Clean water more than a pipe dream
California SI project delivers an efficient control system to provide clean and safe water for its customers.
Water scarcity is an ongoing problem in Southern California. Six of the last seven years have been drought years, leaving most of the region highly dependent upon imported water. By using the best technology, sound management practices, public participation, and a balanced approach to human and environmental needs, Sweetwater Authority—known locally as the Authority—provides its customers clean, safe water from local water supplies.
The Authority is a publicly-owned agency that delivers water via 388 miles of pipeline to serve 190,000 people in a 32-square mile service area in Southern San Diego County. The Authority’s customers were among the first in the region to benefit from a desalination (desal) process designed to treat “brackish,” or saline, groundwater to make it safe for human use.
The Richard A. Reynolds Groundwater Desalination Facility uses reverse-osmosis (R/O) treatment to remove dissolved salts and microscopic particles that can be found in groundwater. The R/O processed water is treated to prevent corrosion; chlorine and ammonia are added to ensure disinfection.
The desal plant began operating in 1999, drawing brackish groundwater from five wells, creating a capacity of four million gallons per day. Later, a sixth well and a side stream process for the treatment of iron and manganese were added, increasing the capacity to five million gallons per day.
In 2017, a $42 million expansion project was completed with the installation of three additional R/O trains, an additional iron and manganese removal system, 23,000 feet of conveyance pipe, and additional system upgrades. The expansion project also included drilling five new brackish groundwater wells. The facility now has a full production capacity of 10 million gallons of drinking water per day and provides the Authority customers with about one-third of their annual water supply.
“For the expansion project, we were looking to automate the desal facility while doubling the capacity of the plant,” said Ron Mosher, director of engineering, Sweetwater Authority. “The original control system never worked the way it was intended. We wanted to update it to match the control scheme established for the Authority’s Perdue Surface Water Treatment Plant, which is our flagship standard in terms of control systems.”
The project already has paid huge dividends in both water quality and system payback. According to the Authority, the control system has already paid itself back. “We produce treated potable water at about $350 an acre foot,” said Mosher. “That compares to over $1,200 an acre foot if we were to buy imported water. Every day that we run this desalination plant, it’s continuing to pay back the cost that we put into making it run right.”
Forging an alliance
Following an interview process where control system integrators were evaluated for water industry experience, technology expertise, communications competence, client references, and emergency response capacity, the Authority hired Enterprise Automation Inc. (EA) as its supervisory control and data acquisition (SCADA) and controls integrator.
Enterprise Automation has been a Schneider Electric System Integrator Alliance partner since 2013 and was the first firm in the United States to become a Schneider Electric Master SI Alliance partner. Master Alliance recognition is reserved for top tier Schneider Electric partners who demonstrate extraordinary professionalism and expertise in multiple areas of automation and process applications.
“Over the years, we’ve run the gamut of implementing control schemes from having a contractor provide them to having an Authority staff member as the programmer,” said Mosher. “Our experience led to the vision that we need a quality platform that we can standardize on and build from. We need a system integrator that understands our unique requirements and has the skills to deliver the ideal automation solution. We developed the best control scheme for our needs. Knowledge of the Schneider Electric products and solutions, along with other demonstrated capabilities, has been instrumental to our success.”
For this project, the Authority saw the immediate benefit in forging a close relationship with the system integrator. Rather than having the control integration done by a party that is subcontracted by an electrical contractor who, in turn, is subcontracted by the general contractor, the team from the Authority worked directly with the team from EA.
“There were many players involved in making this orchestra come together,” said Scott Pickford, principal, Enterprise Automation. “It was a good collaboration between the various representatives of the Authority and our team. We were all working together to ask, ‘How are we going to deal with this problem?’ Ultimately, because of the relationship that the Authority established, and that we both nurture, the Authority ends up getting what they want and need as opposed to simply getting what they are given.”
“The fact that Enterprise Automation is certified in so many Schneider products means the Authority gets an integrated and better designed control ecosystem,” added Luke Stephenson, business operations manager, Enterprise Automation. “Everyone is happy with the install and the benefits.”
Preparation saves time and money
The EA team visited the existing desal facility to watch how it was being currently operated. They observed operators manually starting up and shutting down the plant.
“We noticed the operators had issues trusting the data from the desalination plant,” said Pickford. “One of our first jobs was to audit the data, clean it up, and establish standards. We had to implement the new system such that an operator could come from their other plant over to the desal plant and everything looked and worked the same. That was what we were there to achieve.”
Next, there were several workshops where the Authority staff, EA staff, and others came together to understand how the plant would operate and what the control system needed to do. EA then created a duplicate platform at their Irvine, Calif., facility to conduct factory acceptance testing, evaluate the control logic, and to work out problems before it was deployed in the field. Through several iterations and workshops, the design was brought to a final stage where it could be implemented onsite.
“The entire control scheme was well thought out and thoroughly tested before a single bit of data was entered into the control scheme,” said Pete Baranov, director of water quality, Sweetwater Authority. “When it was deployed, it was essentially flawless. The design and implementation approach EA used allowed us to be up and running in days.”
The methodology resulted in an enormous cost savings. “Where the real money starts flowing is when you are onsite,” said Pickford. “You’ve got engineers, technicians, electricians and others all waiting for the control system integrator to get that system running. If you start adding up all those people’s time, any hour we can save is a massive benefit to the Authority. If we save days, weeks, or months, we are talking about a very quick payback.”
“Then there is the cost of water,” added Mosher. “While the plant is offline, the Authority is buying water at a rate of $9,000 a day beyond what we would have spent treating the water at the desalination plant. That is a tremendous added expense we were happy to avoid.”
The site was using a Schneider Electric Modicon Quantum system with S908 remote input/output (I/O), which was retained. EA installed one master Schneider Electric Modicon Quantum controller that was programmed using EcoStruxure Control Expert (formerly known as Unity Pro). All additional I/O was Modicon Quantum I/O. Citect SCADA was the overall supervisory system. The configuration allowed the Authority’s National City fresh water wells, the Perdue plant, and the desal plant to all be monitored from one location.
“An operator with the right privileges can see anything from anywhere,” said Pickford. “You can be at the Perdue plant and see the desal plant. Also, when you have so many assets relying on a single SCADA system, redundancy is a very important factor. They always had redundancy but both servers were in the same location. Those servers were then moved so that one of them stands at desalination and one of them stands at Perdue. They talk over a microwave ring network. Either server can go down, and they still have complete control and visibility of both plants from either place.”
The team also had a space challenge with the plant’s chemical feed system. Typical for a plant such as this, there are two pumps for every chemical feed system. If one pump fails, the other can take over and maintain operation. “With new OSHA regulations, there was the problem of making sure there were proper working clearances,” said Pickford. “All the variable frequency drives (VFDs) that controlled the chemical feed pumps were feeding to a single cabinet. If they needed to fix one, they had to power both pumps down. Unfortunately, splitting these cabinets meant we needed more space. We put in Schneider Electric Altivar 32s, which are very compact and enabled the size reduction we needed. They are Ethernet-connected so there wasn’t a lot of wiring. They ended up consuming less space than the original cabinet. We then installed the exact same design at their National City wells. We built about 27 of those little things, so they could get a fair bit of value from that single design.”
The six existing wells used Modicon Compact 984 programmable logic controllers (PLCs), which were obsolete and had to be replaced. The new wells were controlled with Modicon M340s, which is a very cost-effective solution. EA designed new I/O and PLC panels at each of the new well sites but they knew that replacing the existing panels would be expensive.
“We used a little trick that Schneider Electric has up their sleeve, which are these compact connector modules that allow you to take the wiring harness off the old PLC, snap it onto this connector, and then snap it onto the new M340,” said Pickford. “We had to program the new unit, of course, so those wells would all work the same and all communicate back to the plant the same. That avoided us having to redo those six panels saving a lot of cost for the Authority.”
From manual to automation
Today, operation of the plant is automated and can be fully controlled remotely. “The control system now works how it should’ve worked all along,” said Justin Brazil, water treatment superintendent, Sweetwater Authority. “The operator starts the wells and the water starts flowing to the plant. When the operator is ready to start the plant, and if all the system permissions are met, they click the ‘enable production’ button.
“Once production is enabled, the control system brings on an R/O train and starts processing water. If it can’t get the pressure down to a predefined setpoint, it calls on another train, and another train and another train, until it can get the pressure to where it needs to be. As trains are coming online, the chemicals will automatically start at their given dosage setpoints based on the dosage the operator has inputted. The flow rate of the chemicals is automatically calculated based on the pacing source. It’s as simple as that.”
“From that point on, it’s adaptive,” added Pickford. “If a well tripped out and stopped working for some reason, it will dial itself down automatically or turn off one of its R/O trains. If that well comes back online again, or if an operator starts up another well, the plant will automatically dial itself back up and increase production automatically without operator intervention.”
“To contrast that with the old plant, if you lost any part of the process, be it a single well or a single train, you would lose the whole plant,” said Brazil. “Now we can control that plant either onsite or remotely, 10 miles away at the Perdue Water Treatment Plant. I can start it remotely as if I am there. If everything is mechanically working, there is no need for an operator to be on location to start or stop the plant.”
Reporting is now easier and more reliable as well. In the past, an operator would walk around with worksheets and manually record data. Now, the process equipment is tied into SCADA and the values are sent automatically to the reporting system.
“Prior to this project, we produced reports for the plant manually,” said Baranov. “It was probably a full day’s worth of work. Shortly after the project was completed, the Ampla Operations Management reports were done. It has really streamlined everything. And pulling data points from SCADA is a lot more reliable than manually taking the daily readings.”
“Once you get into the system-produced spreadsheet, you can calculate whatever you want,” says Brazil. “You can look at: cost per acre foot for power for pumping water into the plant from wells; cost of power for treating the water; cost of power for pushing the water out into the distribution system; and chemical costs, breaking it down as cost per acre foot of water produced. You run the report for any given month and it builds it for you in a few minutes. If I didn’t have the Ampla report for the new plant, it would have been tedious and required a lot of time every month. It’s made the work a lot less now.”
Annette Burak is senior marketing communications specialist, process automation, Schneider Electric.
Original content can be found at Control Engineering.