Laboratory-scale bioreactors for soluble selenium removal from selenium refinery wastewater using anaerobic sludge

• Published in: Desalination 2011-09, Vol.279 (1), p.433-438
• Main Authors: Soda, Satoshi, Kashiwa, Masami, Kagami, Tsubasa, Kuroda, Masashi, Yamashita, Mitsuo, Ike, Michihiko
• Format: Article
• Language: English
• Subjects: Anaerobic sludge; Applied sciences; Biological and medical sciences; Bioreactors; Biotechnology; carbon; Chemical engineering; desalination; ethanol; Ethyl alcohol; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; Metal refinery wastewater; Methods. Procedures. Technologies; Microorganisms; Other industrial wastes. Sewage sludge; Others; Pollution; Reactors; Reduction; salinity; Selenium; sewage sludge; Sludge; UASB reactor; Various methods and equipments; Waste water; Wastes; wastewater; Wastewaters; Water treatment and pollution
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/j.desal.2011.06.031

Laboratory-scale bioreactors were constructed to investigate their applicability for recovery of soluble selenium from industrial wastewater. Microbial reduction of soluble selenium into elemental selenium is the key reaction because, as a result of its insoluble characteristics, it can be removed easily from the aqueous phase. Wastewater of a selenium refinery plant showed extremely low pH (< 1.0), high salinity (6–7%), and various selenium concentrations (mainly selenite, 13.2–74.0 mg l − 1 ). As preconditioning for microbial reduction, the wastewater pH and salinity were adjusted, respectively, to about 7.5 and 1.1%. Granular sludge of an up-flow anaerobic sludge blanket (UASB) reactor and suspended sludge of a sewage sludge digester were seeded respectively to a UASB-type reactor and a suspended sludge bed reactor. The 2.2-l bioreactors were operated at 30 °C and hydraulic retention time of about 24 h for preconditioned wastewater supplemented with ethanol as a carbon source. The removal of 1.5–3.5 mg l − 1 soluble selenium was only 60% in the swim-bed reactor. The selenium concentration in effluent of the UASB-type reactor dropped to less than the regulated amount of the effluent concentration of selenium of 0.1 mg l − 1 by day 15. ► We developed a biological treatment process for Se refinery wastewater with extremely low pH (< 1.0), high salinity (6-7%), and various selenium concentrations (13.2–74.0 mg/L). ► Anaerobic microorganisms in granular sludge showed high selenite reduction. ► With adjustment of pH and salinity and ethanol addition, the Se concentration of the UASB reactor dropped to 0.1 mg/L. ► The removed selenium was accumulated in granular sludge.