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Project Name: Muncipal WWTP Design
Country: None Listed
Description: Initial work with the muncipal client involved identification of process and operational limitations leading to the design and installation of supplemental aeration facilities and nutrient feed at the Client's 1.8 MGD WWTP. On-going operational support was provided including operator training and review of treatment plant performance with recommendations for operational responses. Design for sewerage interceptor systems and pretreatment program evaluation and recommendations were also provided. In addition, design services for an expansion project were provided that included: solids handling building, personnel building, chlorination/dechlorination building and equipment, sludge thickening, recessed plate filter press, chemical feed systems, aerobic digestion and associated equipment and facilities. Construction administrative services, O&M manuals, start-up training and supervision were also provided. As a result of continued growth, additional expansion of the WWTP was required and design services were provided for an additional expansion of the WWTP from 1.8 MGD to 3.6 MGD and for replacement of the two associated influent pumping stations. During this process assistance was provided in obtaining funding through the Virginia Revolving Loan Program. The completed design included: two influent pump stations; headworks with dual train centrifugal grit removal systems with classifier and mechanical filter screen with manual by-pass bar screen; additional extended aeration facilities incorporating two parallel concrete aeration basins with fine-bubble diffusers fed by positive displacement blowers in conjunction with floating mechanical mixers with automatic dissolved oxygen control; a third 80 ft diameter clarifier with suction arm sludge collector directly to its return sludge pumps; a return sludge pump station with duplex centrifugal pumps and automatic batch waste sludge control as well as a scum removal pump; and a second aerobic sludge digester. The design features incorporated into each of the two influent pump stations included: separate wet and dry well portions in a 30 ft deep reinforced concrete structure with appropriate ventilation and lighting; automatic mechanically cleaned bar screen; three close-coupled influent pumps with controls utilizing variable frequency drives on two pumps, flow measurement utilizing electromagnetic flow meter; emergency power generator and automatic transfer switch; and controls and alarms based on wet well level and pump operational status. The design incorporated extensive improvements to the monitoring and control aspects of the WWTP. An integrated system was designed utilizing five programmable logic controllers (PLC's), each contained in a distributed local control panel, with a sixth PLC located 5000 feet from the WWTP in a remote pump station. The PLC's in these panels communicate over a local area network and all can be addressed via a PC-based graphical operator interface software package. Alarm status, operational status, and various flowrate data are brought back to the PC for display, logging, trending, and reporting. The control aspects of the system include: wet well level control in both influent pump stations via VFD's on pumps, operator selectable flow ratio control of RAS relative to final effluent flow, dissolved oxygen control in all four aeration basins, and proportional influent flow sampling based on the sum of flow signals from the two influent pump stations. Assistance was provided to the Client to obtain necessary NPDES and other regulatory permits. This involved extensive negotiations with the State Department of Environmental Quality regarding limitations set forth in the Upper Roanoke River Water Quality Management Plan. Through these negotiations, less stringent permit limits were obtained which avoided the need for tertiary treatment. Construction administrations services were provided for the expansion.
 

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