The Study Of Optimizing Substrate Gradation And Effect Factors For Constructed Wetland Removal Of Ammonia Nitrogen And Phosphorus

Constructed wetland sewage treatment technology with the advantages of high efficiency and low energy consumption and ammonia nitrogen and phosphorus removal rate has gradually be aroused the world's attention. Constructed wetland substrates played an essential role of removal ammonia nitrogen and phosphorus. This paper studied the ammonia nitrogen and phosphorus removal efficiency of several common substrate materials that as the constructed wetland substrate through the experiment of adsorption, and selecting the three kinds of substrate which was the best adsorption effect and then combination of them as a certain proportion, and select the optimal substrate of removing ammonia nitrogen and phosphorus. Experiments show that:the best three substrate of ammonia nitrogen adsorption effect was zeolite, columnar carbon and fly ash; Limestone, the best three substrate of phosphorus adsorption effect was zeolite and fly ash. Zeolite, columnar carbon and fly ash with the quality mix proportion of 3:1:1 ammonia nitrogen adsorption removal efficiency reach to 88.55% in 48 hours, compared with zeolite single adsorption increased 10.45%; Zeolite, limestone and fly ash with the quality mix proportion of 1:3:1 phosphorus removal rate achieve the best 79.68%. Experimental results show that:the factors affecting ammonia nitrogen removal rate reached to 88% when pH 5-7,and ammonia nitrogen removal rate fell rapidly when pH value more than 7 or less than 5; PH value on the adsorption of phosphorus optimal ratio influence was not obvious; When glucose concentrations was 0.10 mg/L, the ammonia nitrogen removal reduced 56.62% compared with blank liquid; When oxalic acid concentration was 0.2 mg/L, samples of ammonia nitrogen removal increased 6.5% compared with the blank, when citric acid concentration in 0.05mg/L of ammonia nitrogen removal dropped 43.4%; Phosphorus removal rate decline along with the increase of concentration of oxalic acid and citric acid, and largest decline drop was 70.4%and 66.6% respectively. Ammonia nitrogen removal reduces as the increase concentration of Cl-, SO42- and NO3-, phosphorus adsorption removal rate fell rapidly as the increase of concentration of SO42-, and Cl- and NO3-had little impact on the optimal proportioning adsorption phosphorus and even improved 8.7% and 8.9%.Ammonia nitrogen adsorption increased with the increase of solution concentration of ammonia nitrogen in optimal combination substrate, ammonia nitrogen adsorption 2.75mg/g by increased to32.5mg/g and 3.31mg/g with the concentration20mg/L increased to25mg/L and 30mg/L. The optimal proportion of ammonia nitrogen adsorption capacity increasing as the temperature increased, and reach of adsorption equilibrium in short time in high temperature.Phosphorus adsorption increased with the increase of solution concentration of phosphorus in optimal combination substrate, phosphorus adsorption 7.36mg/g by increased to12.02mg/g and 16.73 mg/g with the concentration 5mg/L increased to 10mg/L and 15mg/L; increased 4.66mg/g and 9.37mg/g respectively. The optimal proportion of phosphorus adsorption was 13.01 mg/g in 35℃and more than 5℃,15℃and 25℃conditions adsorption 9.80 mg/g,10.70mg/g and 12.02 mg/g increase 3.21 mg/g,2.31mg/g and 0.99 mg/g.Quasi secondary dynamics described the two optimal ratio of ammonia nitrogen and phosphorus adsorption kinetic process than level first, correlation coefficient both reach more than 0.9; The two optimal ratio adsorption thermodynamics showed that△G0<0,△H0>0,and the two optimal ratio adsorptive ammonia nitrogen and phosphorus were spontaneous process.