Simultaneous removal of arsenic and nitrate in absence of iron in an attached growth bioreactor to meet drinking water standards: Importance of sulphate and empty bed contact time. (10th June 2018)

• Record Type: Journal Article
• Authors: Shakya, Arvind Kumar; Ghosh, Pranab Kumar
• Is Part Of: Journal of cleaner production. Volume 186(2018)
• Page Start: 304
• Page End: 312
• Publication Date: 2018-06-10
• Subjects: Arsenic -- Nitrate -- Sulphate -- EBCT -- Arsenosulphides -- Drinking water; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2018.03.139
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: There are several reports on simultaneous occurrence of arsenic and nitrate in drinking water sources especially in groundwater at wide range of concentrations. However, there is no report available, so far, on simultaneous successful removal of arsenic and nitrate from contaminated groundwater in absence of iron, and effects of one contaminant on the overall performance of a biological reactor. The present study investigates the roles of sulphate and empty bed contact time (EBCT) on simultaneous removal of nitrate and arsenic to meet the drinking water standards in an attached growth bioreactor in absence of iron. An attached growth reactor (AGR) was fabricated using Perspex cylinder, inoculated with mixed bacterial culture and operated in downflow mode in absence of oxygen at 30 °C for more than 400 days under varying influent arsenate (200–750 μg/L) and nitrate concentrations (50–200 mg/L), and EBCT of 45–60 min. Acetate was used as external carbon source and electron donor in this study. Complete nitrate removal was observed at all tested concentrations. Arsenic removal was high (up to 99.8%) and was well below drinking water standards from initial concentrations of up to 750 μg/L. The arsenic removal efficiency was found to depend on sulphate reduction and EBCT of the reactor. Results of X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analyses suggested that arsenic precipitation in the form of arsenosulphides (orpiment and realgar) was the removal mechanism. Graphical abstract: Image Highlights: Complete denitrification as well as biological arsenic removal to below 5 μg/L. Successful simultaneous denitrification and arsenic removal in absence of iron. For 750 μg/L arsenic removal only 60 min EBCT and 50 mg/L sulphate was sufficient. Arsenic removal mechanism relies on precipitation as arsenosulphides. First report on biological process to meet drinking water standards for As and nitrate.