The effect of various iron hydroxide concentrations on the anaerobic fermentation of sulfate-containing model wastewater

Abstract

Addition of ferric hydroxide and iron-reducing bacteria in anaerobic treatment of sulphate-containing wastewater reduced sulphate reduction and production of sulphide, increased removal of total organic carbon (TOC) and methane production. Influence of ferric addition on sulphate-containing wastewater treatment depended on Fe(III) dosage, which can be determined as a molar ratio of Fe(ІІІ)/SO42-. Concentration of sulphide constantly increased and consisted on 15 day 91 mg/l and 45 mg/l at ratio of Fe(ІІІ)/SO42- 0.06 and 0.5. However, no production of dissolved sulphide was observed at ratio Fe(ІІІ)/SO42- 1 and 2. Maximum rates of total organic carbon removal were 0.75, 1.15, 1.39, 1.55 g TOC/g of volatile suspended solids (VVS) per hour; rates of methane production were 0.039, 0.047, 0.064 and 0.069 ml/g VVS per hour; contents of methane in biogas were 25, 41, 55 and 62 vol. % at the ratios of Fe(ІІІ)/SO42- 0.06, 0.5, 1 and 2, respectively. These data could be used for the development of a new technology for anaerobic treatment of sulphate containing wastewater.