Pumps & Systems , February 2009
When the City of Delaware, Ohio, expanded its wastewater treatment plant, it looked to increase more than just capacity. It also wanted to increase its efficiency and automation capabilities to benefit the plant's operators and taxpayers.
Known as the Upper Olentangy Water Reclamation Center (UOWRC), the plant increased its capacity from 5.5-mgd average flow and 10 million gallons storm flow to 10-mgd average flow and 30 million gallons storm flow. The expansion was completed in September 2007.
Greg Doubikin, assistant wastewater manager, said the improvements also provided a considerable upgrade to the utility's monitoring and control capabilities.
"We went from being able to take some simple measurements, to being able to monitor exactly what's going on in just about every aspect of the treatment," Doubikin said. "We can also control a large percentage of the equipment and processes from this system."
Expansion Details
Two of the five primary sludge pumps at the City of Delaware wastewater treatment plant.
In the community of 30,000 people, located just north of Columbus, recent growth required more advanced treatment systems and increased capacity. The original facility was a two-stage activated sludge plant with no primary treatment. Wastewater treatment included influent pumping, flow equalization, screening, grit removal, carbonaceous biochemical oxygen demand removal in first stage aeration, intermediate settling, ammonia nitrogen removal in second stage aeration, final settling, tertiary filtration, chlorination and post aeration.
The $25 million upgrade to the plant included the details in Table 1.
|
Additions |
Construction |
Modifications |
Replacement |
Expansion |
|
•· Septage Receiver •· Emergency Generator and Switchgear •· Belt filter press (BFP) and modification to a second BFP to provide thickening of waste solids
|
•· Influent Pump Station •· Pretreatment building with mechanical screening and grit removal that could process the peak wet weather flows •· Primary tanks and raw sludge pumping of facilities •· Aeration tanks with enhancements for biological nitrogen and phosphorus treatment •· Odor control systems for the pretreatment area and the sludge solids dewatering and covered storage tanks
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•· Two intermediate settling tanks and replacement of collectors to improve the capture of solids •· Existing aeration tanks to include biological treatment for nitrogen and phosphorus; chemical additions also were provided to ensure permit compliance •· Two final settling tanks and construction of a new 70-ft diameter final settling tank to assist with solids capture •· Tertiary filters to improve operations and maintenance •· Sludge solids storage tanks |
Chlorine disinfection system with ultraviolet disinfection, followed by improved post-aeration of the treated wastewater |
Administration building to house a large training room and the new SCADA control center
|
Table 1
The expansion was executed as a design/build project with Fredericktown, Ohio-based Kokosing Construction and Lexington, Ky-based Quest Engineers, Inc., selected as the design/build team. Kokosing/Quest organized a project team to address the critical issues of the project, such as design, construction, environmental protection, site development and landscape architecture/restoration.
Advanced Monitoring, Controls and Communications
While the expanded and upgraded treatment facilities provided much-needed capacity for the plant, the monitoring and control technology behind the new equipment made the plant one of the most technologically advanced municipal plants in the country.
At the heart of the installation were four programmable logic controllers (PLCs), tied into a customizable SCADA program.
Jeff Keller, systems integrator for the project and now with Stantec Consulting Services, Inc., said, "The goal of this project was to provide the owner with a modern SCADA HMI control system that would allow them to efficiently control their wastewater treatment process."
Other key technology pieces installed during the upgrade included seven intelligent motor control centers (MCCs) with built-in communication capabilities.
According to the design/build team, the built-in communications in the MCCs made integration into the SCADA system much simpler. Going from a standard MCC to one that actually had the ability to communicate was key. The upgrade also expanded monitoring capabilities on existing equipment with the installation of eight power monitors on existing MCCs.
Jeff Billups, Schneider Electric executive sales engineer, explained the benefits of the expanded communications network. "The communications. . . are fed back through the SCADA system for 24/7 monitoring," said Billups. "They can electrically and mechanically monitor the entire plant either locally or from a remote location through the SCADA system."
New technology available at the plant also helped operators with efforts to protect the environment. The plant is located on the Olentangy River, one of 13 river systems included in the State Scenic Rivers Program as designated by the Ohio Department of Natural Resources. Close control over the plant's effluent was critical.
"One of the things we did was put in recycle pumps for nitrogen removal," said Bill Hill, UOWRC wastewater manager. "The system allows us to control the speed of those pumps to control the rate of nitrogen and phosphorus removal. The Olentangy has very stringent criteria that we have to meet in terms of our discharge. This control system helps us to meet those criteria."
Selecting the System Components
As the systems integrator, Keller primarily evaluated two systems for the upgrade, but said the communications capabilities of the automation products made the most sense for the application.
"The packages we looked at were boiled down to what they could do for the owner. Each was in the same neighborhood for cost," Keller said. "But it ended up that some of the features that were available . . . including some of the Ethernet capabilities, pushed us in that direction. Just the ease of connecting all of the communication sources was important to us."
Improved Reliability and Maintenance Controls
Seeing the current status of any piece of equipment has been a major advantage for plant operators, especially when that equipment malfunctions.
"The motor control centers had communication equipment that came with pre-built web pages designed to help monitor the equipment," said Keller. "The pages are well suited for troubleshooting problems. For example, if you look at a page created for one of the variable frequency drives, it can
