Optimization of biological reactor capacity in a municipal wastewater treatment plant using GPS-X simulation under high nitrogen loads

Abstract

This study focuses on optimizing the biological treatment performance of a municipal wastewater treatment plant (WWTP) operating under the Daewoo nutrient removal process, particularly under conditions of high-strength nitrogen influent. Changes in influent water quality-driven by the increased use of food waste disposers, sewer system separation, and reduced rainwater dilution-have presented challenges for WWTPs in maintaining compliance with effluent nitrogen and phosphorus standards. Using five years of influent and effluent monitoring data, the GPS-X simulation software, combined with the Activated Sludge Model No. 2d model, was employed to evaluate treatment performance under three influent scenarios: designed-level, high-concentration, and low-concentration conditions. The simulation incorporated detailed operational parameters and demonstrated that the current reactor volume is inadequate for regulatory compliance under high nitrogen loads. The process reconfiguration was found to improve nitrate removal and enhance phosphorus release in the anaerobic zone. These modifications led to simulated effluent concentrations of total nitrogen and total phosphorus consistently below target limits, validating the effectiveness of the proposed upgrades. This study highlights the value of simulation-based planning and the need for flexible design strategies in small-to mid-scale WWTPs facing evolving influent conditions.