Biological treatment of refinery spent caustics under halo-alkaline conditions

• Published in: Bioresource technology Vol. 102; no. 15; pp. 7257 - 7264
• Main Authors: de Graaff, Marco, Bijmans, Martijn F.M., Abbas, Ben, Euverink, Gert-J.W., Muyzer, Gerard, Janssen, Albert J.H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-08-2011; Elsevier
• Subjects: Alkalies; Alkalies - chemistry; Bacteria; Bacteria - genetics; Bacteria - metabolism; bacteriochlorophyll; Benzene; Benzene - analysis; Benzene - isolation & purification; Biodegradation, Environmental; Biological; Biological and medical sciences; Biomass; Bioreactors - microbiology; Biotechnology; Caustics; Caustics - isolation & purification; Denaturing Gradient Gel Electrophoresis; diversity; Fundamental and applied biological sciences. Psychology; gen. nov; Gene Library; Haloalkalipilic; Halogens - chemistry; Halomonas; Idiomarina; Industrial Waste - analysis; Marinobacter; Microorganisms; mono lake; oxidation processes; Oxidation-Reduction; Phylogeny; Refineries; RNA, Ribosomal, 16S - genetics; soda lake; Solutions; sp-nov; Spent caustics; Sulfates - analysis; sulfide; Sulfide oxidation; Sulfides; Sulfides - analysis; sulfur-oxidizing bacteria; Thioalkalivibrio; Time Factors; Waste Disposal, Fluid; water; Thioalkalivibrio; Haloalkalipilic; Spent caustics; Benzene; Sulfide oxidation; Sulfides; Basic medium; Oxidation; Alkalinity; Refinery; Biological treatment
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2011.04.095

► The biological treatment of refinery spent caustics in a continuous system was studied. ► Soda lake bacteria that enable operating under halo-alkaline condition were used. ► Thioalkalivibrio species completely oxidized sulfide into sulfate. ► Benzene removal efficiencies of 93% were obtained. ► Several bacteria were identified which might have played a role in benzene removal.
The present research demonstrates the biological treatment of refinery sulfidic spent caustics in a continuously fed system under halo-alkaline conditions (i.e. pH 9.5; Na+= 0.8M). Experiments were performed in identical gas-lift bioreactors operated under aerobic conditions (80–90% saturation) at 35°C. Sulfide loading rates up to 27mmolL−1day−1 were successfully applied at a HRT of 3.5days. Sulfide was completely converted into sulfate by the haloalkaliphilic sulfide-oxidizing bacteria belonging to the genus Thioalkalivibrio. Influent benzene concentrations ranged from 100 to 600μM. At steady state, benzene was removed by 93% due to high stripping efficiencies and biodegradation. Microbial community analysis revealed the presence of haloalkaliphilic heterotrophic bacteria belonging to the genera Marinobacter, Halomonas and Idiomarina which might have been involved in the observed benzene removal. The work shows the potential of halo-alkaliphilic bacteria in mitigating environmental problems caused by alkaline waste.