Upgrades include integrated control electronics and IE4-rated motor efficiency.

Aging infrastructure, global urbanization, increasing energy costs and the need for sustainable solutions make cost reduction and reliability a priority in wastewater pumping.

Small wastewater pumps can be given a new level of functionality and intelligence by integrating advanced software functions and state-of-the-art hardware into a conventional submersible design. Sensing the operating conditions, intelligent pumping systems make smart decisions and provide feedback to the operator.

Understanding Pain Points in Pumping Wastewater

Market survey responses indicate that many pump users are constantly looking to lower energy consumption and overall costs while achieving higher reliability and longer lifetime of the equipment.

sump before trialImage 1. Sump before trial (Images courtesy of Xylem Inc.)

Furthermore, they are keen to implement more remote supervision instead of sending out people to remote areas to manage unplanned maintenance.

Regarding pump clogging, while a full clog is easy to detect, a partially clogged pump often goes unnoticed, since it still delivers reduced flow. This might result in reduced efficiency and substantially increased energy consumption, or even worse—in an unplanned maintenance call to unblock a pump that has operated with a partial clog during an extended period of time.

While the intelligent pump system’s upfront cost is a major consideration, the operational costs over the life of the pump station might help differentiate between competing pump system designs at the time of purchase. Increases in efficiency alone may not always convince a buyer to switch to a better performing system, but a single unscheduled call to clean a clogged pump will easily tip the scales in favor of a system that has proven to be consistently clog-free.

Finally, reduced carbon footprint as well as clean and odor-free pump stations are always desirable. However, many pump systems frequently require expensive pump outs—for example, vacuum cleaning call-outs—to remove bottom sediment, floatables and fat buildup that create odor problems and can cost thousands of dollars annually.

Integrating Intelligence

An answer to these challenges is the creation of integrated intelligence in wastewater pumping. This is made possible by innovation and adaptation of components in a submersible wastewater pump: integrating electronics such as processor, software, sensors, synchronous electric motor and self-cleaning hydraulics inside a submersible shell.

sump after trialImage 2. Sump after trial

The word intelligent in wastewater pumping is a result of factors that contribute to a new level of operational autonomy and efficiency.

Systems designed to automatically deliver the desired performance at minimum energy consumption while reducing the total cost of ownership are considered intelligent.

The practical implication of an integrated intelligent system translates into functionality such as soft-start, pump clog detection, pump cleaning, advanced motor protection and “always correct” impeller rotation. These are features that increase the pump and system life, reducing downtime and giving users peace of mind. The pump station controller provides pump system management functions including:

  • energy minimizer
  • sump
  • pipe cleaning functions
  • other functions

Finally, overall reliability of the entire pumping system is high on an operator’s agenda. This leads to the desire to build future-proof stations that are flexible and resilient, meaning they can easily adapt to changing conditions and can handle extreme flow conditions without failures.

Intelligent Pumping Systems

Among the intelligent pumping system’s hardware components we can highlight:

  • integrated control electronics
  • new generation nonclog self-cleaning hydraulics
  • IE4-rated motor efficiency.

Hydraulics: The key design feature of nonclog technology (N-technology) is the N-impeller’s horizontal backswept leading edges together with the relief groove in the insert ring and the guide pin.

The backswept leading edges work together with the guide pin to sweep solids from the center to the perimeter of the inlet. When solids arrive at the perimeter of the inlet, they get transported inside the relief groove, sliding along the edge of the impeller vane, through the volute and out of the pump.

non-clog impellerImage 3. Non-clog impeller

The mechanical self-cleaning design means that the pump will have the same efficiency in pumping wastewater as when pumping clean water. The conventional pump’s stated efficiency, also measured in clean water, is usually much higher than the actual efficiency in real life applications. But this is not the case with the N-technology.

Advanced drive unit: The pump’s drive unit is an assembly consisting of monitoring and control circuitry, software, power electronics and a synchronous motor in a single package. By using a new concentrated winding motor design, benefits such as increased motor efficiency, controllability and reduced motor size are achieved.

The stator consists of multiple identical stator lamination packages with individual coils that are placed side-by-side inside the stator housing. The concentrated winding stator can be produced efficiently and at a shorter height than an induction motor of corresponding rating.

intelligent pumpingImage 4. Intelligent wastewater pumping

The rotor is equipped with permanent magnets that create and maintain the rotor’s magnetic field, yielding low rotor losses during operation at synchronous speed.

The low losses result in virtually no heat generation in the rotor and no heat transferred to the bearings via the shaft. The cooler running motor increases bearing life due to less thermal stress on the bearings.

With the high motor efficiency, the winding temperature is lower than normal. Add to this the temperature protection system where motor power is reduced—should circumstances warrant it—and the result is a longer motor life.

The concentrated winding synchronous motor requires power electronics to start and run the motor.

The power electronics offer full control of the pump shaft speed and torque; therefore the wastewater pumping system can operate within a large flow/head field. The embedded software serves to control the motor’s speed and torque as well as to read the momentary load requirements.

The intelligence of a wastewater pump: By collecting and analyzing relevant data, an intelligent pumping system can make smart decisions about how it operates and what feedback it will provide the user. This results in:

  • precise process control
  • reduced risk of clogging
  • clean and odor-free pump sumps
  • substantial reductions in energy consumption
  • reduced asset management
  • comprehensive data reporting

The in-pump processor controls the power electronics to achieve variable pump performance. A single impeller size per volute size minimizes the need for multiple spare impellers and yields maximum hydraulic efficiency. Instead of having to remove the pump to trim or change an impeller, a different duty point can be met by an operator who varies the pump speed.

When power electronics and a processor with control software are integrated into a submersible pump, costs are driven down and new functionality is added. The power and control electronics—which are mounted on a back plate in a conventional pump control panel—have been adapted and fitted into the head of a wastewater pump.

This is beneficial since the power electronics are then protected from the exposure to dust, dirt and extreme temperature variations. The cooling is reliable and not dependent on fans or air conditioning units.

The motor leads are as short as possible removing most issues with wave reflections and voltage spikes.

When power electronics are placed between the grid and the motor, the system becomes frequency independent and voltage tolerant.

The pump station controller allows for data communication and measurement or analysis, providing communication via standard communication protocols. The pumping station can be connected to remote station monitoring systems including supervisory control and data acquisition (SCADA) systems.

Case Study Results

Stony Brook, Suffolk County, New York Problem: The Suffolk County Department of Public Works Stony Brook Pump Station receives an average 3 million gallons per day (mgd) of incoming flow and was facing ongoing interruptions to pumping operations as a result of “ragging”—buildup of fibrous materials that lead to frequent pump blockages. Solution: The prototype intelligent pumping system was proposed as a potential solution and it was installed in August 2015. Results: Before installing the system, it was necessary to lift the pump regularly (once every three months approximately) to remove fibrous materials caught in the impeller. Maintenance cost reduction with the prototype intelligent pumping system was about $1,500 for personnel and $2,500 in equipment costs for the year. The pump clogging was eliminated and the energy consumption was reduced about 20 to 30 percent. Fond Du Lac, Wisconsin Problem: The Fond du Lac Regional Wastewater Treatment Facility treats the city of Fond du Lac wastewater along with 18 neighboring entities. Of 17 pump lift stations, 11 are submersible, none of which use variable frequency drives. Overseeing the maintenance of these submersible stations as well as rising energy costs are two growing challenges for Fond du Lac wastewater treatment facility. Solution: The prototype intelligent pumping system was installed in July 2015 in a duplex pump station replacing one of the old pumps as the lead pump. Results: Estimated energy savings of 20 percent, because the new pump runs at 3.3 horsepower while the original ran at 4 hp. Also, expensive call-outs have been reduced as the pump has solved potential blockings, cleaning the sump looks and eliminating debris that could cause clogging.