Susquehanna Water Pollution Control Facility Disinfection Improvements

Key Accomplishments

• Maintained continuous disinfection of plant effluent throughout construction. The work was performed within an operating wastewater treatment facility, and construction sequencing had to maintain plant operation while minimizing utility and treatment-process interruptions.
• Performed general, structural and mechanical demolition required for installation of the new disinfection equipment and systems. The existing sodium hypochlorite storage tanks remained in service, while non-salvaged equipment was removed and selected existing metering pumps were turned over to the Owner.
• Furnished and installed two new sodium hypochlorite variable-speed peristaltic feed pumps and relocated two existing constant-speed sodium hypochlorite pumps. The specified new equipment was based on the Watson-Marlow 620 Series, capable of approximately 1.0 to 70.0 gallons per hour at 30 psig.
• Integrated the new sodium hypochlorite pumps with the existing chemical-storage tanks and the new chemical induction system, furnishing the associated process piping, fittings and accessories necessary to create a complete functional hypochlorite feed system.
• Installed a new sodium bisulfite chemical feed system consisting of three positive-displacement peristaltic metering pumps. The basis-of-design pumps were Watson-Marlow Qdos30 units, capable of approximately 0.1 to 7.9 GPH at 100 psig, with integral variable-speed drives and sealed leak-containment/detection features.
• Installed a new 2,000-gallon sodium bisulfite chemical storage system consisting of a vertical high-density cross-linked polyethylene tank with an integrally molded flanged outlet, fume scrubber and required accessories. The tank was designed for 38–40% sodium bisulfite solution and required PA DEP permitting and registration prior to use.
• Replaced the former sulfur-dioxide-solution piping with a new sodium bisulfite chemical-piping system and installed the process piping, valves and fittings required to connect the new storage tank and chemical feed pumps.
• Installed specialized chemical-service piping and valves, including Schedule 80 PVC, polyethylene and chemical-compatible polypropylene tubing used throughout the sodium hypochlorite and sodium bisulfite systems. The sodium bisulfite fill connection incorporated Schedule 80 PVC piping and dedicated chemical identification.
• Installed Schedule 80 CPVC double-containment chemical piping, consisting of a Schedule 80 CPVC primary carrier pipe supported inside a Schedule 80 CPVC secondary containment system with drain and leak-check provisions.
• Completed rigorous testing of the double-containment piping system. Primary piping was pressure tested at 150% of system design pressure for one hour, while secondary containment was pneumatically tested for a minimum of 2½ hours, with pressure limited to 5 psi and joints inspected for leakage.
• Furnished and installed a new submersible chemical induction system at the Chlorine Contact Tank Flow Division Chamber, modifying the chamber for installation while retaining the existing diffuser system and connecting the sodium hypochlorite feed piping to the new mixer.
• The chemical induction system was designed for a 35.0 MGD peak hourly flow, 15.0 MGD average flow and a chemical feed rate of approximately 70 GPH. The system was designed to rapidly induce and disperse treatment chemical directly into the wastewater stream.