Study On Zero-valent Iron Coupled Biological Phosphate Reduction And Phosphorus Removal And Microbial Population Structur

The existing phosphorus recovery methods mainly rely on the separation of sludge and water,which not only increases the cost of secondary treatment of sludge,but also increases the risk of secondary pollution.Phosphate reduction sludge reduces the phosphate in sewage to hydrogen phosphate gas.No matter the way of product separation or the difficulty of product recovery,it has obvious advantages.At the same time,its mechanism is also worthy of further research and exploration.However,the phosphate-reducing sludge currently studied has low hydrogen phosphate production,weak TP and COD removal functions,and is difficult to be used in practical applications.Therefore,zero-valent iron(ZVI)and Fe2O3 are used to add phosphate-reducing sludge to enhance the water purification effect of phosphate-reducing sludge,and to study the changes in microbial population structure.The returned sludge from the secondary sedimentation tank was used for the cultivation and domestication of phosphate reduction sludge,and the comparative tests were carried out with temperature,influent COD value and influent TP value as influencing factors to determine the optimal operation conditions of phosphate reduction sludge.Studies have shown that steel nails and iron scraps have a certain role in promoting the production of hydrogen phosphate from phosphate-reducing sludge.Therefore,zero-valent iron(ZVI)and Fe2O3 were used as two groups of control experiments to determine their effects on phosphate-reducing sludge.At the same time,the microbial diversity of the experimental group and the culture and domestication group with better results was analyzed to study the microbial population structure of the sludge,and to determine the microorganisms related to the phosphate reduction reaction and the microorganisms that compete them.After acclimation and cultivation of phosphate reduction sludge,the COD removal efficiency was between 30 % and 40 %,and the TP removal efficiency was about 8 %.The average yield of hydrogen phosphate for 70 days was about 0.218 mg / L.The optimal conditions obtained by grouping experiments were as follows : temperature was about 35 °C,TP influent concentration was about 50 mg / L,and COD influent concentration was about3000 mg / L.The 33-day average phosphine production in the ZVI group was 0.479 mg / d,the average TP removal amount was 5.15 mg / d,and the average COD removal amount was1020 mg / d.The 33-day average phosphine production in the Fe2O3 group was 0.207 mg /d,the average TP removal amount was-1.3 mg / d,and the average COD removal amount was 509 mg / d,indicating that the data in the ZVI group were all better than those in the Fe2O3.The biological diversity of ZVI group and domesticated phosphate-reducing sludge was analyzed from the aspects of biological diversity,abundance and population structure changes to find strains related to phosphate reduction reaction and strains competing or antagonistic with this strain.The phosphate reduction sludge was domesticated and cultured,and the optimal values of temperature,COD and TP were obtained,which verified the feasibility of the combination of ZVI and phosphate reduction sludge.The thermodynamic mechanism provided a theoretical support for the promotion of phosphate reduction by ZVI to produce hydrogen phosphate,and the microbial population structure of phosphate reduction sludge under the influence of ZVI was studied.