Impact of bioaugmentation on the bioremediation of saline produced waters supplemented with anaerobic digestate

Bioremediation of produced waters has been widely investigated in the last decades. More recently, microalgae-based treatments have been developed to produce biomass. The ob-jective of this study was to determine, at lab scale, the remediation efficiency of 3 origin of microorganisms: a consortium of 3 halotolerant and halophilic microalgae and their as-sociated bacteria, bacteria from liquid digestate and aromatic-degrading bacteria selected to perform bioaugmentation. The medium was composed of artificial oil produced water and seawater, and contained nutrients from liquid digestate. In order to identify who plays a role in nitrogen, chemical oxygen demand and aromatics compounds elimination, and to determine the effectiveness of bioaugmentation to treat this mix of waters, 16S rRNA analyses were performed. Combination of microorganisms from different origins with the selected aromatic-degrading bacteria were also realized, to determine the effec-tiveness of bioaugmentation to treat these waters. Each population of microorganisms achieved similar percentage of removal during the biological treatment, with 43-76%, 59-77% and 86-93% of elimination for ammonium, chemical oxygen demand and aro-matic compounds (with 50% of volatilization), respectively, after 7 days, and up to with 100%, 77% and 99% after 23 days, demonstrating that in the case of this produced water, bioaugmentation with the specialized aromatic-degrading bacteria had no significant impact on the treatment. Regarding in detail at the populations present and active during the tests, those from genus Marinobacter always appeared among the most active microor-ganisms, some strains of this genus being known to degrade aromatic compounds.