June 2012, Vol. 24, No.6

Problem Solvers

Electronic communication system optimizes regional reclaimed-water delivery

Problem: Four pump stations in a regional reclaimed-water distribution system had to compete to pump water into the system.

Solution: Installing new software improved pump-station communication and system operation.

 

More than 1.4 million people live in Orlando, Fla., and the population is growing. The city also is home to some of Florida’s most fertile agricultural areas and the headquarters of large companies. The growing need for water services required an expansion of wastewater treatment at the same time the area faced a state requirement to eliminate effluent discharges to surface waters. In response, Orlando and Orange County, Fla., developed an integrated water reclamation program called the Eastern Regional Reclaimed Water Distribution System.

The system extends the entire length of Orange County and provides reclaimed water to many residential and commercial customers. The pump stations at each treatment plant send reclaimed water to a common transmission force main. The transmission main extends 34 km (21 mi) to deliver the combined flows to the distribution system and out to the customers.

Both Orange County and Orlando pump reclaimed water into the system. It was the first reuse program permitted in Florida and is one of the largest in the country. The system provides approximately 105,980 m3/d (28 mgd) of reclaimed water for landscaping and crop irrigation.

 

Competing for room

The project’s major challenge emerged only after the system was formed: Four different pump stations all vie to pump at the same time. This created competition to put water into the system and caused problems with pressure and maintenance.

“It would take the operations staff[s] of three different facilities to communicate with each other in order to get the system to function correctly,” said Guy Mecabe, wastewater systems manager for the City of Orlando. Even with a concerted effort, the staffs of the three facilities only received updates from each other by phone throughout the week, he explained. “It proved difficult to make operational decisions with such infrequent data,” he said.

Because both the city and county are “selling” water for irrigation through the system, “each is only compensated based on the flow that was delivered to the system,” Mecabe said. “There were several instances where one municipality’s revenues were impacted due to the other [municipality] overpressurizing and delivering more flow,” Mecabe said. “For example, if Orange County’s pressure setpoint was higher than that of the city, then the city delivered no flow and, therefore, collected no revenue for that period.”

System managers needed to collect data from the different supervisory control and data acquisition systems from each pumping station and display it on a single human–machine interface screen. This solution would enable operators to view pump status, valve positions, flows, tank levels, and pressure from each of the pumps stations so they could make informed operational and maintenance decisions.

 

Finding a connection

The city and county met to talk about how to connect the systems and solve the problem. The city’s team already was familiar with Kepware Technologies (Portland, Maine) and suggested using the LinkMaster Software as the application layer solution. However, they discovered an existing connection for law enforcement between the two networks. Using the same link for reclaimed-water pumping only required changing settings on the existing firewalls and assigning network address translation addresses. Both municipalities agreed to purchase the needed servers and software.

The team worked with the LinkMaster Software for a few weeks, creating a virtual environment to simulate the network technology. Due to distributed component object model limitations using open-process-control-data access components, the implementation team exchanged the software for Kepware’s KEPServerEX with both open-process-control-data access and unified architecture drivers, which created a successful exchange across the domains.

 

Measuring success

The results were “exactly as expected,” Mecabe said. Once communication was established, each entity created a read-only tag database based on the others’ open-process control data, and the city and county were each able to build their respective human–machine interfaces.

“Since the implementation, there is no need for anyone to call, and they have up-to-the-second, real-time values with trending,” Mecabe said. “This has saved an estimated 5 to 7 man-hours per week.”

 

©2012 Water Environment Federation. All rights reserved.