Today’s residential wastewater stream poses more problems to plumbing systems than ever before with the proliferation of “flushable” wipes and other unconventional solids such as baby wipes, paper towels and feminine hygiene products.
Touted as modern conveniences, these products are anything but, considering the detrimental effects they can have on residential plumbing systems. Although disposable cleaning wipes and personal hygiene products should be tossed in the trash, many consumers instead flush them down the toilet, 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. Clogging can occur when many wipes get stuck in the pump or if debris builds upon the flushable wipes already stuck in the system.
Consequently, residential wastewater pumps are working overtime to handle these challenges. New solutions in pump engineering are being developed to help avoid unintended consequences such as clogging and system damage caused by the modern waste stream.
Fats, cooking oil and grease (FOG) present another challenge for residential and municipal wastewater pumping stations. When poured down kitchen drains, FOG accumulates inside sewer pipe, restricting flow and causing 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.
New pump technology battles back
Along with public awareness campaigns to reduce the amount of nonflushable materials entering the wastewater stream, equipment manufacturers are expanding their wastewater product portfolio and technologies to combat contemporary wastewater issues. Grinder pumps and vortex impellers are among the most popular pump technologies used to address modern wastewater challenges and help avoid system damage.
• Grinder pumps. These pumps are a wastewater transportation device that helps transfer household waste, such as flushable wipes, to the larger sewer system. Waste from toilets or sinks flows 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, cuts the waste materials into tiny bits and pumps the slurry to the central sewage system or septic tank.
Outfitted with steel blades, the grinder pump cuts solids found in sewage into tiny pieces, which are then passed down the piping network before being discharged at a collection point. 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 umps featuring a powerful axial grinder and semi-open impeller design — including an eight-hole cutter plate and three-blade cutter — to easily slice through the solids, flushables and trash found in the modern wastewater stream without roping or clogging. This technology reduces waste to a fine slurry, resulting in minimal downtime and service issues.
While grinder pumps are a good choice if solids such as 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 impeller pumps. The design of this type of pump includes 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, which is a common residential wastewater specification, the 2-inch sphere does not need to touch the impeller when it passes through the volute — the curved funnel that enlarges as it approaches the discharge port — 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.
Although the vortex impeller pump is a popular choice for demanding residential wastewater applications, the impeller design has its downsides. The vortex impeller is recessed, which keeps it out of the wastewater flow path, which greatly reduces the potential for clogging. However, this same design also results in lower wire to water efficiency.
Despite the practice of backflushing, which entails running the pump backward to clear the leading edges of the impeller and push the build-up of solids through the pump’s suction opening back into the sump pump, these solids return during normal operation, leading to decreased efficiency and higher operational costs.
• Self-cleaning impeller pumps. 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 — an anti-clog impeller design for residential wastewater pumps that easily devours solids and fibers while it consumes less energy than ordinary pumps.
Key to the K-impeller design is the 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 making these pumps a practical solution for residential applications. Unlike standard residential wastewater pumps, a pump with self-cleaning hydraulics will not accumulate the solid objects more likely to be found in modern wastewater.
The K-impeller’s increased clog resistance results in minimized costs for operation, service and maintenance, which in turn improves overall reliability and energy efficiency.
In addition to newer nonclog technology, smart pumping systems are entering the residential wastewater market. Equipped with integrated intelligence, 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 such as 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.
Today, equipment manufacturers are continuously introducing new and smarter pump technologies to stay abreast of the ever-changing residential wastewater environment. With the U.S. wastewater infrastructure facing a daunting investment gap, these critical systems are at risk and leave our communities vulnerable to the consequences of system failures. The need to leverage technology to develop new, more sustainable solutions has never been more evident.