Research On Denitrification And Denitrification Of Immobilized Slow-release Carbon Sources Based On Natural Plant Materials

Due to the low C/N of the secondary effluent of the urban sewage treatment plant,the denitrification is not complete,the denitrification efficiency is low,and the generation of intermediate produces cause the secondary pollution of water body,and an external carbon source is needed to strengthen the deep denitrification treatment process.At present,the addition of traditional liquid carbon sources such as methanol,glucose,and acetate has become the main method to solve low-carbon source sewage treatment plants,but there are problems such as the inaccurate control of the dosage and the low utilization rate,which is not a long-term solution to this problem.Therefore,looking for a new type of immobilized carbon source with slow release,high efficiency and no by-products as a solid carbon source for biological carriers has become a new hot spot in the study of denitrification and denitrification.In this study,natural plant materials with rich cellulose content were selected and subjected to static release test and denitrification test after alkali treatment.Plant materials were screened according to the effluent water quality,and the selected plant materials were blended with polymer materials.An immobilized slow-release carbon source was prepared,the best plant material was determined through denitrification experiments,and the influence of the material ratio on the denitrification effect was explored.On this basis,an SBR denitrification reactor was constructed,focusing on the influence of HRT,influent nitrate load,and wastewater types on the denitrification effect of the SBR reactor.Finally,the microbial community structure in the reactor was characterized and analyzed.The results of the study are as follows:（1）Canna,arundo,lemongrass,and cattails with relatively rich fiber content were selected as the research objects,and static release experiments were carried out after alkali treatment.The results showed that lemongrass and arundinacea had relatively high carbon release capacity and nitrogen The release of element and phosphorus is within a controllable range.Scanning electron microscopy was used to observe the changes in the surface morphology of plant materials before and after alkali treatment.It was found that alkali treatment effectively destroyed the internal structure of plant materials and reduced the crystallinity of cellulose.Among them,the surface of reed bamboo and lemongrass materials were rougher,which was more conducive to the growth of microorganisms.The three-dimensional fluorescence analysis of the plant extracts showed that the soluble substances in the extracts of Arundo and Citronella are rich in types and content,which can provide rich nutrients for microorganisms after degradation.Denitrification and denitrification experiments show that Arundinacea and Citronella have good denitrification potential as additional carbon sources.（2）Using plant materials,attapulgite,polyethylene glycol,polysulfone（PS）and N,N dimethylacetamide（DMAC）as raw materials,an immobilized slow-release carbon source was prepared by blending,using scanning electron microscopy Observing the surface morphology of different ratios of carbon source materials,and analyzing the calculation results from the specific surface area,increasing the amount of plant added to the carbon source material and reducing the amount of PS added will make the surface of the carbon source rougher,increase the specific surface area of the carbon source,and increase In the process of denitrification,the contact area between the carbon source and the water body and bacteria is created,which creates a favorable environment for the survival of microorganisms.Through denitrification and denitrification experiments,it is concluded that the best material ratio for preparing slow-release carbon source is citronella:attapulgite:polyethylene glycol:PS:DMAC=15:2:5:18:53.（3）The optimal HRT of the SBR reactor with citronella slow-release carbon source as the external carbon source is 12 h;with the increase of the influent nitrate load,the NO₃^--N removal rate decreases significantly,and intermediate products accumulate,and the final result is When the effluent nitrate concentration is less than 50 mg·L^-1,the effluent effect is better;when the SBR reactor is operated under the best operating conditions,the effluent quality of the actual wastewater after denitrification is better than that of the synthetic wastewater.Through high-throughput sequencing,it was found that the inoculated domesticated sludge was at the phylum level,mainly the Proteobacteria phylum,followed by the Bacteroides phylum;at the genus level,the detected bacterial genera were mainly Sorberia and Aquamonas Genus,Diaphorobacter;After denitrification experiments,the abundance of Bacteroides phylum increased at the phylum level,and the proportion in reactors S3 and S4 even exceeded the Proteobacteria;at the genus level,the proportion of bacteria in reactor S1 and S2 Evenly distributed,the main genus and species of reactor S3 and S4 become Pseudoxanthomonas.