Automation and Control Systems at Wastewater Treatment Plants


Written by:
Siemens Energy & Automation, Inc.

Pumps & Systems, January 2009 

The residents of Orlando and nearby communities are more likely to see lightning strike than have their toilets run dry. Extensive high-tech upgrades at Orlando's three advanced wastewater treatment plants, including new automation and control systems, have helped city staff process more sewage and gray water effectively and reliably. 

As population growth continues to put more demand on Florida's fresh water supplies, more communities in and around Orlando are counting on reclaimed water to meet many residential and business needs. Water shortages, stringent environmental protection laws, surging sewer service demand, fewer qualified workers and a virtual rate freeze are the big challenges that this smaller, but smarter, wastewater management team tackles in Orlando.

"It is expensive and tough to find experienced and qualified people in this business. Automation has solved that issue for us," explained industrial automation manager, Bill Wood, as he walked the southern end of the city's Iron Bridge Regional Water Reclamation Facility. "It used to take a dozen or more operators to run this plant alone. Even though the operation has grown significantly in scope, running the plant is now more manageable and precise thanks to the vision of Orlando's public works and environmental leadership."

The Iron Bridge plant was originally built in the 1980s to treat about 5 million gallons of wastewater per day. After several modifications and upgrades, it can now treat and reclaim up to 40 million gallons in that same 24 hours.

"The automation simplifies operators' decision making. All the information they need to run the plant is at their fingertips no matter where they are," said Wood, whose team has installed a totally integrated automation and energy system to assist in the operations and power distribution throughout the plant.

Automation Platform

Standardized on a programmable logic controller (PLC) and PROFIBUS and Industrial Ethernet networks, the automation platform controls everything from the flow of electricity to the amount of reclaimed water safely discharged from the plant. Treated water is sent to the Little Econ River and the Orlando Wetlands Park, while pipelines also deliver purchased reclaimed water to residential neighborhoods, golf courses, citrus groves and other customers as far as 20 miles away.

"Our daily objectives focus on keeping the toilets flushing and meeting the growing demand for wastewater treatment and reclaimed water across the region," Wood noted. "We cannot reach those goals without the reliability and flexibility provided by Siemens automation and communication systems."

Iron Bridge is a 320-acre operation-a series of treatment processes that must be closely monitored and managed. A PLC at the master pumping station reads real-time intake levels and signals variable frequency drives (VFD) when to speed up or slow down the eight 400-hp pumps designed to handle peak loads of wastewater rushing into the facility through an 84-in pipe.

Midway through the plant, flowmeters measure the air pumped into aeration tanks where organic waste is consumed by bacteria. A PLC controls the air flow and records and stores data produced during the intricate, five-stage biological process known as Bardenpho.

Human machine interface (HMI) touch screens located inside every process station and linked to the facility-wide Industrial Ethernet network offer operators a real-time view into every layer of the plant. Supervisory control and data acquisition (SCADA) software offers that same vantage on the laptops, desktops and kitchen countertops of authorized plant and city personnel.

"It used to be a real juggling act for an operator to ensure that water leaving the plant through three separate exits met a variety of strict environmental standards for the river, wetlands and irrigation," explained Wood, as he clicked on the latest plant discharge readings on his office computer. "Now we trust. . . automation to handle this once-intimidating task with web-based. . . software integrated over our. . . platform that provides reliable snapshots of our operation status and water conditions anytime, anywhere. Coupled with the operator's expertise, the PLCs have become the eyes and ears of the plant, and they have changed the way we do business," Wood noted.

Lower Operating Costs

Orlando has three advanced wastewater treatment facilities and 210 lift stations, which pump sewage away from the homes and neighborhoods to Iron Bridge or one of two other plants, Water Conserv I and Water Conserv II. Orlando, like most municipalities, treated and operated each facility autonomously for decades. To reduce costs and increase efficiency, the plants were integrated using automation, SCADA and PROFIBUS and Industrial Ethernet networks.

"Rate freezes and infrastructure, inventory and labor requirements put a real squeeze on productivity, so we had to find a solution that would benefit all of our facilities," Wood explained. "Instead of having staff dedicated to a single plant, we now share our resources across the entire enterprise using. . . automation."

"As the treatment plant grows with the city, we simply cannot continue to staff up. It is too costly," noted Guy Mecabe, wastewater systems manager, who has been instrumental in the deployment of the automation system and the PROFIBUS and Industrial Ethernet networks. "The reach of our networks has grown ten times over in the last two years, as we have expanded our ability to monitor and manage the whole system 24/7 from just about anywhere using. . . SCADA software."

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See also:

Upstream Pumping Solutions

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