title: Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch.
abstract: A pilot-scale Orbal oxidation ditch was operated for 17 months to optimize nitrogen removal from domestic wastewater of average COD to total nitrogen ratio of 2.7, with particular concern about the roles of dissolved oxygen (DO), mixed liquor suspended solids (MLSS) and return activated sludge (RAS) recycle ratio. Remarkable simultaneous nitrification and denitrification (SND) was observed and mean total nitrogen (TN) removal efficiency up to 72.1% was steadily achieved, at DO concentration in the out, middle and inner channel of 0.1, 0.4 and 0.7 mg/L, respectively, with an average MLSS of 5.5 g/L and RAS recycle ratio of 150%. Although the out channel took the major role in TN removal, the role of middle channel should never be ignored. The denitrification potential could be fully developed under low DO, high MLSS with adequate RAS ratio. The sludge settleability was amazingly improved under low DO operation mode, and some explanations were tried. In addition, a series of simplified batch tests were done to determine whether novel microorganisms could make substantial contribution to the performance of nitrogen removal. The results indicated that the SND observed in this Orbal oxidation ditch was more likely a physical phenomenon.
authors.affiliation: School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors.forename: Shou-you
authors.initials: SY
authors.lastname: Gao
authors.forename: Yong-zhen
authors.initials: YZ
authors.lastname: Peng
authors.forename: Shu-ying
authors.initials: SY
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Yan
mesh_terms: D052918:Environmental Restoration and Remediation / Q000379:methods*; D009584:Nitrogen / Q000302:isolation & purification* / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis; D012722:Sewage / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; D009584:Nitrogen; D010100:Oxygen