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Colona Wastewater Treatment Plant Upgrade


With a 40-year-old activated sludge wastewater treatment plant (WWTP) that consumed energy at an unacceptable rate, the City of Colona knew that its plant was approaching the end of its operational life. Although Colona’s population is just over 5,000 now, a 40% increase is expected in the next two decades. To keep up with this future growth, WWTP efficiency and reliability upgrades were necessary.


Shive-Hattery worked with the City of Colona to design and install several WWTP facility improvements to increase energy efficiency and reduce power consumption, boost plant operating capacity, and extend the service lifetime of the plant. Topographic surveys, 3D scanning, design, construction document preparation, Illinois Environmental Protection Agency (IL-EPA) permitting application services and assistance, and bidding and construction services were all included in the project.
After completing a study to compare Colona’s WWTP processes to current IL-EPA design guidelines, most of the original equipment in the plant was replaced due to age. Raw sewage pumps, aeration tank diffusers and blowers, sludge pumps, the supervisory control and data acquisition (SCADA) system, emergency generators, and other electrical equipment were all traded for new, state-of-the-art equipment that consumes less energy and streamlines plant operations.
This extensive WWTP overhaul was led by Shive-Hattery and helped the City of Colona reduce energy usage in several ways. Blowers were resized and equipped with variable frequency drives (VFDs) that adjust the blowers’ electric motor speeds by modulating power delivery. The worn raw sewage pumps at the head of the plant were replaced with new, energy-efficient models and also equipped with VFDs. A new SCADA system now allows for precise regulation of DO (dissolved oxygen) levels and aeration throughout the plant, reducing energy waste. Alarms are integrated with the facility’s SCADA system so that operators receive early warning of potential problems.
Sludge-handling capability was increased significantly with the addition of a new, two-compartment aerobic digester that offers nearly twice the capacity of the existing system. The existing aerobic digesters were fitted with fine-bubble diffusers and converted to additional aeration tanks that are designed for maximum oxygen transfer. This update prepares the City of Colona for future nitrogen removal requirements set forth by the IL-EPA.
To extend equipment life, Shive-Hattery also completed necessary WWTP maintenance tasks. The north secondary unit was repainted to protect against corrosion. Press cloths and frames were replaced to improve the performance of the plant’s filter press.
The facility emergency load was also evaluated, and a new generator was sized correctly in order to maintain minimal facility operation during a power outage. To accommodate this emergency generator load and new equipment, the power distribution system was analyzed and updated. 


The City of Colona plant upgrade serves as a prime example of how wastewater treatment plants can improve energy usage in aeration projects without breaking the bank. By replacing outdated equipment that was at (or beyond) its useful life on a planned schedule before equipment failed, the City of Colona doesn’t have to worry about emergency shutdowns or failure.
Environmental impacts were significantly reduced as a result of the WWTP upgrades. Average ammonia levels were reduced by 92%; average TSS (total suspended solids) concentrations were reduced by 20%.
The City of Colona is also experiencing significant financial savings as a result of these improvements. The facility expends 46% less energy per volume treated per day (equating to more than $17,000 in annual savings). Due to the energy-efficient improvements made, the local utility provided $20,630 in rebates for the project (equaling 1.2% of total construction costs).
Despite energy rate volatility, Colona will be able to keep wastewater treatment expenditures low as the community continues to grow in the future.
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