With a population of 677, the town of Harleyville, S.C., located 60 miles northwest of Charleston, was looking to upgrade its aging lift stations to increase efficiencies, lower utility costs and reduce overall pump maintenance for its municipal wastewater facility.
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.
The 25-year-old lift stations each suffered frequent clogging, expensive maintenance and repair, and skyrocketing monthly utility bills related to extended pump run times. The reliability of the entire wastewater transfer system derailed every three to six months, when a pump failed or a station backed up because the pumps were unable to keep up with demand.
Working with global engineering consultant URS Corp., the town began its system update by retrofitting one lift station with energy-efficient wastewater pumps from Grundfos. The improvement led to upgrades at two additional lifting stations. As a result, Harleyville has reduced energy use by 35% and cut $25,000 in annual maintenance and repair expenditures.
“Due to the greater pumping capacity of the Grundfos SLV pumps, the station’s run time dropped by roughly 80%,” said Dan Huggins, P.E., project manager, URS Corp., who noted that peak pump operation fell from an average of 18 hours per day to 3.5 hours per day (factoring in median rainfall and infiltration amounts).
The additional pump capacity combined with the reliability of the SLV Series’ pumps made an immediate impact on the system.
“Since power consumption accounts for 85% of a pump’s life-cycle costs, likely the most dramatic savings for this project is the ability to maximize pumping performance, across each lift station,” noted Robert Pruit, principal of Carolina Pumpworks, who worked with engineer Huggins to incorporate the SLV pumps. “Some of the town’s outdated pumps were running nearly non-stop during increased flow events to keep the wet wells from overflowing. 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 to deal with the increased flow.”
In all, the three newly upgraded duplex lift stations each feature two 5.5-hp, 1,750-RPM three-phase pumps that alternate operation according to the station’s level control system, which offers both 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-in. in diameter pass freely through the solids-handling pump without jamming.
Carolina Pumpworks also provided custom-designed control panels to meet Harleyville’s requirements. The control panels included the Grundfos IO113 pump monitor relays, that together with the pump sensors, provides more protection against thermal overload and seal leakage.
The transformation began in October 2011 when—with the aid of state grants— the town installed its first SLV pump system at Pump Station 5 as a retrofit application. This aging lift station served 125 residents and pumps sewage one-quarter mile to the next manhole and was plagued with service issues.
“The old pumps frequently clogged and the resulting motor stress forced a pump removal—and repair— roughly every six months,” said Harleyville Maintenance Superintendent Tommy Weeks. “Pump maintenance for this station alone was running nearly $4,000 a year.”
Designed to handle raw unscreened sewage, effluent and process water in municipal applications, the SLV series pump with its recessed super vortex impeller was an ideal solution for the initial lift station retrofit. The upgraded Lift Station 5 has been operating maintenance-free from its initial start-up in 2011 without a single incident of clogging.
URS project engineer Dan Huggins knew that when the time came to rebuild Lift Station 4—the weakest link in the town’s wastewater system—they would tailor the station around the Grundfos SLV pumps.
When more state funding became available in 2013, Harleyville upgraded two additional lift stations with the SLV submersible pumps. Both projects were up and running by December 2013.
The original 4-ft 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 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 estimated that the new pumps at Lift Station 2 will eliminate approximately $4,000 in annual maintenance costs.
The goal moving forward for Harleyville will be to upgrade the remaining lift stations with the SLV pumps, when more state funding becomes available.
Source: Grundfos
