Study On The Effect Of SBBR Simultaneous Nitrification And Denitrification On The Distribution Of Dissolved Oxygen In Biofilm

As a new nitrogen removal technology,because Simultaneous nitrification and denitrification(SND)has advantagies suah as saving cost consumption,low energy consumption and less land,so in recent years SND has become a new a concerned nitrogen removal technology.With the studying by the scholars both at home and abroad,it’s known that the key factor of SND is thegradient distribution of dissolved oxygen in the activated sludge folc and biofilm.At present,the domestic research on SND mainly rests on the optimization of process parameters and the optimization of reactors,carriers and so on,lacking of in-depth study of microenvironment in biofilm.In this paper,the microeletrode technology was used to detect dissolved oxygen concentration in biofilm.Combining the nitrogen removal with the the distribution of dissolved oxygen in biofilm,theoxygen diffusion in biofilm would be dissolved from the angle of microenvironment.In this paper,SBBR was used to domesticate bilfilm and then the effects of DO,pH,C / N and HRT on the SND were studied in the SBBR.The distribution of DO in the microenvironment was measured by oxygen microelectrode system,and the oxygen effective diffusion coefficient was calculated by the diffusion-reaction equation.Combined with the above study,the last step was to explore the impact of various factors on the distribution of DO in thebiofilm.The conclusions are as follows:(1)When the DO was 2.5 ~ 5.5mg / l,the removal rate of NH4+-N was above 93%,and the TN removal rate was 84.92% which was the maximum.The effection of pH on SND was not significant,the removal rate of NH4+-N and TN increased with the increase of p H,and the highest removal rate of TN was about 95% at pH = 8.The Simultaneous nitrification and denitrification efficiency and the removal rate of NH4+-Nand TNincreased when the C/N increased.When the C/N was 12,the removal rate of NH4+-N and TN was 98% and 97% respectively,which were the highest.The HRT was higher,the efficiency of Simultaneous nitrification and denitrification was lower.And when the HRT was10,the nitrogen removal effect wasthe best,the removal rate of TN was 85%.(2)The greater the depth of the biofilm carrier,the smaller the DO,and the decreasing trend of DOwashigher It was obvious for the effection of DO on the proportion of aerobic zone in the biofilm.When the DO was higher,the proportion of aerobic zone in the biofilm was greater.But the influence of pH for the proportion of aerobic zone in the biofilm was not obvious,the proportion of aerobic zone in the biofilm decreased with the pH increasing from 6.5 to 8.For the influence of C/N,the proportion of aerobic zone in the biofilm decreased with the C/N increasing from 6 to 12,and when the C/N increased 12 to 14.the proportion of aerobic zone in the biofilm increased.HRT had little effect on theproportion of aerobic zone in the biofilm,and the proportion was the highest at HRT=10.When the SBBR obtained the best denitrification effect,the proportion of aerobic zone in the biofilm was in the range of 11.64%-12.58%.(3)The concentration of DO was higher,the value of De is greater.For the influence of pH,C/N and HRT on the value of De,when the SBBR obtained the best denitrification effect,the value of De was the highest.