Fundamental Study On Application Of Low Consumption Biofilter Reactor To Treat Municipal Sewage

A single-stage simultaneous partial nitritation,anammox,and denitrification（SNAD）biofilter reactor（BFR）and a two-stage partial nitritation anammox（PN/A）BFR were used for simulated municipal sewage treatment in this paper to explore an high efficiency and energy-saving method for municipal sewage treatment.First,the anaerobic ammonium-oxidizing bacteria（An AOB）were enriched in the upper part of the single-stage BFR through a continuous flow mode of the top influent and bottom effluent.Then,the single-stage BFR was inoculated with activated sludge and aerated continuously at the bottom to realize the coupling of SNAD accompanied by two-point influent from the bottom and top effluent,and the removal characteristics of nitrogen and carbon and microbial community distribution were studied.Finally,partial nitritation BFR and anammox BFR were started up to explore the feasibility of stable operation of partial nitritation BFR and the effect of temperature on nitrogen removal efficiency and microbial community distribution of anammox BFR.This study could provide theoretical support for the treatment of simulated municipal sewage in the BFR.The main conclusions were drawn as the following:（1）The anammox of the single-stage BFR was started successfully in 55 days.The average effluent concentrations of NH₄⁺-N and NO₂^--N remained at 0.33 and13.34 mg/L when NLR of 0.83 kg·（m³·d）^-1,HRT of 3 h and the influent concentrations of NH₄⁺-N and NO₂^--N remained at 47.0±3.0 and 53.0±4.0 mg/L,respectively.The average effluent concentrations of NH₄⁺-N,NO₂^--N and SCOD were reduced to 4.23,6.44 and 11.29 mg/L,and the average removal rates were up to 93.40%,89.95%and92.68%,respectively in the steady phase of the single-stage BFR（HRT of 6 h and Air/Water ratio of 4.29）with the influent of 65.0±4.0 mg NH₄⁺-N/L and 150.0±5.0SCOD mg/L.（2）The 0～12.5 cm water inlet zone and 57.5～82.5 cm water inlet zone are the two main nitrogen and carbon removal zones of the single-stage BFR.The two zones contributed 77.61%and 96.91%to the TN and SCOD removal of the entire reactor,respectively.The relative abundance of Nitrosomonas（AOB）,Candida brocadia（An AOB）and Denitisoma（DB）in 0～12.5 cm zone were 0.77%,0.43%and 4.07%,respectively.The specific ammonia oxidation activity,specific anammox activity and specific denitrification activity of the 0～12.5 cm zone were 30.90,11.20 and 57.25 mg N·（g VSS·h）^-1,respectively.It showed that the high activity of functional bacteria was the key to maintain the high efficiency of nitrogen and carbon removal in the single-stage BFR.（3）The NAR of partial nitritation BFR gradually decreased from 98.12%to 13.39%with intermittent aeration mode,which could not be improved through increasing the stop-exposure ratio of intermittent aeration and adding hydroxylamine（NH₂OH）.（4）The longest adaptation period of the anammox BFR was 36 days when its operating temperature gradually decreased from 31±1℃to 22±1℃.the average effluent concentrations of NH₄⁺-N and TN were as low as 1.64 and 13.79 mg/L,respectively when NLR was 1.64 kg·（m³·d）^-1and water temperature was 22℃.In addition,the water flow distance of 0-25 cm was the main nitrogen removal zone of the anammox BFR,where specific ammonia oxidation activity and biomass were up to0.84 mg N·（g VSS·h）^-1 and 11.28 g SS/L,respectively while the contribution rate of TN was 44.58%～84.20%in the whole operation process.（5）The contribution rate of TN removal in the water flow distance of 0～25 cm accounted for 74.81%of the entire anammox BFR under NLR of 1.64 kg·（m³·d）^-1 and22±1℃,indicating that more than half of the reactor space was not fully utilized,which further proved that the reactor could withstand the shock of higher NLR and lower temperature.Candidatus brocadia was the An AOB with the highest abundance on the biofilm from the BFR inlet to 75 cm zone,which had the relative abundances of more than 5%,was up to the relative abundance of 19.25%along the water flow distance of 0～25 cm.