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Disposable Wipes Threaten Wastewater Systems
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Published on Pumps & Systems (http://www.pumpsandsystems.com)
Home > Disposable Wipes Threaten Wastewater Systems
Disposable Wipes Threaten Wastewater SystemsNew shredder pump technology can prevent costly clogging and minimize damage to equipment and municipal reclamationfacilities.by Mike Bjorkman (BJM Corp.)
While manufacturers claim these wipes are flushable, they have been causing major problems for wastewater facilities, and theproblem has only worsened in recent years. New York City alone claims that more than $18 million has been spent during the pastfive years to remedy wiperelated problems in their 14 wastewater treatment plants.
In the Southwest, a Tucson, Arizonabased news crew visited a regional reclamation center and documented that "white wipeswere everywhere." The operator suspects the wipes are not biodegrading as fast as the general public is being led to believe. Thewipes cake the walls and eventually get stuck in the sewers where they clog pumps and pipes. When blockages occur, there isjust one way to clear them—by hand.
Image 1. Jae Wilson, service managerat Williamson New England Electric Motor and Pump Company, consulted with the pump manufacturer while reviewing the systemand its requirements. (Images courtesy of BJM Pumps)
In Vancouver, Washington, sewer officials performed their own experiment after spending more than $1 million replacing 11pumps that regularly became clogged as a result of wipe ingestion. They dyed wipes labeled "flushable" and sent them on a onemile journey through the system. They did not break up.
One major producer of flushable wipes claims that the problem is caused by products not meant to be flushed. They explain that
flushable wipes, when used as directed, break up after flushing and clear properly maintained toilets, drain lines, sewers, pumps,and septic and municipal treatment systems.
Consumer Reports performed tests that dispute these claims. The magazine ran vortex and mixer tests on several major flushablewipe brands that claimed to be safe for sewer and septic systems. After 10 minutes of agitation, the wipes did not break down.Consumer Reports states that the public must understand what is safe to flush and what is not. Their advice: "Do not flushflushable wipes."
Until industry standards for all wipes meet wastewater handling equipment requirements, the public must be informed andresponsive to minimize system downtime and the resulting costs to taxpayers. In the meantime, wastehandling equipment mustbe upgraded to handle a large volume of these wipes in the system.
Image 2. While manufacturers claimwipes are flushable, they have been causing major problems for wastewater facilities, and the problem has only worsened.
Facing the ProblemSeveral pump companies have attacked the problem by developing equipment that will shred wipes and other solids to make themsafe for wastewater systems. The engineers at one company have developed dual shredding technology that features radial andaxial shredding elements. This design obliterates wipes and other hardtohandle solids.
"Incorporating both radial shredding and axial cutting achieves optimum results on hard, to near impossible to pump liquidscontaining fibrous solids like wet wipes," said Brian Mitsch, the company's VP of operations and engineering. "The radialshredding is achieved by a rotating cutter bar with serrated edges, which traps and shreds solids against the sharp grooves of theradial cutting ring. Wipes and other fibrous debris are efficiently ripped apart. The complementary axial cutting utilizes dual cuttingelements operating in tandem to multiply the shearing action. As the material exits the radial shredding area, the axial cuttingcomponents shear any remaining pieces using multiple cutting bars. The impeller design expedites flow and hydraulicperformance, preventing wrapping and clogging."
These pumps feature shredding elements that are cast in hardened 440C stainless steel (Rockwell hardness above 55C), and thepatentpending design provides excellent solidspassage efficiency through its impeller and volute. Available with 2, 3 or 5horsepower (HP) hightorque fourpole motors, these pumps are ideal for smaller wastewater stations.
Image 3 . This dual shreddingtechnology with radial and axial shredding elements provides solids passage efficiency.
Case StudyFoxRock Properties owns and operates two massive office and medical complexes in Norwell, Massachusetts. The first of theneighboring properties is Longwater Place, a 27,000squarefoot office building, part of a larger 26acre campus that includes84,000 square feet of corporate offices and a 160,000squarefoot wellness center. Longwater Place incorporates a full cafeteria,and fitness center, featuring a gymnasium with squash courts and locker/shower facilities.
The adjoining property is South Shore Medical Center, an 85,000squarefoot facility comprised of 100 medical examinationrooms, 70 medical offices and a complete range of diagnostic equipment.
Image 4. The new pump was placed inthe sump without a screen, alongside a shredder pump.
Because of the expansive size of these buildings, property management faces major wastewater handling challenges. Thecomplex has 30 bathrooms and 64 toilets that pass flow content consisting of sanitary waste, wipes and feminine hygieneproducts flushed by staff, patients and visitors. All of it travels through the sewer lines of both properties and is funneled into anoutside 10,000gallon overflow tank. The wastewater is then pumped through a 4inch PVC discharge pipe more than oneeighthof a mile from the tank into the municipal sewer system. Two solidshandling submersible pumps are at the heart of the system.
Although not required by local regulations, FoxRock Properties maintains this pumping system to ensure that discharges to themunicipal sewer system can be handled effectively by the local treatment facilities.
"Given the buildings' populations, professional range of clients and types of services provided, it is expected that we would seemore than our fair share of flushables," said Dan Snyder, property manager for FoxRock. "In the past, we experienced frequentfailures as wipes blocked screens protecting the pumps and wrapped around impellers, clogging the volute and eventually burningout the pumps' submersible motors. Even with a backup pump in place, the service interruptions and maintenance costs becameunacceptable."
The average pump service life was less than 1.5 years.
After one of the 460volt submersible pumps failed again, Snyder asked the water and waste equipment specialists at WilliamsonNew England Electric Motor and Pump Company to examine the problem and recommend a solution.
Jae Wilson, service manager at Williamson New England Electric Motor and Pump Company reviewed the system and itshydraulic requirements, including the difficulttopump wastewater content. Although numerous solidshandling pumps wereavailable, none presented the perfect solution.
Research indicated that the heavy wipe content would still tend to wrap and clog pumps with traditional nonclog impellers. Theresulting failure meant lifting the pump, disassembling and manually clearing the blockage, and possibly replacing the motor.
Wilson consulted with one of his pump suppliers and decided to install a shredder pump with dual shredding technology. Becauseit used both radial shearing and axial cutting to pass hardtopump items such as wipes, this new design was ideal for theapplication.
One important advantage of the new system was immediately noticeable. Most nonclogs, including the second wastewater sumpon the FoxRock property, must be surrounded by a screen. The solids and debris that get caught in that screen must be routinelycleared by hand. The installed pump does not require a screen. A postinstallation inspection showed no debris in the sump.
"So far, I am very happy with the pump. It was installed in July 2014 and continues to operate without clogging," Snyder said.
While preventing nonflushable materials from entering the wastewater system is impossible, FoxRock Properties has a pump thatcan minimize the possibility of clogging and improve downstream conditions.
About the AuthorMike Bjorkman is vice president of BJM Corp. and has more than 30 years of experience in the pump industry. He serves asmarketing and IT director for BJM Pumps LLC and All Test Pro LLC, both subsidiaries of BJM Corp. For more information, call8603995937 or visit bjmpumps.com.
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