Challenge
Missouri City, Texas needed to expand and modernize the Steep Bank Flat Bank Wastewater Treatment Plant (WWTP) to consolidate an aging Municipal Utility District facility. The existing plant design limited capacity and efficiency, while increasing maintenance demands and power costs. The City required a solution that could increase treatment capacity without constructing new secondary treatment structures, while also improving energy efficiency and long-term operational performance.
Solution
HR Green was retained as Owner’s Advisor to guide the expansion. Key improvements included:
- Process Conversion: Transitioned from extended aeration to complete mix with nitrification, allowing higher organic loading and process consolidation.
- Aeration System Upgrades: Installed fine bubble diffusers and high-efficiency turbo blowers to reduce connected horsepower requirements while increasing aeration capacity by 150%.
- Automation and Controls: Implemented automated dissolved oxygen blower control and open-valve routines to optimize energy use and reduce manual oversight.
Together, these measures modernized the plant’s biological treatment process, streamlined operations, and addressed growing demand.
Benefit
The expansion increased treatment capacity from 3.0 MGD to 4.5 MGD without constructing additional secondary treatment structures. Aeration horsepower requirements dropped from 638 HP to 510 HP, saving approximately $176,000 annually in power costs. These upgrades not only improved efficiency and reliability but also delivered long-term cost savings for the City, allowing the facility to continue serving the community sustainably.
