Study On The Pre-ammonia Nitrogen Stripping Of Domestic Sewage And Its Effect On Subsequent Biological Treatment

In the “12th Five-Year Plan” of the National Economic and Social Development Plan,the goal of reducing ammonia nitrogen by 10% was clearly stated.As a main place for treating AN in domestic sewage,urban sewage treatment plants have occasionally exceeded the standard of nitrogen,and in recent years,they have gradually changed from secondary treatment to advanced treatment.During the operation of the wastewater treatment plant,the complexity of the treatment process and the variability of the operating parameters severely restrict the development of the wastewater treatment plant.The influent of a sewage treatment plant in Chongqing was used as the test water sample.According to the characteristics of the water sample that the AN accounts for a large proportion of TN,the blown off method is used to conduct the blown-off method pretreatment of sewage plant.The more economical and reasonable experimental conditions for stripping pretreatment were obtained by orthogonal experiment and single factor experiment.At the same time,the C/N of the sewage is changed after the stripping.The raw water is used as the control,and the different influent waters of the two groups were respectively subjected to subsequent biological treatment to detect the water quality index in order to verify the feasibility of stripping pretreatment for wastewater treatment.The economic benefits have been estimated to provide a new solution for nitrogen removing in wastewater plants in the future.The sludge in the two groups(T and Y)of devices were subjected to breathing measurement and high-throughput sequencing to detect the difference in sludge activity and microbial population between the two sets of devices with different carbon-nitrogen ratios as the influent.The main achievements of this article are summarized as follows:(1)The results of single factor experiment show that the removal rate of ammonia nitrogen increases with the increase of temperature at the beginning,and reaches a decreasing trend with the increase of temperature after reaching 60 °C.The ammonia nitrogen removal rate increases with increasing pH,increasing gas-liquid ratio,and increasing blow-off time.Considering the economic factors,the selected stripping conditions are: T=60°C,pH=11,D=5000,t=1h.At this time,the removal rate of ammonia nitrogen is about 90%,and the residual ammonia nitrogen content is about 3.46mg/L.(2)The results of orthogonal experiment show that the order of influencing factors of the stripping experiment in wastewater treatment plant are: stripping temperature > pH > gas-liquid ratio > strippingtime.(3)In the subsequent biological treatment process,the pollutants in the sewage group(T group)and the unbleached sewage group(Y group)are simultaneously met,and the results of the two groups of devices under different reaction conditions are displayed.The T group can reach the standard after aeration for 2 hours under the aeration condition of 300L/h,and the Y group needs to aerate for 3h and then sink for 2h to reach the standard when operating at 600L/h.For the T group,aeration of 300 L/h is more suitable.In the Y group,oxygen is also required due to nitrification,so the aeration amount of 600 L/h is more suitable,and the aeration time and the static settling time of the Y group are significantly larger than the T group.(4)Respiratory measurement experiments were carried out on the sludge of the two groups.The results showed that the OUR of the sludge of Y group was 0.120 mgO2/min,and the T group was 0.112 mgO2/min.It indicates that the removal effect of organic matter matrix in Y group is slightly higher than that in T group.(5)By comparison with the Greengene database,there were 13 species with relative abundances greater than 1% in both Y and T samples.It is mainly composed of Proteobacteria,Bacteroides,Chloroflexi and Acidobacteria.Proteobacteria is the most abundant species of the two species,and it is the important species for the removal of organic matter,nitrogen and phosphorus in the sewage.At the genus level,the norank-f-Saprospiraceae,Xanthomonas etc are all genus of bacteria detected relating to the COD degradation.The norank_f__Nitrosomonadaceae was the maily AOB bacteria detected in the two samples,followed by Nitrosomonas.Nitrospira is the main NOB and dominates the nitrification reaction.Dechloromonas and Desmoococcus are the major denitrifying genus,in addition to a variety of aerobic denitrifying bacteria.(6)Through preliminary economic analysis of the two groups of devices,it can be seen that the stripping pretreatment of the T group increases the cost of the medicament and the power consumption to a certain extent,but reduces the aeration amount and aeration time of the subsequent biological treatment process.The floor space is also reduced to 1/2.5 times that of the Y group.