Advanced pump technologies take on modern wastewater challenges

Modern trash has become the number one enemy of the residential wastewater stream.

Touted as new conveniences, disposable consumer products like disinfecting wipes, makeup remover pads and feminine hygiene products are anything but, considering the havoc they can wreak on residential plumbing systems. Intended to be tossed in the trash, many consumers instead flush these products, adding harmful synthetic material and artificial fibers to the wastewater stream. Unlike toilet paper, wipes don’t break up easily or quickly and can clog sewage treatment equipment and home septic systems. Clogs occur when a number of wipes get stuck in the pump, or if debris builds up on the flushable wipes that are already stuck in the system.

Fats, cooking oil and grease (or FOG) pose similar challenges to residential and municipal wastewater systems. When poured down kitchen drains, FOG accumulate inside sewer pipes, restricting flow and causing sewer blockages. The resulting buildup can lead to operational problems and the need for costly maintenance. FOG is one of the leading causes of sewer overflows and blockages, costing the wastewater industry billions of dollars annually.

With disposable products and other harmful materials finding their way into today’s wastewater, it’s obvious wastewater pumps are being asked to handle more today than ever before. In turn, pump manufacturers are developing new technologies to help alleviate issues like clogging and system damage caused by the modern waste stream.

New pump technology to the rescue

Many large cities in the U.S. have mounted public awareness campaigns to inform citizens about wastewater infrastructure challenges and to encourage them to avoid throwing wipes, rags and other nondegradables in the toilet.

Along with public education to change consumer behavior, equipment manufacturers are creating new products and pumping technologies to mitigate the problems, costs and inconvenience caused by modern trash. Grinder pumps and vortex impellers are among the advanced pump technologies being used to handle the growing challenges of today’s debris-laden residential wastewater flows.

Grinder pumps — A grinder pump is a wastewater transportation device that helps transfer household waste, like flushable wipes, to the larger sewer system. Waste from toilets or sinks flow through a home’s pipes into a grinder pump’s holding tank. Once the wastewater inside the holding tank reaches a certain level, the grinder pump turns on, chopping waste materials into tiny bits and then pumping the slurry to the central sewage system or septic tank. Residential grinder pumps are designed for continuous use and are capable of grinding domestic sewage in high head sewage applications.

Goulds Water Technology recently introduced its new AGS series axial grinder pumps featuring a powerful axial grinder and semi-open impeller design, including an eight-hole cutter plate and three-blade cutter, to reduce problem waste to fine slurry, minimizing downtime and service challenges.

While grinder pumps are a good choice if solids like flushable wipes are present in the wastewater stream, it is important to understand that these pump installations still need to follow the rules of pump hydraulics. For example, a minimum scouring velocity needs to be maintained so solids are not permitted to settle down, which can cause issues further down the sewage line.

Vortex impellers — Vortex impellers are designed with a semi-open impeller recessed into the volute section of the pump. A recessed impeller design allows for the clear passage of solids which helps prevent stringy, cloth-like materials and abrasive solids from collecting on the impeller and eventually clogging the system.

For example, if a pump has a 2-inch solids handling requirement, a common residential wastewater specification, the 2-inch sphere does not need to touch the impeller when it passes through the volute (the funnel shaped opening) of the vortex pump. If the waste material traveling through the pump is stringy, stranded or even cloth-like, a vortex impeller helps prevent the slurry from forming a twisted mess that would otherwise bind or clog the pump.

Despite being a popular choice for demanding residential wastewater applications, the vortex impeller design isn’t without its downsides. The vortex impeller is recessed, which keeps it out of the wastewater flow path, which greatly reduces the potential for clogging, but this same design also results in lower hydraulic efficiency.

Self-cleaning impellers — Today, more advanced hydraulic designs are available to increase a residential wastewater pump’s clog resistance and maintain pump efficiency. A revolutionary self-cleaning design, with horizontal backswept leading edges and a relief groove, is proving to be a reliable solution to prevent clogging problems.

In 2018, Goulds Water Technology introduced the Xylem patented K-impeller technology — a unique anti-clog impeller design for residential wastewater pumps that easily devours solids and fibers and consumes less energy than ordinary pumps.

Key to the K-impeller design is the dynamic interaction of the extreme back-swept impeller vanes and the stationary relief groove in the volute suction where the leading edge of each impeller vane is cleaned during pump rotation. The reliability of the K-impeller can be attributed to the semi-open, screw-shaped impeller that prevents clogging and facilitates the unobstructed flow of fibrous material. The leading edge of the pump’s rotating impeller passes across a stationary relief groove located in the pump suction port. The dynamic action cleans and pumps away any rags, stringy materials and solids from the impeller without compromising the hydraulic efficiency.

The self-cleaning impeller design provides a flow path through the pump, greatly reducing the risk of clogging and makes the pumps with a K-impeller design a practical solution for residential applications. Unlike standard residential wastewater pumps, a pump with self-cleaning hydraulics will not accumulate the solid objects that are more likely to be found in modern wastewater.

By eliminating ragging, the K-impeller prevents the steady buildup of fibrous material that can otherwise impose drag and compromise respective energy usage and operating efficiency. Due to its unique ability to consistently handle materials flowing through the system, the pump retains an exceptionally high level of function, resulting in minimized costs for operation, service and maintenance, which in turn improves overall reliability and energy efficiency.

Smarter control

In addition to non-clog technology, equipment manufacturers are introducing smart pumping systems to the residential wastewater market. Equipped with predictive monitoring and controls, these wastewater pumping systems sense the operating conditions of their environment and provide feedback to help minimize downtime and enhance efficiency.

Smart monitoring technologies that detect high temperatures and seal leaks or failure provide peace of mind through real-time insights into the status of the wastewater pump system, sending alerts when maintenance is required.

While dual seal design and sensors for high temperature and seal leak detection come standard on pumps with K-impeller technology like the GFK Series Submersible Sewage Pump, homeowners can right size the pump installation and opt out of connecting the smart pump controls, which are more commonly used in commercial applications, reducing the installation cost dramatically.

Although it’s impossible to prevent 100 percent of nondegradable materials from entering the wastewater stream, leveraging advanced pump technologies is helping to reduce the strain on residential wastewater systems.