The Construction Of One-stage Deammonification System With Granular Sluge And The Study Of Its Nitrogen Removal Performance

Deammonification is the most popular form for anammox-based technology,by copupling partial nitritation and anammox.Compared to the traditional nitrificationdenitrification process,deammonificaion is more economical and efficient,and suitable for treating wastewater with high ammonium and low COD/TN.Deammonifiction has been successfully applied to full-scale installations,such as sludge digestion,and one-stage deammonification is the most popular type.Next,applying one-stage deammonification into the mian line of domestic sewage treatment（mianstream deammonification）is meaningful and hot point.But nitrate build-up is easy happened for low ammonia concentration.It’s necessary to note that low ammonia is the ammonia concentration of domestic sewage（30-90mg/L）.And granular deammonification is ideal but not easy to culture.In this study,the deamonification granules were fastly cultured.By exploring the effect of ammonia concentrations on deammonification,the threshold concentration of influent ammonium was studied.The control strategy for nitrate build-up and restoration after deterioration in situ were tested for granular deammonification fed with low ammonia.Anammox bacteria and aerobic ammonia oxidizing bacteria（AOB）are the functional bacteria of deammonification,so the startup needs the enrichment of Aanammox bacteria and AOB,meantime suppressing nitrite oxidizing bacteria（NOB）.By using MUFB（Microaerobic Upflow Fluidized Bed）under 280mg/L NH₄⁺-N,based on the control of aeration,influent nitrite and nitrogen loading,the anammox granules were transformed into grey-red deammonification granules in 100 d.The two stoichiometric ratios of ΔTN/ΔNH₄⁺ and ΔNO3-/ΔNH₄⁺ were 0.90 and 0.08,respectively,suggesting that deammonification dominated this system.The final ammonia and TN removal efficiencies were 99% and 88%,respectively.Nitroge removal rate（NRR）was 2.3g N/L/d.Brocadia,Nitrospira,and Rhodocyclales dominated anammox bacteria,AOB,and denitrifying bacteria（DNB）,respectively.Nitrosomonas europaea dominated NOB,and its activity and abundance were suppressed efficiently by limited dissolved oxygen and high FA under elevated p H during the entire operation.The influent NH₄⁺-N concentrations had significant effect on deammonification.In a stable deammonification process without aeration,the influent NH₄⁺-N stepwised decreased（280,140,70mg/L）to explore the threshold concentration of influent NH₄⁺-N（the influent NH₄⁺-N when ΔNO3-/ΔNH₄⁺ was around 0.20）.At both high NH₄⁺-N levels（280mg/L and 140mg/L）,similar performances were obtained,with ammonia and TN removal efficiencies of 94% and 80%,respectively,and stoichiometric ratios of ΔTN/ΔNH₄⁺ and ΔNO3-/ΔNH₄⁺ were as good as 0.87 and 0.11,respectively.While under low NH₄⁺-N level（70mg/L）,nitrate build-up happened with ammonia and TN removal efficiencies of 91% and 71%,respectively,and ΔNO3-/ΔNH₄⁺ was 0.20.The final NRR was 0.44 g N/L/d.With the decreasing ammonia,Brocadia-like anammox bacteria,Nitrosomonas-like AOB,and DNB decreased while Nitrospira-like NOB increased,which lead to the deterioration.So 70mg/L was the threshold of influent NH₄⁺-N concentration for stable deammonification without organic influent under 33℃.H₂H₄ was used to enhance the nitrogen removal performance.To the granular deammonification fed with 70mg/L NH₄⁺-N,5mg/L H₂H₄ could intensify the deammonification performance effectively.Because the NOB suppression from 5mg/L H₂H₄ was reversible,continuous addition was needed.Long-term addition of 5mg/L H₂H₄ had no bad influence on the deammonification performance fed with 70mg/L NH₄⁺-N.The activity test proved that 5mg/L H₂H₄ could promote anammox bacteria and not affect AOB,while suppress NOB activity by 40%.However,longterm addition of 5mg/L H₂H₄ into deammonification fed with as low as 42mg/L ammonia would cause serious nitrite build-up.To restore the deteriorative deammonification system with serious nitrate buildup,high concentrations of substrates was considered to suppressing NOB activity.In another deteriorative one-stage deammonification process with 30% nitrate build-up in the effluent,additional nitrite was introduced and the influent nitrite and ammonia were elevated to 420mg/L and maintained for one week on the premise of 95% removal efficiencies under low dissolved oxygen.Through the NOB suppression by high FA under limited DO level,the ratio of ΔNO3-/ΔNH₄⁺ decreased from 0.3 to 0.12,combined with the growth of Anammox bacteria abundance with stable AOB abundance,this deteriorative deammonification process was recovered in situ.