Study On High Efficiency Phosphorus Removal Of Floating Bed Plant Promoted By Phosphorus Accumulation/phosphorus Release Hydroponics Substrates

Plant floating bed technology was mostly applied to remove phosphorus from aquaculture tail water because of its obvious advantages in water purification,bioavailability and economic cost.However,in practice,there was a conflict between the area covered by plant floating beds and aquaculture area,and the effect of phosphorus removal from plant floating beds was restricted by the fluctuation of phosphorus content in water,resulting in a technical bottleneck in plant floating bed purification of aquaculture tailwater,making it difficult to win both economic and environmental benefits.To this end,this study aimed at this technical problem,starting from the plant floating bed hydroponic substrate,and prepared a hydroponic substrate with dual functions of phosphorus absorption and phosphorus release,so as to supply phosphorus to floating bed plants,in order to achieved efficient removal of phosphorus from aquaculture tail water.In this study,phosphorus accumulation/phosphorus release hydroponic substrates AC-Fe-Mg was prepared using granular activated carbon（AC）loaded with nano-iron-magnesium hydroxide,and the phosphorus adsorption and slow-release performance of AC-Fe-Mg were evaluated.The results showed that AC-Fe-Mg has good phosphorus adsorption and slow release performance in the p H range of 5-9.The amount of phosphorus adsorbed of AC-Fe-Mg reached 0.76 mg/g,and it could sustainably release phosphorus within 5 days;in addition,AC-Fe-Mg was highly selective for phosphorus adsorption and was basically undisturbed by coexisting substances such as Cl^-,NO₃^-,and humic acid（HA）.The results of phosphorus removal tests with hydroponic substrate（AC-Fe-Mg）combined with floating bed plants（I.pseudacorus L.）showed that the phosphorus removal rate increased by 48.73%and 35.32%in high and low phosphorus water bodies under the same conditions using hydroponic substrate than floating bed plants alone,respectively.The experimental results showed that in high phosphorus level,AC-Fe-Mg adsorbed and stored phosphorus;in low phosphorus level,AC-Fe-Mg-P released phosphorus for the growth of floating bed plants（I.pseudacorus L.）,thus achieved high efficiency removal of phosphorus.The experimental results of phosphorus removal from natural water bodies by hydroponic substrate AC-Fe-Mg and floating bed plant I.pseudacorus L.showed that the phosphorus adsorption and slow release performance of AC-Fe-Mg was not affected by the environment of natural water bodies and could promote the removal of phosphorus by I.pseudacorus L.in natural water bodies.In addition,the use of AC-Fe-Mg made nitrogenophilic and phosphorusophilic bacteria the dominant inter-rhizosphere strain of I.pseudacorus L.,which further promoted the degradation of nitrogen and phosphorus.Moreover,the experiment of plant floating bed combined with phosphorus accumulation/phosphate release hydroponics substrates showed that AC-Fe-Mg and I.pseudacorus L.could be recycled for many times,which is expected to achieve efficient removal of phosphorus from aquaculture tail water in production.