Reducing energy costs in wastewater treatment: Exploring low DO and suboxic approaches

Energy is one of the most significant operating costs at Water Resource Recovery Facilities (WRRFs), and aeration alone can account for nearly 60% of that energy use. As utilities seek cost-saving strategies that also support sustainability goals, many are exploring how to optimize biological nutrient removal processes without compromising performance.

That’s where low dissolved oxygen (DO) and suboxic biological nutrient removal (SBNR) come in. These approaches, which operate at DO levels as low as 0.2 mg/L, are proving that WRRFs can reduce energy use and still meet stringent nutrient removal requirements.

In their recent article in The Wastewatcher, Carollo’s Michelle Young and Natalie Beach explore two real-world examples of facilities successfully implementing low DO strategies.

Real-World Applications of Low DO Wastewater Treatment

The article showcases two facilities taking different paths toward low DO optimization: the City of St. Cloud’s NEW Recovery Facility (NEWRF) and the Sanitation Districts of Los Angeles County’s Pomona Water Reclamation Facility (WRF).

NEWRF retrofitted its existing system to transition from traditional DO setpoints of 2.5 mg/L to low DO conditions below 0.8 mg/L. By leveraging a most-open valve aeration control strategy, the facility achieved up to 30% energy savings while improving nutrient removal consistency and system reliability.

Meanwhile, Pomona WRF underwent a retrofit, adding high-efficiency blowers, precision valves, and advanced control systems. The result? Aeration energy consumption dropped from 1,300 kWh/MG to just 550 kWh/MG, well below industry norms, while maintaining excellent effluent quality.

A Scalable Approach to Energy Savings in WRRFs

Low DO and suboxic BNR strategies are not one-size-fits-all, but as Michelle and Natalie note, they’re becoming increasingly viable for WRRFs of all sizes. With the right planning, monitoring, and control systems in place, facilities can reduce their energy footprint and build long-term operational resilience.

Want to learn more about how low DO treatment strategies are reshaping the energy future of wastewater? Read the full article in The Wastewatcher.