Creating State-of-the-Art Water Treatment Plants

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.

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 tell you whether you are getting appropriate power to that drive, if it is operating at the right speed, if there is some internal electronic error in it or even if a cooling fan is broken. Almost anything that could go wrong will be reported.

The Upper Olentangy Water Reclamation Center's newly installed influent pump control panels.

"If you are having a problem with a process in your plant, it is usually due to one piece of equipment affecting that process. With Web monitoring, it allows you to look into each piece of equipment and see if anything is having issues at that time."

The SCADA design displays the entire plant on one computer screen, with each building represented. Double clicking on any of the buildings displays the one-line diagrams for each piece of equipment in that particular process building.

Alarms also are built into the system to notify operators of any potential equipment problems. "While I was at the plant one day, they were having a problem with one of their pumps," Billups said. "An alarm went off, and it let them know exactly where and what piece of equipment was having a loading issue. This type of quick identification allows for shorter downtime and protects the equipment from being damaged."

Equipment maintenance is also improved. "We now take consistent readings of usage hours on equipment, which was difficult before," said Hill. "Knowing how many hours each piece of equipment has on it helps us with maintenance."

Hill added that the city recently adopted a computerized maintenance scheduling program, which the new SCADA system can help to integrate into the plant.

Treatment Process Improvements

Plant operators saw process improvements accompany the technological advancements. For example, variable frequency drives control several pumps managing the influent. The SCADA system can control these pumps to automatically engage and adjust depending upon the current wet well level. If the level falls above or below the target, the pumps increase or decrease the flow until the target level is achieved.

"The influent flow comes into a wet well at the head of the plant, and these are some of our biggest power users," said Hill. "Now they are totally automated and we can use the pumps at a variable speed and number to maintain the wet well level. This amounts to a lot of savings and stabilizes the flow rate, really helping with treatment consistency."

The automated influent pumping has been particularly useful in wet weather conditions. "We have to handle the flow that is coming to us," said Hill. "So depending on weather conditions or what industry is doing, that flow changes constantly. You need to have a system that gives you the capacity to adjust for the variation in flow. This is where the automatic system has been a big help."

The increased monitoring also helps with the expanded sludge facilities, giving operators better control and more up-to-the-minute data. The result: the percentage of solids in the sludge hauled away from the plant has increased from about 14 percent before the expansion to more than 20 percent today. That increase provides a major cost savings to the city taxpayers.

"We are seeing a huge reduction in the amount of water in the sludge. That means we are handling sludge solids, not water in each load," said Hill.

Hill also notes that, "Although we dramatically increased processing capacity, we did not require additional operators. The dollars saved as a result of this technology are dollars the taxpayer saves as well."

Improved Access to Information

With multiple access points to the SCADA system now installed, plant operators no longer need to go to the control room to access system information as often. That information can be accessed from two points within the plant.

"The original system had a single computer that sat in an operator's office," Keller said. "That was the only location they could go to and look at what's happening around the plant. With this system, we put computer stations out in the plant area so that if an operator noticed a situation in a certain building or area, or if there was a problem with a particular piece of equipment, they could address that situation and then view what was happening to the plant from a local computer station. Afterward, the operator or maintenance person could continue to monitor the situation from any of the other computer stations and remain local to the situation without having to return to the ‘central' computer station.

"It allows them to have additional access points to see what's going on within the plant. It also allows more than one person at different computers to see what's going on."

The City of Delaware wastewater treatment facility's newly installed aeration tanks.

Power Monitoring

With each motor control center monitored for power consumption, operators are able to collect data that will help them find the most energy efficient method for controlling any process. By using the data, energy consumption can be minimized when utility rates are higher and maximized when they are lower.

Keller also noted that power monitoring is a key tool in analyzing how to reduce harmful harmonics that VFDs produce on the system.

"In plants like these, one of the big issues that develops is with variable frequency drives," Keller said. "They tend to put harmonics back onto the electrical distribution system at the plant. Those harmonics can be disruptive and they also can destroy other electrical equipment. The power monitors and analyzers allow them to see if they have a situation where harmonics are creating issues with other electrical equipment.

"They also are able to see if their utility is providing them clean power or if there are a lot of voltage dips and spikes, which can cause equipment to fail prematurely or drop off line."

Keller added that despite the obvious benefits, many plants still do not include both power monitoring and process controls in their systems.

"In most projects that I am seeing today, very few people are making that bridge between power monitoring and the process controls, simply because cost can be a factor," Keller said. "There is an ever-increasing eye on public spending and taxes, and sometimes they just cannot make that extra investment in a more advanced system, even if it will save them money in the long run."

Creating a World-Class System

According to Billups, the level of monitoring and control technology used in the UOWRC system as a result of the expansion project has turned the facility into one of the most advanced plants in the country.

Keller concurred that the UOWRC was one of the most advanced municipal plants he has seen. "For municipal treatment systems, this is pretty much cutting edge. Most everyone uses some piece or part of this control equipment, but this is one of the first plants I have seen that has this level of control in every area."