Removal of nitrate and typical pharmaceuticals in anoxic biofilters under different nutrition and filter media types: with an emphasis on microbial community assembly
The simultaneous removal of nitrate and pharmaceuticals from secondary effluents is increasingly in demand. However, little is known regarding the mechanisms underlying microbial community differentiation and assembly associated with this process in anoxic filters. This study represented a pioneering investigation into anoxic filters by employing microbial community assembly mechanisms, which systematically examined the influence of nutrient and filter media types on the removal of mixed pharmaceuticals. The results indicated that autotrophic bio-ceramic filters exhibited superior overall performance. Total nitrogen (TN) removal was excellent across all filters; however, it displayed contrasting trends with variations in C/N and S/N ratios. Bio-ceramic filters outperformed Polyurethane (PU) filters in terms of pharmaceutical elimination efficiency, with autotrophic bio-ceramic filters exhibiting the best overall removal performance. Following the introduction of pharmaceuticals, the co-occurrence network among all reactors became increasingly complex; additionally, community stability and adaptability to pharmaceuticals were better under autotrophic conditions. The null model analysis revealed that drift predominantly influenced community assembly across all reactors; nevertheless, pharmaceuticals shifted community towards increased deterministic assembly while significantly enhancing homogeneous selection within autotrophic bio-ceramic filters (34.59%), where Thiobacillus emerged as a pivotal genus contributing to both homogeneous selection and biofilm stability. A positive correlation was identified between hydrogen bond donors/acceptors in pharmaceuticals, their molecular weight, and their respective removal rates . These results elucidated the ecological patterns exhibited by microbes under the stress of mixed pharmaceuticals, and contributed to the understanding of how nutrient and filter media types influence and shape distinct microcosms, thereby providing valuable insights for the precise regulation and construction of biomes in anoxic filters.