ARTICLE
PEI treatment plant simplifies batch sludge handling with VEPAS polymer system
A compact, non-mechanical polymer mixing system is making sludge dewatering easier and more efficient for the North Rustico Wastewater Treatment Facility (WWRF) in Prince Edward Island. Since its commissioning, in May 2014, the plant has relied on a Venturi Emulsified Liquid Polymer Activation System (VEPAS) to inject and activate polymer in a single pass with no mechanical agitation needed.
The one-step, venturi-based VEPAS eliminates many of the components used in mechanical polymer systems, such as mixers and aging tanks. These components not only increase system size, but also require operator attention for maintenance and cleaning. VEPAS also enables operators to easily change the rate of polymer flow—a feature that is particularly important for the North Rustico WWRF, which processes highly variable sludge in batches for dewatering in Geotube® containers.
Allan Nisbet, Operator, at the North Rustico WWRF says that waste sludge from the plant is pumped to a storage tank and dewatered in batches about every six to eight weeks. Since the composition of the sludge varies greatly from batch to batch, Allan always tests the sludge to determine the proper polymer dose rate before pumping sludge to the Geotube® dewatering containers.
“The VEPAS is very simple to operate and provides precise control of the polymer dose, which helps maximize dewatering and reduce our polymer use,” Allan says. “Our system is equipped with an HMI operating panel where we can easily change and monitor the polymer dose rate.” Once the batch is complete, Allan says it takes only about an hour to completely disassemble, clean and reassemble all components – the polymer pump, lines and injector.
“We’ve had great communication and support from Bishop Water, not only during plant commissioning, but on an ongoing basis,” Allan says. “The team recently suggested a new polymer for the dewatering process after reviewing one of our sludge tests. This new polymer should work better with our variable sludge and improve dewatering.”
VEPAS Polymer Dosing System
The VEPAS and Geotube® dewatering has enabled the North Rustico WWRF to become self-sufficient for sludge handling. Solids are dewatered, composted and distributed at the site as landscaping material, eliminating the need for hauling it away for treatment and disposal.
