The Effect Of Pyridine On Heterotrophic/Autotrophic Simultaneous Nitrogen Removal System And Degradation Mechanism

Pyridine is a kind of typical nitrogen heterocyclic compound which is difficult to degrade and exists widely in coking wastewater.Application of anaerobic ammonia oxidation （ANAMMOX）technology to coking wastewater can not only enhance the nitrogen removal performance,but also significantly reduce the operating cost.However,the mechanism of the influence of pyridine addition on ANAMMOX is still unknown.Therefore,this study explored in detail the effects of short-term and long-term addition of pyridine on the nitrogen and pyridine removal performance of ammonia-containing wastewater in the ANAMMOX system.Static batch experiments showed that the contribution of anammox to nitrogen removal dropped from 99.3%to 79.1%,as pyridine gradually increased（25-150 mg/L）.When pyridine concentration was as high as 150 mg/L,the anaerobic ammonia oxidation activity （SAA）decreased by 56.7%while denitrification increased,indicating that pyridine as an alternative organic substrate for denitrification.The inhibition kinetics showed that the IC₅₀of short-term pyridine addition on An AOB was 84.18 mg/L.The long-term experimental results of the treatment of ammonia-pyridine wastewater by low oxygen ANAMMOX-SBBR system showed that the system could tolerate high concentration of pyridine when the pyridine addition was up to 500 mg/L.In addition,the IC₅₀ value of functional microorganism for pyridine inhibition was significantly increased compared with the short-term experiment.With the increase of ammonia nitrogen concentration,the system gradually realized high efficiency nitrogen removal through heterotrophic/autotrophic simultaneous nitrogen removal system（HCANR）,and the maximum TN removal rate reached 93.9%.High throughput sequencing showed that Aquabacterium,Longilinea,Candidatus Kuenenia,Azohydromonas,Ornatilinea,Saccharibacteria＿genera＿incertae＿sedis,Defluviimonas,Acinetobacter, Nitrosomona and Armatimonadetes＿gp5 were the main functional bacteria genera of the system.Furthermore,UV-Vis combined with GC-MS techniques were used to infer the response mechanism and removal mechanism of HCANR system to long-term pyridine addition.The results of this study provide valuable theoretical and scientific basis for the successful application of Anammox in the treatment of refractory coking wastewater in the future.