KWS Manufacturing

Shaftless Screw Conveyor System for Conveying Biosolids in Florida Keys

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Plant Name and Location

Cudjoe Keys AWRF
Cudjoe Key, FL

End User or Owner

Florida Keys Aqueduct Authority
Key West, FL

Consulting Engineer

Black & Veatch
Orlando, FL
B&V Project: 163528

Contractor

Wharton-Smith, Inc.
Palm City, FL

Wastewater Rep. for KWS

ENVIROSALES OF FLORIDA
Sarasota, FL

General Description of the Application

The Florida Keys Aqueduct Authority (FKAA) was created in 1937 by Special Legislation of the State of Florida and is the sole provider of potable water for all the residents of the Florida Keys. In 1998, the Authority’s primary purpose was redefined to include collecting, treating and disposing of wastewater in certain areas of the Florida Keys. In accordance with the later mandate, a new 0.94-mgd advanced water reclamation facility for an environmentally sensitive area in the Florida Keys was constructed.

The project included:

  • An Operations Building
  • Influent Screening Facilities
  • Flow Equalization Basis
  • Biological Nutrient Removal Systems
  • Secondary Clarifiers

The biological residuals from the above processes are dewatered in a centrifuge and conveyed using a shaftless screw conveyor to a disposal bin for landfill.

Design Parameters of Application

  1. Sludge: Dewatered Biosolids
  2. Capacity: 150 Cubic Feet per Hour
  3. Density: 60 lbs. per Cubic Foot
  4. Solids Content: 15 to 21-percent Dry Solids
  5. Location: Outdoors

Advantages Provided by KWS

KWS has the experience and expertise to design equipment for unique and challenging conditions. The dewatering system including the centrifuge and shaftless screw conveyor was located outdoors in an open-air structure and subjected to salt water mist, storm surges and hurricane force winds. Also, the dry solids range was large and the conveyor had to be designed to convey without a significant loss of efficiency or blockage. The conveyor was designed to convey very watery biosolids to a drain at the lower end of the conveyor and dry, dewatered biosolids to a bin at the upper end of the conveyor for disposal at a landfill.

Special Features of KWS Design

With a full understanding of the service conditions and design requirements, KWS designed a shaftless screw conveyor system complete with structural supports and both rigid and flexible chutes. 316-stainless steel provided the greatest corrosion resistance to the salt water environment and was used for shaftless screw conveyor housing, chutes and structural supports. KWS designed the shaftless screw conveyor and supports to withstand hurricane wind loading and made the system water-tight to prevent water entry during storm surges.

An oversized drain with flushing provision was included at the lower end of the conveyor. The drain location was optimized to limit potential egress of higher solids material. The conveyor was designed to operate in reverse to allow lower solids material produced by the centrifuge at startup and during cleaning to be separated from the dry, higher solids cake going to disposal.

Testimonial

"The shaftless screw conveyor system provided by KWS fit up perfectly with no issues. We appreciate your attention to detail and your quick response to our needs. KWS is a professional organization and we hope to work with you on many future projects."

Philip Mintzer, Project Manager – Wharton Smith, Inc.

Biosolids / Sludge

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