Rapid Start-up Of CANON Process And Activity Recovery Of Autotrophic Denitrification Sludge

The complete autotrophic nitrogen removal over nitrite?CANON?system is short-cut nitrification?also referred to as nitrosation,hemi-nitrification,nitrite nitration,simple nitration,etc.?and anaerobic ammonia oxidation?Anammox?coupling system.Compared with the traditional nitrification and denitrification process,the CANON process reduces the oxygen demand by 85%,100%carbon source and83%biosolids production.At present,the practical application of CANON process is mainly focused on the treatment of high ammonia nitrogen?NH₄⁺-N?wastewater with low C/N ratio,such as sludge digestion liquid and leachate.For low NH₄⁺-N domestic sewage,the application of this process is relatively small.The development of this process is limited mainly due to the following factors,such as the limited treatment of high ammonia nitrogen wastewater,the difficult and time-consuming start-up process,and the inability to stabilize the operating performance.In view of the above problems,this paper proposes to apply the Hybrid Anaerobic Baffled Reactor?HABR?to start the CANON process.The feasibility of starting CANON process with low concentration of NH₄⁺-N was investigated.After the CANON process was successfully started,the concentration of the influent NH₄⁺-N was changed to investigate the stability of the treatment of the low concentration NH₄⁺-N.Finally,batch experiments were carried out to explore the preservation and recovery methods of functional bacteria in CANON process,in order to build CANON mixed bacteria mud base,shorten the start-up time of CANON process,and further promote CANON technology applied to denitrification of urban domestic sewage.The research process of this paper is divided into three stages.The first stage mainly explored the rapid start-up of the HABR-CANON process,and the changes in the activity of functional microbes during the start-up process.The changes in nitrogen and pH along the reactor and the morphology of the biofilm during steady operation were analyzed.The main conclusions are as follows:?1?It is feasible to start the CANON process by a low concentration of NH₄⁺-N.In this experiment,under the condition of temperature?30±2?,pH?7.9±0.1?and aeration of the first three compartments,we use continuous water,and control NOB activity by adjusting various parameters,and last for 56d to achieve the start of CANON process.?2?Changes in the activity of functional micro-organisms during the start-up of the CANON process.During the start-up phase,NOR gradually decreased,and AOR?ammonia oxidation rate?and ANR?AnAOB rate?gradually increased,indicating that AOB and AnAOB gradually became predominant bacteria in the CANON system,while NOB was gradually completely suppressed.?3?The variation of nitrogen and pH along the reactor during steady operation.During the stable operation,the removal of NH₄⁺-N and TN occurred mainly in the first three compartments,and the first compartment had the best effect of removing NH₄⁺-N;the p H value showed a trend of decreasing first and then increasing.Taking into account the variation of nitrogen and pH along the course,it was found that in the first three compartments the nitrosation and Anammox were both present in the compartment,and the acid produced by nitrosation was larger than the alkali generated by Anammox.The Anammox reaction was mainly performed in the latter three compartments.?4?Observe the morphological structure of the autotrophic denitrifying biofilm.The SEM results showed that AOB and AnAOB were dominant strains of CANON system,and NOB was not detected.The second stage mainly studied the stability of CANON process to treat wastewater with low NH₄⁺-N concentration.The main conclusions are as follows:The stability of low concentration NH₄⁺-N wastewater treated by CANON process was investigated when the influent NH₄⁺-N concentration changed.In this experiment,the CANON process was operated by adding sulphuric acid hydrazine and changing the influent NH₄⁺-N concentration continuously in the concentration range of 32-60 mg/L without changing the conditions of HRT and temperature.The results showed that the CANON process still had higher denitrification performance under the condition that the concentration of the influent NH₄⁺-N was constantly changed.The third stage mainly studied the preservation of autotrophic and denitrification sludge under different temperature conditions?30?,20?,4?,-20??,followed by the activity recovery experiment And,the activity of sludge,the distribution and structure of EPS in sludge,the species diversity and structural characteristics of the microbial community were further analyzed.The main conclusions are as follows:?1?Examine the sludge activity before,after preservation,and after activity recovery.The autotrophic nitrogen-removing sludge deposited under 4°C had the best activity,and the sludge with the best activity recovery was deposited at 4°C.?2?The activity of autotrophic denitrification sludge recovered after short-term preservation under different temperature conditions.After the autotrophic denitrification sludge was preserved for a short time under different storage temperatures,it was found during the process of recovering its denitrification performance that the activity of AnAOB became a key factor limiting the denitrification performance.The reactor with low AnAOB activity was susceptible to the influent NH₄⁺-N.?3?Inspect the composition characteristics of EPS of sludge flocs before preservation,after preservation and after recovery.The composition characteristics of EPS before,after preservation,and after recovery of the sludge were examined.Studies have shown that the EPS of the sludge before preservation,preservation and after activity recovery has the same compositional characteristics:whether in the sludge flocculate Total-EPS or in the sludge flocculation EPS,the content of PN is much higher than that of PS.?4?The structure characteristics of EPS before,after preservation,and after recovery of the sludge were examined.The pre-conservation,activity recovery and sludge flocculation after 20°C,4°C,and-20°C storage have the same structural characteristics:S-EPS>TB-EPS>LB-EPS.However,the proportion of S-EPS and TB-EPS in the sludge flocs before and after storage?20°C,4°C,and-20°C?is basically the same,and the proportion of S-EPS in the sludge after preservation is far away higher than TB-EPS.?5?Examine the species abundance,species diversity,and structural characteristics of the microorganisms.In CANON systems without extreme environmental interference,the diversity and abundance of organisms is positively correlated with the nitrogen removal performance of the system.The relationship between the magnitude of biodiversity and abundance in the recovered sludge was consistent with the magnitude of AnAOB activity in the system.