Application Of Calcium Peroxide Composite Material To Control Phosphorus In Water

At present,the mulching method to control the endogenous phosphorus pollution in sediment to prevent water eutrophication has been a research hotspot.CaO₂,as an environmentally friendly material with both oxygen release and oxidation properties,has attracted wide attention.Researchers have prepared different composite materials with CaO₂as the core.These materials either have a short release period or cannot be effectively used.Although they have advantages in the control of endogenous phosphorus,the use of these materials is controversial when water phosphorus pollution is in urgent need of emergency or long-term maintenance.Based on this,this study,with calcium peroxide as the core,synthesized a new type of calcium peroxide composite material,investigated its emergency effect on water,and analyzed the control effect on other water quality indicators such as organic matter,algae;The long-term control effect on the release of endogenous phosphorus was investigated,and its mechanism on the form of endogenous phosphorus was analyzed.In this study,the actual water depth（water depth≥1m）was simulated to provide theoretical and data support for the engineering application of materials.Two kinds of covering materials(ACPM and Phoslock^?)were added to the typical eutrophic river channel in Suzhou City for a 38-day experimental study.The results showed that the concentration of NH₄⁺-N and Fe²⁺in the CaO₂ modified material（ACPM）covered condition was lower than that in the phosphorus locking agent(Phoslock^?)group,and the microbial activity value of FDA increased by 42.57%,indicating that the microbial activity of ACPM was higher.It was also shown that the REDOX potential under ACPM coverage was higher than Phoslock^?,and the sediment microenvironment was in an aerobic state.Compared with Phoslock^?group,the DIP concentrations in overlying water and pore water were higher in ACPM group,indicating that Phoslock^?had better phosphate adsorption capacity than ACPM,and suggesting that the sediment microenvironment was not the only criterion for phosphorus adsorption.In the process of endogenous P fixation,the two kinds of cover materials are beneficial to the fixation of endogenous P,and the Ca-P increases significantly.However,oxidizing ACPM resulted in the increase of NH₄Cl-P and the decrease of Fe/Al-P,which promoted the release of active P and made the P in the sediment migrate to the overburden.The control effect of new calcium peroxide composite material（short-term emergency material）on phosphorus in water was investigated.The optimal dosage of emergency materials in general water is 0.015g/LCaO₂+0.1g/LPAC,and the maximum theoretical adsorption capacity is 176.58mg·g.Then it is added to different eutrophic water bodies for application research.The results show that the treatment effect of Yushan Road,Aihe Bridge,Zhongshi Bridge,Yingcheng City,Laohe Canal,Shihu Bridge and other actual eutrophic water is good,and the removal rate of turbidity,DIP and COD is more than 60%.In addition,the prepared calcium peroxide composite material has the function of phosphorus removal and algae inhibition within 30min,and has the effect of short-term emergency.In addition,the process treatment effect of emergency materials after wastewater treatment plant A2O is better,and the removal rates of TP,NH₄⁺-N,Chl-a and COD are 89.24%,34.73%,70.64%and 75%,respectively.Then,a new type of calcium peroxide composite material（CPML）,a long-term covering material,was prepared by pressing the tablet,and the application study of the phosphorus control effect of CPML in the actual eutrophic water collected was explored.The best ratio of materials is 10%CaO₂+10%PAC+20%Mg O+57%water purification sludge+3%magnesium stearate,and the maximum theoretical adsorption capacity was101.2mg·g.After that,CPML was added into the simulated actual water body at different dosage levels of 1:80,1:100,1:120（2cm Pmobile:material on the surface of sediments）for application research,and it was compared with lanthum-modified bentonite（LMB）.The emergency material was added before the start of the experiment,and it was found that it could remove phosphate in the water body in a short time.The long-term coverage results showed that the removal rate of COD in the overlaying water was higher with the increase of CPML dosage.The turbidity,TP and DIP of the overlaying water in the dosage of 1:100and 1:120 groups had certain removal effect,but it was still weaker than that in the LMB group.In the clearance water,1:120 group has the best effect on the DIP treatment of clearance water,with the removal rates of 85.9%（Ⅰ）and 79.5%（Ⅱ）.It also has a certain removal effect on Fe²⁺and NH₄⁺-N,and is more conducive to the transformation of unstable form of phosphorus Fe/Al-P in the sediment to stable state of Ca-P.DGT-P concentration diagram also showed that CPML with 1:120 dosage had a better effect on the treatment of sediment endogenous phosphorus,which was conducive to the migration of sediment phosphorus to deep layers.However,the treatment effect of LMB on sediment phosphorus was not significant.Based on the overlying water and sediment,the optimal dosage of CPML should be between 1:100 and 1:120.To sum up,the calcium peroxide emergency materials prepared in this project can remove phosphorus and restrain algae in a short time.The long-term covering material CPML has a better effect on the treatment of sediment phosphorus,and has a significant improvement effect on the sediment microenvironment.It is found that part of CPML promotes the release of surface phosphorus,which is conducive to cleaning the sediment,while the other part promotes the migration of endogenous phosphorus to the deep layer,which is conducive to the fixation of sediment phosphorus.The prepared combination of short-term emergency materials and long-term covering materials,CPML,achieves the purpose of short-term emergency and long-term efficient covering of phosphorus in water,and provides technical support for the practical application of covering materials in eutrophic water.Besides,they are cheap and have a good application prospect.