Located 45 miles south of Nashville, the city of Columbia, Tenn., has a population of approximately 36,000 people and is the county seat of Maury County.
As part of its wastewater system, the city maintains 317 miles of gravity-enforced main sewer lines, 25 pump stations and a 14 million-gallon-per-day (MGD) wastewater treatment plant. In recent years, Columbia has engaged in sewer rehabilitation projects to help reduce or eliminate system overflows, including renovating and replacing several existing pump stations.
Among the pump stations slated to undergo scheduled upgrades in early 2020 was the Santa Fe Pike pump station. But before those repairs could begin, the station experienced a major pump failure during the spring of 2020 that led to sewage overflows, spurring the city of Columbia to enlist Xylem Rental Solutions for emergency pump rental. The local Nashville branch quickly dispatched a Godwin HL250 diesel pump for an emergency sewer bypass system.
Once the initial crisis was under control, the city of Columbia decided to move ahead with the $1.2 million planned upgrades for the Santa Fe Pike facility. City officials hired W&O Construction as the contractor on the project.
To maintain treatment operations while the upgrades were completed, W&O Construction needed to set up a temporary sewer bypass system, and because rehabbing the pump station would take several months to complete, the Columbia Wastewater Department made the decision to switch to electric-drive pumps to improve pumping efficiency and reduce operating costs. For temporary bypass projects that last longer than three months, electric bypass pumps are a cost-effective option as they do not rely on expensive diesel fuel.
However, Xylem Rental Solutions hit a snag in the process — the only Godwin electric option in the local fleet (Godwin HL250 pump with a 450 hp motor) was too powerful for the site’s 400-amp service. An alternative pump solution wasn’t suitable to handle modern trash like baby wipes and disposable cleaning wipes often found in today’s wastewater stream, which would lead to frequent clogs.
“The local station didn’t have the correct electrical setup for the 450 hp pump,” explained a pump supplier representative for Xylem. “We knew clogging would be an issue [with an alternative].”
Seeking to ensure the Columbia Wastewater Department had the right electric pump and equipment for its temporary bypass system, Xylem’s Nashville branch tapped the experience and expertise of its national Xylem Rental Solutions base to identify the best solution within its expansive rental fleet.
Working with Xylem’s Ken Albaugh, the Nashville team looked to Xylem’s Flygt pump line. The pump supplier representative said that within 90 seconds, Albaugh went through the Flygt options and identified a 3000 series Flygt pump with priming for the Santa Fe Pike pump station project.
For municipalities like the city of Columbia that need to engage in lift station repairs or plant upgrades, Flygt 3000 Series submersible pumps are a cost-effective and environmentally friendly rental alternative that provide a quiet, efficient, and easy-to-install bypass solution for many applications.
Additionally, Xylem offers a wide horsepower range for its Flygt 3000 electric submersible pumps — from 2 to 470
hp — that can handle flow rates up to 16,000 gallons per minute (GPM) with heads up to 400 feet. The broad parameters of the Flygt 3000 series enabled Xylem to deliver the proper pump for this application.
In particular, the Flygt 3000 Series pumps feature patented N-technology with innovative self-cleaning impellers, which are designed to prevent clogs and build ups. Made with robust, hard iron impellers that are corrosion and abrasion resistant, they also offer a long life span.
The Xylem team quickly identified the Flygt N 3312 submersible pump as the best model for the Santa Fe Pike pump station bypass. But while the Flygt N 3312 met the flow and head characteristics, it was too large to fit down the sewer manhole. To address this new challenge, the Xylem team used a horizontal, dry pump installation. The Flygt N 3312 pump was delivered to Xylem’s dewatering fabrication center in Carterville, Ill., where a crew built stands for both the pump and priming system within one working day. By the end of the weekend, the custom-engineered pump and priming system were delivered to the temporary bypass site in Columbia, Tenn., where the rental solution operated continuously for the duration of the bypass.
“We took the technology off the Godwin priming system and married it to the Flygt pump performance,” explained the pump supplier representative of the unique solution.
With the Flygt N 3312 electric pump serving as the primary pump and the HL250 diesel pump still on-site as the backup pump, the temporary bypass system has been running continuously for several months with no issues and no clogging.
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 combination of diesel pumps and electric submersible pumps allowed the temporary bypass to operate at maximum efficiency, offering a flexible solution for fluctuating wastewater flow levels. Additionally, the use of an electric bypass pump as the primary pump has improved pump efficiency and reduced costs, resulting in savings to the city of nearly $124,000 to date.
Renting the equipment versus the capital expenditure of purchasing it outright provided another significant cost savings for the city of Columbia. 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.
For larger bypass projects, end users do not have justification for the cost of the pumps. 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. WW
About the Author: Bill Beasley is a regional sales manager with Xylem.