Absorption of Ammonium by Three Substrates Materials in Constructed Wetland System

Abstract

The adsorption characteristics of ammonia nitrogen for constructed wetland were studied with ceramsite, quartz sand, and gravel. The material was characterized using scanning electron microscopy and a BET-specific surface area analyzer. It was found that the surface of ceramide was coarser than that of quartz sand and gravel, and the internal pores were more developed. The specific surface area of ceramide (18.97 m2·g-1) was higher than that of quartz sand and gravel. In the pure ammonia nitrogen solution and Grade I B standard for the wastewater treatment plant effluent ammonia nitrogen solution of the effluent from the simulated sewage plant, the adsorption capacity of the three substrates was as follows:ceramsite > gravel > quartz sand. The saturated adsorption capacity (63.55 m2·g-1) of ceramides was the highest in the mixed solution. The adsorption process of ammonia nitrogen by ceramides accorded with the pseudo-second-order kinetic model (R2 of 0.99 in the pure ammonia nitrogen solution and 0.98 in the mixed solution). The Freundlich and Langmuir models were used to fit the isothermal adsorption results in a pure ammonia nitrogen solution. It was found that the Freundlich model described the adsorption characteristics of the ceramics more accurately than the Langmuir model (R2=0.93), indicating that the adsorption of ammonia nitrogen by the ceramics was multilayer adsorption. In conclusion, the adsorption capacity of ceramide was strong, and the adsorption capacity of ceramide in the mixed solution was 31% higher than that in the pure ammonia nitrogen solution, which was suitable to be used as the matrix filler of constructed wetland.