Phosphorus Adsorption Capacity of Filter Media in Constructed Wetlands

Adsorption and precipitation of phosphorus(P) on filter media is a major P removal mechanism in constructed wetlands.Therefore,determining the P adsorption capacity of filter media is vital to the design of wetland systems with high P removal efficiency.Adsorption and column experiments were conducted to discover the P adsorption capacity of four filter media.Meanwhile,extraction toxicity identification of the filter media was carried out to ensure the safety of the media.The adsorption experiment showed that the Langmuir and Freundlich models described the adsorption data well(R~(2)= 0.956-0.989),with an estimated P adsorption capacity by the Langmuir model between 2.274 and 3.637(mg/g).During the 144 days column experiment,the columns filled with Baogang and Shougang slags had relatively higher removal rates,while the columns filled with Shuicui slag and zeolite reached P saturation after about 90 days.The accumulated P adsorption capacity from the column experiment was as follows: Baogang slag 7.921 (mg/g),Shougang slag 7.495(mg/g),Shuicui slag 3.317(mg/g) and zeolite 1.627(mg/g).Due to their high removal efficiency and low cost,the Baogang,Shougang and Shuicui slags have potential to be widely utilized in the wetland system.