AWWA ACE63039

The city of Jackson, Mississippi, is served by two surface water treatment plants: the 25- million-gallon-per-day (mgd) O.B. Curtis plant; and, the 42-mgd J.H. Fewell plant. To meet increasing water demands and future water quality regulations, the city is expanding the O.B. Curtis facility to 50 mgd with the addition of a new 25 mgd ultrafiltration (UF) membrane facility. In addition to the onsite addition of the UF membrane plant, improvements include: expansion of the raw water pump station; modifications to the chemical systems and sedimentation basins; new ultraviolet (UV) disinfection for the conventional filters; addition of a second clear well; and, new conventional plant human machine interface/programmable logic controller (HMI/PLC) control system, high-service pump station, and closed circuit television security system. Since the UF membrane facility will treat coagulated/flocculated water and then be pumped to the new clear well, controlling the raw water flow and chemical feed addition prior to its reaching the membrane system is critical. This paper demonstrates the difficulty of incorporating the UF membrane plant instrumentation with the overall conventional plant supervisory control and data acquisition (SCADA) system. To avoid problems in the construction phase, it was essential that consideration be given during the design phase to process design, construction sequencing, and conventional plant HMI/PLC control systems design. Consideration also had to be given to merging the new stand-alone HMI/PLC UF membrane plant control system with the new conventional plant HMI/PLC control system, thus forming a single plant-wide control system. Because the UF membrane operation relies on proper raw water flow rates and dosing of chemicals, responsibility for control of these systems belongs to the UF membrane manufacturer. This paper provides insight into the decision making process of the design team as they worked together with the UF membrane system supplier to incorporate the new UF membrane control system into the overall conventional plant control system.