title: Seawater denitrification in a closed mesocosm by a submerged moving bed biofilm reactor.
abstract: The performance of a submerged moving bed biofilm reactor (MBBR) for the denitrification of seawater in a 3.25 million closed circuit mesocosm was investigated at pilot scale, using methanol as a carbon source at various C/N ratios. Nitrate accumulation in closed systems where water changes are expensive and problematic may cause toxicity problems to marine life. Seawater was pretreated in a recirculated fixed bed to remove oxygen prior to the denitrification step. The 110l MBBR was partly filled (25%) with spherical positively buoyant polyethylene carriers with an effective surface area of approximately 100 m2 m(-3), which represents 35% of the total surface area. Carriers were maintained submerged by a conical grid and circulated by the downflow jet of an eductor. The MBBR mixing system was designed to prevent dead mixing zones and carrier fouling to avoid sulfate reduction while treating seawater containing as high as 2150 mg SO4-Sl(-1). NO3-N reduction from 53 to as low as 1.7+/-0.7 mg l(-1) and a maximum denitrification rate of 17.7+/-1.4 g Nm(-2) d(-1) were achieved at 4.2-4.3 applied COD/N (w/w) ratio. Methanol consumption corresponded to denitrification stoichiometric values, indicating the absence of sulfate reduction. Denitrification rates and effluent residual dissolved organic carbon were proportional to the C/N ratio. Such reactors could be scaled up in closed systems where water changes must be minimized.
authors: Department of Civil, Geological and Mining Engineering, Ecole Polytechnique of Montreal, P.O. Box 6079, Station Centre-ville, Montreal (QC) Canada H3C 3A7. marc-andre.labelle@polymtl.ca
authors: Marc-André
authors: MA
authors: Labelle
authors: Pierre
authors: P
authors: Juteau
authors: Mario
authors: M
authors: Jolicoeur
authors: Richard
authors: R
authors: Villemur
authors: Serge
authors: S
authors: Parent
authors: Yves
authors: Y
authors: Comeau
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors; D002244:Carbon / Q000032:analysis / Q000378:metabolism; D017753:Ecosystem; D000432:Methanol / Q000378:metabolism; D009566:Nitrates / Q000302:isolation & purification / Q000378:metabolism; D009573:Nitrites / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D009930:Organic Chemicals / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D020959:Polyethylene / Q000737:chemistry; D012623:Seawater / Q000737:chemistry*; D013431:Sulfates / Q000378:metabolism; D013997:Time Factors; D018508:Water Purification / Q000379:methods*
chemical_list: D009566:Nitrates; D009573:Nitrites; D009930:Organic Chemicals; D013431:Sulfates; D002244:Carbon; D020959:Polyethylene; D009584:Nitrogen; D010100:Oxygen; D000432:Methanol