| Anammox process has been considered to be a sustainab le and environment friendly way to treat wastewater containing high concentration of ammonium,owing to its simultaneous removing of nitrite and ammonium effectively under anaerobic conditions with low operation cost and little sludge production.The actual removal ratio of nitrite/ammonium was lower than that of the theoretical?i.e.the removal of ammonium was over-consumpted?was found in many studies,but there was little explanation for this phenomenon.The UASB was used to buld-up of Anammox in this study.The effect of upward-flow velocity in the reactor on the nitrogen removal was studied.The effects of no feeding of nitrite chronicly and its resupplying on ammonium and nitrogen removal in the reactor were investigated.The microbial community structures was analyzed by high throughput sequencing technology to discuss the mechanism of nitrogen removal of the reactor.The results obtained were as follows:?1?The Anammox-UASB was set up in 35 d with a total of ammonium and nitrite removal rate of 122 mg/?L·d?.A optimal nitrogen removal efficiency can be achieved when the upward-flow velocity of the reactor was 1.14 m/h.When the influent nitrite/ammonium ratio was changed,the removal ratio of nitrite/ammonium and the amount of over-consumption of ammonium changed too.When the nitrite/ammonium ratio was 1.11 and 1,the removal ratio of nitrite/ammonium was 1.19 and 1.14,and the percentage of over-consumption of ammonium was 8.19%and 13.31%.?2?When the nitrite was supplied alternately to the reactor,the p H value of the effluent from the reactor was lower than that of the influent,and the over-consumption of ammonium was higher than before.After no feeding of nitrite in the reactor,it could also realize the ammonium removal chronically stable with a removal rate up to 68.77mg/?L·d?,and a small amount accumulation of NO2--N and NO3--N in the effluent were observed.?3?The microbial community structures of the Anammox system of chronically no feeding of nitrite was analysised at the first time.The characteristics of the function microbial of nitrogen removal were comparative ana lyzed before and after no feeding of nitrite.The results indicated that the microbial diversity increased and the relative abundance of the Ammonia Oxidizing Bacteria?AOB?,Anammox bacteria and Denitrifying bacteria in the reactor proliferated without any nitrite supply.Combined with nitrogen removal,a large number of proliferated AOB?mainly N itrosomonas?in anaerobic conditions in this reactor can convert the ammonium to nitrite under anaerobic conditions and cooperate with Anammox bacteria to achieve total nitrogen removal.In the condition of high-ammonium and low-nitrite concentration,Candidatus Jettenia would adapt and grow in large quantities,while Candidatus Brocadia was not suitable for this condition and the abundance decreased.?4?The performance of nitrogen removal restored immediately after the nitrite resupplied.When the influent nitrogen/ammonium ratio increased from 0.17 to 1.30,ammonium removal efficient and the removal ratio o f nitrite/ammonium increased,but the percentage of over-consumption of ammonium decreased.The best removal of total nitrogen in the reactor would reached while the influent nitrite/ammonium ratio was1.14 to 1.20.?5?The removal of nitrogen in the reactor was the result of the interactions of various function microbial of nitrogen removal.The excess re moval of the ammonium in the reactor was caused by the ammoxidation,which carried out under anaerobic conditions and was affected by the concentration of nitrite in the influent.There was cooperation and competition betweed Anammox bacteria and AOB. |
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