Easier to Control Plant with Upgraded Computer
A $4.66 million project will improve a set of industrial computers and a monitoring system DSRSD staff use to operate the Regional Wastewater Treatment Facility. The project includes upgrading the Supervisory Control and Data Acquisition (SCADA) system that issues commands and reports data at the facility such as flow readings, temperatures, and tank levels.
This project replaces about 35 (almost half) of the plant’s programmable logic controllers (PLCs) that act as computers to process information from devices such as flow meters and chlorine analyzers. The PLCs alert operators if something is wrong and can automatically control processes, such as adjusting the dosage rate of chemicals added to influent (sewage coming into the wastewater treatment plant).
“Without PLCs, running the plant would be very challenging,” Associate Engineer Jason Ching says. “We would need more operators, each one assigned to a specific process. But each process is connected to another, so operators would still need to communicate with each other, which would be challenging since adjusting one process potentially affects others. PLCs talk to one another and make calculations and adjustments in almost real-time. Without them, operators would need to make calculations by hand.”
The project also upgrades the fiber optic communications network and will replace nine variable frequency drives that operate the facility’s largest pumps, including the influent and effluent pump stations. (Effluent is sewage leaving the plant.)
“We’re ensuring that our new SCADA system will be reliable by upgrading our fiber optic communications network, optimizing our SCADA server architecture, and replacing older equipment with new equipment that meets current industry standards,” Associate Engineer Jason Ching says.
Wastewater Treatment Plant Operations Superintendent Virgil Sevilla uses the SCADA system in the control room at the plant. |
The SCADA system allows wastewater treatment plant operators to monitor the facility not only from a control room, but also when they are out at various locations throughout the District’s 29-square-mile service area.
“Nowadays, we have SCADA in our cell phones,” Wastewater Treatment Plant Operations Superintendent Virgil Sevilla says. “Even if we’re walking around the plant or at other facilities, we can still know what’s going on. That’s a good feature for us.”
Operators can receive alarms via SCADA that tell them the location of an alert, then they can address the issue manually when needed by physically examining the equipment—listening to the noise of a pump and how it vibrates, for example. The improvements include developing a more user-friendly interface that will be intuitive for staff. Each PLC has an uninterruptable power supply with about 30 minutes of temporary power. In the event of a power loss, SCADA automatically switches to backup generators.
The project also involves having a contractor develop SCADA standards as part of preliminary design concepts. DSRSD hired engineering and operations firm Woodard & Curran as the design-build contractor in early 2021. They are working with DSRSD staff—Engineering; Instrumentation, Controls & Electrical; Plant Operations; Information Technology; and Mechanical Maintenance—to assess various parts of the SCADA system including the design of a user-interface to help Operations staff more efficiently and effectively monitor and control the various components of the treatment process. “The project will provide the capability to upgrade later and have more flexibility in the future,” Ching says.
District staff make educated guesses on what challenges may lie ahead in the next 10 to 20 years, such as regulatory requirements, emerging contaminants, biosolids, and nutrient removal. Upgrading older equipment will make future replacements easier and allow engineers to better understand how the plant has been operating over time.
Having a design-build contractor, instead of a separate contractor for the design and construction, makes it easier when planning how to install the new equipment and computer systems once construction begins.
Because the facility is operational 24/7/365, “We want the designer to think about how to perform construction while, for example, taking the aeration basin blowers offline for any period of time,” Ching says. “We want them to be thinking about how we 'cut-over’ from the existing system to the new infrastructure, while also minimizing impacts to the treatment plant operation.”
Construction is expected to start in early 2022 and span about six to nine months based on seasonal variations. The District considers the demand on different parts of the plant throughout the year. For example, the best time to replace the PLCs that affect the water recycling portion of the facility is when demand is lower during rainy winter months. The design-build contractor will also consider the best ways to integrate these upgrades while keeping the plant running 24/7/365. Temporary pumps, generators, and diverting water to holding basins may all be part of installing the new systems and keeping the plant operational.
“The big push is to get work going in early 2022 so we can tackle any upgrades on the recycled water side when consumption is the lowest,” Ching said. “We want recycled water full steam in the summer, and then we can work on the wastewater treatment plant upgrades. We don’t want to touch everything at once. Each of the 35 new PLCs will be installed and tested to make sure all stakeholders are comfortable.”
Posted: July 14, 2021