Synergistic waste-based substrates: Optimizing constructed wetland performance for rural wastewater remediation

This study established four constructed wetlands (CWs) using different substrate combinations derived from local rural wastes. The aim was to investigate the influence of these waste-derived substrates on CW performance. Results showed that the CW-ZR system (zeolite: reed biochar = 2:2) exhibited the highest removal efficiencies for COD, NH₄⁺-N, and TN with average removal efficiencies of 64.39 %, 61.98 %, and 59.88 %, respectively, attributed to the abundant oxygen-containing functional groups and aromatic functional groups, porous structure, and good ion exchange capacity of reed biochar. Additionally, the CW-ZO system (zeolite: oyster shells = 2:2) exhibited the highest TP removal efficiency (49.02 %). This enhanced performance may be attributed to the alkaline oyster shells, which contain high concentrations of calcium carbonate and active calcium oxide. These components facilitate phosphate adsorption through anion exchange, effectively binding negatively charged phosphate ions to the shells. Further investigation revealed that the system with reed biochar had the best performance in promoting plant growth among the three substrate materials, which can be attributed to the synergistic effects of the substrate characteristics, high nutrient removal efficiencies, and the enriched microbial communities within the combined systems. Consequently, the addition of reed biochar elevated the relative abundances of bacterial groups associated with nitrogen and organic matter degradation, while oyster shells promoted the proliferation of phosphorus-degrading microbial communities. These studies confirm that optimizing substrates with rural waste can strengthen the comprehensive treatment performance of CWs.