Using computational fluid dynamic modeling, engineers can improve clarifier capacity greatly to accommodate peak wet weather flows. Peak wet weather flow (PWWF) can present a substantial challenge for wastewater treatment plants, potentially causing such problems as collection system overflows, hydraulic failures within a plant, process failures in any number of process units, or a combination of these events. A municipal wastewater treatment plant’s critical design condition usually is met under PWWF conditions. The capacity of an activated sludge process often depends on the performance of a secondary clarifier. Failure of a secondary clarifier can cause elevated effluent suspended solids (ESS) concentrations that may lead to permit violations. For plants required to perform nutrient removal, elevated ESS levels may result in violation regardless of how other aspects of the biological process perform. However, if an activated sludge process can be optimized to handle PWWFs, the expense associated with constructing additional secondary clarifiers can be avoided.