title: Nitrate removal by a combination of elemental sulfur-based denitrification and membrane filtration.
abstract: In this paper, a new method for removal of nitrate from groundwater, in which elemental sulfur-based denitrification (autotrophic denitrification) and membrane separation are combined, is proposed. By using a membrane, autotrophic denitrifiers, whose growth rate is considerably low, can be kept at a high concentration. The performance of the proposed process was examined through a long-term experiment in the laboratory using synthetic feed water. A rotating membrane disk module equipped with UF membrane (750,000 Da) was used in this study. Complete removal of nitrate (25 mg N/L) was achieved under the conditions of a biomass concentration of about 1000 mg protein/L and HRT of 160 min. Dissolved oxygen concentration and sulfur/biomass ratio in the membrane chamber were found to be the key factors in maintenance of high-process performance. Deterioration in membrane permeability was insignificant. It was found that membrane filtration could be continued with a water flux of 0.5 m3/m2/day for about 100 days without any chemical membrane cleaning. The proposed process, however, caused a slight increase in assimilable organic carbon. Sulfide was not detected in the denitrified water.
authors.affiliation: Department of Urban and Environmental Engineering, Hokkaido University, Sapporo, Japan. kkatsu@eng.hokudai.ac.jp
authors.forename: Katsuki
authors.initials: K
authors.lastname: Kimura
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nakamura
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism; D005374:Filtration; D008567:Membranes, Artificial; D009566:Nitrates / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D010100:Oxygen / Q000032:analysis; D010539:Permeability; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism*; D013997:Time Factors; D018508:Water Purification / Q000379:methods*
chemical_list: D008567:Membranes, Artificial; D009566:Nitrates; D012722:Sewage; D013455:Sulfur; D002244:Carbon; D010100:Oxygen