COMPARISON OF UASB AND FLUIDIZED-BED REACTORS FOR SULFATE REDUCTION

• Main Authors: S. M. Bertolino, L. A. M. Silva, S. F. Aquino, V. A. Leão
• Format: Article
• Language: English
• Published: Brazilian Society of Chemical Engineering 2015-03-01
• Series: Brazilian Journal of Chemical Engineering
• Subjects: Sulfate reduction; Anaerobic processes; Fluidized bed bioreactors; Glycerol; Upflow anaerobic sludge blanket; Wastewater treatment
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322015000100059&lng=en&tlng=en

Abstract Reactor hydrodynamics is important for sulfidogenesis because sulfate reduction bacteria (SRB) do not granulate easily. In this work, the sulfate reduction performance of two continuous anaerobic bioreactors was investigated: (i) an upflow anaerobic sludge blanket (UASB) reactor and (ii) a fluidized bed reactor (FBR). Organic loading, sulfate reduction, and COD removal were the main parameters monitored during lactate and glycerol degradation. The UASB reactor with biomass recirculation showed a specific sulfate reduction rate of 0.089±0.014 g.gSSV-1.d-1 (89% reduction), whereas values twice as high were achieved in the FBR treating either lactate (0.200±0.017 g.gSSV-1.d-1) or glycerol (0.178±0.010 g.gSSV-1.d-1). Sulfate reduction with pure glycerol produced a smaller residual COD (1700 mg.L-1) than that produced with lactate (2500 mg.L-1) at the same COD.sulfate-1 mass ratio. It was estimated that 50% of glycerol degradation was due to sulfate reduction and 50% to fermentation, which was supported by the presence of butyrate in the FBR effluent. The UASB reactor was unable to produce effluents with sulfate concentrations below 250 mg.L-1 due to poor mixing conditions, whereas the FBR consistently ensured residual sulfate concentrations below such a value.