title: Enhancing nitrogen removal efficiency and reducing nitrate liquor recirculation ratio by improving simultaneous nitrification and denitrification in integrated fixed-film activated sludge (IFAS) process.
abstract: An integrated fixed-film activated sludge (IFAS) process (G1) and an activated sludge anoxic-oxic process (G2) were operated at nitrate liquor recirculation ratio (R) of 100, 200 and 300% to investigate the feasibility of enhancing nitrogen removal efficiency (RTN) and reducing R by improving simultaneous nitrification and denitrification (SND) in the IFAS process. The results showed that the effluent NH4(+)-N and total nitrogen (TN) of G1 at R of 200% were less than 1.5 and 14.5 mg/L, satisfying the Chinese discharge standard (NH4(+)-N < 5 mg/L; TN < 15 mg/L). However, the effluent NH4(+)-N and TN of G2 at R of 300% were higher than 8.5 and 15.3 mg/L. It indicated that better RTN could be achieved at a lower R in the IFAS process. The polymerase chain reaction-denaturing gradient gel electrophoresis results implied that nitrifiers and denitrifiers co-existed in one microbial community, facilitating the occurrence of SND in the aerobic reactor of G1, and the contribution of SND to TN removal efficiency ranged 15-19%, which was the main reason that the RTN was improved in the IFAS process. Therefore, the IFAS process was an effective method for improving RTN and reducing R. In practical application, this advantage of the IFAS process can decrease the electricity consumption for nitrate liquor recirculation flow, thereby saving operational costs.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China E-mail: quanxie@dlut.edu.cn.
authors.forename: Yang
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China E-mail: quanxie@dlut.edu.cn.
authors.forename: Yaobin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China E-mail: quanxie@dlut.edu.cn.
authors.forename: Xie
authors.initials: X
authors.lastname: Quan
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China E-mail: quanxie@dlut.edu.cn.
authors.forename: Shuo
authors.initials: S
authors.lastname: Chen
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D058440:Denitrification; D009566:Nitrates / Q000378:metabolism*; D058465:Nitrification; D009584:Nitrogen / Q000378:metabolism*; D009589:Nitrogen Oxides; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D009566:Nitrates; D009584:Nitrogen; D009589:Nitrogen Oxides; D012722:Sewage; D062065:Wastewater