Building Design > Project Case Study

SCADA and Automation Upgrade

The city of Haverhill owns and operates a conventional activated sludge treatment facility that treats an average dry weather flow of approximately 7 MGD. During peak flow conditions the facility can receive flows up to 60 MGD. For centralized monitoring of the facility, an antiquated graphical display panel shows equipment motor status, and strip-chart recorders for various process parameters, and an annunciator panel for alarm indication. This panel had served the City from plant inception with no modification for decades.

Wright-Pierce was retained to design upgrades for a facility-wide SCADA and distributed logic control system. There has been a phased implementation of the upgrades including the dewatering system and primary sedimentation basins equipped with PLC-based control panels. To address the need for a centralized collection of data and an alarm system, Wright-Pierce instrumentation engineers designed and installed a new fiber optic, ethernet-based PLC network, based on the RING configuration. It provides several new PLC-based control panels to automate the aeration, chlorination and sludge thickening processes.

In this configuration the fiber optic network cable is installed between each control panel and then ultimately back to the first control panel in a "ring" formation. The major advantage is that the network is fault tolerant. Should a break in the network occur between panels, the communications are automatically redirected in the opposite direction maintaining communications between remote panels and SCADA.

In addition to the work at the facility, a new communication panel was provided at the main influent pump station to the facility that is responsible for 99% of the flow to the plant. This panel provided a link between a new pump station control panel and the treatment plant via a wireless ethernet bridge.

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