Municipal Water Treatment
Feeding activated carbon for drinking water treatment
The Cambridge, Ohio Water Treatment Plant wanted to upgrade its aging screw feed system for the dispensing of powdered activated carbon into the municipal water system. The plant used the carbon to control algae blooms, oil and other industrial wastes in the water supply.
The goal was to improve the control of the carbon levels in the municipal water system. Weighing accuracy was a major concern as the current screw feeder lacked the ability to weigh the carbon and thus was producing wide swings in the amount of carbon dispensed resulting in inaccurate dosing and varying levels throughout the water supply.
Operational efficiency was also a concern as on/off loading of the bags was both time consuming and extremely dirty. Daily, three to four 50 lb. bags had to be slit open and poured into the hopper. This created large plumes of carbon dust that spread throughout the treatment room, making it a dirty and messy job for the plant’s employees.
Scaletron’s application engineers working in conjunction with their local distributor, Dye & Associates recommended the Scaletron Model VMF-28™ Volumetric Screw Feeder with an integrated “Loss in Weight” system as an excellent solution to both control the carbon dust and accurately dispense and weigh the carbon. Specifically designed for accurate feeding powdered chemicals, the Model VMF-28™ features a heavy-duty, gear-driven auger metering mechanism and a built-in Scaletron scale with four load cells for maximum accuracy.
Besides saving operators time, VMF feeders improve accuracy because the integrated scale continually monitors weight loss or gain. Heat, moisture and other environmental variables can cause additives like lime and carbon to absorb or dissipate water. When the material absorbs moisture, its density increases and it is subject to clumping making dispensing by screw feed alone subject to wide swings in the amount of carbon injected into the water system. This can result in not enough, or too much material being introduced into the treatment process. The Scaletron feeders eliminate this risk by providing operators with constant real time assessment of the total mass of additive being used. Precise dosage amounts are automatically weighed and added to treatment processes without requiring an operator to measure and weigh amounts.
In addition, the feeder features a quick change auger that allows the plant to quickly ramp up their feeding capacity in the event of an oil spill or sudden algae bloom.
To reduce the carbon dust, the optional bag loader was added making it a partially sealed operation. To load carbon the operator simply opens the door on the bag loader which automatically turns off the auger. The unopened bag is placed inside the box and slit open using the built-in bag break capturing most of the dust within the system.
The new Scaletron feeding system enabled the Cambridge Water Plant to meet its goal of improving the accuracy of dispensing and monitoring the amount of carbon added to the municipal drinking water supply. In addition, it enabled clean and easy loading of the bags, reducing the problem with carbon dust and improved the employees’ working conditions.