No Wasted Energy for Water Utility
Supervisory control and data acquisition (SCADA) systems—computerized systems to monitor and control treatment processes—are widely used in the water and wastewater industry these days. And so, the benefits are well-known. Birmingham, Ala., is one municipality that understands the value of SCADA.
Supervisory control and data acquisition (SCADA) systems—computerized systems to monitor and control treatment processes—are widely used in the water and wastewater industry these days. And so, the benefits are well-known.
Birmingham, Ala., is one municipality that understands the value of SCADA. The local water utility is using this state-of-the-art information technology to produce reliable knowledge and decision-making power that meets virtually all the needs of its large, complex water/wastewater system. A significant impact of the SCADA system was on the utility's energy usage and efficiency.
Managing the Large and Complex
Actually, the Birmingham Water Works and Sewer Board (BWWSB) operates water and wastewater facilities beyond the city limits. It serves a nine-county, 920-sq.-mi. area that serves some 630,000 people—almost one-sixth of Alabama's population. Its operations include four water filtration plants, three raw-water systems, two wastewater treatment plants, 145 remote facilities, more than 3,630 miles of distribution mains and 16 different pressure gradients.
Historically, the utility has had a reputation for very high water quality, but by the early 1990s, the BWWSB recognized the need to improve operational, maintenance, engineering and management functions.
Data management throughout the utility was one area that required special attention. In-plant process information was recorded on chart recorders and transferred manually to hourly logs, as were other data reports—a labor-intensive process that provided only isolated snapshots of operating conditions. This system was inadequate for planning or decision-making.
The problems were manifold. Aging and often obsolete instrumentation, telemetry and control equipment were increasingly difficult to maintain, with spare parts unavailable. Moreover, communication between plants and remote sites depended on unreliable, inflexible and expensive tone telephone lines.
Also, engineering, modeling and system management were complicated by the lack of historical data, which prevented accurate calculation of the system's peak hourly flow, a fundamental measurement for planning and modeling.
Finding a Center
With no system-wide information center, the water system was operating as six independent subsystems, each unable to monitor the others effectively. Since many distribution system pressure gradients are fed by more than one subsystem, the lack of information-sharing inhibited coordination of operations among plants and hindered planning for improvements.
The inability to monitor power usage precluded analysis of the cost of supplying water from different facilities within the system. While the operations staffs were confident that energy efficiency could be improved, they lacked the information to make that analysis.
Recognizing these shortcomings, BWWSB developed an ambitious long-term vision for integrating information systems into a single system that would promote understanding and facilitate decision making, improve efficiency, enhance operational effectiveness and avoid future problems. The first step in achieving this vision was to ask White Plains, N.Y.-based Malcolm Pirnie, Inc./Red Oak Consulting to plan and create a comprehensive SCADA system. (For an overview of the system, see "SCADA System Highlights," p. 22.)
This pioneering project used innovative information technology to solve specific BWWSB needs. While conventional WANs utilize data mapping for information transfer, severely limiting control functionality and system support, the use of X-Windows provides access from any SCADA hub to any other, allowing all functions to be completed locally. Activities from troubleshooting to correcting software problems can now occur over the WAN from any SCADA hub.
Unlike conventional radio systems, which are limited by rigid, inflexible routing configurations, the BWWSB "smart" radio network provides a flexible mesh of coverage, routing and re-routing messages until they get through, providing complete communications redundancy between hubs and remote sites. In addition, system software allows complete diagnostics of the radio mesh—graphical links showing the location, signal strength and accessibility of each radio in the network—from laptop computers in BWWSB vehicles virtually anywhere in the Birmingham area.
Redundancy of all critical components, data security and "fail-safe" configuration assure the system's reliability. The real-time and historical data provided facilitate system analysis and modeling, so improvements can be planned effectively.
Positive Impact on Power
The impact of reliable communication on power consumption is subtle, but significant. Starting and stopping equipment at just the right time is key to minimizing power demand and consumption. For example, in the event of a power outage, elevated storage tanks provide a source of pressure that typically is built up at night, when demand for water and electricity is low, and used during the day. Local protective strategies start and stop booster pumps in response to high and low limits to maintain minimum tank levels. During periods of high demand, system-wide strategies start filling tanks sooner, often eliminating the need to start a second fill pump. Demand is reduced and pumping efficiency is slightly improved.
The system also provides BWWSB with new reporting capabilities that further increase its efficiency and access to information. The SCADA system database is accessible for queries in real time, with web pages illustrating real-time system flow, pressure and level data, providing external monitoring capabilities without compromising security. The system also exports historical data, produces draft reports automatically and notifies superintendents for report approval. Approved reports make the BWWSB knowledge system available through an Intranet browser, helping to ease the flow of information throughout the organization.
Results Meet Expectations
Designed with input from all stakeholders, the project has been a tremendous success—more than meeting BWWSB's vision and exceeding expectations. The SCADA system has provided the desired platform for a true knowledge system.
At the same time, it has had an important impact on the utility's power strategies. By monitoring energy usage of large motors, and variations in demand patterns, management has developed effective peak power shaving strategies as well as intelligent approaches to energy optimization and system planning.
For the first time, the BWWSB is now able to track costs and manage energy usage by better planning where and when pumping occurs—a critical energy concern in a system that includes scores of motors that are greater than 4,000 hp. By using real-time power, flow and pressure information to calibrate the hydraulic model, and using the model to develop operating strategies, BWWSB has developed control strategies so demand charges and power usage charges can be significantly reduced.
Since most pumping stations serve multiple pressure gradients and the efficiency (wire-to-water) of a given system is affected by the overall distribution system demand pattern, BWWSB can now constantly monitor power distribution and make shifts when necessary.
For example, at a given time, station A might be the most efficient and would be employed, but six hours later, a firefighting demand near station B makes it the more efficient choice and the swap is made.
This largely self-diagnostic system also provides excellent troubleshooting tools that allow BWWSB staff to pinpoint problem locations quickly and correct many problems remotely via laptop or from the CORE. By tracking the hours of run-time on all motors, BWWSB operators can plan more effective preventive maintenance. Cost savings are also achieved through automatic data collection, eliminating the need for manual hourly logs.
The system provides user-friendly graphics and efficient alarm management-prioritizing and displaying alarms as they occur and, by predicting alarms, prompting operators to take action before problems occur.
The value of these predictive capabilities was proven when the BWWSB modeled the effect on water distribution of taking a storage tank off-line. Using model output, they developed an automatic control strategy to bypass water at a remote site and prompt operators to run pumps—a far more effective operating strategy than reacting without advance knowledge of consequences.
Completed at a construction cost of $5.7 million—substantially below budget-in addition to the savings achieved by the system itself, the new SCADA system has had a very positive economic and operational impact.
SCADA System Highlights
Working closely with the Birmingham, Ala., Water Works and Sewer Board, Pirnie/Red Oak, White Plains, N.Y., devised a unique supervisory control and data acquisition systems solution, combining distributed control architecture for the operational subsystems and a remote telemetry unit (RTU) architecture for remote sites. The major features of the plan include:
Full power monitoring units (multi-line) for large pumps over 1,000 hp, and watt and VAR transducers on all pumps larger than 50 hp.
Redundant operator interface computers, controllers and data highways at the four water plants, two wastewater plants and six large raw water pumping stations, each serving as a SCADA "hub."
Central operations room and emergency recovery (CORE) center to monitor the entire system and provide historical data logging and archiving.
Wide area network (WAN) connecting the SCADA hubs and the CORE.
"Smart" radio network, owned and operated by BWWSB, providing redundant communications paths between SCADA hubs and remote sites.
RTUs at each monitored remote site providing flexible local equipment protection, with software able to be edited and downloaded over the radio network.
Local area network (LAN) Interface with the BWWSB's PC network, for real-time and historical data.