Piscataway WWTP – Grit Bucket Elevator No. 1 Rebuild

Key Accomplishments

• JCC coordinated removal of the existing components being replaced and installation of the new bucket-elevator equipment within the existing wastewater-treatment facility.
• Furnished and installed malleable iron grit buckets attached to a corrosion-resistant steel-reinforced urethane elevator chain in accordance with the WSSC contract requirements.
• Rebuilt major mechanical components including the headshaft, upper idler shaft, lower footshaft, sprockets, drive assembly, gear reducer, chain-tightening system, bearings, receiving/discharge trough, and associated guards and supports.
• Installed a 1.5 HP washdown-duty drive motor and gear-reduction system designed for an elevator-chain speed of approximately 10 feet per minute, with torque-limiting overload protection.
• JCC integrated the replacement elevator into the existing structure using the existing operating-area floor penetrations, avoiding unnecessary modifications to the surrounding concrete.
• Installed a stainless-steel-supported wash-water system with spray header, non-clogging nozzles, flushing connection, valves, strainer, solenoid valve, bypass piping, and heat tracing for cold-weather operation.
• Incorporated Type 304 stainless-steel equipment supports and Type 316 stainless-steel enclosure panels for durability in the wastewater-treatment environment.
• Installed and integrated electrical/control interfaces between the grit elevator and associated grit-processing equipment, including an interlocked control arrangement with independent manual operating capability.
• JCC coordinated factory-representative inspection, dry testing, full-load operational testing, commissioning, and operator training before final acceptance by WSSC.
• Completed additional modifications under the final change order to improve cold-weather operation, safety, and maintainability of the rebuilt system.
• Johnston Construction Company served as Prime Contractor for the Grit Bucket Elevator No. 1 Rebuild at the Washington Suburban Sanitary Commission's Piscataway Wastewater Treatment Plant in Accokeek, Maryland. The project consisted of a substantial rebuild of the existing Keene Corporation/AMWELL grit-elevator system and was delivered as a complete turnkey installation incorporating equipment supply, removal of replaced components, installation, testing, commissioning, and startup.
• The grit elevator formed an important part of the plant's grit-removal process. Grit collected at the end of the screw conveyor was picked up by a continuous series of buckets and elevated vertically to a discharge point, where the grit slurry flowed by gravity to the downstream grit washer. The three-shaft system incorporated a motor-driven headshaft, upper idler shaft, lower footshaft, chain, buckets, sprockets, gear reduction, and chain-tensioning equipment.