Purification Effect And Mechanism Of Submerged Plant Rotala Rotundifolia For Eutrophic Water

Submerged plants are the main plants of freshwater lake and ri-ver ecosystems.The whole plant is immersed in water.The stems,leaves,epidermis and roots have the same absorption effect,and t-he cortical cells containing chlorophyll makes a good absorption of nitrogen and phosphorus.In this study,a new cold-resistant submer-ged plant,Rotala rotundifolia,was found in the wild.In order to e-xplore the growth characteristics of the plant,the purification effect and the mechanism of nitrogen and phosphorus,the growth charact-eristics,the purification effect of nitrogen and phosphorus under di-fferent initial pH,nitrogen and phosphorus concentrations were stud-ied in this paper.The migration and transformation of nitrogen and phosphorus in water,plant and sediment system were investigated,The contribution of Rotala rotundifolia to the removal of nitrogen a-nd phosphorus was analyzed.The Eco-tank system based on Rotal a rotundifolia was established by simulating the natural river,The p-urification performance of the Eco-tank system under different hydr-aulic load were discussed.The purpose of this paper is to provide t-he basis for the popularization and application of Rotala rotundifoli-a in the field of water restoration.The main conclusions were as f ollows:(1)Rotala rotundifolia in the silt sediment,pH=7 when the be-st growth.The growth indexes of the silting group were higher tha-n sand and gravel treated groups,and the biomass and plant height growth rate were higher than the other groups more than 19%.T-he biomass and plant height growth rate at pH=7 higher than other treatments more than 14%,5%,the highest tiller number was pH=6,but the other growth indexes were lower.(2)When the initial ammonia nitrogen(NH4+-N)in the range of 1-10mg L-1,the total nitrogen(TN),total phosphorus(TP)decreased to below 1mg L-1,0.1mg·L-1 for 24 days,up to the class ? standa-rd of environmental quality standards for surface water(GB3838-2002);NH4+-N concentration of 15mg·L-1 will inhibit the growth of Ro-tala rotundifolia,the biomass growth rate is only 14.25%,and TN of this group did not meet the class V water standard after 24 da-ys;the final nitrogen absorption of Rotala rotundifolia accounted for 15.84%-38.82%of the TN removal.(3)When the initial TP was 0.5-2.5mg·L-1,TN and TP decre-ased to 1mg·L-1,0.1mg·L-1 for 24 days,up to class ? water stand-ard.Rotala rotundifolia can withstand high phosphorus concentratio--n of water,TP concentration of 0.5mg L-1 will hinder its growth,and the growth rate of biomass in C1 and C5 treatment groups wa-s the lowest and the highest,respectively.Final the phosphorus cont-ent in the plant was.1.519g·kg-1-4.319g·kg-1,which was positively correlated with the initial TP concentration.(4)The Eco-tank system based on Rotala rotundifolia can eff-ectively reduce the nitrogen and phosphorus concentration of the ef-fluent,and the vermiculite could improve the growth of Rotala rot-undifolia and the removal of nitrogen and phosphorus.When the h-ydraulic load reached 100L·d1·m-2,NH4+-N,TN and TP of effluent-are less than 1.01mg·L-1,1.64mg·L-1,0.039mg·L-1,up to the class V water standard.The average TP of effluent is less than 0.05mg·L-1 when the hydraulic load is increased to 150L·d-1·m-2,but TN is m-ore than 3mg·L-1,which did not meet the class V water standard;The final biomass of Rotala rotundifolia in Eco-tank system with v-ermiculite was higher than control 446.2g.The concentration of N H4+-N,TN and TP at three stage were lower than the control grou-p 0.46-1.27mg·L-1,0.53-1.5mg·L-1,0.004-0.009mg·L-1.