Ceramic Lined Sludge Conveyors for Lewiston WWTP Lewistown, PA
Borough of Lewistown
Lewistown, PA
Gannett Fleming Inc.
Harrisburg, PA
G. M. McCrossin Inc.
Bellefonte, PA
Lewistown WWTP
Lewistown, PA
General Description
The Lewistown WWTP was originally built from 1949 to 1954 as a primary treatment facility. From 1979 to 1981 the plant expanded to treat 2.82 million gallons per day (MGD) and improved to a secondary treatment facility utilizing the complete mix activated sludge process. In the mid-1990s a new headworks facility was constructed. In 2008, the entire anaerobic digester system was upgraded to include a new methane/natural gas boiler. In November 2011, construction started for a new upgrade at the plant to incorporate an updated treatment process to meet the nutrient reduction requirements as required by the Chesapeake Bay Nutrient Reduction Act.
The updated process included two new centrifuges to dewater the sludge. KWS Environmental provided a system of shaftless screw conveyors and gates to transport the dewatered biosolids from the centrifuge room to an outside discharge location to safely load trucks for disposal.
Design Parameters
- Product Type: Dewatered Biosolids/Sludge
- Material Density: 50 to 80 Lbs. per Cubic Foot
- Max Capacity: 1,080 Cubic Feet per Hour
- Duty: 7 days a week, 24 Hours per Day
KWS Advantages
Two Centrifuges Discharge Sludge to Horizontal Shaftless Screw Conveyor
Screw Conveyors are in Tandem and Layout is Simplified
The engineer and owner selected KWS Environmental shaftless screw conveyors early in the project. Grit and other abrasives can sometimes make it into the sludge and go all the way through the dewatering process to the conveyors. KWS provided the ideal solution for conveying the abrasive sludge by using the super durable KWS-350 spiral with ceramic lined troughs. KWS located the centrifuge loadout screw conveyor only a few feet off the ground so the centrifuges sit on short piers; making everything very accessible and maintenance friendly. KWS utilized a tandem connection where the centrifuge loadout screw conveyor directly couples end-to-end to the truck loadout incline screw conveyor.
The simple, clean layout was reviewed and approved by the owner and engineer with no modifications. Attention to detail and the use of 3D modeling by the KWS engineering team made the design process simple. The conveyor system was started up by a member of KWS’s engineering team with no issues.
Special Features
The KWS Environmental shaftless screw conveyor troughs and covers were constructed from 304 stainless, typical for a sludge application. The shaftless spirals were made from the exclusive KWS-350 micro-alloy material that is the strongest and most durable spiral on the market. The troughs were lined with 3/8-inch thick ceramic tiles, ensuring an extremely long maintenance life.
KWS also provided two dewatering slide gates below the centrifuge outlets. The dewatering slide gates, also known as diverter gates, are designed to be closed while the centrifuge is ramping up at the beginning of its dewatering cycle. A drain above the gates captures low solids liquid that cannot be loaded out to trucks. Once the centrifuge reaches the point in its cycle where the desired dryness of cake is achieved, the diverter gates open and transfer the sludge to the conveyors. The gates featured multiturn electrical actuators to move the slide gate plate reliably and precisely.
Testimonial
"The KWS system is well-designed and very reliable."
Don Dippery – Superintendent, Borough of Lewistown
Truck Loadout Incline Screw Conveyor Projects Through Wall
Trucks are Loaded with Sludge and Taken to Disposal
Low Solids Liquids are Diverted to Drain Line
Electrically Operated Diverter Gates Open When Sludge Dryness is Sufficient
