation of 5-phenylvalveric acid (PVA) and up to 99% degradation of various organics in OSPW were achieved by the solar activated SR-AOPs. Radical scavenger and spin-trap electroparamagnetic spectrometry analysis showed that hydroxyl ( • OH) and sulfate (SO 4 •− ) radicals were the major reactive species generated and participated in the oxidation of organics in SR-AOPs treatment with either PS or PMS along with a small proportion of singlet oxygen. The biofiltration post-treatment showed significant mineralization of dissolved organics in treated OSPW, achieving over 60% and 40% reduction in DOC and COD, respectively, surpassing most of the reported studies for such combined approach. The bacterial metataxonomic analysis indicated significant enrichment of hydrocarbons and carboxylic acid degraders ( Sphingomonas and Sphingopyxis ) in the biofilters treating PMS pre-treated OSPW. However, for biofilters treating raw OSPW and PS, the bacterial community was dominated by hydrocarbon degraders and methanotrophs. The treated OSPW was found completely non-toxic for the OSPW treated with PMS-9 h and biofiltration. This demonstrates the potential of combined treatment for the effective remediation of the oil sand industry effluent.