KWS Manufacturing

Reversible Shafted Screw Conveyor for Biosolids Handling at Terminal Island Waste Treatment Facilities

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End User or Owner

City of Los Angeles Public Works Department
Los Angeles, CA

Consulting Engineer

MWH Global, Inc.
Pasadena, CA

Contractor

Norman Olsson Construction, Inc.
Orange, CA

Plant Name and Location

Terminal Island Water Treatment Facilities
Los Angeles, CA

General Description of the Application

The Terminal Island Water Reclamation Plant/Advanced Water Treatment Facilities are located 20 miles south of downtown Los Angeles in San Pedro. The plant treats wastewater from over 130,000 people and 100 businesses in the heavily industrialized Los Angeles Harbor area, including the communities of Wilmington, San Pedro, and a portion of Harbor City.

The plant has recently become the third Los Angeles wastewater treatment plant to produce reclaimed water and one of the few plants in the country that produce water using reverse osmosis. This exceptional quality water will soon be used as a potable water replacement in Harbor area industrial applications and as a barrier against seawater intrusion. The plant also produces 50 wet tons of biosolids per day that is trucked to Green Acres Farm in Kern County. Green Acres Farm produces 239,000 cubic feet per day of biogas that is used to produce steam for the digesters for beneficial reuse.

As part of a project to improve their dewatering facility, the City of LA undertook a project to upgrade their dewatering capability. Three new centrifuges were added and screw conveyors were required to take biosolids from the centrifuges and transfer it to the loading area. KWS was asked to participate by providing a reversing, shafted screw conveyor located below the three centrifuges.

Design Parameters of Application

  1. Material: Dewatered Biosolids
  2. Solids Content: 25 to 30-percent by weight
  3. Material Density: 40 to 60-Lbs. per Cubic Foot
  4. Maximum Design Capacity: 25 to 550 Cubic Feet per Hour
  5. Duty: 24 Hours per Day, 7 Days per Week

Advantages Provided by KWS

KWS used 3D modeling to custom design a shafted screw conveyor with slide gates to fit into an existing building and that interfaced with both existing and new equipment. Installation was accomplished quickly and efficiently which allowed the Contractor to deliver on time and within budget.

The plant layout required three centrifuges to discharge into the screw conveyor designed and manufactured by KWS. The screw conveyor then directed biosolids to equipment at either end, making the screw conveyor reversible. Although there was redundancy built into the dewatering equipment, there was none for the screw conveyor. If the screw conveyor fails, then the dewatering facility must shut down. It was essential that the screw conveyor be reliable, robust and that any required maintenance involved little or no downtime.

KWS supported the installation, commissioning and training by providing a qualified and registered professional engineer familiar with the project, design requirements and equipment delivered.

Special Features of KWS Design

KWS exceeded the design and operating requirements of the specifications by providing a shafted screw conveyor constructed from 316 stainless steel with KWS Tor-Ri-Flex intermediate bearings. Each screw length was approximately 16-feet, allowing for the use of two KWS Tor-Ri-Flex intermediate bearings. KWS located the bearings for easy accessibility and maintenance. Routine bearing lubrication is achieved automatically using spring-actuated lubrication pots which can be replaced without tools. Should major maintenance be required, the bearing assembly can be removed without interrupting the adjacent screw sections.

Testimonial

"The screw conveyor has been operating flawlessly for over three years now. The overall quality provided by KWS is excellent. We hope to purchase more conveyors from KWS in the future. Thank You!!"

Tom, Maintenance Mechanic – Terminal Island Water Treatment Facilities

Biosolids / Sludge

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