Study On The Characteristics Of Nitrate Removal By Enhanced Treatment Of Loofa Sponge Coupled With Sulfur/iron Composite Fillers

The upgrading of wastewater treatment plants（WWTPs）has become the general trend for solve the problem of water shortage.In order to find an efficient,economical,green and sustainable process to strengthen the deep denitrification treatment of secondary effluent of WWTPs,the characteristics of denitrification filter column composed of loofa sponge complex coupled with sulfur/iron composite fillers was studied,impacts of different HRT,mass ratio of loofa sponge,sulfur and iron on denitrification performance were investigated,denitrification performance of loofa sponge denitrification filter column and loofa sponge coupled with sulfur/iron composite fillers of denitrification filter column were compared and analyzed as well.The microbial population structure of the samples was compared and analyzed with the help of Miseq high-throughput sequencing technology to explore the effect of sulfur/iron composite fillers on denitrification performance.Finally,the denitrification effect of denitrification filter column in the treatment of secondary effluent was investigated under the optimal operating conditions,The main conclusions are as follows:（1）When 120 g loofa sponge coupled with 380 g sulfur/iron composite fillers（Fe:S:Cement=5:2:3）was used as the denitrification filter column filler,after the start-up,the nitrate removal rate is more than 94%,the highest can reach 100%,the average TN removal rate is about 83%,and the released carbon source is sufficient.Until 60 days,the nitrate removal rate is still 65%,and the TN removal rate is still 54%,which is better than the other three groups.（2）HRT=8H is the best HRT,when the denitrification is complete and the by-product yield is small,the average removal rate of nitrate is about 97%,and the average removal rate of TN is about 86%,which is higher than HRT=20H and HRT=2H.（3）The denitrification performance of loofa sponge complex single packing denitrification filter column（SG filter column）and loofa sponge coupled with sulfur/iron composite fillers packing denitrification filter column（SG-S/Fe filter column）was compared and analyzed.The results showed that the SG-S/Fe filter column constituted a heterotrophic autotrophic denitrification system,which had the ability of low consumption and high efficiency of denitrification,and was more resistant to impact load.The addition of sulfur/iron composite fillers packing was conducive to delay the release of carbon source and prolong the life of silk The service life of loofa sponge is prolonged.（4）According to the analysis of high-throughput sequencing results,the dominant bacteria in the two reactors were Actinobacteria,Chloroflexi,Proteobacteria,Patesicibacteria,Firmicutes and Bacteroidetes.The relative abundances of Sulfurimonas and Hydrogenophaga in SG-S/Fe filter column increased significantly,and the relative abundances were much higher than those in SG filter column.In SG-S/Fe filter column,autotrophic denitrifiers increased by about 219%,heterotrophic denitrifiers increased by about 33%,while the relative abundance of autotrophic denitrifiers and heterotrophic denitrifiers in SG filter column decreased.Therefore,the addition of sulfur/iron composite fillers is beneficial to enrich autotrophic denitrifiers,strengthen heterotrophic combined autotrophic denitrification and improve nitrogen removal efficiency.（5）Loofa sponge coupled with sulfur/iron composite fillers of denitrification filter column has a high denitrification efficiency in the treatment of the secondary effluent of the actual sewage plant,when the influent NO₃^--N is 9～11mg/L,the average removal rate of NO^-₃-N is about 85%,and the average removal rate of TN is about 39%.When the influent NO^-₃-N is increased to 11～20mg/L,the average removal rate of NO^-₃-N is about 94%,and the average removal rate of TN can reach 76%,the removal effect of nitrate in the reactor is good Better.It can be seen that loofa sponge coupled with sulfur/iron composite fillers of denitrification filter column has high nitrogen removal ability under certain conditions,which is of great significance for the deep nitrogen removal treatment of WWPTs and the improvement of effluent quality,and provides technical reference and theoretical basis for the practical engineering application of the process.