Investigation Of The Removal Of Ammonia Nitrogen And TP In Rural River Water By Ecological Floating Bed

Ecological floating bed is a kind of green economy,convenient management,sensory comfort water ecological treatment technology,widely used in the treatment and restoration of surface water bodies such as rivers and lakes at home and abroad.In actual engineering,the construction scale of ecological floating bed and the selection of plants lack quantitative basis,so it is of great significance to quantitatively screen out hydrophytes and fillers with good absorption effect and ecological aesthetics.First of all,the static adsorption experiments and theoretical simulations of aquatic plants and fillers were carried out.and then the experimental of the water purification capacity of ecological floating bed was carried out.The effects of water temperature（T）,inlet water pollutant concentration(C_in),hydraulic residence time（HRT）and p H value on the water purification capacity of ecological floating bed were investigated,and the water purification mechanism was analyzed to obtain the best operating conditions.On this basis,the relationship between significant influencing factors and reaction rate（K）was analyzed.The extended first-order kinetics model of the ecological floating bed for the removal of ammonia nitrogen and TP was constructed,which provided a theoretical basis for the optimization of the ecological floating bed design.The conclusion is as follow:（1）There were significant differences in the dynamic characteristics of ammonia nitrogen and TP between Iris tectorum,Phyllostachys heteroclada,Iris pseudacorus and Juncus effuses.Iris tectorum had the greatest affinity of ammonia nitrogen and TP.Phyllostachys heteroclada had a high maximum absorption rate(I_max)and large Michael’s constant（K_m）of ammonia nitrogen,adapting to high concentration of ammonia nitrogen,but was not suitable to absorb TP.Iris pseudacorus was adapted to high concentration of ammonia nitrogen and different TP concentration of contaminated water bodies.Juncus effuses was not recommended as ecological floating bed plant because of its lower I_max and greater K_m.Iris pseudacorus was chosen as the hydrophyte of the ecological floating bed.（2）The adsorption process of ammonia nitrogen and TP in four matrices,such as gravel and green zeolite,was in line with the Langmuir isothermal equation and the quasi-secondary kinetic equation.The adsorption capacity of ammonia nitrogen was,from strong to weak,as follows:zeolite>gravel>vermiculite>sponge iron,and the adsorption capacity of TP was:sponge iron>zeolite>gravel>vermiculite.Zeolite and sponge iron were chosen as the filler of the ecological floating bed.（3）Water temperature（T）,inlet pollutant concentration(C_in),hydraulic retension time（HRT）and p H value all had an impact on the water purification effect of ecological floating bed,of which T,C_in and HRT were significant influencing factors.The increase in water temperature promoted the removal of ammonia nitrogen and TP,and the removal efficiency of ammonia nitrogen and TP in low temperature areas was improved rapidly.The increase of C_in was not conducive to the removal of ammonia nitrogen and TP in the ecological floating bed.When the concentrations of ammonia nitrogen and TP were 1.86 and 0.51 mg/L,the removal efficiency was the highest,which was 65.57%and 33.90%,respectively.The prolongation of HRT had a significant role in promoting the removal of ammonia nitrogen and TP in ecological floating bed.With the increase of HRT,the rate of increase in the removal efficiency of ammonia nitrogen and TP in ecological floating bed had slowed down slightly.When the p H value was 7.4,the removal efficiency of ammonia nitrogen and TP was the highest,and the removal efficiency of ammonia nitrogen and TP were the lowest when the p H was 6.1 and 9.4,respectively.（4）The factor that had more significant impact on the effect of water purification were T,C_in,HRT,and then the relationship between the three factors and the reaction rate constant（K）were coupled.The extended first-order kinetics model was constructed.The fitting results show that the K of ammonia nitrogen and TP were in line with the Arrhenius function relationship,of which the temperature coefficient（θ）of ammonia nitrogen and TP was 1.069,1.037,respectively.The larger the value ofθ,the greater the effect of water temperature on the removal effect.The exponential regression better reflected the relationship between K₂₀ and the initial pollutant concentration of ammonia nitrogen and TP;K_20,NH4、K_20,TP were related HRT with hyperbolic function;Finally,the extended first-order kinetics model,which considering the influences of water temperature,initial pollutant concentration and HRT,had higher accuracy on the prediction of ammonia nitrogen and TP effluent concentration of ecological floating bed（m=0.987、R²=0.991;m=0.988、R²=0.995）.