Custom-Designed Screw Feeder with Hopper to Distribute Dewatered Biosolids to Belt Dryer Pottstown, PA

General Description

Pottstown is a borough in Montgomery County, about 40 miles northwest of Philadelphia on the Schuylkill River. Pottstown’s Wastewater Treatment Plant treats sewage from the Borough of Pottstown and West, Upper, and Lower Pottsgrove Townships. The Wastewater Treatment Plant was upgraded to 15.6 million gallons per day (MGD) 1992. The plant treats waste generated by 15,000 area homes, commercial businesses, and industrial sites. Working around the clock, seven days a week, 14 employees at the plant treat an average of six MGD of sewage a day. Flows can reach as high as 40 MGD during heavy rain.

The existing dryer for dewatered biosolids at the Pottstown plant had incurred tremendous amounts of maintenance costs over the last few years. The Pottstown Borough Authority decided to purchase a new belt dryer from Gryphon Environmental. The Gryphon dryer is energy efficient and creates higher quality fertilizer to be used on local farmland, creating increased revenues for the borough. Gryphon requested that KWS design and build a special screw feeder with surge hopper to evenly feed their belt dryer.

Design Parameters

1. Product Type: Dewatered Biosolids
2. Material Density: 45 Lbs. per Cubic Foot
3. Rate: 268 Cubic Feet per Hour
4. Hopper Capacity: 96 Cubic Feet
5. Duty: 7 Days a Week, 24 Hours per Day

KWS Advantages

The Pottstown project was a design-build effort between KWS and Gryphon. Gryphon and KWS have worked as a partnership on several previous projects and have a very successful working relationship because both companies offer professional engineering services and quality workmanship. The two teams worked together for several months to determine the desired capacity, hopper footprint, and features.

Since both KWS and Gryphon use 3D CAD programs to better conceptualize the integration of complex machines, the coordination was seamless and once the design was realized it was quickly put to paper and built. KWS sent a licensed professional engineer to the site for conveyor startup and training. The startup test went very smoothly, the concept was proved to the customer’s satisfaction within minutes.

Special Features

The screw feeder and surge hopper were designed to store an exact volume of dewatered biosolids needed to accurately feed the belt dryer. The screw feeder, surge hopper and structural supports were constructed from heavy duty carbon steel. Two view ports with clear plastic covers were added so the operator could see how the pile of dewatered biosolids formed inside the hopper.

The biosolids are leveled in the hopper with a leveling screw to utilize the complete hopper volume. The screw feeder was designed with variable pitch to accurately meter biosolids to the distributing screw. All the screws were integral post ribbon screws to prevent material from sticking to the center pipe. KWS devised a unique method to deliver an even, controlled feed across the 10-foot wide belt dryer using adjustable plate slide gates.