Clean Water Plant (CWP) in Grandville, Michigan
Secondary treatment aerial view
In 2024, the city of Grandville completed a FlexZone Adaptive Process Volume System upgrade at the Clean Water Plant (CWP) to optimize its bioreactor environment and improve aeration control of dissolved oxygen (DO).
Challenge
The system was designed to prevent over-aeration and enable denitrification via anoxic environments for nitrate reduction and alkalinity recovery. The Grandville CWP was focused on addressing three main goals:
- Reclaim alkalinity
- Reduce aeration energy consumption
- Lower effluent nitrate (NO3-N)
Solution
Released by EnviroMix in 2022, the FlexZone is a patented, versatile secondary treatment solution that integrates BioMix Compressed Gas Mixing, diffused aeration, instrumentation, and proprietary control algorithms to ensure precise aeration control and meet treatment objectives.
The FlexZone was easily incorporated into Grandville’s existing bioreactor, utilizing existing aeration grids and instrumentation while adding new air flow control equipment, BioMix Compressed Gas Mixing, and upgraded controls.
The FlexZone dynamically adapts anoxic and aerobic environments to changes in loading and temperature. In addition to managing bioreactor volume utilization, Grandville’s FlexZone was designed to control DO with two primary benefits in mind: prevent over-aeration and incorporate denitrification to recover alkalinity.
Grandville’s FlexZone configuration
Grandville’s FlexZone was strategically placed in the second pass of a three-pass aeration train. The first pass and the last pass remained aeration only. The design minimized modifications to the existing equipment, ensuring minimal downtime and cost-effective installation. The FlexZone is divided into three subzones, each of which can be independently controlled with its own mixing and aeration grid.
As the system’s oxygen demand increases, the subzones individually transition from mix-only to aerated environments. Likewise, as oxygen demand declines, the subzones transition to mix-only, anoxic environments.
The FlexZone’s complementary mixing and aeration equipment offer concurrent operation, allowing Grandville to adapt process environments to meet current conditions without sacrificing treatment capacity to meet future design loading conditions.
BioMix Compressed Gas Mixing in operation
Results
The FlexZone upgrade has delivered Grandville the following benefits:
- 20% reduction in aeration energy consumption for an estimated annual energy cost savings of $60,000.
- Immediate process improvements due to the adaptable transition between aerobic and anoxic environments within the same reactor.
- Promotion of denitrification to reduce effluent nitrate and reclaim alkalinity.
0.16 HP/1,000 FT3 Mixing Efficiency
40% effluent nitrate reduction