Experimental Study On Sewage Treatment By Fillings In Constructed Wetlands

Fillings in constructed wetland have an important part of removing nitrogen and phosphorus. Therefore, the problem studied mostly capabilities, mechanism of removing contamination, characteristic of forming membrane, in order to seeking the filling with good effect of removing contamination.The text selected four fillings that include bulgy vermiculites, zeolites, blast furnace slag, limestone. Many tests are hold including the static adsorption test, the dynamic adsorption test, the test of forming membrane, the influencing factor test of simulate construted wetland and the test of simulate constructed wetland disposing sewage. The tests show that:①In the four filings, the adsorption capacity of zeolite to ammonium is the biggest, the adsorption capacity of vermiculites to TP is the biggest;in the range of 10℃~30℃, temperature has less effect in adsorping nitrogen and phosphorus.②It is better that adsorption of zeolite to ammonium was described in Freundlich, and limestone, blast furnace slag and vermiculites were described in Langmuir, their correlation coefficients achieved separately 0.9086, 0.8712, 0.9271, 0.9648;it is better that the adsorption of zeolite, limestone and blast furnace slag to TP were described in Langmuir, and the adsorption of vermiculites to TP was described in Freundlich, their correlation coefficients achieved separately 0.8588,0.9297,0.9656,0.8401.③In the dynamic adsorption test of single filling, removal effect of zeolites to COD, ammonium, TN is the best, removal rate achieved separately 69.5%, 94.1%, 92.1%;removal effect of vermiculites to TP is the best, removal rate achieved 74.9%.④In the dynamic adsorption test of mixable fillings, the mixable fillings of zeolites and vermiculites of one to one were confirmed to be the best mixable fillings.⑤In the test of simulate constructed wetland disposing sewage, the simulate constructed wetland system had formed membrane successfully during two weeks in 20℃. After two weeks, removal rate of the system to COD and ammonium achieved separately 97.2% and 96.4%, and the membrane-formed system had stronger ability to resist hydraulic and pollution loading.