title: Tertiary nitrogen removal for municipal wastewater using a solid-phase denitrifying biofilter with polycaprolactone as the carbon source and filtration medium.
abstract: Tertiary nitrogen removal technologies are needed to reduce the excess nitrogen that is discharged into sensitive aquatic ecosystems. An integrated solid-phase denitrification biofilter (SDNF) was developed with dual media to remove nitrate and suspended solids (SS) from the secondary effluent of municipal wastewater treatment plants. Biodegradable polymer pellets of polycaprolactone (PCL) served as the biofiltration medium and carbon source for denitrification. Long-term continuous operation of the SDNF was conducted with real secondary effluent to evaluate the denitrification performance and effects of influent nitrate loading rates (NLR) and operating temperatures. The results indicated that both nitrate and SS were effectively removed. The SDNF had a strong tolerance for fluctuations in influent NLR, and a maximum denitrification rate of 3.80 g N/(L·d) was achieved. The low temperature had a significant impact on nitrogen removal, yet the denitrification rate was still maintained at a relative high level to as much as 1.23 g N/(L·d) even at approximately 8.0 °C in winter. Nitrite accumulation and excessive organics residue in the effluent were avoided throughout the whole experiment, except on occasional days in the lag phase. The observed biomass yield was calculated to be 0.44 kgVSS/kgPCL. The microbial diversity and community structure of the biofilm in the SDNF were revealed by Illumina high-throughput sequencing. The special carbon source led to an obvious succession of microbial community from the initial inoculum (activated sludge from aerobic tanks), and included a decrease in microbial diversity and a shift in the dominant groups, which were identified to be members of the family Comamonadaceae in the SDNF. The SDNF developed in this study was verified to be an efficient technology for tertiary nitrogen removal from secondary effluent.
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address: jiane.zuo@tsinghua.edu.cn.
authors.forename: Jiane
authors.initials: J
authors.lastname: Zuo
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China.
authors.forename: Yajiao
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.affiliation: School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Tang
authors.affiliation: School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, 050018, China.
authors.forename: Zaixing
authors.initials: Z
authors.lastname: Li
mesh_terms: D018441:Biofilms; D018533:Biomass; D002244:Carbon / Q000737:chemistry; D002947:Cities; D042621:Comamonadaceae / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D058440:Denitrification; D005374:Filtration / Q000295:instrumentation / Q000379:methods*; D009566:Nitrates / Q000737:chemistry / Q000302:isolation & purification; D009584:Nitrogen / Q000737:chemistry* / Q000302:isolation & purification; D011091:Polyesters / Q000737:chemistry*; D015203:Reproducibility of Results; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*; D062065:Wastewater / Q000737:chemistry* / Q000382:microbiology; D014871:Water Microbiology; D018508:Water Purification / Q000295:instrumentation / Q000379:methods
chemical_list: D002244:Carbon; D009566:Nitrates; D009584:Nitrogen; D011091:Polyesters; D012722:Sewage; D062065:Wastewater; C016240:polycaprolactone
keywords: Denitrifying biofilter; High-throughput sequencing; Polycaprolactone; Post-denitrification; Solid carbon resource