Characteristics Of Phosphorus And Nitrogen Removal By Using Ecological Floating Bed With Filamentous Bamboo

In recent decades,water eutrophication has been one of the hot topics and research hotspots in the world.Due to the discharge of agricultural non-point source water,industrial wastewater and domestic sewage,the concentration of nitrogen and phosphorus nutrients in surface water exceeds the standard,resulting in eutrophication of water,and the blackening and odorous phenomenon in large areas of rivers and lakes has aroused widespread concern.Ecological floating bed technology is an ecological engineering technology.Compared with physical,chemical and biological methods,it has the advantages of no land area,good effect and obvious ecological benefits.The optimization,research and application of ecological floating bed technology are more active,which is the need to further improve the ability of removing phosphorus and nitrogen of ecological floating bed technology.This research took ecological floating bed as the research object,and selected filamentous bamboos and artificial plastic as the substrate.With ecological floating bed with plastics substrates(EFB-PS)for the control group,the effects and characteristics of phosphorus and nitrogen removal in the ecological floating with bamboo substrates(EFB-BS)were researched.The plant growth,nitrogen and phosphorus removal efficiency,substrate surface microstructure evolution characteristics,characteristics of indicative microorganisms,microbial population structure and diversity change features and biochemical reaction kinetics were researched,and the following conclusions were drawn:(1)The average removal rates of EFB-PS for TN,NH4--N,COD and TP were 58.19%± 5.28%,70.50%± 2.28%,75.14%± 3.20%and 70.89%±3.54%.The average removal rates of EFB-BS for TN,NH4+-N,COD and TP were 64.02%±4.98%,76.10%±3.90%,81.96%±4.07%and 75.59%±10.94%.Compared with EFB-PS,EFB-BS has more significant synchronous transformation of NH4--N and NO3--N.The average removal rate of TN,NH4--N,COD and TP by EFB-BS was 10.02%,7.94%,9.08%and 6.63%higher than that by EFB-PS.When the C/N ratio decreased from 15:1 to 10:1,the removal rates of EFB-PS on TN,COD and TP decreased by 13.67%,14.50%and 59.44%,and the removal effect of NH4+-N was stable.However,the removal effects of EFB-BS on TN remained stable,the removal rate of NH4+-N was increased by 16.13%,while the removal rates of COD and TP decreased by 12.14%and 49.19%.The main stem height of Oenanthe javanica in EFB-BS was better than that in EFB-PS.The average growth rate of the Oenanthe javanica main stem in EFB-PS and EFB-BS was 29.80%and 74.63%.Thus,filamentous bamboos have a strong ability to withstand impact load,and EFB-BS has a significant effect on nutrient removal.The ecological floating bed based on bamboo substrates has better phosphorus and nitrogen removal ability than the ecological floating bed based on plastic substrates.(2)Through the characterization of high-throughput sequencing,it can be known that the microbial diversity on plastic surface is better than that on filamentous bamboo surface,and the system stability is stronger.There are similarities and differences between microorganisms on the surface of plastic and filamentous bamboos,among which 865 species are common.At the genus level,the abundance of dominant bacteria on filamentous bamboo surface far outnumbers that on plastic surface,such as phosphate-removing functional bacteria:Massilia(39.93%),and nitrogen-removing functional bacteria:Pseudomonas(12.75%),Flavobacterium(3.35%),Janthinobacterizum(3.96%)and Hydrogenophaga(2.54%).(3)According to the results of microbiological examination,it was found that the zoogloea in the biofilm on the surface of filamentous bamboos had a large structure and transparent color,and miniature metazoan such as Aeolosoma hemprichicii and Nematode were found in the zoogloea.Indicative microorganisms are rich,protozoa such as kidneyworm,bellworm and so on.(4)By means of scanning electron microscopy,the surface structure of filamentous bamboos was destroyed after use,and there were a large number of holes of different sizes and depths,which proved that filamentous bamboos were consumed and carbon source was released,which was consistent with the theory that filamentous bamboos were used as a sustained-release carbon source of ecological floating bed.By observing the biofilm on the substrate surface,it was found that the biofilm on the plastic surface was thin,while the biofilm on the filamentous bamboos was thick and wrapped with filamentous bamboos.It was found that there were a lot of bacteria on the surface of plastic,but not a lot of bacteria on the surface of filamentous bamboos,only a lot of extracellular matter.However,a large number of anaerobic bacteria,and the abundance was significantly different,such as Flavobacterium(3.35%),Janthinobacterium(3.96%)and Hydrogenophaga(2.54%)were found in the holes of filamentous bamboos.These dominant functional species play an important role in the removal of phosphorus and nitrogen in ecological floating bed.(5)The correlation coefficient R2 of the Monod dynamic equation for the degradation process of total nitrogen described by the ecological floating bed is all above 0.98.The kinetic equation of the degradation of total nitrogen by EFB-PS is v=18.03c/26.67+c,where k0,v and k are 18.03 and 26.67 respectively,and the correlation coefficient R2 is 0.9895.The kinetic equation of the degradation of total nitrogen by EFB-BS is v=163.68c/334.96+c,where k0,v and k are 163.68 and 334.96,respectively,and the correlation coefficient R2 is 0.9835.Therefore,the Monod dynamic equation is used to predict the degradation and removal effect of pollutants in the ecological floating bed dominated by microorganisms,and continuously optimize the management and design,so as to make the removal effect of the ecological floating bed more efficient.