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Water Treatment Plant Cuts Energy Costs by 47 Percent with Automation

Integrated control and information system increases operator efficiency

Challenge

  • Obsolete equipment provided little visibility into production resulting in equipment blowouts, increased risk and high energy consumption

Solutions

Results

  • Reduced time manually controlling process, increasing operator productivity and process flexibility
  • Reduced energy consumption by 47 percent resulting in $400,000 state rebate

The sanitation district in one California county provides wastewater services to residential, commercial and industrial customers – including multiple major manufacturers. The sanitation district’s lone water treatment plant processes approximately 3 million gallons of waste per day, with a potential capacity to service 8 million gallons of waste from expanding cities.

Incoming wastewater enters the plant and flows through a variety of treatments, such as the grit chamber, aeration and clarification tanks. As suspended solids rise to the top, enabling the plant to remove toxins and solids, diffused air is then administered to the waste. This advanced treatment phase allows additional solids to decompose through a process called aerobic digestion.

In recent years, the sanitation district determined the plant lacked the automation needed to support the county’s anticipated growth. To prepare for the future, the district invested in automation and a supervisory control and data acquisition (SCADA) system that would increase the plant’s productivity while reducing its energy costs and emissions.

Flying Blind Without Automation

Plant managers hired the services of an independent engineering firm to assess the plant’s conditions and determine a migration plan that allowed for future growth. The assessment found numerous gaps in the plant’s current operations, including high energy consumption and a lack of standardization.

“We found out that the amount of waste coming into the plant was increasing substantially, and we were running low on the oxygen needed to treat the water properly,” said an operations supervisor for the sanitation district. “That is not a good condition.”

Since blowers in the aeration basin were not automated, operators had to manually turn them on and off to adjust oxygen levels. This resulted in additional labor and increased energy consumption in a process that already accounted for 85 percent of the plant’s electric bill.

The lack of an automated system not only created inefficient operations but also put the plant at risk for blowouts and potential discharge violations due to inaccurate measurement techniques. The plant also lacked historical electronic data and reporting tools to identify and better manage energy consumption.

“We had no monitoring equipment at all – we were basically flying blind,” said the general manager for the sanitation district. “My vision was to automate the entire facility. We kicked off our first project when we brought in Rockwell Automation.”

SCADA System Creates Plantwide Flexibility

Management’s goal was to standardize the plant’s production and better manage energy costs by implementing a SCADA system to automate the water treatment process. An automated system not only promised the hope of a more efficient process, but also a state rebate if the new solution reduced energy consumption by at least 50 percent.

The first step in the renovation process was to replace the existing system in the aeration basin with new diffusers and install six high-speed turbo blowers. Working with Automated Control & Technical Services, a Rockwell Automation Recognized System Integrator, plant personnel installed a SCADA system based on an automation control system. With the addition of FactoryTalk® software from Rockwell Automation communicating over wireless EtherNet/IP, the new SCADA system could be monitored by redundant servers for added reliability.

The flexible automation allowed the plant’s treatment process to be consistently controlled.

“We have the visibility to continue to produce a good, quality product all the time,” the operations supervisor explained. “I don’t have to worry about the process changing, because it looks the same day in and day out.”

On top of regulated control, the SCADA system has also created improved reliability and peace of mind for operators in the facility. Before, if a problem were to occur, workers were alerted through a blinking light in the control room without explanation. Now, thanks to a variety of detailed alarms, operators can identify problems instantly – even remotely.

After the installation of the FactoryTalk Historian application, the facility was able to identify specific times when industrial companies discharged higher amounts of waste into the facility. This allowed workers to adjust operations and determine trends for future modification.

After the success of the first project, the sanitation district moved forward with a motor control refurbishment. Plant managers worked with system integrator Telstar Inc. to replace the plant’s existing aerobic digester blowers. They also integrated SCADA controls and installed an automated valve on the second basin.

As part of the upgrade, Telstar also replaced the outdated equipment in the backup aeration basin with two Allen-Bradley EtherNet/IP-enabled CENTERLINE motor control centers for increased safety and plantwide control. Automation was also incorporated into the scum-removal system through the addition of Allen-Bradley PowerFlex drives and ControlLogix® controllers.

Reducing Energy Costs by 47 Percent

“We partnered with the CalPOP program for a $400,000 rebate payback,” said a district engineer for the sanitation district. “Our capital monetary outlay was a four- to five-year payback, so it was really a happy ending. Our board was delighted.”

In addition to the monetary savings, the project reduced the carbon dioxide emissions by half a million tons annually, which is equivalent to approximately 89,000 passenger vehicles.

Through the installation of the SCADA system, the water treatment plant can now aggregate, monitor and optimize data. The remote capabilities also allow plant managers to monitor and control the plant at all times, providing complete visibility to help prevent downtime.

Since the completion of both developments, the plant has received numerous state awards for its energy management, including an Engineering Achievement award and Plant of the Year award.

“In order to get a project approved, we really need to educate our board of directors and show them the value of the investment,” the engineer said. “In this case, the value was improved energy efficiency and reliability, and decreased maintenance costs. Once the board saw the results, they were excited for the next phase.”

The results mentioned above are specific to this customer’s use of Rockwell Automation products and services in conjunction with other products. Specific results may vary for other customers.

Allen-Bradley, ControlLogix, FactoryTalk, PowerFlex and VantagePoint are trademarks of Rockwell Automation Inc.

EtherNet/IP is a trademark of ODVA Inc.

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