Study On The Modification Of Natural Zeolite And Fly Ash And Removal Of Ammonia-nitrogen And Phosphorus From Urban Landscape Water

The urban landscape water which is closed,of low-pollutant carrying capacity and rapid changes in water quality characteristics will be prone to eutrophication.This paper researched the modified method of natural zeolite and fly ash and the removal effect of ammonia nitrogen and phosphorus using modified zeolite and modified fly ash from the urban landscape eutrophication water.The result and conclusions were shown as follows:It is difficult for ammonia nitrogen removal to use natural zeolite because of the structure and other reasons.In order to exploit its potential capacity fully it need modifying.After using NaCl,AlCl₃,MgCl₂,HCl,calcining and other modification methods to modified the zeolite,the absorption capacity of the zeolite was improved, and the study also showed that among all modification methods the effect of NaCl was the best.The experiment was carried out under the condition that the concentration of NaCl was 1mol/L,the ratio of solid to liquid was 1:5 in the case of the modified 30 min, which showed that the zeolite had a good performance of ammonia nitrogen removal; under the experimental condition that the size of zeolite was 60～100 mesh,pH was 6～8 and the G was 126.2s^-1and stirring time was 25 min,the good efficiency of ammonia nitrogen removal was achieved.This study also showed that the adsorption reaction of ammonia nitrogen by modified zeolite could be described through Langmuir formula with R² of 0.9937,and on this condition the absorption capacity of ammonia nitrogen is 2.42 mg/g.The experiments of modified zeolite filter beds showed that the filtration rate plays a trivial role in the removal rate of ammonia nitrogen without changing the pH and temperature of the raw water,and when the filtration rate below 8m/h,the removal rate of ammonia nitrogen is more than 94%.When the experiment to treating the simulate urban landscape water was carried out with the filtration rate of 8m/h and the concentration of ammonia nitrogen changing between 5.25～0.51mg/L, the removal rate of ammonia nitrogen by zeolite filter bed is high,and the highest removal rate was up to 95.6%,then the concentration of ammonia nitrogen could be reduced to 0.23mg/L.The fly ash remove phosphate from water rely mainly on the CaO hydrolysis,it is necessary of high pH to getting a good effect.So the practical applications is largely limited,and the pH of output water is too high to reach the standards.In order to further enhance the ability of removing phosphorus and solve the problem of high pH of output water,it has to modify,the fly ash.After Modified by sulfuric acid,the fly ash has a very.good capacity of phosphorus removal.under the condition that the concentration of sulfuric acid was 0.5mol/L and the ratio of solid to liquid was 1:4,the modified fly ash has a good performance to remove phosphorus.The experiment showed that the modified fly ash has much faster absorption rate than the fly ash,.and it takes less than 5 min to reach P-adsorption-Balance;pH plays an important role on the absorption of phosphorus,when the pH was 6～7 and about 12 respectively,the modified fly ash has the best absorption effect,but the mechanism of phosphorus removal is different from each other.The P-adsorption reaction of the fly ash and the modified fly ash are both follow with Langmuir equation with the R² of 0.997 and 0.998 respectively,and the greatest absorption capacity reached 14.88mg/g and 9.34mg/g respectively.The biggest absorption capacity of modified fly ash decline,but its mechanism of phosphorus removal has much more significance of practical application.When the ratio of ash to water was 1/500,1/4500 and 1/10000 respectively,and the phosphorus concentration of simulated urban landscape water was 1mg/L,0.2mg/L and 0.04mg/L respectively,the phosphorus concentration of output water dropped to about 0.02mg/L under the condition that the pH was 6～7,the G was 49.7s^-1and stirring time was 5 min.while the ratio of ash to water up to 1/1000,1/4000 and 1/8000 respectively,the concentrations of phosphorus of the three output water can not be detected,if the ratio of ash to water was too low,the phosphorus concentration of output water rise slightly When dealing with the water of very low phosphorus concentration,so we should avoid such a situation in practical application.After treating by adding modified fly ash with the ratio of ash to water at 1/4000,TP of both the two urban landscape water dropped to 0.02mg/L,and DP dropped to 0.0101mg/L;when the ratio of ash to water was enhanced to 1/2000,TP reduced to 0.01mg/L.The pH of effluent water all was neutral,and the COD also had a good removal effect,COD removal ratio were up to 88.81%and 66.37%respectively.Experimental results showed that the modified fly ash has a very good prospect in the eutrophication-control of the urban landscape water.The fly ash almost has no capacity of exchanging adsorption with ammonia nitrogen since lacking the structure of zeolite,After using H₂SO₄ and NaOH to modify the fly ash,the absorption capacity of the fly ash had great increase,The experiment was carried out under the condition that the concentration of NaOH was 3mol/L,the ratio of solid to liquid was 1:4 in the case of the modified 1h,which showed that the fly ash has a good performance of ammonia nitrogen removal;under the experimental condition that the pH was 6～8 and the G was 49.7 s^-1and stirring time was 15 min,the good efficiency of ammonia nitrogen was achieved.This study also showed that the adsorption reaction of ammonia nitrogen by modified fly ash could be described through Langmuir formula with R² of 0.9924,and on this condition the absorption capacity of ammonia nitrogen is 26.18mg/g.The experiments of modified fly ash filter beds showed that the filtration rate plays a trivial role in the removal rate of ammonia nitrogen without changing the pH and temperature of the raw water,and when the filtration rate below 8m/h,the removal rate of ammonia nitrogen is more than 97%. When the experiment to treating the simulate urban landscape water was carried out with filtration rate of 8m/h and the concentration of ammonia nitrogen changing between 5.25～0.32 mg/L,the removal rate of ammonia nitrogen by fly ash filter bed is high,and the highest removal rate was up to 97.7%,then the concentration of ammonia nitrogen could be reduced to 0.12 mg/L.