Direct Inline Pumping of Influent Boosts Efficiency and Eliminates a Confined-Space Hazard

Direct inline pumping of influent boosts efficiency and eliminates a confined-space hazard for a small clean-water plant in western New York.

Direct Inline Pumping of Influent Boosts Efficiency and Eliminates a Confined-Space Hazard

Flanges connect the lift station inlets directly to the pumps.

The team at the village of Sherman’s clean-water plant in New York faced frequent and hazardous confined-space entries to de-rag pumps in the influent wet well. A new pump installation lasting just under 12 hours made the problem go away.

The village team installed a direct inline pumping, or DIP, system in which submersible pumps installed in a wet well and activated by floats are replaced by pumps that are directly connected to the lift station inlet and outlet.

The pumps run continuously, ramping their speed up and down according to the incoming volume. In the process, the pumps grind up wipes and other trash so that it can pass through without causing clogs. Online since mid-January, the system has been trouble-free and has saved significantly on labor.

Troublesome entries

Sherman, a rural community of 730 on the far west end of New York, has a 40-year-old 140,000 gpd (design) package treatment plant that achieves more than 99 percent BOD and TSS removal. It includes two circular process tanks (only one in operation), each with an aeration zone, a contact stabilization zone, a digester, and a stilling well in the middle.

Wastewater from the village flows entirely by gravity to an influent wet well on the plant property. The lift station lies 20 feet in the ground. Before the DIP system was installed, a pair of centrifugal pumps lifted the influent to the plant headworks.

“The biggest concern I had was a safety issue with climbing down into that steel lift station vault through a 36-inch silo access,” says Jay Irwin, chief operator. Those entries required complete confined-space entry gear and safety procedures.

“Second, with those pumps aging, we were having to go down quite often, shutting down one pump and taking it apart to clean it,” Irwin says. “The pumps would get clogged quite often with mop rags that would build in the wet well. We would go in there once a week to clean the bar screen, and we would also go down every two to three months, using a septic tank cleaning truck to pull everything out of there and start over.”

A better way

While looking to solve those problems, Irwin read about the DIP technology in Treatment Plant Operator magazine (June 2016 issue). He contacted Jon Dunham, key accounts manager for the vendor, C&B Equipment. “I sent him the engineering specifications for our lift station and wet well, and he emailed a quote for the system at $63,000,” Irwin says.

The installation includes a pair of 15 hp 1 System DIP101R/4VV pumps, each rated for 360 gpm at 40 feet of total dynamic head. The pumps are equipped with variable-frequency drives, dry-run protection, and DIPCUT impellers, changeable without special tools.

“One pump can handle 100 percent of our normal flow,” Irwin says. “It’s nice to know we have plenty of pump power, especially since we have an I&I issue. When we get heavy rains or thaws, we have enough capacity without any problem.”

The system was delivered essentially plug-and-play. Wastewater from the collections system enters the vault through a 12-inch pipe, and wastewater from the plant itself enters through an 8-inch pipe. Flanges anchored to the vault wall deliver influent directly to the pump inlets. On the discharge side, 6-inch PVC pipe connects the pumps to the existing 6-inch lift station discharge line.

“It turned the wet well into a dry pit,” Irwin says. “Eventually we will fill the bottom of the well with stone and pour a concrete floor.”

Quick install

After preparations were made, the actual DIP system installation took just 11.5 hours. During the project, wastewater was bypassed using a trailer-mounted trash pump. Koester Associates, local representative for C&B Equipment, led the installation, the first DIP system in the state.

Irwin and assistant Dennis Watson helped Koester Associates workers Chris Frechette, Brian Osborn, and Rick Hoffman with the project, as did Doug Crane and Larry Meeder from the Sherman Street Department. Matt Oehlbeck of the nearby North County Chautauqua Lake Sewer District brought a truck with a crane to lower the equipment into the well. Byron Gens from the neighboring village of Westfield brought a vacuum truck to empty the wet well before installation. A month earlier, Oehlbeck and Gens helped remove a catwalk and other structures to prepare for the project. “Getting the system into the well in one day was a big feat, and I couldn’t have asked for a better crew,” Irwin says.

Startup ran smoothly with assistance from Stefane Dumonceaux, owner of S.I.D.E. Industrie, the DIP Systeme manufacturer. An OmniDIP control enables the system to continuously send operating data for remote monitoring. The pumps are installed about 10 feet below the surface in an 8-foot-diameter space. “Essentially it’s like a workroom,” Irwin says. “It’s still a confined space, but not nearly as hazardous an environment as when it was a wet well with open water.”

Reliable performance

In operation, the pumps run continuously; the variable-frequency drives adjust the speed according to the influent flow. The flow rate is measured by a transducer installed in the lower part of the inlet; it measures the depth of the flow over it, and the output from the transducer determines the speed of the pumps. If there is no flow, the pumps stop until flow begins again.

The pumps are self-cleaning with a special impeller design that allows wipes, rags and other trash to pass through after being shredded. When a solid object impedes the impeller, the torque increases and the control system senses that the pump is becoming clogged. The pump then automatically slows down, stops and reverses direction.

At that point, knives on the impeller pop up and shred the trash. When the control senses that the pump is running free again, it slows down, stops, and returns to the normal pumping direction. The control system is fully programmable. Users can check on or adjust pump operation remotely using a smartphone, tablet or desktop computer.

Irwin observes, “It’s a very innovative technology. It got rid of our confined-space issues. I know it’s going to save us a lot of man-hours. If we have issues, the equipment is easily accessible. We don’t have go down into a silo 20 feet deep. Everything is right there.”


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