Dorsey Run Advanced Wastewater Treatment Plant Sludge Dewatering Upgrade

Key Accomplishments

Johnston Construction Company

• The project included demolition and removal of existing belt filter presses, chemical tanks, associated piping, supports, electrical equipment, controls, and other sludge-processing components.
• JCC installed new shaftless screw conveyors to transfer dewatered sludge cake from the centrifuges to the existing downstream belt conveyor and lime-stabilization system.
• The work was carefully phased so that one existing belt filter press or one new centrifuge remained available for operation throughout construction, except for approved short-duration shutdowns.
• JCC coordinated structural modifications, equipment supports, process piping, electrical distribution, programmable controls, instrumentation, equipment integration, startup, performance testing, and operator training while the wastewater treatment plant remained fully operational.
• Maryland Environmental Service awarded Johnston Construction Company Contract No. 1-24-2-01-5 .The contract required JCC to furnish the supervision, labor, tools, equipment, materials, services, and incidental work necessary to upgrade the sludge-processing and dewatering systems at the Dorsey Run Advanced Wastewater Treatment Plant.
• The project focused on replacing the wastewater treatment plant’s aging belt filter press equipment with modern centrifuge-based sludge-dewatering systems. The improvements were designed to provide a complete, coordinated, and operable dewatering process capable of handling the plant’s blend of primary sludge, waste-activated sludge, and septage.
• JCC coordinated the overall construction effort, including project management, scheduling, submittals, demolition, equipment procurement, structural modifications, metal fabrications, process piping, polymer systems, sludge conveyors, electrical work, instrumentation, controls, testing, startup, training, and project closeout.
• The principal process improvement included removal of two existing belt filter presses and installation of two new high-speed, horizontal, solid-bowl centrifuges.
• Each centrifuge system included the centrifuge bowl and scroll assembly, main drive motor, variable-frequency drive, back-drive system, lubrication system, control panels, starters, instrumentation, flexible connectors, sludge-feed connections, centrate-discharge piping, dewatered-sludge chutes, and related appurtenances.
• The centrifuges were designed for intermittent or continuous operation and were capable of operating up to 24 hours per day, seven days per week. The systems were specified to process approximately 75 gallons per minute of sludge per unit while producing dewatered sludge cake suitable for downstream lime stabilization and disposal.
• Dewatered sludge discharged from each centrifuge into new inclined shaftless screw conveyors. The conveyors transferred sludge cake to the plant’s existing belt conveyor system and then to the existing lime-stabilization and truck-loading equipment.
• The new screw-conveyor system included stainless-steel troughs, spiral conveying elements, liners, covers, supports, drives, discharge chutes, and controls. The conveyors were coordinated with the centrifuge discharge elevations and the existing downstream sludge-handling equipment.

Concrete Services Division

• CSD constructed concrete curbs, equipment pads, troughs, slabs, walls, columns, and pedestals required to support the new centrifuges, polymer-storage and feed equipment, shaftless screw conveyors, process piping, and related sludge-dewatering systems.
• The work included footing forms, slab-on-grade forms, straight-wall forms, column forms, concrete placement, floating, screeding, machine troweling, pointing, patching, floor hardener, curing, and concrete accessories.
• CSD installed approximately 150 square feet of footing forms, 195 square feet of slab-on-grade forms, 200 square feet of straight-wall forms, and 256 square feet of column forms.
• CSD placed approximately 27.51 cubic yards of slab-on-grade concrete, 1.85 cubic yards of wall concrete, and 3.16 cubic yards of column concrete.
• Concrete accessories included vapor barrier, special waterstop, premolded joint material, joint sealing, anchor-bolt and dowel coordination, and related materials necessary for complete concrete construction.
• CSD coordinated its work with Johnston Construction Company, the equipment manufacturers, reinforcing-steel installation, concrete deliveries, pumping services, testing, embedded items, and the phased construction required to keep the active wastewater treatment plant operational.
• The overall project replaced two existing belt filter presses with two new sludge-dewatering centrifuges and associated piping, valves, electrical systems, instrumentation, and controls. The project also included a new liquid-polymer storage and feed system, shaftless screw conveyors, structural modifications, and related process improvements.
• CSD’s work provided the structural concrete improvements required to support the new sludge-dewatering equipment and associated systems.
• CSD coordinated its work with Johnston Construction Company’s overall project schedule, the approved equipment layouts, reinforcing steel, anchor bolts, dowels, piping penetrations, electrical conduits, embedded components, and equipment-clearance requirements.
• The forming scope included approximately 150.15 square feet of footing formwork, 195.33 square feet of slab-on-grade formwork, 200 square feet of straight-wall formwork, and 256 square feet of column formwork.
• CSD furnished the rental form materials, form lumber, fasteners, bracing, tools, and labor required to install, support, align, and strip the forms.
• The formwork established the required dimensions, elevations, slopes, openings, edges, and equipment-support configurations shown on the structural drawings.
• The concrete-placement scope included approximately 27.51 cubic yards of slab-on-grade concrete, 1.85 cubic yards of wall concrete, and 3.16 cubic yards of column concrete.
• Johnston Construction Company purchased the ready-mixed concrete and paid for concrete-pumping and testing services. CSD coordinated the concrete deliveries, pumping operations, testing laboratory, placement sequence, and use of equipment furnished by JCC.

B & R Electrical Contractors

• BRE’s scope included electrical demolition, conduit, conductors, boxes, devices, equipment connections, switchgear modifications, instrumentation wiring, inspection, testing, startup, and project closeout.
• BRE made the existing electrical equipment safe for demolition before Johnston Construction Company removed the existing belt filter presses, chemical tanks, piping, and associated sludge-processing equipment.
• The work included two new 125-amp motor-control-center buckets, one dual-mounted 20-amp MCC bucket assembly, a 15 kVA transformer, 100-amp Panel D, and a 30-amp non-fused disconnect switch.
• BRE modified the existing conveyor control panel to integrate the new centrifuge and shaftless screw-conveyor equipment with the plant’s existing sludge-handling system.
• Electrical and instrumentation raceways and conductors were installed for the two new centrifuges, polymer storage and feed system, conveyors, process equipment, control panels, and associated field devices.
• BRE coordinated electrical shutdowns, demolition, installation, energization, testing, and startup so that one existing belt filter press or one new centrifuge remained available for plant operation throughout the phased construction work.
• The overall project replaced the wastewater treatment plant’s two existing belt filter presses with two new centrifuge systems. The work also included a new polymer storage and feed system, shaftless screw conveyors, process piping, structural modifications, instrumentation, programmable controls, and related improvements.
• BRE coordinated its electrical work with JCC’s overall construction schedule, equipment demolition, centrifuge installation, conveyor installation, polymer-system improvements, process piping, instrumentation, control-system integration, and plant operations.
• The electrical scope began with demolition and make-safe work associated with the existing sludge-dewatering equipment.
• BRE identified, isolated, disconnected, and made safe the electrical circuits serving the belt filter presses, polymer equipment, controls, conveyors, and other components scheduled for removal.
• This work allowed JCC and the responsible equipment trades to remove the existing equipment without exposing personnel or operating plant systems to energized electrical hazards.
• The project was carefully phased to maintain sludge-dewatering capacity throughout construction. The existing out-of-service Belt Filter Press No. 1 was removed first, followed by installation of the first new centrifuge.
• The first centrifuge had to be electrically connected, tested, started, and accepted before the second existing belt filter press could be removed. BRE coordinated its electrical demolition and new installations around this operating sequence.
• The electrical installation included new conduit, conductors, boxes, devices, supports, flexible connections, grounding, identification, and equipment terminations shown on the electrical and instrumentation drawings.