EnviroMix BioMix provides BNR benefits in Olympia, WA

Located in downtown Olympia, Washington, the Budd Inlet Treatment Plant is part of the LOTT Clean Water Alliance, a nonprofit organization that includes the cities of Lacey, Olympia, and Tumwater and Thurston County. For more than three decades, the plant has been providing advanced secondary treatment that includes biological nutrient removal (BNR) to improve the effluent discharged to Budd Inlet, which is located at the southern end of Puget Sound.

Patented, engineered BioMix nozzles located near the tank floor integrate seamlessly with aeration diffusers for anoxic swing zone and mixing limited applications.

Challenge

The LOTT Clean Water Alliance completed construction in 2023 on a landmark BNR process improvement project to significantly reduce the plant’s nutrient discharge and meet Washington State’s removal requirement of less than 3 mg/l total inorganic nitrogen (TIN). The goals of the project were to optimize the BNR process, replace aging equipment, enhance operational control and flexibility, and increase process reliability.

Solution

In lieu of 20+ mechanical mixers, EnviroMix’s BioMix compressed gas mixing system was selected to mix the influent and effluent BNR channels, anoxic selectors, swing zones, and deaeration tanks — all utilizing one centralized compressed air system. Chosen for its industry-leading energy efficiency, BioMix delivers mixing across the entire secondary treatment process while supporting stringent nutrient requirements.

The centralized compressed air system adjusts output to meet the BioMix air demand for mixing multiple applications.

All in-tank components of a BioMix system are maintenance free, non-clogging, and self-cleaning. The system provides complete mixing with proven negligible oxygen transfer. BioMix provides 60% or greater reduction in power usage versus mechanical mixers. The system can accommodate multiple applications, leveraging common compressors and controls, and BioMix’s patented nozzles and headers are compatible with any tank geometry or configuration.

Results

With the inclusion of the BioMix system, this BNR improvement project met LOTT’s unique requirements.

• This project eliminated high internal recycle pumping costs by integrating the first anoxic volume in the existing aeration basins reconfigured into BNR reactors.
• The swing zones can automatically turn anoxic during periods of low loading, e.g. the middle of the night.
• The plant can aerate and mix at the same time in dedicated zones to enable simultaneous nitrification and denitrification, reducing carbon addition in the second stage anoxic tanks.

BioMix delivered the Budd Inlet Treatment Plant enhanced BNR capabilities, the highest energy efficiency versus all alternatives, and the lowest maintenance requirements – with only two duty pieces of equipment (compressors) versus more than 20 mechanical mixers.

Start-up testing demonstration of the BioMix system mixing pattern.