Managing water and wastewater systems is challenging during the best of times. But COVID-19 has exacerbated the challenge and maintaining normal operations while keeping the residential wastewater stream clear of clogs from nonflushable materials is more critical than ever.
Touted as modern conveniences, disposable consumer products such as disinfecting wipes and personal hygiene wipes 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.
These materials are marketed to go through your toilet, but 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 wipes that are already stuck in the system.
Since COVID-19 outbreak began, utilities have reported more frequent clogging caused by consumers flushing disinfectant wipes and other materials, causing sewer overflows and backups. If not retrieved by hard-pressed plant technicians, the debris can literally shut down sewer systems, creating a cascading series of health emergencies.
Facing increasing amounts of nonflushable materials in the wastewater stream, several U.S. cities 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.
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 flow or 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. Although that feature greatly reduces the potential for clogging, 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’s 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 backswept 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.
As a result, the K-impeller design prevents the steady buildup of fibrous material that can otherwise impose drag and compromise respective energy usage and operating efficiency.
Due to this 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.
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.
As the coronavirus pandemic endures, residential water systems are being compromised by an increase of nonflushable materials being flushed down household toilets. Although it may be impossible to prevent 100 percent of nondegradable materials from entering the wastewater stream, leveraging advanced pump technologies can help reduce the strain on residential wastewater systems.