The Route 108 pumping station located in Howard County, Md., serves a large, affluent and mostly residential area. The station pumps 3.5 million gal per day (gpd) of wastewater to the Patapsco Wastewater Treatment Plant in Baltimore for further processing. When necessary, the treatment plant is bypassed and the wastewater is sent instead to the Little Patuxent Water Reclamation Plant. This arrangement, though uncommon, had worked, but one day, things took a turn for the worse.
“The problems began when the station was taken offline while we did some upgrades to it,” said Bob Funk, the superintendent. “When we went back online a year later, the pumps were unable to run a full day without clogging up with rags.”
Something had changed. “We think that it was the construction of some nursing homes nearby," Funk explained. "We began to see a lot more rags that were probably flushed down the toilets including shredded diapers, cleaning cloths and other debris. It was a real mess. Every day, someone had to spend up to four hours cleaning out the pumps. We desperately needed to find a solution and soon.”
Funk contacted several vendors for ideas on how to best manage the situation. “One suggestion was a climber screen to catch the rags before they entered the pumps. But that meant dealing with the collected screenings. A better option was a grinder placed in front of the pumps to grind the debris finely enough so that it could be passed along to the treatment plants for further processing,” he said.
The first choice was a Franklin Miller Dimminutor T25 Channel Disintegrator  , which was ultimately purchased. Before making the decision, they were invited to Ocean City, Md., where staff could see the Dimminutor in operation and talk to the operators using it.
“ Franklin Miller  did a great job of engineering the Dimminutor for our conditions,” Funk said. “Everything was prefabricated, making it easy for our maintenance crew to install and maintain. We are now able to run our pumps 24 hours a day every day with virtually no pump clogging. In the time we’ve owned the unit, we’ve cleaned out just two jams: one caused by a log and the other by a plastic manhole cover. In both cases, the Dimminutor went right back to work.”
The Dimminutor  offers effective, automatic screening and disintegrating of wastewater solids in straight through channels and wet wells. The unit reduces plastics, wood, rags and other solids to fine bits, improving the reliability of pumps and other downstream equipment.
The unit employs a smooth, continuously rotating design with high torque. As its three bi-directional rotary cutters intermesh at close clearance with stationary cutters, solids are finely reduced to a size small enough to pass through a sizing screen. With no gaps or openings between the screen and cutters, output is controlled and complete reduction assured.
The Dimminutor has an intrinsically open design to handle high flow rates with low head-loss. This unit is easy to maintain and features individually replaceable cutters, oil lubrication. A unique, cantilevered design eliminates seals or bearings near the gritty channel floor. Every component of the unit is constructed for precision and long life.