title: A novel elemental sulfur-based mixotrophic denitrifying membrane bioreactor for simultaneous Cr(VI) and nitrate reduction.
abstract: This study aims at investigating the simultaneous nitrate and chromate reduction by combining the advantages of sulfur-based autotrophic denitrification, heterotrophic denitrification and membrane bioreactor (MBR) technologies. A laboratory-scale MBR equipped with hydrophilic flat sheet polyethersulfone (PES) membranes (0.45μm) was used to evaluate the performance of mixotrophic denitrification at varying nitrate and Cr(VI) concentrations. Methanol was supplied at C/N (mg methanol/mg NO3--N) ratio of 1.33. In the absence of Cr(VI), almost complete denitrification of 50mg/L NO3--N was obtained and the methanol requirement (3.60±0.9mg COD/(mg NO3--N)) for heterotrophic denitrifiers, was quite close to the theoretical value (3.7mg COD/(mg NO3--N)). Around 54% of the influent nitrate was denitrified by heterotrophs and the rest (56%) was denitrified by autotrophic sulfur oxidizers. The effluent sulfate averaged around 200mg/L, which was below than the theoretical sulfate concentration if autotrophic denitrification process was used alone. Autotrophic denitrification activity completely ceased at 5mg/L Cr(VI), but heterotrophic denitrification did not show any inhibition. Almost complete chromate and nitrate reduction was observed at 1mg/L Cr(VI). MBR was operated for around 200days and a weekly physical membrane cleaning was enough at a flux of 15 LMH.
authors.affiliation: Istanbul Medeniyet University, Bioengineering Department, Goztepe, Istanbul, Turkey. Electronic address: erkansahinkaya@gmail.com.
authors.forename: Erkan
authors.initials: E
authors.lastname: Sahinkaya
authors.affiliation: Yildiz Technical University, Department of Environmental Engineering, Istanbul, Turkey.
authors.forename: Adem
authors.initials: A
authors.lastname: Yurtsever
authors.affiliation: Harran University, Environmental Engineering Department, Osmanbey Campus, 63000 Sanliurfa, Turkey.
authors.forename: Deniz
authors.initials: D
authors.lastname: Ucar
mesh_terms: D019149:Bioreactors; D002857:Chromium / Q000737:chemistry*; D058440:Denitrification; D052836:Heterotrophic Processes; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D000432:Methanol / Q000737:chemistry; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry*; D014462:Ultrafiltration; D018508:Water Purification
chemical_list: D008567:Membranes, Artificial; D009566:Nitrates; D013431:Sulfates; D002857:Chromium; C074702:chromium hexavalent ion; D013455:Sulfur; D000432:Methanol
keywords: Autotrophic denitrification; Drinking water; Membrane bioreactor; Mixotrophic denitrification; Sulfur-based autotrophic denitrification