With population growth in South Florida came the inevitable strain on the local infrastructure, such as wastewater treatment. Palm Beach County recognized what lay ahead and moved forward with a $1.3 million expansion project that doubled the capacity of its existing treatment plant.
The Palm Beach County, Southern Region Water Reclamation Facility, located within viewing distance of the Florida Turnpike, now serves this growing area of the eastern Florida coast with a capacity of 30 mgd. The plant was designed by Hazen and Sawyer, Environmental Engineers and Scientists, to accommodate population growth many years into the future.
A major part of the expansion project involved retrofitting an existing control system and adding a new SCADA system to support the newly constructed portion of the facility. A key factor in the system design was automating the 24-hour monitoring and data acquisition and control functions, with the goal of minimizing operator-machine interfacing and reducing the associated operations manpower.
The SCADA system designed, constructed, and installed by Revere Control Systems of Birmingham, Ala., consisted of 10 Allen-Bradley PLC-5s networked to seven Pentium PCs. Software included Intellution-Fix 32, Release 6.12, providing plant operators with multiple screens of information. Operators can also perform machine interface functions, log equipment runs, and generate trending graphs to support overall plant operations. Reliability was a major factor, and this was accommodated with redundant instrumentation, alternate control algorithms, and online backup systems. The system runs on a Windows NT" platform, with WIN-911" for handling annunciated alarms and Microsoft Excel" for report generation.
The countys remote pump stations communicate with the plants operation center using radios in the 450 MHz range for both receiving and transmitting data. Sites communicate with each other without having to go through the operation center. Alarm conditions at a given site are transmitted directly to the in-plant radio system using a wide area network and WIN-911. This process gives voice messages of the alarms to the appropriate plant personnel.
A significant challenge in the Palm Beach County system was the effluent pump station, consisting of four high-volume pumps. Revere implemented level-based algorithms to achieve automatic control for the adjustable and variable speed pumps in the station. This was critical in maintaining the plant?s balance and effectiveness. The plant?s effluent is used to water golf courses and lawns in the area.
Another challenge was the combined size and complexity of the system?s database. In total, there were approximately 5,000 data points and 5,000 I/O connections, with 2100 annunciated alarms and more than 200 monitor screens. Extensive programming was required to archive existing data, provide local dynamic data exchange, and log equipment run time. The system was designed to predict power usage at 15-minute intervals. By predicting peak energy usage, plant operators are able to use internal energy sources at the appropriate times to lessen the need for utility demands, thus achieving cost savings.
South Florida is known for its lightning, having one of the highest incident rates of lightning strikes in the country. To counter this natural hazard and minimize the potential for damage to expensive equipment, fiber optic cable was employed extensively. Since fiber optic cable is not a conductor for electrical energy, paths through which lightning could enter the equipment were eliminated. Additionally, the cable was installed in mirror runs to provide a redundant signal path that could be rapidly brought into play in the event of cable damage to minimize system down time.
Palm Beach County officials performed a week of factory acceptance testing at Revere?s Birmingham plant, including full system simulation. In conjunction with the factory testing, Palm Beach County operations personnel were able to train on their exact system and be involved in the simulations. Testing was completed on schedule with no major issues identified.
The size of the project required Revere personnel to be on site for almost 12 months, coordinating the retrofit process and installing the new equipment. Throughout the retrofit process, the plant was able to operate normally and without service interruptions. Such a requirement for service continuation is typical of retrofit projects and represents a major challenge to installation and startup personnel.
