title: Application of a 2-step process for the biological treatment of sulfidic spent caustics.
abstract: This research demonstrates the feasibility and advantages of a 2-step process for the biological treatment of sulfidic spent caustics under halo-alkaline conditions (i.e. pH 9.5; Na(+) = 0.8 M). Experiments with synthetically prepared solutions were performed in a continuously fed system consisting of two gas-lift reactors in series operated at aerobic conditions at 35 °C. The detoxification of sulfide to thiosulfate in the first step allowed the successful biological treatment of total-S loading rates up to 33 mmol L(-1) day(-1). In the second, biological step, the remaining sulfide and thiosulfate was completely converted to sulfate by haloalkaliphilic sulfide oxidizing bacteria. Mathematical modeling of the 2-step process shows that under the prevailing conditions an optimal reactor configuration consists of 40% 'abiotic' and 60% 'biological' volume, whilst the total reactor volume is 22% smaller than for the 1-step process.
authors.affiliation: Sub-department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Marco.degraaff@wetsus.nl
authors.forename: Marco
authors.initials: M
authors.lastname: de Graaff
authors.forename: Johannes B M
authors.initials: JB
authors.lastname: Klok
authors.forename: Martijn F M
authors.initials: MF
authors.lastname: Bijmans
authors.forename: Gerard
authors.initials: G
authors.lastname: Muyzer
authors.forename: Albert J H
authors.initials: AJ
authors.lastname: Janssen
mesh_terms: D001673:Biodegradation, Environmental; D019149:Bioreactors; D002424:Caustics / Q000302:isolation & purification*; D003198:Computer Simulation; D010084:Oxidation-Reduction; D013440:Sulfides / Q000302:isolation & purification*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D002424:Caustics; D013440:Sulfides; D014874:Water Pollutants, Chemical