Efficiency and Microbial Community Analysis of Aeration Biofilters in Treating Rural Domestic Wastewater

The expansion of rural water supply amplifies the quantity of domestic wastewater, thus demanding focused investigation into wastewater treatment technologies suitable for rural settings. This research analyzed the effect of divergent packing materials and air-to-water ratios in biological aerated filters on the treatment efficiency of rural domestic wastewater and its affiliated microbial communities. Experiments employed four reaction columns with varied packing materials and air-to-water ratios. Column 1 utilized gravel, sorted by particle size from top to bottom: 8–10 mm, 10–20 mm, and 20–30 mm. Column 2 employed a 1:1 mixture of zeolite and 8–10 mm gravel; Column 3 used a layered arrangement of the same materials. A layer of cobblestone supported all columns. Column 4 served as the control, using the same packing structure as Column 2 but with a 3:1 air-to-water ratio versus the 5:1 ratio in other columns. The research assessed pollutant removal efficiency and performed microbial detection via high-throughput sequencing to analyze microbial community structures. The results demonstrated that Columns 1, 2, and 3 effectively eliminated BOD5, CODcr, and ammonia nitrogen, with removal rates ranging from 84.51% to 96.49%, complying with Grade A criteria specified by GB18918-2002. Column 4 displayed reduced BOD5 and CODcr removal efficiency, indicating that increased air-to-water ratios enhance organic matter removal. However, phosphorus removal was insufficient in all columns, ranging from 29.62% to 65.81%, underscoring the necessity for improved phosphorus elimination mechanisms. Microbial operational taxonomic units in Columns 1, 2, and 3 were similar at 1,533, 1,550, and 1,530, respectively. Notably, Column 2 had more unique operational taxonomic units than Column 4, affirming that higher air-to-water ratios boost microbial diversity. All columns exhibited high microbial richness, with marginal variations in diversity. Dominant microbial taxa in Columns 1, 2, and 3 included Proteobacteria, Gemmatimonadetes, Chloroflexi, Bacteroidetes, Actinobacteria, and Acidobacteria, in descending order of abundance. The dominant microbial taxa remained consistent across different elevations within each column, albeit with variances in abundance. Polyphosphate-accumulating organisms were predominantly observed among Proteobacteria, contributing to suboptimal phosphorus removal.