Optimization of Four Kinds of Constructed Wetlands Substrate Combination Treating Domestic Sewage

Based on the static and dynamic experiments, this paper has analyzed the adsorbing capacity for domestic wastewa-ter pollutant (COD, NH4+-N and TP) of four kinds of constructed wetlands substrate which were fly ash, hollow brick crumbs, coal cinder and activated carbon pellets in single and combined condi-tion. In the static experiments, the adsorbing capacity of four sub-strates all grew as the adsorbing dose increased. In adsorbing COD, each substrate’s adsorbing capacity rises with the adsorbing dos-age. Simultaneously, experiments show that all the adsorption of the four kinds of substrate for COD, NH4+-N and TP follows the Freundich Rule. The dynamic experiment demonstrated that the adsorbing capacity of combined substrates is bigger than that of single substrate. Fly ash in combination with small coal cinder adsorbs COD the best, while it takes in NH4+-N and TP the best when working with hollow brick crumbs. The combination of the two raises the removal rates up to 89% and 81% respectively. Given high cost and low adsorbing effect, activated carbon is not a suitable candidate for constructed wetlands substrate.