Mount Pleasant Waterworks (MPW) owns and operates two wastewater treatment plants (WWTPs): Center Street and Rifle Range Road. In 2014, the Center Street WWTP was comprehensively upgraded to provide improved treatment and increased capacity.
Nozzle headers are custom designed to avoid tank obstructions.
0,13
hp/1,000 FT3 mixing efficiency
70
% energy savings
Challenge
As part of the upgrade, MPW needed to replace inefficient positive displacement blowers and coarse bubble aerated mixing in the flow equalization basin. They also needed a mixing solution for two biological nutrient removal (BNR) anoxic selector basins which were converted from primary clarifiers.
Solution
EnviroMix’s BioMix Compressed Gas Mixing was selected for both applications.
BioMix systems provide significant power savings compared to mechanical mixers by uniformly distributing mixing energy across the basin floor rather than directing it outward from a localized point. Multiple studies have documented a 60% or greater reduction in power usage versus mechanical mixers and even more versus diffused air mixing.
The BioMix system’s projected energy efficiency was proven during field performance testing; the technology demonstrated a competitive advantage over conventional diffused air or mechanical mixers by providing uniform mixing throughout the basin. The BioMix system provided less than 1% coefficient of variation of solids concentration throughout the tanks, delivering complete mixing with proven negligible oxygen transfer.
Short duration, sequential bursts of compressed air uniformly mix the tank contents.
Due to the energy efficiency of the technology, the work related to the design and installation of BioMix qualified for Green Project Reserve (GPR) funding, a lower interest rate than traditional funding. Black & Veatch submitted a GPR Business Case to South Carolina’s Department of Health and Environmental Control that provided a cost/benefit analysis indicating the expected “green” benefits associated with the upgrade including BioMix. The case indicated a 70% decrease in the power demand versus alternative mixing technology and highlighted the operational benefits of a mixing technology that requires no in-tank maintenance.
Results
BioMix Compressed Gas Mixing technology offers MPW the following advantages:
- Bottom-up mixing in any size tanks
- Uniformly distributed mixing energy
- Improved mixing versus alternatives
- Lowest energy consumption mixing technology
- Minimized and localized maintenance requirements
Due to the years of efficient and low maintenance operations at Center Street, Operations Manager Greg Hill selected BioMix to be installed at MPW’s other facility, Rifle Range Road, when that plant was upgraded in 2020. He stated, “We’ve seen the benefits at Center Street, that’s why we employed BioMix at Rifle Range. It’s very easy to maintain and the efficiency is a big deal for us.”