Case Studies - July 2019

Chopper pump helps stop clogging at lift station

Problem: At a Texas wastewater treatment plant’s main lift station, better mixing was needed to break up persistent grease and scum layers. Three small pumps could no longer cope with grease and objects such as mopheads that caused blockages. The maintenance team was always on call to help keep the wastewater flowing and prevent overflows. In some cases, a vacuum truck had to be called at significant cost.

Solution: After testing, the municipality chose a Gator submersible chopper pump from Landia. The Gator series was developed to eliminate lift station clogging caused by wet wipes and other debris. It has a hardened steel knife system at its inlet that continuously macerates and mixes solids. Its open impeller enables it to pump even high-viscosity flows.

Result: The existing duty pumps are now better protected. The chopper pump picks up the solids from the bottom of the lift station and breaks them up so that they do not accumulate and cause clogging. 919-466-0603;

Grit classifiers reduce maintenance

Problem: The grit classifiers at DC Water’s Blue Plains site had structural defects, causing leaking. Each time, a unit had to be taken offline to open the hatch, take the screw out, get inside to clean it, buckle in a new liner and weld it. Increasing downtime, maintenance and cleaning required fresh investment.

Solution: The new grit classifiers had to match the existing classifier envelope. Using 3D modeling, Lakeside Equipment worked with DC Water to match the grit classifiers with the inlet and outlet pipes. Sixteen grit classifiers, each handling a slurry flow of 400 gpm, have significantly reduced maintenance issues.

Result: Maintenance is now much easier, as there is much better access. An automatic lubricator on the end of the bearing eliminates the labor of replacing a plastic liner. 630-837-5640;

Pinch valves replace plastic ball valves 

Problem: A drinking water plant in Arizona used plastic ball valves on pipelines to transport 12.5% sodium hypochlorite. The valves had problems with the rubber liners swelling, preventing them from shutting off completely. The packing also had problems with leaking hypochlorite on the floor.

Solution: The valves were replaced with Flowrox PVEG polyamide-bodied pinch valves with EPDM rubber sleeves. The sleeve is the only component in contact with the flowing medium. The pinch valves do not have stem packing, so no sodium hypochlorite has leaked from them. The valves are lightweight: A 2-inch valve weighs only 17 pounds, and a 6-inch valve weighs less than 60 pounds. The valves are also full port. Pinch valves also save energy and are easy to open and close.

Result: The valves have been operational with no repairs or leakage for more than two years. 888-356-9797;

Aboveground lift station simplifies operations, reduces costs

Problem: Tough-to-access submersible pumps complicated life and increased costs for maintenance workers at the Royal Cornwall Hospital in Truro, United Kingdom. “Our original submersible pump stations were no longer maintainable by our in-house staff,” says Leslie Dey, estates officer. “Keeping up with the training to send anyone down there would have been a massive cost.” Routine maintenance like pulling a pump to change a seal or impeller required confined-space entry. “A lot of it was far too costly to do in-house,” Dey says. “It was eventually all contracted out.”

Solution: The hospital converted from submersible pumps to the EVERLAST wet-well-mounted pump station from Smith & Loveless. The station simplifies access and eliminates confined-space concerns by mounting a complete lift station above ground and inside a quick-access enclosure. “The beauty of the equipment all being above ground is that all of our guys can access that fairly easy,” Dey says.

Result: Dey and his staff inspect the station daily and conduct routine maintenance with ease. Contractor costs have been eliminated. “The aboveground pump station allowed us to take back ownership of our equipment and maintain it in-house,” Dey says. 800-898-9122;

Chopper pump used to clear wet well of grease blanket

Problem: The Otay River Pump Station, which pumps 7 to 9 mgd of raw sewage to the South Bay Water Reclamation Facility for water recovery in San Diego, had a problem in the 50-foot-long, 10-foot-wide, 30-foot-deep wet well. A floating blanket of grease and debris, sometimes as thick as 4 feet, would form regularly. The city was hiring two vacuum trucks to clean the station every three to four months at a cost of $50,000 to $100,000 per year.  

Solution: The city installed Vaughan chopper pumps, which are suitable for use in pump and lift stations as conditioning pumps when fitted with a nozzle to provide high-velocity mixing. They were placed in the problem wet well on a portable stand to recirculate and chop the contents. The company selected an 8-inch submersible chopper pump with a 25 hp, 1,200 rpm motor with mixing nozzle and portable stand.

Result: In 18 months of use, the wet well has not required cleaning. The pump paid for itself in 2 1/2 months. 888-249-2467;


Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.