Lift stations are an essential component of many municipal and industrial wastewater collection systems to move sewage from low to high elevation. Such is the case for the John Street lift station in Monroe County, New York, which serves both a large residential community and the nearby campus of Rochester Institute of Technology (RIT).

Seeking to increase efficiencies, lower utility costs and reduce overall pump maintenance for the facility, Monroe County commissioned system upgrades for the lift station, requiring a bypass system to move a peak flow of 12 million gallons per day. Dakksco Pipeline Corp. was named the bypass contractor for the project and worked with Xylem to design and install a temporary system to transfer water and effluent, ensuring an uninterrupted ow of wastewater for both the RIT campus and neighboring residential area.

“There was quite a bit of flow from both directions to maintain until the new station came online,” said Dakksco Pipeline Corp. owner Dan Morin.

Existing flows had to be maintained during construction so the design for the pump station improvements featured a layout that would accommodate a temporary bypass pump and a construction sequence that would provide for continuous service. The fluctuating student population at the RIT campus significantly impacted flow conditions, which range from 5 million gallons per day on average to a peak flow of 12 million gallons per day, and just 1.5 million gallons per day during the summer months when fewer students stay on campus.

Solution

To handle the lift station’s extremely varied flow, Xylem designed a temporary bypass system that used several pumps, including a Godwin Dri-Prime CD225M 8-in. electric pump, a Godwin Dri-Prime CD300M 12-in. diesel pump and a Flygt N-Technology N 3301 electric submersible pump.

Using a combination of diesel pumps and electric submersible pumps allowed the temporary bypass to operate at maximum efficiency and offered a flexible solution for fluctuating wastewater flow levels.

The Godwin Dri-Prime CD225M electric pump and Flygt N 3301 electric submersible pump served as the primary pumps for the bypass. Using the electric pumps allowed the contractor to plumb into the existing piping system, which helped improve pump efficiency and reduce costs. With limited space near the RIT campus, the flexible, modular design of the Flygt submersible pump easily fit the project’s compact footprint.

Backup systems are essential in any bypass operation as they protect against instances of unexpected high flows or primary system failure during pipe rehabilitation. The combination of reliable primary pumps, supported by a robust backup system, offers peace of mind as service is guaranteed to be maintained during loss of power, whether from a scheduled outage or a natural disaster.

The Godwin Dri-Prime CD300M 12-inch diesel pump was used as a backup pump in case of a power outage or system clog shut down the other two pumps. Housed in a specially designed acoustically silenced enclosure to minimize noise pollution, the pump reduced sound levels to 69 decibels at 30 ft, meeting OSHA noise exposure standards.

“Diesel pumps can get pretty loud. The critically silenced Xylem unit drastically reduces noise levels,” said the pump supplier representative. “This was important because the project was located close to student housing on the RIT campus. Ultimately, there was no impact on student life.”

The diesel pump model used for this project also has the capacity to handle solids up to 3.7 inches in diameter, allowing a range of slurries and fibrous materials to easily pass through the pump’s impeller and resist clogging.

To better handle the lift station’s varied flow, Xylem enhanced the temporary bypass system with two Godwin variable frequency drives (VFDs). The addition of VFDs enabled operators to control the motor speed and reach the required duty point to ensure optimum operating efficiency throughout the project.

Each pump activated only when increased flows called for additional pump activity. When students were in class, the VFDs reduced the speed of the pumps or put them in sleep mode and when students returned to their residence halls, the VFDs would level up.

Results

The systems started bypassing in August 2018 and ran 24/7 until November. It was set to emulate the response and flows of the station’s permanent equipment.

Leveraging its broad product portfolio and engineering expertise, Xylem helped Dakksco overcome unique site challenges with a rental solution that combined pumps and specialty products from proven brands, resulting in greater efficiency and peace of mind.

Remote connectivity eliminated the need for onsite 24/7 pump watch duty, saving Dakksco — and Monroe County — thousands of dollars in man hours. The bypass system also was equipped with an auto-dialer alarm agent to alert Dakksco employees about potential pump issues via any smart device, giving remote visibility to pump activity in real time.

Although the remote monitoring capability provided additional reassurance, Morin said his team never had to engage the feature because the bypass system performed as designed.

“It’s a valuable feature, but we never had to use it because the bypass system worked flawlessly,” Morin said.

Renting the equipment vs. the capital expenditure of purchasing it outright also provided a significant cost savings for Monroe County. Pump rental solutions offer the flexibility to handle complex and evolving applications without having to invest in expensive pumping equipment that is not required on an ongoing basis.

Due to aging infrastructure and increased system demand, sewage bypass projects have become a critical component of many community investment projects to allow for necessary maintenance and repair.

Darrin Ruiz is senior applications engineer for Xylem Dewatering Solutions.

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