The Fond du Lac, Wis., Regional Wastewater Treatment Facility treats the city of Fond du Lac’s wastewater along with that of 18 neighboring entities. The water is then discharged to nearby Lake Winnebago. The city’s population is 45,000, but with neighboring communities included, the plant handles flow from about 75,000 people. The average hydraulic flow capacity of the plant is 9.84 million gal per day (mgd) with a peak flow of 50 mgd. On average, the facility, which is located at the south end of Lake Winnebago, treats approximately 7.5 mgd of wastewater.
Neighborhood wastewater collection systems are primarily gravity-driven. The wastewater is then collected at 17 area lift stations, where it is pumped into a system of mains—also gravity-driven—that lead to the wastewater treatment plant. Of the 17 pump lift stations, 11 are submersible and do not use variable-frequency drives. Overseeing the maintenance of these submersible stations—which basically consist of a pit and a panel—as well as rising energy costs, are two stiff challenges for Fond du Lac’s wastewater treatment facility.
Pump System Solution
In July 2015, Fond du Lac, under the guidance of Flygt engineers and overseen by city personnel, installed a Concertor pump system in a duplex pump station located at Wild Life Acres, replacing one of the old 5-hp pumps with a new Flygt Concertor. The Concertor in the well is the lead pump and is expected to handle all flows in normal operation. The Wild Life Acres station was selected because of the long length of the lateral.
Concertor is the world’s first wastewater pumping system with integrated intelligence. It combines a fully integrated control system with IE4 motor efficiency, patented adaptive impeller N-hydraulics, and intelligent functionalities. Its control system integrates a processor, software, sensors, power electronics, a synchronous electric motor and self-cleaning hydraulics into a submersible shell.
The term “intelligent” refers to the system’s ability to automatically deliver optimal pumping performance while reducing the total cost of ownership. This system delivers cost savings, a more precise level of motor control, reduced risk of clogging, energy savings and comprehensive data reporting.
By integrating a control system that can automatically adapt to a changing pumping environment, optimal performance is achieved, while total cost of ownership is reduced. Built-in intelligence makes it quicker and easier to set up and operate functions that would otherwise require a sophisticated monitoring and control system. All of this is achieved with a smaller control cabinet footprint.
The system’s users are able to select from a variety of performance fields instead of being limited to a fixed performance curve, which allows for enhanced operational flexibility. The system’s adaptive technology automatically selects the duty points to optimize performance; fine-tuning on site also is available without having to change the impeller.
Concertor’s built-in sump and pipe cleaning reduce odor and maintenance, delivering a clean, safe system. Clog detection and pump cleaning functions ensure clog-free operation. On-board self-monitoring functionality prevents overheating and extends pump lifetime, while automatic rotation settings prevent incorrect impeller rotation.
Energy savings have the potential to be substantial, starting with the efficiency of IE4 motors. The system’s patented Energy Minimizer automatically optimizes performance to reduce energy costs, while adaptive N-technology impellers deliver sustained efficiency.
Lastly, the system offers reduced inventories. A pre-engineered installation solution with a simple set-up wizard saves engineering time and makes start-up quick and easy. A smaller, simplified cabinet frees up space and reduces costs.
A Concerted Effort
The Concertor pump is running at 3.3 hp, as compared to the original pump, which was running at about 4 hp. The new pump is using about 90 kWh per month.
Since its installation, the pump has undergone more than 50 cleaning cycles—for example, the pump detected a blockage and completed its cleaning cycle by reversing rotation at a reduced speed, jogging back and forth until the blockage cleared. This results in a cleaner sump and no costly call outs. Additionally, these cleaning cycles prevent buildup and potential clogs that would eventually have to be cleared manually, an unpleasant and unsafe situation.
The pump acceleration and deceleration cycles are designed to limit the maximum torque so that the pump life will not be compromised. The pump cleaning cycle will often free a clog within minutes, but may continue for up to one hour.
The city of Fond du Lac estimates energy savings at 20% at the Wild Life Acres lift station after installing the new pump system. Time-consuming and expensive cleaning call outs also have been reduced. In the past, to have the vacuum truck and operator on site for one hour would have cost the city $120. To have city personnel unplug a pump would have required approximately two hours and would have cost $70. Previously, the station would have been cleaned out twice a year. Following the installation of the Concertor, these expenses have been reduced, as confirmed by the monitoring system tracking lift station operation before and after the pump’s introduction.
Since the pump can automatically drop down to a snore condition—when the water level has dropped to such a low level that the pump begins to draw air—grease and grit do not build up, keeping the sump clean. Furthermore, the adjustability of the pump to handle different conditions within a range, with no need to change impellers, provides flexibility and reduces the number of spare pumps and related inventory required. The city appreciates that the intelligent controls are in the pump and do not require a separate control located at the panel, a major consideration since most of these stations are located in residential areas.
The operation continues, but thus far Fond du Lac is confident in the pump and finds value in the benefits of reduced energy consumption, minimized service and decreased inventory. According to maintenance foreman Steve Durocher, in the future, when existing pumps are due for replacement or major overhaul, Fond du Lac will consider Concertor.