Identical Shaftless Screw Conveyor Loadout Systems for Dewatered Biosolids Dry Creek WWTP in Decatur, Alabama

General Description

Decatur is a city in Morgan and Limestone counties in the state of Alabama. Decatur’s Dry Creek WWTP is a 36 million gallon per day (MGD) secondary treatment facility. The plant recently underwent an improvement project to upgrade their dewatering process with two new screw presses along with associated loadout systems. The advantages of using a screw press in mid-size plants include high-percentage dewatering, little operator attention required, and low maintenance.

The addition of the new presses required new shaftless screw conveyor systems to convey the dewatered biosolids to trucks outside of the dewatering building. KWS supplied two identical conveyor systems since redundant presses were required to ensure the plant’s dewatering process would not have any downtime.

Design Parameters

1. Product Type: Dewatered Biosolids
2. Material Density: 65 Lbs. per Cubic Foot
3. Capacity: 144 Cubic Feet per Hour
4. Duty: 7 days a week, 24 Hours per Day

KWS Advantages

The consulting engineer named KWS Environmental as the source of the shaftless conveyors in the specification due to the success of KWS at several projects in the area. KWS was also selected by the mechanical contractor since KWS met the specification with no deviations and provided a competitive price, excellent quality, and quick delivery.

The KWS design team worked closely with the screw press manufacturer, Process Water Technologies, to ensure a seamless connection between the dewatering equipment and screw conveyors. KWS utilized a tandem layout, reducing head room requirements and simplifying conveyor transitions. The design and layout were submitted and approved with minor changes. KWS used 3D CAD to model the screw presses and conveyors to properly fit within the building. A degreed mechanical engineer from KWS performed startup and equipment training.

Special Features

The KWS tandem arrangement consists of a horizontal conveyor discharging directly into an incline conveyor without the use of a transition chute. The horizontal screw conveyor can be installed close to the floor, reducing the height of the screw presses. KWS designs the tandem arrangement to ensure dewatered biosolids convey smoothly from the horizontal to the incline.

KWS chose shaftless screw conveyors to efficiently convey the sticky and wet biosolids. KWS is the industry leader in shaftless screw conveyor design. All exterior components of the conveyors were manufactured from 304 stainless steel for corrosion resistance. The incline screw conveyors were cantilevered over the truck loadout area with counter-balanced structural supports to provide clearance for the trucks and ensure rigidity. The structural supports were built from carbon steel and hot-dipped galvanized.