title: Using a two-stage hydrogen-based membrane biofilm reactor (MBfR) to achieve complete perchlorate reduction in the presence of nitrate and sulfate.
abstract: We evaluated a strategy for achieving complete reduction of perchlorate (ClO(4)(-)) in the presence of much higher concentrations of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) in a hydrogen-based membrane biofilm reactor (MBfR). Full ClO(4)(-) reduction was achieved by using a two-stage MBfR with controlled NO(3)(-) surface loadings to each stage. With an equivalent NO(3)(-) surface loading larger than 0.65 ± 0.04 g N/m(2)-day, the lead MBfR removed about 87 ± 4% of NO(3)(-) and 30 ± 8% of ClO(4)(-). This decreased the equivalent surface loading of NO(3)(-) to 0.34 ± 0.04-0.53 ± 0.03 g N/m(2)-day for the lag MBfR, in which ClO(4)(-) was reduced to nondetectable. SO(4)(2-) reduction was eliminated without compromising full ClO(4)(-) reduction using a higher flow rate that gave an equivalent NO(3)(-) surface loading of 0.94 ± 0.05 g N/m(2)-day in the lead MBfR and 0.53 ± 0.03 g N/m(2)-day in the lag MBfR. Results from qPCR and pyrosequencing showed that the lead and lag MBfRs had distinctly different microbial communities when SO(4)(2-) reduction took place. Denitrifying bacteria (DB), quantified using the nirS and nirK genes, dominated the biofilm in the lead MBfR, but perchlorate-reducing bacteria (PRB), quantified using the pcrA gene, became more important in the lag MBfR. The facultative anaerobic bacteria Dechloromonas, Rubrivivax, and Enterobacter were dominant genera in the lead MBfR, where their main function was to reduce NO(3)(-). With a small NO(3)(-) surface loading and full ClO(4)(-) reduction, the dominant genera shifted to ClO(4)(-)-reducing bacteria Sphaerotilus, Rhodocyclaceae, and Rhodobacter in the lag MBfR.
authors.affiliation: MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou 310058, China. hopechoil@gmail.com
authors.forename: He-Ping
authors.initials: HP
authors.lastname: Zhao
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.forename: Youneng
authors.initials: Y
authors.lastname: Tang
authors.forename: Bi O
authors.initials: BO
authors.lastname: Kim
authors.forename: Zehra Esra
authors.initials: ZE
authors.lastname: Ilhan
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
authors.forename: Bruce
authors.initials: B
authors.lastname: Rittmann
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000235:genetics; D001673:Biodegradation, Environmental / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects; D019149:Bioreactors / Q000382:microbiology*; D004583:Electrons; D006859:Hydrogen / Q000494:pharmacology*; D008567:Membranes, Artificial; D009566:Nitrates / Q000302:isolation & purification*; D010472:Perchlorates / Q000302:isolation & purification*; D013431:Sulfates / Q000302:isolation & purification*
chemical_list: D008567:Membranes, Artificial; D009566:Nitrates; D010472:Perchlorates; D013431:Sulfates; D006859:Hydrogen; C494474:perchlorate