Study on the adsorption characteristics of nitrogen and phosphorus on three substrates of constructed wetland

Sponge iron,zeolite and gravel were selected as substrates of constructed wetland to treat wastewater containing excessive nitrogen and phosphorus.The isotherm adsorption experiments and adsorption kinetics experiments were conducted to study the adsorption characteristics of nitrogen and phosphorus on three substrates of constructed wetland.Results showed that the behaviors of nitrogen and phosphorus adsorption on substrate could be well fitted by both Langmuir and Freundlich isothermal model,the phosphorus adsorption capacity of 3 substrates in order of sponge ironzeolitegravel,the nitrogen adsorption capacity of substrates followed the order of zeolite sponge irongravel.The dynamic adsorption process was described by two-constant equation,first order kinetics equation and Elovich equations,Elovich equations was the best for simulated the phosphorus adsorption process,while the first order kinetics equation could accurately fitted the nitrogen adsorption process.The adsorption process of nitrogen and phosphorus overall appears first quick back slow trend.Comparison from adsorption capacity and adsorption rate,the iron and zeolite were suitable substrates of constructed wetland for remove of nitrogen and phosphorus.