title: Autotrophic denitrification via a novel membrane-attached biofilm reactor.
abstract: OBJECTIVE
  A laboratory-scale autotrophic membrane-attached biofilm reactor was developed to remove nitrate from drinking water.
  
  
  RESULTS
  Hydrogen and carbon dioxide flowed together into the lumem side of a gas-permeable silicone tube. The gases diffused through the membrane wall to feed Alcaligenes eutrophus that formed a biofilm on the surface of the silicone tube for autotrophic denitrification. Hydrogen provided the energy source, and carbon dioxide, besides serving as the carbon source, was employed to neutralize the alkalinity from denitrification. The optimal carbon dioxide concentration in the silicone tube was between 20% and 50%.
  
  
  CONCLUSIONS
  This study has demonstrated that a gas-permeable silicone tube is a convenient and efficient method to feed A. eutrophus for autotrophic denitrification. Supplying a suitable amount of carbon dioxide together with hydrogen into the silicone tube solved the problem that alkalinity formation caused during denitrification. The pH of the bioreactor was maintained at about 7 to avoid nitrite accumulation, and then the nitrogen removal rate was increased. A high specific nitrogen removal rate (1.6-5.4 g Nm(2)d(-1-1) of surface area of silicone tube) was achieved.
  
  
  CONCLUSIONS
  In addition to combining the advantages of the hydrogenotrophic denitrification process and a membrane feeding substrate bioreactor (MFSB), this bioreactor achieved a high nitrogen removal rate and is simple to operate. It therefore is highly promising in drinking-water treatment.
authors.affiliation: Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd. Taipei, Taiwan, R. O. C. d88541003@ms88.ntu.edu.tw
authors.forename: C M
authors.initials: CM
authors.lastname: Ho
authors.forename: S K
authors.initials: SK
authors.lastname: Tseng
authors.forename: Y J
authors.initials: YJ
authors.lastname: Chang
mesh_terms: D018441:Biofilms; D018533:Biomass; D019149:Bioreactors; D002245:Carbon Dioxide / Q000378:metabolism; D020118:Cupriavidus necator / Q000254:growth & development / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D010084:Oxidation-Reduction; D014871:Water Microbiology; D018508:Water Purification; D014881:Water Supply
chemical_list: D009566:Nitrates; D009573:Nitrites; D002245:Carbon Dioxide; D006859:Hydrogen