Arsenic removal in a sulfidogenic fixed-bed column bioreactor

• Published in: Journal of hazardous materials 2014-03, Vol.269, p.31-37
• Main Authors: Altun, Muslum, Sahinkaya, Erkan, Durukan, Ilknur, Bektas, Sema, Komnitsas, Kostas
• Format: Article
• Language: English
• Subjects: Acid mine drainage; Applied sciences; Arsenic removal; Arsenicals - isolation & purification; Biological and medical sciences; Bioreactors; Biotechnology; Chemical engineering; Desulfovibrio - chemistry; Desulfovibrio - genetics; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; Hydrogen-Ion Concentration; Iron - chemistry; Metals - chemistry; Metals - isolation & purification; Methods. Procedures. Technologies; Microscopy, Electron, Scanning; Others; Oxidation-Reduction; Oxygen - chemistry; Pollution; Reactors; Spectrometry, X-Ray Emission; Sulfate reduction; Sulfates - chemistry; Sulfides - chemistry; Sulfur-Reducing Bacteria - chemistry; Sulfur-Reducing Bacteria - metabolism; Sulfur-Reducing Bacteria - ultrastructure; Various methods and equipments; Waste Water - analysis; Wastewaters; Water Pollutants, Chemical - isolation & purification; Water treatment and pollution; X-Ray Diffraction
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2013.11.047

•Sulfidogenic treatment of As-containing AMD was investigated.•High rate simultaneous removal of As and Fe was achieved.•As was removed without adding alkalinity or adjusting pH.•As and Fe removal mechanisms were elucidated. In the present study, the bioremoval of arsenic from synthetic acidic wastewater containing arsenate (As5+) (0.5–20mg/L), ferrous iron (Fe2+) (100–200mg/L) and sulfate (2000mg/L) was investigated in an ethanol fed (780–1560mg/L chemical oxygen demand (COD)) anaerobic up-flow fixed bed column bioreactor at constant hydraulic retention time (HRT) of 9.6h. Arsenic removal efficiency was low and averaged 8% in case iron was not supplemented to the synthetic wastewater. Neutral to slightly alkaline pH and high sulfide concentration in the bioreactor retarded the precipitation of arsenic. Addition of 100mg/L Fe2+ increased arsenic removal efficiency to 63%. Further increase of influent Fe2+ concentration to 200mg/L improved arsenic removal to 85%. Decrease of influent COD concentration to its half, 780mg/L, resulted in further increase of As removal to 96% when Fe2+ and As5+ concentrations remained at 200mg/L and 20mg/L, respectively. As a result of the sulfidogenic activity in the bioreactor the effluent pH and alkalinity concentration averaged 7.4±0.2 and 1736±239mg CaCO3/L respectively. Electron flow from ethanol to sulfate averaged 72±10%. X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses were carried out to identify the nature of the precipitate generated by sulfate reducing bacteria (SRB) activity. Precipitation of arsenic in the form of As2S3 (orpiment) and co-precipitation with ferrous sulfide (FeS), pyrite (FeS2) or arsenopyrite (FeAsS) were the main arsenic removal mechanisms.