Synchronous and efficient removal of carbon, nitrogen, and phosphorus from actual rural sewage by composite wetlands enhanced with functional fillers.

A composite wetland (CECW) was constructed by introducing P-adsorption filler (EPAF) and activated sludge into traditional wetlands for treating actual sewage. The results showed that EPAF improved P removal through physico-chemical adsorption, and it could be stably regenerated after adsorption saturation without potential risks. Meanwhile, zeolite promoted NH4+-N reduction in sewage by cation exchange. In addition, simultaneous biological removal of carbon, nitrogen, and phosphorus was achieved through nitrification, denitrification, anammox, and aerobic P-accumulation processes induced by Nitrobacter, Proteus Hauser, Candidatus Paracaedibacter, and Brevundimonas. Under the coupling of filler interception/adsorption, microbial assimilation/transformation, flocculation, and plant uptake, CECW obtained the removal rates of 93.22 %, 85.75 %, 91.80 %, 95.38 %, 97.07 %, and 78.05 % for turbidity, TN, NH4+-N, TP, PO43--P, and TCOD, which met the Class 1A standard (GB18918-2002). Therefore, the experiment systematically investigated the effects and mechanism of CECW in treating actual sewage, which could provide reference for rural sewage treatment and sludge utilization.