It's the mission control center. A semicircular counter lined with keyboards, monitors and telephones sits in front of a wall of four 72-inch projection displays. Is it the Starship Enterprise? NASA headquarters? The Monday Night Football control room?

Actually, this control center monitors processing of 180 million gallons of wastewater everyday. It's the city of San Diego's Clean Water Operations Management Network (COMNET) – one of the world's largest integrated control and information systems linking wastewater facilities.

COMNET uses process control technology from Emerson Process Management to coordinate operations at more than 200 locations over 450 sq. miles, including Point Loma Wastewater Treatment Plant, North City Water Reclamation Plant, the Metro Biosolids Center numerous pump stations in the San Diego area, and South Bay, a fourth water reclamation plant.

To control this expanding wastewater treatment system, San Diego worked with their Program Manager and Emerson Process Management to develop COMNET, a management system integrating all automation, monitoring and information systems for its entire wastewater process. The system was designed to do more than just control a new four-plant structure during and after the expansion – it also improved efficiency and reduced overall costs.

Jim Mueller, senior civil engineer for the San Diego Metropolitan Wastewater Department, for one, is proud of the accomplishment.

“We managed to upgrade a modern wastewater facility that provides our residents with a safe and effective sewer system that is friendly to the environment, fits in well with the local community, and incorporates state-of-the-art technology,” he said.

Safdar Khwaja, Water/Wastewater projects director for Emerson Process Management on the San Diego COMNET Program agrees. “These plants are pieces of art,” he said.

In the Beginning
San Diego and Emerson began the project by installing the WDPF Ò distributed control system (DCS) at the city's Point Loma plant in the early 1990s, and then in the North City Wastewater Reclamation Plant and Metro Biosolids Center (MBC) as they were constructed. WDPF also controlled the associated pump stations.

By 1997, when the city was ready to design and construct the South Bay Water Reclamation Plant and modernize several pump stations, Emerson had developed the Ovation Ò Information & Control system through advances in computer and networking technology.

Ovation, the first DCS to offer real-time, mission-critical control on a PC platform, provides an unprecedented level of performance and power. The system's open architecture reduces the risk of obsolescence often associated with proprietary control systems and is easily incorporated into existing IT strategies, providing better and more accessible facility operation information.

San Diego chose this system to continue its clean water project, which allowed for integration of SCADA (Supervisory Control and Data Acquisition) technology, which will monitor and control more than 100 smaller pumping plants and valve stations using spread-spectrum radio communication through the Ovation base.

The COMNET central control station has two operations consoles with five computer workstations and printers, telephone and radio communications and access to closed-circuit television at each of the four primary wastewater facilities. Four 72-inch projection displays on the wall allow for additional monitoring. Information is displayed in real time – continuously updated every second, with realistic 3-D graphical representations of the treatment process at each facility. Closed-circuit TV images from each plant are viewed through a moveable window on the process displays, eliminating the need for TV monitors.

The 24-hour-staffed central station provides full remote control of each facility without a local operator.

“The system has 45-miles of fiber running through the city. Each facility can be controlled from five to 20 miles away,” Khwaja said.

Different Plants, Different Process Challenges
Although each of the four primary San Diego wastewater facilities can be controlled centrally through COMNET, automating each plant individually posed a new challenge for Emerson Process Management engineers.

In 1990, the Point Loma Wastewater Treatment Plant (PLWTP), was San Diego's only wastewater facility. Expanding the plant, which included a complete retrofit of all equipment, the construction of two new digesters and an upgrade of the cogeneration facility that powers the facility's operation.

According to Khwaja, installing a control system in an existing large manually operated facility like Point Loma, while another construction crew was attempting to expand the plant, was the single most challenging piece of the San Diego COMNET Program.

“Point Loma was the most arduous because it had to be heavily modified to install components of the control system like I/O and sensors,” Khwaja said. “It became quite a surgical undertaking with technical, logistical and operational challenges.”

While it may have been easier to install process control components in the North City, MBC and South Bay facilities as they were constructed, MBC presented its own set of challenges for engineers, because it involved a complex sludge process.

“It is a very complex system,” Khwaja said. “Designing a process control system for that facility was like trying to design retrofit controls for an airplane as big as a 747.”

The work – and challenges – are not complete yet.

The North City plant, which was finished in 1997 with a WDPF system, is already undergoing an expansion, to be completed by the end of 2003. Emerson Process Management will migrate North City to Ovation as part of the expansion. The upgrade, which can be accomplished more quickly with new engineering tools developed by Emerson for the power generation market, will allow operators the flexibility and maintenance ease of PC-based control, and provide the city with freedom from component obsolescence issues that eventually surface from the use of proprietary systems like WDPF.

Before the Clean Water Program was initiated, San Diego had only the Point Loma facility, manually operated with a workforce of 250 people. Despite that plant's expansion and the addition of three facilities and various pump stations to the overall network, only 65 additional employees have been needed for the entire system.

“If these new facilities were operated as the Point Loma facility used to be operated, we would need more than 600 employees to operate everything,” Mueller said. “Instead, we now have 315 total employees, and we avoided layoffs by retraining the previous employees to work in the new environment.”

Employees have been shifted from functions such as pump and valve monitoring, meter reading and the performance of various repetitive tasks. In addition, operations and management reports are now generated automatically.

Savings are also being realized by better control over the amounts of chemicals used in the normal sewage treatment process. Ovation constantly adjusts chemical deployment based on flow levels to optimize usage.

“In the past, in order to have the right amount of chemicals on hand for fluctuating flows, we had to overcompensate and often overused chemicals in the treatment process,” Mueller said. “Now, process control allows the Point Loma plant to flow-pace its chemicals. There is pinpoint accuracy in the chemical releasing process, which allows us to avoid wasting chemicals and results in big savings.”

Another advantage of Ovation is increased energy efficiency. The energy usage of all equipment, like large pumps, is constantly monitored and controlled to operate within the most efficient range.

“A Value Engineering Study done in 1996 showed that we will realize a cost savings of more than $100 million over 20 years because of central automation and control,” Mueller said.

Recognized As a Leader
Serving nearly two million customers in the San Diego regional area, the San Diego Metropolitan Wastewater Department is meeting increased wastewater system capacity demands while building facilities that have been nationally recognized with several awards. The city received the National Wastewater Management Excellence Award from the Environmental Protection Agency, the Gold Award from the Association of Metropolitan Sewerage Agencies and the 1999 Engineering Award form the California Water Environment Association.