MPW selects EnviroMix BioMix for upgrade at second plant

The population of Mount Pleasant, SC, has more than doubled since 1990 and is expected to increase another 44% by 2050. Rapid levels of growth and development, along with evolving regulations and aging infrastructure, put pressure on the city’s water and wastewater systems to meet the increased demand. Mount Pleasant Waterworks (MPW), the water and sewer utility that serves the community, owns and operates two wastewater treatment plants (WWTPs): Center Street and Rifle Range Road.

The anoxic zone, mixed by BioMix, provides the optimal conditions for denitrification.

Challenge

MPW expanded the Rifle Range Road WWTP in 2020, increasing the facility’s treatment capacity from an annual average of 6 MGD to 9.2 MGD to meet the city’s anticipated needs through 2035. The Rifle Range Road upgrade covered nearly all aspects of the facility, including the activated sludge process. The project utilized a construction management at risk (CMAR) delivery method which allowed for nearly 15%, or $8.7 million, in value engineering savings.

Solution 

As part of the expansion and upgrade, the existing bioreactors with anoxic selectors were converted to flow equalization tanks, and three new bioreactors were constructed. EnviroMix’s BioMix Compressed Gas Mixing was utilized in the new anoxic selectors.

BioMix provides optimal anoxic mixed conditions by firing programmed, short-duration bursts of compressed air through patented, engineered nozzles located near the tank floor. BioMix enables the Rifle Range Road WWTP to save approximately 40% on operations and maintenance versus conventional submersible mixing technology.

Located beside the tank, the valve module is easily accessible. 

Results

MPW had previously worked with EnviroMix at their Center Street WWTP where the BioMix system was selected for their flow equalization tank and anoxic selectors. Based on their outstanding experience with the technology — where BioMix utilizes adjustable firing parameters that enable ideal mixed conditions with proven negligible oxygen transfer — they insisted on installing BioMix in the new anoxic selectors.

With this expansion and upgrade, MPW is positioned to protect the environment and support the community’s quality of life for years to come.

Duty and standby compressors charge the receiver tank which supplies compressed air to the valve module.