Experimental On Recovery Of Nitrogen Removal Efficiency Of Long-term Idle Anammox Sludge

Anaerobic ammonia oxidation（anammox）is one of the most promising new biological denitrification techniques in the future.However,anammox are not widely used due to slow growth and long starting cycle of the reactor.Therefore,it is significant to restore the de-nitrogenization performance of anammox sludge and shorten the reactor start-up time in a long-term idle reactor.In this thesis,the differences and differences of anammox sludge before and after dormancy were studied from the apparent characteristics,composition of sludge,microbial community and the effect of anaerobic section active sludge on the denitrification of anammox was investigated.Finally,the recovery of nano-Fe₃O₄and nano-CuO on the denitrification effect of dormant sludge was studied,and the in situ recovery process of the idle UASB reactor was investigated with nano-Fe₃O₄.The specific findings are as follows:（1）Most of the sludge in the anammox reactor that has been idle for about 240 days at room temperature cannot meet the anabolic effect of bacteria due to long-term starvation,and the granular sludge in the reactor disintegrates,so that most of the sludge has lost its original form.There is peculiar smell,a small part of the sludge maintains the original granular form,the average particle size is reduced from 0.40mm to 0.20mm,the contents of the reactor are in the state of solid-liquid mixture,dark brown,and the liquid part is sticky and turbid;anaerobic ammonia The relative abundances of the phylum Planktophyta and Candidatus Kuenenia were increased by 34.20%and 36.91%,respectively;Armatimonadetes＿gp5 was eliminated under long-term starvation,and the abundance decreased from 2.12%to 0.00%.（2）The SBR reactor was used to restore the activity of the dormant anammox,and100%,75%,25%and 0%of the sludge in the anaerobic section of the AAO process of the sewage treatment plant were inoculated in the reactor for batch tests.Proportion of anaerobic stage sludge post-reactor denitrification efficiency recovery characteristics.Among them,the reactor inoculated with anammox in a dormant state has completely recovered its denitrification performance after 92 days of operation.In the experimental group of sludge in the anaerobic stage,the removal rates of NH₄⁺-N and NO₂^--N only reached 75.06%and78.30%by the end of the test;inoculating the sludge in the anaerobic stage of the sewage plant would increase the denitrification of the dormant anammox sludge.The recovery time of performance;while the dormant anammox sludge has no active hysteresis stage in the restart process.（3）The batch test was carried out by inoculating dormant anammox sludge in the SBR reactor,and it was found that the optimal dosage of nano-Fe₃O₄during the process of activity recovery was 4 mg/L,which increased the removal rate of NH₄⁺-N by 16.13%;The optimal dosage was 3 mg/L,which increased the removal rate of NH₄⁺-N by 15.36%;in addition,8～10 mg/L nano-CuO and 11～14 mg/L nano-Fe₃O₄slightly inhibited the activity of anammox bacteria.The removal rate of NH₄⁺-N is reduced within 5%,while the denitrification efficiency of the reactor is sharply weakened when the content of nano-Fe₃O₄exceeds 15mg/L and nano-CuO exceeds 11mg/L,which reduces the removal rate of NH₄⁺-N by more than10%.（4）Adding 4 mg/L of nano-Fe₃O₄in each influent cycle can enhance the recovery of the denitrification performance of the idle UASB reactor and increase the NH₄⁺-N removal rate by about 12%;Armatimonadetes＿gp5 can be re-enriched after the in-situ recovery of the reactor,and nano-Fe₃O₄inhibited the enrichment of Armatimonadetes＿gp5,reducing its relative abundance by 1.40%;while Candidatus Kuenenia was still the dominant anammox genus in the system,adding nano-Fe₃O₄increased the abundance of Candidatus Kuenenia by14.94%.