| As an in-situ remediation technology,floating-beds were widely used for eutrophic water treatment.The efficiency of traditional floating-beds is very limited due to their single structure.To solve this problem,the combined floating-beds filling with artificial substrate which was helpful for the introduction of biofilm carriers and microbe enrichment,were developed.Hence,exploring the new-type artificial substrate with additional function such as adsorption capacity for pollutant is necessary for the further improve floating-beds technology.The previous work showed that waterworks sludge was a potential adsorbent because of high phosphorus adsorption ability.The purpose of this paper is to explore the purification efficiency of eutrophic water by using the floating-bed combined with ceramsites made from waterworks sludge.The main conclusions were listed as follows:?1?The firing process of waterworks sludge ceramsite was conducted on four steps:kneading sludge ball,air drying,preheating at 400°C for 10 min and firing at 600°C for 5 min.Under this process,waterworks sludge can be firing to the ceramsite with a good appearance.Compared with other firing method,the preparation process in this study is simpler and more economical.?2?The results of physicochemical properties of sludge ceramsite showed that there was no difference on the phase structure between the sludge ceramsite and the dry sludge ball,but a certain amount of Al-OH group loss in the sludge ceramsite.The surface of sludge ceramsite was rough as same as the dry sludge ball,while the sludge ceramsite possessed more abundant pore structure and specific surface area.The physicochemical properties had changed in the process of firing,but from the aspects of application,the sludge ceramsite in this study with good physical performance still has a potential as the artificial substrate in floating-beds.?3?Sludge ceramsite showed the similar P-adsorption ability as the air-dried sludge ball,and its adsorption kinetics accorded with the two-step adsorption kinetics rate equation and pseudo-second-order kinetics equation.The maximum adsorption capacity of sludge ceramsite fitted by Langmuir model is 1.66 mg/g,lower than the 1.89 mg/g of air-dried sludge ball.However,compared with other adsorbent owning similar size,sludge ceramsite still had a higher ability to adsorb phosphorus.?4?By adjusting the operation conditions of sludge ceramsite-based floating-bed and planted floating-bed as a control,sludge ceramsite-based floating-bed showed that the highest average efficiencies of COD,TN,NH4+-N and TP removals during the four operating stages were 78.2%,58.1%,46.7%,and 53.2%,respectively,which were higher than those of 53.5%,32.4%,27.2%and 25.8%of the planted floating bed,respectively.Therefore,the sludge ceramsite-based floating-bed had a better purification effect on eutrophic water than the planted floating bed.Furthermore,the sludge ceramsite-based floating bed showed a superiority in the removal of TP,resulting from the remarkable adsorption capacity of phosphorus by the sludge ceramsite substrate.In brief,the material with admirable adsorption capacity selected as the substrate of floating beds could be helpful for improving the purification efficiency.?5?Canna grew well in sludge ceramsite-based floating-bed and the control.The sludge ceramsite had not damaged the plant in the floating-bed,on the contrary,it can support and protect the roots of plants.Ceramsite did not disintegrate or run off along with the water flow.After the test,a variety of microorganisms were attached to the surface of the sludge ceramsite,which proved that the introduction of sludge ceramsite in floating-bed system can significantly improve the microbial diversity.Totally,the sludge ceramsite in the combined floating bed had multiple functions such as microbial carrier,plant growth substrate and adsorption material,and it's a new-type floating-bed substrate and has a wide prospect of application. |
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