Influence of Filler Types on the Treatment of Rural Domestic Wastewater in a Biological Trickling Filter: Simultaneous Nitrogen and Phosphorus Removal Performance, Microbial Community, and Metabolic Functions

Biological trickling filtration (BTF) has the advantages of simple operation, low energy consumption, and low sludge production, and its application in the treatment of domestic wastewater in rural areas has been widely discussed. In this study, ceramic granule (R1), zeolite (R2), and sponge (R3), three typical nitrogen and phosphorus removal fillers, were selected to investigate the differences in the removal performance of COD, nitrogen, and phosphorus in BTF, analyze the characteristics of the fillers and biofilm, and determine the performance of simultaneous nitrogen and phosphorus removal. The results show that among the three fillers, zeolite has the larger specific surface area and roughness and has the best treatment effect on the adhesion performance of sewage and biofilm. The richness and diversity of the microbial community are higher, and the system is more stable, with a COD removal rate of 77.10 ± 8.67% and an NH4+-N removal rate of 75.20 ± 6.64%. The TP removal rate was 22.04 ± 10.27%. The surface of ceramic particles showed a regular cluster structure with a loose distribution. The removal rate of COD was 78.49 ± 6.92%, the concentration of NH4+-N in the effluent was 27.95 ± 8.23 mg/L, and the removal rate of TP was 38.83 ± 12.14%. As a polymer composite material, the sponge has large internal pores and a smooth surface, which is not conducive to biofilm adhesion. Therefore, the removal rate of nitrogen and phosphorus in sewage is poor; the removal rate of COD is 75.94 ± 6.98%, NH4+-N is 27.89 ± 21.06%, and the removal rate of TP is 14.07 ± 11.76%. Compared with the metabolic function of genes, zeolites have a more stable enzyme digestion ability than the other two fillers, and the genes related to the nitrification process (amo, hao, nxr, etc.) and functional genes encoding key enzymes related to the TCA cycle are relatively abundant. © 2024 by the authors.