Research On Preparation And Properties Of High Strength Carbon Source Carriers

Aiming at the low carbon and high nitrogen water pollution in some urban rivers,it has become a new research hotspot to develop new carbon source materials to improve the carbon/nitrogen ratio of the river,and meanwhile remove the nitrogen pollution of the river.However,existing carbon source materials did not have both high strengths and denitrification capacities,and there were few studies on the influence of preparation methods such as different proportions and curing methods on the strength,carbon release,denitrification and other properties of carbon source materials.In this paper,a high-strength carbon source carrier could not only provide added carbon source for water,but also provide stable growth and attachment space for microorganisms in water to improve the nitrogen removal efficiency of water.Firstly,the composition ratio and curing conditions of the high strength carbon source carrier were optimized to make the strength better.Secondly,the carbon release performance and nitrogen removal effect of the high strength carbon source carrier with different preparation methods were analyzed.Finally,compare it with other materials to provide technical reference for the engineering application of carbon source materials in the purification of low C/N ratio river.The main research results were as follows:（1）Twenty kinds of mixture ratios were designed by mixture design to investigate the influence of different raw material ratios on the compressive strength of the carrier.The results showed that the Y17 carrier with the proportion of 34%cement,34%zeolite powder,22%diatomite,7%bentonite clay and 3%corn cob had the highest compressive strength as well as he Y18 carrier with the proportion of 34%cement,10%fly ash,21%zeolite powder,23%diatomite,9%bentonite and 3%corn cob.The contents of cement,fly ash,zeolite,diatomite and bentonite were selected as independent variables,which were denoted as X₁,X₂,X₃,X₄ and X₅ respectively.The compressive strength of the carrier was taken as the response value,and the regression model obtained by fitting was significant.The fitting multiple quadratic equation can reasonably reflect the interactive relationship between the compressive strength value and the content of five raw materials,among which the significant influences were:X₃X₄,X₁X₄ and X₂X₄.The recommended proportion with high compressive strength was obtained by optimization of the Design Expert software.The predicted value was close to the actual value.（2）The single factor experiment showed that the compressive strength of the carbon source carrier was inversely proportional to the water-solid ratio and it was found that the best maintenance frequency was for sprinkler 3 times a day,the best curing age for 3 days,the best curing temperature was 20²5℃.The center combination design was carried out by using the Design Expert software.The water-solid ratio,proportion and curing temperature were selected as independent variables,and the compressive strength of the carrier was taken as the response value.The regression model obtained by fitting was significant,and the fitting multiple quadratic equation could reasonably reflect the interaction relationship between the compressive strength value and the three factors of water-solid ratio,proportion and curing temperature,among which temperature and water-solid ratio had significant influences.The recommended preparation conditions with high compressive strength obtained from software were as follows:water solid ratio of 0.5,composition ratio of T4,temperature of 20℃,and its actual strength was 347.1 N,differing less with prediction value 345.3 N.（3）It was found that Z9 carriers with preparation methods for water solid ratio0.52,composition Y18 and 20℃had high mechanical strength and good effect of carbon release and nitrogen removal through the study of carbon source carriers with different preparation methods.SEM results showed that Z9 carrier had compact surface,obvious internal material hydration and highest mechanical strength.The carbon release process of Z9 carrier was more in line with the characteristics of secondary kinetics and Fick diffusion.The saturated carbon release amount per unit mass of Z9carrier in solution was 129.87 mg/L,and the mass transfer coefficient was 19.05mg·（h·L）^-1.When temperature was 25℃,water nitrate concentration 20 mg/L,after the stabilization of Z9 groups,the NO₃^--N concentrations in effluent were 2.44 mg/L,and the total nitrogen concentrations were 2.904 mg/L.In addition,comparing with traditional materials such as straw,ceramsite and zeolite,Z9 carrier had advantages in strength,properties of carbon release and nitrogen removal.