The Study Of Denitrification By Anoxic Granular Sludge In SBR

Compared to the traditional activated sludge,granular sludge have high biological activity and good settling property,which have been paid more attention on biological wastewater treatment.Artificial wastewater was adopted in this study,a stable and high activity of denitrification granular sludge was cultured in anoxic conditions in SBR,the denitrification property and sludge characters was studied.The study involved the influence of denitrification rate in different C/N ratio and NO₃^--N concentration, synthesis and utilization of PHB in denitrification process and the influence of different concentration of NO₃^--N,NO₂^--N on denitrification of granular sludge.The results were showed as follows:(1) The different C/N ratio,NO₃^--N concentration and the morphology of anoxic granular sludge had a significant impact to denitrification rate.When the mixing rate was 80rpm,anoxic granular sludge had a loose structure,with diameter between 2～3mm.The denitrification rate was between 0.092～0.096mgNOx-N/mgVSS·h as the C/N ratio was 5. When the mixing rate was 150rpm,anoxic granular sludge had a compact structure,with diameter between 1～2mm.The denitrification rate was between 0.034～0.073mgNOx-N/mgVSS·h as the C/N ratio was 5.In the same C/N ratio,with the increase of influent NO₃^--N concentration,there was a significant relationship between sludge &nitrification rate and the concentration of NO₂^--N in the process of denitrification.When the concentration of accumulated NO₂^--N was higher,the denitrification property reduced obviously.(2) The synthesis and utilization of PHB in anoxic granular sludge was mainly depended on the C/N ratio and COD concentration.When the C/N ratio was 5,the influent COD was 200,300,400mg/L,the synthetic quantity of PHB was 0.0250,0.0326,0.0444mg/mgVSS respectively.The synthetic quantity of PHB by anoxic granular sludge was increased with the increasing initial COD concentration in the influent,and the synthesis of PHB in initial stage would participate in the denitrification.In the condition of C/N ratio was 7.5,when the influent COD was 300,450,600mg/L,the synthetic quantity of PHB was 0.0515,0.0784,0.0942mg/mgVSS respectively,In the situation,the synthesis of PHB would not participate in the denitrification because of the sufficient COD.(3) The rate of utilizing PHB was 0.123～0.243mgPHB/mgVSS.h,less then the rate of utilizing COD.(4) At the end of famine period of the denitrification,the excessive PHB ferment to SMP,a kind of metabolites with sugar as main material,which led to an increase of soluble COD.