Solids Load Out System for South WWTP McAllen, TX

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McAllen Public Utility
McAllen, Tx

Consulting Engineer

Carollo Engineers
Houston, TX

Contractor

CSA Construction, Inc.
Wyoming

Plant Name and Location

South WWTP
McAllen, TX

General Description

The South wastewater treatment plant in McAllen, TX is the largest Biological Nutrient Removal (BNR) plant south of San Antonio. The plant is permitted for treating up to 10 MGD (million gallons per day). The most recent plant improvements included expansion of the dewatering system to include two belt filter presses and conveyors for solids load. The new system makes use of the existing solids collection area and is designed to load two dumpsters at a time. The new load out building is covered to protect the equipment from the sun. The new KWS Environmental solids load out system included shafted screw conveyors, supports, slide gates, motion sensing, and emergency stop devices.

Design Parameters

Product Type: Dewatered Biosolids
Material Density: 60 Lbs. per Cubic Foot
Capacity: 400 Cubic Feet per Hour
Duty: 5 Days a Week, 8 Hours per Day

KWS Advantages

Solids Load Out System for South WWTP in McAllen, TX - KWS

Dewatered Biosolids Discharge from Two Belt Filter Presses to KWS Transfer Screw Conveyor

KWS Environmental worked very closely with Carollo Engineers and local operators over several years to design the new solids load out system to the fit the existing building at the South plant. Utilizing the best conveying technology available, KWS chose shafted screw conveyors for the application. Dewatered biosolids are discharged from two belt filter presses to a KWS horizontal transfer screw conveyor and elevated with a KWS vertical screw conveyor.

The biosolids are then transferred to one of two truck bays for load out to containers. Pneumatic controls were provided to supply the operators with manual and automatic control of the loadout conveyor slide gates. The reduced operator intervention and direct loading of containers greatly reduces the man hours associated with operating the system. KWS quickly assisted the Contractor during installation to ensure that all equipment was installed properly.

Special Features

KWS Environmental chose shafted screw conveyors for the solids load out system. Shafted ribbon screws with flanged shafts and the unique KWS Tor-Ri-Flex intermediate bearings are perfect for applications where limited access for maintenance is available. The Tor-Ri-Flex intermediate bearing design requires only periodic lubrication and will last the life of the equipment.

A KWS vertical screw conveyor was used to elevate the biosolids and reduce the footprint of the loadout system. Loadout screw conveyors were located over the truck bays and each conveyor had multiple discharge locations with air-operated slide gates. The slide gates can be opened and closed to evenly load the containers in each bay.

KWS Environmental provided custom supports that bolted together so no welding or field modification was required. Each screw conveyor was equipped with under-speed sensors and emergency pull cord safety stop systems. All conveyor covers were secured with safety bolts that require a special tool to remove. The motors were selected to meet the specifications for the elevation and electrical requirements.