The Mectan V induced vortex grit removal system from John Meunier, Inc., a Veolia Water Solutions & Technologies company, is engineered to remove a range of particle sizes in municipal wastewater pretreatment.

The system offers multiple outlet channel positioning options, low headloss, energy savings and a small carbon footprint. The paddle-mixer design optimizes grit removal while limiting accumulation of organics in the grit well. The system can remove 68 percent of grit particles smaller than 150 microns and 96 percent of particles 300 microns or larger.

An evolution of the original Mectan conical grit removal system, the Mectan V preserves the system’s simple operation and full access to all mechanical components, while adding flexibility and increased efficiency, says Martin Couture, equipment department director.

The device is available in models from 4 to 24 feet in diameter and can handle flows from 0.8 to 78 mgd. “There’s no minimal flow because you can use a smaller model to address very low flows,” he says.

Influent is fed tangentially into the lower portion of the separation chamber, ensuring proper flow and velocity inside the conical tank. Paddles maintain the influent at maximum rotational velocity, holding organics in suspension while allowing grit to settle.

“If we didn’t have the paddles or a motion-inducing system inside the tank, we would have more organics being removed, which is not the purpose,” Couture says. “The chambers are made to remove grit. Grit eventually touches the sidewalls inside the cone and falls to the bottom of the cone, where it is slowly brought back into the main grit hopper in the middle of the equipment and removed.”

Water escapes through the top of the separation chamber and is redirected toward the outlet channel. A steel disc in the tank separates the vortex grit removal zone from the flow outlet zone, so the outlet channel can be positioned in any direction. “It could be straight in line with the inlet channel. It could be 90 degrees; it could come back the other way,” Couture says.

The system is essentially self-cleaning: grit is contained in a single hopper and transferred from the well by an airlift device or extraction pump. An optional scour using air, water or both fluidizes the bed before grit removal.

The system requires minimal maintenance and can operate for extended periods when properly serviced. “This is mechanical equipment, so you need to grease it periodically, and do inspections to make sure you don’t have any wearing or tearing of parts,” Couture says. “The main paddle drive is turning all the time.”

The system’s small footprint makes it easily adaptable to smaller treatment plants or for retrofitting older facilities. “Many of these units are fabricated for retrofits,” Couture says. “The units can be manufactured in steel tanks or simply cast in concrete to fit existing basins in wastewater treatment plants, if required.” 888/638-6437; www.johnmeunier.com.