Research On Pathways And Mechanisms Of Anaerobic Removal Of Ammonia From Wastewater

Compared with traditional nitrification and denitrification nitrogen removal of anaerobic ammonia oxidation that does not need carbon source,environmental alternation,and its low sludge yield has attracted wide attention.During the start-up and operation of the anaerobic ammonia oxidation reactor,even under the condition of no nitrite nitrogen in the influent,there is a general excessive removal of ammonium nitrogen,which makes the actual anammox reactor the ratio of nitrite nitrogen and ammonium nitrogen consumption（Rs）is lower than the theoretical value of 1.32.However,there are still controversies about the ammonium nitrogen removal pathway,mechanism and influence mechanism,and further study is needed.In this thesis,the pathway and mechanism of anaerobic ammonia removal are studied.The main research results obtained are as follows:（1）Inoculate mixed sludge（denitrification sludge,anaerobic ammonia oxidation sludge）was inoculated in a UASB reactor.After 30 days,when the influent ammonium nitrogen and nitrite nitrogen concentrations are respectively 225 mg·L^-1 and 297 mg·L^-1,the reactor of ammonium nitrogen and nitrite nitrogen removal rate were 99.78%and94.07%respectively.The anaerobic ammonia oxidation reactor Rs and the ratio of ammonium nitrogen consumption to nitrate nitrogen production（Rp）were 1.30,0.25,respectively.It shows that the typical anaerobic ammonia oxidation reaction occurred first in the load increase process.When the hydraulic residence time of the reactor was 12 h,the total nitrogen removal rate of the reactor was 886 mg·（L·d）^-1.Meanwhile,by reducing the hydraulic retention time in the case of a high concentration of substrates,it should be noted that the reduction should not be too large,which was likely to cause instability of the anammox reactor’s denitrification performance and even inhibition.（2）After the anammox reactor that was stopped operation for a long time was restarted for 13 days,activity of the reactor was restored,the denitrification performance of the anammox reactor was returned to the level before the shutdown,but the anammox activity was 0.035 g（NH₄⁺-N）·（g VSS·d）^-1,which was 53.85%of the original anammox activity compared to the anammox activity before shutdown.By observing the morphology of the sludge in the reactor before and after the recovery,it was found that the reactor was transformed from mainly filamentous bacteria to mainly spherical and ovoid bacteria.（3）With the decrease of the concentration of influent nitrite nitrogen,the amount of excessive removal of ammonia in the anammox reactor increased,and the hydraulic retention time in the reactor was 24 h,55 mg·L^-1 of ammonium nitrogen was removed from the reactor.Sulfate and Fe（Ⅲ）EDTA were not electron acceptors for ammonia oxidation,but aerobic nitrification of ammonium nitrogen.Catalase determination combined with molecular biology technical analysis showed that the amount of oxygen required for aerobic nitrification came from influent water and catalase oxygen production.Therefore,the excessive removal of ammonia nitrogen in the reactor was mainly through ammonia oxidation and anaerobic ammonia oxidation.（4）By studying the activities of ammonia oxidizing bacteria（AOB）,nitrite oxidizing bacteria（NOB）,anaerobic ammonia oxidizing bacteria（An AOB）,heterotrophic denitrifying bacteria（HDB）and enzyme activities in the sludge layer of different heights in the reactor,the results showed that the activity of AOB and An AOB at the bottom was higher than that of the upper sludge layer,but the HDB activity of the upper sludge layer was higher than that of the bottom sludge layer,and the NOB activity in the reactor was extremely low,almost undetectable.In this study,the conversion of ammonia nitrogen to nitrogen in the reactor was caused by the synergistic effect of the bottom and upper sludge layers.