In 2009, the City of Menominee, Mich., decided its wastewater treatment plant was consuming excessive electrical power and faced a much-needed upgrade. The plant was using a 1044-unit ceramic disc system with an acid gas cleaning system. This system, installed in 1988, was deteriorating and needed to be replaced. The city worked with Honeywell Energy Services Group to reduce its electrical power consumption under a guaranteed contract. The city’s wastewater treatment plant had a significant potential to reduce power consumed, specifically in the activated sludge process. However, with the existing ceramic disc system, it was consuming 1,800 kWh per day.
Solution
Honeywell contracted with Energenecs and Environmental Dynamics International (EDI) to provide a cost-effective solution. The city wanted a new system that offered operating flexibility and low power consumption. Honeywell evaluated several options, and selected the option that provided the highest system efficiency. EDI installed a MiniPanel fine-bubble aeration system with a membrane density exceeding 30%, greater than the old ceramic disc system. Energenecs provided new Kaeser positive displacement blowers and an advanced dissolved oxygen monitoring system. This new control system allows the plant to monitor the levels of dissolved oxygen in the basin, so that it can more accurately gauge the amount of air the pumps are required to provide during a 24-hour period. This further reduces the electric power consumption during periods of low oxygen demand.
Results
Initially, the new EDI aeration system paired with the existing blowers and controls reduced the electrical power consumption from 97 bhp to 43 bhp. After the new blowers and control system were in operation, the electrical power consumption was reduced by an additional 12%, bringing the total reduction to 56%. This translates into an average annual savings of $29,000. The new system is expected to pay for itself by 2016.
“Working with EDI was great,” said Mike Thorsen, Infrastructure Alternatives employee and Menominee plant superintendent. “The guys we worked with were efficient and easy to work with. The plant has been running smoothly since putting in the system.”