Development and application of a hydraulic performance evaluation method for denitrification reactors.

The hydraulic characteristics of denitrification reactors are crucial for their efficient and stable operation. The absence of a quantitative assessment framework for reactor flow field structures hinders the establishment of a clear relationship between hydrodynamic conditions and denitrification performance, limiting wastewater treatment optimization. This study proposes a hydraulic performance evaluation method based on cross-sectional velocity distribution uniformity. By integrating computational fluid dynamics simulations with physical experimental validation, the internal flow characteristics of three reactor configurations with different water distributors - spiral flow reactor (SFR), upflow reactor (UFR), and downflow reactor (DFR) - were systematically analyzed. The results demonstrated that the SFR consistently formed a stable three-dimensional spiral flow pattern, exhibiting significantly higher velocity distribution uniformity in the 0.3-0.75 m core reaction zone compared with the UFR and DFR, thereby effectively mitigating short-circuiting and dead zones. All three reactors achieved optimal uniformity at a flow rate of 20 L/min, indicating the existence of an optimal operational condition. Robustness analysis confirmed that the proposed uniformity evaluation method was minimally influenced by the number and arrangement of monitoring points, with the coefficient of variation remaining below 14% under all tested conditions, demonstrating the method's strong stability and practical applicability.