Optimizing Clarifier Performance Using Hydrocyclone Technology: Lessons from Full-Scale Implementation

Presentation Description: The Los Angeles County Sanitation Districts (Districts) operate the Whittier Narrows Water Reclamation Plant (WNWRP), a 60-year-old facility originally designed for organic matter removal. While the plant has been upgraded to meet nutrient limits and support recycled water production, its ability to handle higher flows is constrained by overloaded and shallow clarifiers and a limited site footprint. Compounding these challenges, the plant often experiences poor sludge settleability during the rainy winter season, which reduces solids removal efficiency and impacts effluent quality.

To address these challenges, the Districts implemented hydrocyclone technology to improve clarifier performance without physical expansion. Installed on the return activated sludge (RAS) line, the hydrocyclone system works by separating heavier, better-settling biomass from lighter, filamentous material. Denser sludge is recycled back into the system, while lighter solids are wasted. This selective separation process improves sludge compaction, supports bioflocculation, and lowers the sludge volume index (SVI), a key indicator of settleability.

Full-scale testing showed that initial hydrocyclone operation effectively reduced SVI and stabilized clarifier operation, especially during periods of seasonal stress. However, extended or intensive operation revealed trade-offs: excessive shear within the system began to degrade floc structure, leading to deflocculation and an increase in turbidity and suspended solids in the clarifier effluent. Microscopic analysis helped confirm and explain these trends, providing visual evidence of changes in sludge structure that aligned with observed performance issues.

In response to these findings, the team adopted a dynamic control strategy—adjusting the number of active hydrocyclone units and cycling operation based on real-time performance data. This flexible approach allowed the plant to maintain improved settleability while avoiding negative impacts on effluent quality.

This presentation will highlight key takeaways from over a year of full-scale operation, including performance trends, practical implementation strategies, and the role of visual observations in process optimization. Attendees will gain insight into how hydrocyclone systems can enhance clarifier performance in existing facilities, especially where expansion is limited, and seasonal variability presents ongoing challenges. The presentation will also touch on plans to expand the technology to other Districts’ facilities and refine control strategies for broader application.