Nearly 15,000 hours without breakdown in wastewater plant upgrade
With a population of 677, the small town of Harleyville, South Carolina, was looking to upgrade its aging lift stations to increase efficiencies, lower utility costs and reduce overall pump maintenance for its municipal wastewater collection system.
The old lift stations suffered frequent clogging, and were too expensive to maintain and repair. Every three to six months, a pump failed, or a station backed up because the pumps were unable to keep up with demand.
Working with global engineering consultant AECOM, the town began its system update by replacing one lift station with energy-efficient wastewater pumps from Grundfos. The improvement was dramatic and led to upgrades at two additional lifting stations.
“We now have a combined total of 14,593 operating hours without experiencing a single clog or need for service on the Grundfos pumps,” says Maintenance Superintendent for the Town of Harleyville, Tommy Weeks.
The town has also reduced energy use by 35 percent, resulting in an annual cost saving of $10,000.00 in electricity, and cut $25,000 in annual maintenance and repair expenditures.
The town employed six lift stations – five of which utilized grinder pump systems from 1985 – to consolidate wastewater and pump it to a centralized wastewater processing and treatment plant.
Efficient pumps reduce run times and energy use
Dan Huggins, P.E., project manager, AECOM, says that the station’s run time dropped by roughly 80 percent, adding that pump operation fell from an average of 18 hours per day to 3.5 hours per day.
Robert Pruit, principal of Carolina Pumpworks, worked with Huggins to incorporate the SLV pumps to the station. He adds that since power consumption accounts for 85 percent of a pump’s life-cycle costs, the most dramatic savings for the project was the ability to maximize pumping performance, across each lift station.
“Some of the town’s outdated pumps were running nearly non-stop,” he says, “for example, when rainfall swelled the volume of flow into the town’s sewer lines, both of the pumps at each of the individual lift stations would typically run for extended periods of time.”
Added Capacity and Redundancy
In all, the three upgraded duplex lift stations each feature two pumps that alternate operation according to the station’s level control system. This offers system redundancy and added capacity during increased flow events.
To overcome prior difficulties with pumps clogging, the team selected the optional SuperVortex impeller, to help ensure that solids up to 3-inches in diameter pass freely through the solids-handling pump without jamming.
Carolina Pumpworks also provided custom-designed control panels to meet Harleyville’s requirements, including the Grundfos IO113 pump monitor relays, that together with the pump sensors, provides protection against thermal overload and seal leakage.
“The old pumps frequently clogged and the resulting motor stress forced a pump removal and repair, roughly every six months,” recalls Weeks. “The new pumps have really helped mitigate any maintenance costs that we have had in the past due to pump ‘burn-out’ and clogging. Pump maintenance for this station alone was running nearly $4,000 a year.”
State Funding Leads to Additional Pump Upgrades
With the help of state funding in 2013, the success of Lift Station 5 led Harleyville to upgrade two additional lift stations with the SLV submersible pumps.
The original 1.2-metre (4 foot) wet well at Lift Station 4 was too small for the raw sewage intake and required a complete overhaul. The pumps in Station 4, which serves 250 people, were running nearly continuously in an attempt to keep up with the sewage flow. As a result, the station lost a pump to repairs roughly every three months, resulting in an annual maintenance cost of $15,000.
Following completion of the Lift Station 4, a local hotel and an apartment complex were constructed nearby. The high-performing lifting station has not faltered in managing the increased sewage flow from these facilities.
No repairman needed
Following the reconstruction of Lift Station 4, the town upgraded an additional lift station with two similar Grundfos SLV series pumps. Like the other aging lift stations in the Harleyville system, the outdated pumps in Lift Station 2 required service every six to seven months.
Weeks estimates that the new pumps at Lift Station 2 will eliminate approximately $4,000 in annual maintenance costs.
When more state funding becomes available, Harleyville will upgrade the remaining lift stations with the SLV pumps.
“We’ve come a long way to ensuring the integrity and operational efficiencies of our wastewater system,” Weeks says, “there are zero maintenance costs or issues with the new pumps. I chuckle each time the repairman—accustomed to a significant amount of business from us—calls to ask when we think one of the pumps will be in for repair.”