| The Anaerobic ammonia oxidation?Anammox?process has broad application prospects in biological nitrogen removal wastewater due to its advantages as high efficiency,greenness and economy.However,the generation time of the functional bacteria as anaerobic ammonia-oxidising bacteria in this process is as long as 10?14days,which leads to a longer start-up time of the Anammox process,which limits the engineering application of the process.At present,most start-up studies have focused on directly using Anammox sludge as seed sludge,but the source of Anammox sludge is generally scarce,and the price is high.It is not practical to select Anammox sludge as seed sludge to start up the Anammox process.It is necessary to discuss how to start up an Anammox-EGSB reactor through elected ordinary sludges from a wide range of sources.The reflux ratio is a significant parameter of the EGSB reactor.It is particularly consequential to investigate the effect of the reflux ratio on the performance of nitrogen removal in the Anammox process.Therefore,this study explored a quick start-up strategy of Anammox process selected anaerobic granular sludge?AGS?from starch plant wastewater treatment as seed sludge and the effect of the reflux ratio on the nitrogen removal performance of the reactor.Main research achievements were as follows.?1?A quick start-up strategy of Anammox process has achieved the enrichment of Anammox bacteria,which is selected AGS from a starch plant wastewater treatment as seed sludge,through the modification and adjusting of operational procedure in the reactor,a transformation of UASB to EGSB achieved.A strategy as the gradually increasing the nitrogen loading firstly and then reducing the time of HRT was implemented.After 86 days of operation,the reactor successfully started up the Anammox process,and the nitrogen removal rate increased from 0.02 kg N·m-3·d-1to0.52 kg N·m-3·d-1.?2?Low nitrogen loading rate,pretreatment of seed sludge,as well as controlling the growth conditions,has provided a guarantee to reduce the time of cell lysis phase and activity lag phase.Reducing sludge loss and gradually increasing nitrogen loading rate has achieved the enrichment of Anammox bacteria.?3?Analysis of the microbial community structures in the strat-up period revealed that as the start-up time is prolonged,the diversity of archaea community and bacteria community decreased,and the effects of functional microbes became outstanding.At the phyla level,the dominant of archaea was Euryarchaeota throughout,but the dominant in the community structure of bacteria changed significantly.After achieving the start-up of the reactor,the dominant phylum changed to Planctomycetes.At the genus level,by the benefit of microenvironment suited for anaerobic ammonia oxidizing bacteria,it gradually formed a mini-type microbial ecosystem.In addition to Anammox bacteria,various functional bacteria such as that denitrifying bacteria,nitrifying bacteria,methanogens,heterotrophic bacteria;and archaea from AGS seed sludge were also played important roles in accelerating start-up of Anammox process.?4?The reflux ratio experiment showed that when the Anammox-EGSB reactor was suddenly changed from the reflux state to the non-reflux state,the nitrogen removal performance became worse.When the reflux ratio is 100%,200%,the nitrogen removal performance was significantly improved,and when the reflux ratio is 200%,the nitrogen removal is better than 100%.However,when the reflux ratio raised to 250%,the matter of sludge loss or clogging will occur and affect the performance of nitrogen removal.This study reveals that selecting the AGS from starch industry wastewater treatment as seed sludge has the advantage of the rapid start-up.The proper reflux ratio parameters of Anammox-EGSB reactor was obtained and provides support for the quick start-up and engineering application of the Anammox process. |
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