Effect of electron donors on the performance of haloalkaliphilic sulfate-reducing bioreactors for flue gas treatment and microbial degradation patterns related to sulfate reduction of different electron donors

• Haloalkaliphilic bioreactors were started up using different electron donors.
• Sulfide concentration reached 3294 mg l−1.
• There was no sulfide inhibition to haloalkaliphilic microorganisms.
• Microbial degradation patterns related to sulfate reduction were determined.

Haloalkaliphilic microorganisms were used to treat wastewater from adsorption alkaline solution of flue gas characterized by high pH and salinity. Lactate, glucose, methanol, ethanol, formate, and acetate were used to investigate the effect of different electron donors on the performance of haloalkaliphilic sulfate-reducing bioreactors. At pH 9.5 and 1.0 M of Na+, the optimum electron donor was found to be ethanol with the shortest lag period (31 days) and the highest sulfate removal rate (8.60 ± 0.129 kg m−3 d−1). Bioreactors were stable after they were successfully started up. High sulfide concentration (3294 ± 18.8 mg l−1) did not inhibit the activity of sulfate-reducing bacteria (SRB). Microbial degradation patterns related to sulfate reduction of different electron donors were determined. Oxidation process of propionate was coupled with sulfate reduction process in the lactate- and glucose-fed bioreactor. Glucose can be directly utilized by haloalkaliphilic SRB. The pathway of ethanol to pyruvate and Wood–Ljungdahl pathway were found in the ethanol- and formate-fed bioreactor, respectively. Some haloalkaliphilic SRB of the complete oxidation type may be present in the formate-fed bioreactor.