Experiment On Biofilm Growth Of Cohesive Sediment And Effect On Adsorption Or Desorption

Microorganisms are the important components of aquatic ecosystems and widely distributed in aqueous environment.Sediment,a special realm in aquatic ecosystems,provides excellent substratum for microorganism colonization.The secretion of metabolic products by microorganisms causes the formation and growth of biofilm on the sediment surfaces.Biofilm growth could influence the original physical properties of sediment and their transport processes,on the other hand,influence the adsorption and degradation properties of pollutants and nutrients in waterbody.The previous research usually focused on the impact on biofilm growth of sediment morphology features?floc density,size gradation?,sediment movement process?settling velocity,rheological properties?,sediment transport processes?incipient velocity?and bed surface morphology?sediment transport rate,roughness?,but little is about the influence on the chemical properties?adsorption and desorption etc.?and environmental effects.And there is also little research about the quantitative analysis of the biofilm growth,which is the important aspect of sediment and aquatic ecological environment.In this paper,the research mainly includes three aspects:the dynamic model of the biofilm growth on the sediment surface,the community diversity of the bio-sediment,as well as the adsorption and desorption properties of the sediment.The research on the model of biofilm growth is directed through the culture experiment of biofilm vegetating using sediment as the substratum,and focuses on the growing process of the biofilm.We use the loss on ignition?LOI?measured by muffle furnace as the variable in this model,consider the influence of the different flow velocity and sediment particle size on the biofilm formation and growth,and base on the classical theory of biofilm growth.Therefore a model of biomass that changed with time is proposed.Research shows that the biofilm growth rate and biomass was closely related with the sediment particle size and flow velocity.The smaller the sediment particle size and flow velocity,the larger the biomass.The above research could be well calibrated by the following model.The research on the community diversity of biofilm is based on the sequencing technology.The relations of the bacteria community are reflected using the sequencing technology called 16sRDNA.The analysis community diversity included basic diversity analysis?diversity index,taxonomic analysis,etc.?and senior diversity analysis?Veen figure,Hclust_bar,PCA analysis,etc.?.The results of community diversity analysis can well reflect the abundance and diversity of bacteria under different conditions,and reveal the influence of sediment partical size and flow velocity on the diversity,as well as lay a good foundation for the research of the environmental effect of biofilm.The research on the changes of the adsorption properties when growing biofilm on sediment surface is based on the model of adsorption isotherm.The study performed some laboratory experiments using Cu?NO₃?₂ solution and KH₂PO₄ solution as the adsorbent at different biofilm growth stage.The results of the adsorption experiment show that the growth of biofilm on the sediment surface has a more promoting effect on adsorption of KH₂PO₄ solutions but a less promoting effect on adsorption of Cu?NO₃?₂solution,for the sediment has a strong adsorption ability of the Cu?NO₃?₂ solution.