Characterization Of MAAO Process And Its Phosphorus Removal Characteristics

In recent years,in the face of increasingly severe water pollution problems,countries are increasingly strict with the emission of nitrogen and phosphorus,a variety of biological nitrogen and phosphorus removal process has gradually emerged,but most of the nitrogen and phosphorus removal process are facing the problems like carbon source shortage,high operating costs.The step feed process has been applied in more and more in the domestic urban sewage treatment plant reconstructed and new projects because of its full use of carbon sources,high sludge concentration,shock resistance and other advantages.The general step feed process is a step feed AO process,The multi-stage AAO(MAAO)process is developed on the basis of the rational improvement of the step feed AO dephosphorization and denitrification process.This paper conducts on-site investigation on the MAAO dephosphorization and dephosphorization process of the low-oxygen aeration and step feed technology in the first phase of the Beishiqiao Sewage Treatment Project in Xi'an.Under the existing field operation condition,the Respirogram technique is introduced to quantitative analyse the sludge characteristics.The operation and management status of the process are evaluated,and the great potential of the process is analyzed from the perspective of microbes.At the same time,At the same time,the self-developed Nitrate Respirogram was used to characterize the phosphorus removal characteristics of MAAO activated sludge process.The relationship between OUR and water quality parameters of phosphorus uptake process was established by Nitrate Respirogram,so as to achieve the determination of the phosphorus removal characteristics while the MAAO process activated sludge is accurately determined.To lay the foundation for the establishment of quantitative operation management technology system based on Respirogram.The main results of this study are as follows:(1)From the oxygen uptake rate,the traditional oxidation ditch value is higher than that of MAAO process.From one to four aerobic tank,there is a tendency of MAAO moving closer to the traditional OD process,and the obvious feature is that the MAAO process has a high on-site oxygen uptake rate.From the oxygen uptake rate ratio,MAAO process autotrophic bacteria oxygen uptake rate ratio is slightly lower than the traditional oxidation ditch process,heterotrophic bacteria oxygen uptake rate ratio of two processes of is not that different,which indicates that MAAO and oxidation ditch process shows the similar effect of denitrification.Endogenous respiration rate ratio of MAAO process is slightly higher than the oxidation ditch process,quasi-endogenous rate ratio is slightly higher than the traditional oxidation ditch process,which shows that under the same water conditions,the oxidation ditch process activated sludge is less impacted and the impact resistance of it is strong.(2)Autotrophic bacteria,heterotrophic bacteria respiration oxygen uptake rate and autotrophic bacteria,heterotrophic respiration rate ratio in MAAO process decrease and increase then from autumn to the next spring,Autotrophic bacteria oxygen uptake rate even down to zero and keep this state for more than a month in winter,heterotrophic bacteria oxygen uptake rate decline,but soon rebounded to a higher value in winter,which indicates that compared to the heterotrophic bacteria,autotrophic bacteria have a strong ability to adapt,and the autotrophic bacteria are more fragile;This shows that the COD and ammonia nitrogen degradation capacity of MAAO process decrease in winter,but gradually increase in spring.The endogenous and quasi-endogenous respiration rate of MAAO process showed the first increase and then decreased in the spring from the autumn to the next spring,and there will be some fluctuation in the winter.The corresponding endogenous respiration rate ratio also has the same regularity.The endogenous respiration rate ratio of MAAO process activated sludge enters the high steady area in the winter,and the sludge activity deteriorates.As the temperature rises in the spring,the activated sludge gradually returns to the high efficiency(healthy)state;the quasi-endogenous respiration ratio is earlier than the endogenous respiration rate entering the rising and fluctuating state,but the time of gradual declining is similar.It can be seen that MAAO process activated sludge is subject to greater impact in winter,with the spring temperature rise,this shock is gradually reduced(3)The characteristic of Nitrate Respirogram is with the increase of the peak D of the OUR curve of Respirogram(BKX group)after adding the nitrate,and the change of the curve is more intense,but the linearity is more regular,and the higher the nitrate concentration the higher the peak value of the OUR curve of the Nitrate Respirogram,indicating that the addition of nitrate to the activated sludge can improve the sensitivity and accuracy of its Respirogram changes.(4)Nitrate Respirogram can reflect the sludge dephosphorization performance of MAAO process.When the sludge dephosphorization performance is better,the lower the OUR peak D of the Nitrate Respirogram(BKX group).(5)The concentration of phosphate and organic matter in the process of phosphorus uptake by MAAO process can be sensitively and accurately characterized by Nitrate Respirogram.The higher the OUR peak D,the lower the removal efficiency of organic matter and phosphorus,the use of Nitrate Respirogram(BKX group)can establish the linear relationship between OUR and TOC and PO43--P,the correlation coefficient is between 0.83 and 0.96.