Regulatory strategies and microbial response characteristics of single-level biological aerated filter-enhanced nitrogen removal

A single-level biological aerated filter (BAF) was used to treat domestic wastewater. The response surface method (RSM) model was applied to optimize the operating parameters such as hydraulic retention time (HRT), reflux ratio (R), and aeration-stop ratio. The characteristics of the wastewater were analyzed. The results showed the average removal efficiencies for COD, TN, and NH4+-N were 87.77, 75.41, and 87.28%, for a COD/N ratio of 3.44 under the RSM optimized conditions of HRT = 7 h, R = 105%, and aeration-stop ratio of 1:1. The environment was favorable for enhanced denitrification in the 30-70 cm section. The proportion of Proteobacteria showed a valley pattern along the range direction, while Planctomycetes and Nitrospirae were gradually increasing. The microorganisms involved in denitrification were more abundant at the phylum level, notably Proteobacteria (22.87-47.56%), Planctomycetes (6.62-10.68%), Nitrospirae (0.79-3.02%), and denitrifying bacteria were also evident at the genus level, i.e., Flavobacterium (0.21-1.43%). The BAF system with internal reflux-coupled intermittent aeration enhances nitrification and denitrification, thereby facilitating nitrogen removal.

Automated summary

A single-level BAF system was used to treat domestic wastewater, with optimized operating parameters achieving high removal efficiencies for COD, TN, and NH4+-N. The environment was conducive to enhanced denitrification, and the system showed potential for nitrification and denitrification enhancement.