LACSD Adopts an Innovative Baffle System for Restoring Clarifier Capacity and Maximizing Performance

Presentation Description: A simple and affordable approach to achieve fast process improvement and easy capacity gains has been adopted by LACSD. This method utilizes plant-specific data and computational fluid dynamics (CFD) analysis to determine the most cost-effective baffle system to increase capacity and improve performance. A CFD model was developed to replicate the physical characteristics and performance of secondary clarifiers at LACSD’s Pomona Water Reclamation Plant (WRP). Four baffles were proposed: a flocculation perforated baffle, a mid-tank perforated baffle, a surface deflector, and a deep canopy. The baffle system improves the hydraulic regime within the clarifier by minimizing the adverse effects of density currents and reduces the level of dispersed solids (pin floc) by creating an optimal flocculation environment. This baffle system was designed and installed in one of the secondary clarifiers at the Pomona WRP. A pilot study was initiated to perform a parallel comparison between modified and unmodified clarifiers.

The pilot study demonstrated that the modified clarifier consistently outperformed the unmodified one, particularly under higher hydraulic and solids loadings. Significant improvement in effluent quality was achieved, with a 95% reduction in ESS. Under stress testing, the modified clarifier maintained low ESS levels around 1.5 mg/L, while the unmodified clarifier exhibited elevated ESS concentrations with a median of 18 mg/L. Settling performance was markedly improved in the modified clarifier, with ESS levels an order of magnitude lower. Additionally, the modified clarifier sustained a more compacted sludge blanket, 4-5 ft lower than the unmodified clarifier. The insights gained from the pilot study informed further design improvements for plant-wide secondary clarifier enhancement feature implementations. A resiliency test was also performed, and the results showed that the modified clarifier did not experience solids washout for at least 1.5 hours under up to 58% more flow. This performance aligns with the CFD transient analysis results and provides clear evidence that the modifications significantly improved solids capture and increased clarifier capacity. The baffle systems will enhance clarifier resiliency, providing extended operational stability and delaying failure during storm events. Building on these findings, LACSD is in the process of implementing the baffle systems at other treatment plants.