City of Dartmouth Reduces Polymer Usage and Improves Dry Solids with Polyblend® Polymer Preparation Systems

Dartmouth Seal

Located about 60 miles from Boston with over 21,000 residents, the City of Dartmouth, Massachusetts is one of the oldest communities in the country, having been incorporated in 1664. The City of Dartmouth, Massachusetts Water Pollution Control Division is responsible for operating the town's 3 million gallon per day wastewater treatment facility, a testing laboratory, a composting site, a sludge facility, and 21 sewerage-pumping stations. Interestingly, the wastewater treatment plant also composts its biosolids residuals (combined with brush and yard waste from local landscapers) into marketable quality product, which is sold commercially.

"The Polyblend® polymer activation systems have performed flawlessly since installation and will result in very significant polymer saving for our facility"

Carlos Cardoso, Water Pollution Control Manager
City of Dartmouth, MA

The Dartmouth facility utilizes emulsion polymers to aid in the dewatering of the sludge. With plant personnel always striving for improved efficiencies, polymer usage was targeted as an area for improvement. Prior to 2014, the plant used hydraulic polymer mixing systems to feed two belt filter presses which operate four days a week for 8 hour shifts. Hydraulic polymer mixing systems rely on a significant pressure drop as the driving force for polymer activation and most often require booster pumps to achieve an adequate influent pressure. Low or variable influent water pressures can result in inadequate energy at the moment of initial polymer wetting. The outcome is less than optimal polymer chain "relaxation" and ultimately more polymer use for the dewatering application.

Two Polyblend® M-series units were installed in 2014. The Polyblend® systems utilize a two-zone mechanical mixing regimen to generate the correct amount of shear force on the polymer mixture ("G-value") to properly and consistently activate modern wastewater treatment polymers. Since installation by Methuen Construction, the Polyblendsup>® polymer activation units have run flawlessly and resulted in significant polymer savings for the Dartmouth plant.

Polyblend<sup>®</sup> M-series

One of two Polyblend® M-series polymer activation units
in the City of Dartmouth Water Pollution Control Facility