| Recently the problem of nitrogen pollution in water body has become worse,therefore,the control of nitrogen pollution is the key factor to improve water quality.The search for efficient and economical nitrogen removal technology has become an urgent problem to improve water quality.Anaerobic ammonium oxidation?Anammox?is the most promising new biological nitrogen removal technology,whereas the single ANAMMOX process is difficult to remove the nitrogen in the actual nitrogen-containing organic wastewater effectively,and the simultaneous anaerobic ammonium oxidation coupling heterotrophic denitrification process?SAD?can further improve the nitrogen removal performance.In this paper,the suspended carriers were selected to construct the symbiosis of sludge and biofilm MBR nitrogen removal system,to enhance the start-up of the symbiosis of sludge and biofilm SAD biological nitrogen removal system under the basement of achievement of the rapid start-up of ANAMMOX process,to investigate the impacts of C/N ratios on SAD process in order to optimize the C/N ratios,and to investigate the membrane fouling behaviors of the symbiosis of sludge and biofilm MBR-SAD nitrogen removal process.The start-up and enhancement of the Anammox biological nitrogen removal process was studied.The start-up phase of Anammox process:the removal efficiencies of NH4+-N and NO2--N were 87.51%and 81.98%,and total nitrogen loading rate?NLR?and nitrogen removal rate?NRR?reached 0.41 kg/?m3·d?and 0.31kg/?m3·d?,respectively;when the influent NH4+-N and NO2--N concentrations increased to 150 and 198 mg/L,respectively;secondly,the SPR-type suspended carriers with a volume filling ratio of 15%were successfully coated after 26-day operation.After 32 day-operation,the removal efficiencies of NH4+-N and NO2--N increased to 94.05%and 91.22%.,respectively.When HRT was adjusted to 20 h,the removal efficiencies of NH4+-N and NO2--N reached 93.64%and 94.04%,and NLR NRR reached 0.47 kg/?m3·d?and 0.35 kg/?m3·d?,respectively.The start-up of Anammox process was completed.The start-up of SAD process and the impacts of influent C/N ratios on the SAD process were studied.The process was successfully started up when the final removal efficiencies of NH4+-N and NO2--N,TN and COD reached 89.04%,91.96%,80.61%and 53.42%,respectively,by using sodium acetate as the organic carbon source under the condition of the C/N ratio of 0.2.When the C/N ratio increased from 0.5 to 0.8,the activity of denitrifying bacteria gradually increased;when the C/N ratio increased to 1.1 and above,the activity of anaerobic ammonium oxidizing bacteria was significantly inhibited,and the contribution rate of nitrogen removal gradually decreased.When the C/N ratio decreased to 0.8,the anammox bacteria activity was recovered.The optimal of C/N ratio of 0.8 was identified and the removal efficiencies of NH4+-N and NO2--N,TN and COD reached 80.49%,98.61%,87.27%and 74.46%,respectively.The NLR and NRR reached 0.46 kg/?m3·d?and 0.40 kg/?m3·d?,respectively.The ratio of?NO2--N/?NH4+-N was higher than 1.32 and the ratio of?NO3--N/?NH4+-N is less than 0.26.At the same time,the contribution rate of nitrigen removal via denitrification and Anammox were 29%and 71%,respectively.The membrane fouling behavior of the symbiosis of sludge and biofilm MBR-SAD nitrogen removal process was studied.It was found that the increase of NLR,the shortening of HRT,and the increase of C/N ratio increased the contents of polysaccharides and protein fractions in SMP and EPS under the constant flux of 21L/?m2·h?resluting in the increased membrane fouling rate.Membrane fouling behavior was mainly affected by the protein content in EPS and SMP and the EPSp-2 content was significantly higher than that of the EPSp-1.The FT-IR analysis showed no changes in the major compositions of the membrane foulants.Analysis of the measured functional groups reveals the existence of polysaccharides-like and protein-like substances in the membrane fouling substances. |
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