Efficiency in the Air

Contract wastewater operators—Alliance Water Resources (AWR)—for the City of Bowling Green, Mo., wanted to reduce overall operating costs at their facility. The existing positive displacement blowers, jet aeration system and motive mixing pumps were targeted for evaluation and potential upgrade.

To achieve these goals, the city looked to AWR and Environmental Dynamics Inc. (EDI) for answers.

Solution

AWR partnered with EDI to improve the plant’s aeration system. AWR and EDI analyzed the existing system against a fixed grid fine-bubble membrane aeration system for the two aeration basins. The energy savings of the fine-bubble system and the corresponding return on investment proved attractive. AWR applied for and obtained an energy efficiency grant from the local electric company to help pay for the conversion.

EDI replaced the plant’s jet aeration system with 96 FlexAir MiniPanel fine-bubble tube diffusers in each of the plant’s aeration basins. The increased oxygen transfer capabilities of the fine-bubble system compared to the jet aeration system results in a reduced overall airflow requirement. The blowers were also outfitted with variable frequency drives linked to dissolved oxygen meters, which allow for efficient pacing of the blowers to meet plant loading dynamics.

Results

With AWR’s improvements to the plant’s blowers and EDI’s fine-bubble aeration system in place, electricity consumption dropped by 40% per month on average. Before the project, monthly energy consumption for the plant averaged 117,480 kWh; after the project was completed, the plant’s monthly energy consumption on average measured 68,394 kWh. The city expects a payback on the investment well before its three-year projection.

“We were very pleased with EDI’s work,” said Daniel Gummersheimer, division manager for Alliance Water Resources. “From the proposal to the installation, there were no hiccups. Their design and products worked perfectly from the first time we turned the blowers on. Everything went very smoothly.”