Editor’s Note:In the October 2012 issue of Flow Control, 11 case studies/application stories featured the winners of our 2012 Innovation Awards program. In the following weeks, each winner will be featured on the FlowStream blog. The following post focuses on seepex’s Cake Pump System with Load Cell.
The Harpers Ferry & Bolivar W.V. Public Service District Waste Water Treatment Plant is home to the first fully integrated seepex cake pump system. The towns are located near the Potomac and Shenandoah river fork. Quaint, quiet and serene, with a population of around 1,500, the towns never had a huge need for waste treatment. However, new, more stringent environmental laws are pushing for better, more contained systems. Replacing drying beds and front-end loaders, the new, more compact system is more efficient and environmentally friendly. Load cells, discharge pressure protection, run-dry (TSE) protection, and thermal motor overheat protection are connected to a custom control system, which allows for easy adjustments and monitoring.
|The Harpers Ferry & Bolivar W.V. Public Service District Waste Water Treatment Plant is home to the first fully integrated seepex cake pump system. (Photo courtesy of seepex)|
Before seepex, the combined WWT service district utilized drying beds. The cake was open-air dried and then loaded into dump trucks and hauled off to a local landfill.
seepex replaced this method of open-air cake dewatering and front-end loader disposal. The plant has installed a belt press machine that squeezes the solids to reduce the moisture content. The belt press is being fed by a seepex BN 30-6LT progressive cavity pump. The dewatered remains have a solid content of 16 to 18 percent. The dewatered cake solids are doctored off of the belt and fall into the hopper of the seepex BTI 17-12 progressive cavity pump. When the cake reaches a certain level, the load cell system will register the increase and it will tell the pump to turn on. The pump will increase or decrease production as needed; when the belt stops feeding the hopper, the pump will turn off.
As a preventative measure, the system is also outfitted with TSE – run dry protection, which will shut off the pump if it senses temperatures above safe levels. Motor thermal overheat protection is similar to the TSE. It will shut off the pump if the motor temperature reaches unsafe levels. Finally, the discharge pressure ring will protect the discharge piping from catastrophic failure due to overpressure.
All of theses sensors are monitored through a seepex control panel. The control panel shows the load cell weight level, shutoff button, cake output temperature, lime feed signal, and various fault signals for the above-mentioned sensors.
The system is equipped with a lime feed system, which enables operators to create Class-A bio-solids. Class A can be used in agriculture as fertilizer. To reach Class A, cake pathogens are reduced to non-detectable levels through chemical and heat treatments.
Jimmy Williams, Harpers Ferry-Bolivar WWTP Supervisor says, “We are happy with the product that seepex has provided. The pumps are running without issues.”