Performance Evaluation of Diverse Filter Media Combinations Under Different Pollution and Hydraulic Loads in Constructed Wetlands

During rapid social and economic growth, large amounts of organic matter, nitrogen, and phosphorus are released into the environment with wastewater, and constructed wetlands (CWs) play a key role in water pollution prevention and control. This study employed six test columns to evaluate the pollutant removal performance of various filter media combinations in CWs when treating synthetic sewage under different pollution and hydraulic loads. The results showed that all columns containing bio-ceramsite exhibited superior pollutant removal performance, especially for organics and phosphorus. A synergistic effect was observed between bio-ceramsite and volcanic rock in enhancing pollutant removal, with average removal rates of 88.02%, 69.69%, 62.96%, and 88.22% for COD, NH4+, TN, and TP, respectively, under the nine experimental conditions. Scanning Electron Microscopy (SEM), BET surface area testing, and microbial community structure analysis were conducted to investigate the reasons for the differences in pollutant removal efficiency among the columns. The results showed that bio-ceramsite exhibits a highly microporous structure and a large surface area of 1.3816 m2/g, which provides abundant adsorption sites for microorganisms and pollutant molecules. The microbial community structure on bio-ceramsite remained highly consistent across all column tests, with dominant microbial species playing a key role in enhancing pollutant removal efficiency. The conclusions of this study indicate the potential application of some filter media combinations in CW design for environmental conservation.