MA wastewater treatment plant improves operations with sludge grinder

Sept. 19, 2014
The Lynn Wastewater Treatment Plant in Swampscott, Mass., has improved capacity and reduced maintenance intervals thanks to a pair of Series-A Munchers from NOV Mono.

Sept. 19, 2014 -- In recent months, the Lynn Wastewater Treatment Plant, located in the city of Swampscott, Mass., has significantly improved capacity and reduced maintenance intervals thanks to a pair of Series-A Munchers from NOV Mono, a progressing cavity pump manufacturer. The special construction of the grinders -- and their ability to handle up to 11 million gallons per day (MGD) -- has also contributed to reducing the risk of overflows during storm periods.

The Lynn treatment plant had previously been using a single large grinder unit to process wastewater. However, the unit's 50-inch-tall cutter stack and single 10-inch-diameter drum were struggling to cope with the excessively high flows experienced during intense rain storms, and the cost of replacing it with a similar alternative was prohibitive. Given their sizeable handling capacity, the two Mono CA215 units were selected as a replacement solution.

The Swampscott station receives roughly 2 MGD of inflow, but the Mono units can accommodate 5.5 MGD each, offering a combined total of 11 MGD. Paired with an initial filter installed upstream to limit any extreme flow, this virtually eliminates any risk of overflow, even during major storms. The units have also been built on 6-foot extended shafts and fitted with extra-high sides to mitigate the risk of the flow over the top of the inlet channel, where both are used alternately during normal flow levels on a monthly basis.

Two Series-A Munchers from NOV Mono have helped reduce maintenance intervals and improve capacity at the Lynn Wastewater Treatment Plant.

The Mono Muncher is a twin-shaft, slow-speed, high-torque grinder offering an ideal solution for the maceration of sludges and solids within a flow. Their twin shafts have a series of interleaved cutters and spacers that create a powerful 'positive displacement' grinding action. Once solids are trapped in the slowly-revolving cutters, the differential speed of the cutter stacks pulls apart fibrous material, crops and shears plastic, and crushes brittle materials, while the low cutter tip speeds reduce wear rates by minimizing any impact loading.

Suitable for either pipeline or channel installations, the Series-A Muncher eliminates the need for manual handling of screening debris and the associated transport costs. It can be installed into an existing concrete channel or in a fabricated frame, complete with guide rails, into an existing submersible pump station as a simple and quick retrofit.

The Munchers are ideal for high-volume grinding applications and offer rugged and reliable protection for pumps and other downstream process equipment. The Munchers are supplied with a programmable logic controller (PLC) to protect the machine against damage and overloads. An optional Profibus data capture system is available to record operational information.

About NOV Mono Group

NOV Mono is a division of National Oilwell Varco. It comprises a group of specialist companies offering progressing cavity pumps, artificial lift systems, industrial mixers, heat exchangers, grinders, screens and aftermarket replacement parts and services, across a broad spectrum of industrial sectors including water and wastewater, oil and gas, chemical, pulp and paper, food and beverage and agriculture. The company first began manufacturing progressing cavity pumps in 1935 and industrial mixers in 1952, giving it a heritage of over 75 years. For more information, visit


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