If you want some of the best tasting water in the country, you might want to head to Kent, Ohio. It gained the title of “Best Tasting Municipality Water” at the Berkeley Springs International Water Tasting in 1995, and has placed in the Top 5 six times since then.
But taste isn’t the only thing the city is concerned about. Since 2002, the city’s water/wastewater utility has gone through several upgrade projects to improve water quality, communications and efficiency, and to reduce power consumption significantly.
Kent’s Water Treatment Division is responsible for the supply, filtration, pumping and storage of potable water for the city. The water plant treats more than 2 million gallons of water per day (MGD), and has a capacity of 6 MGD.
The separate Water Reclamation Division has responsibility for the Water Reclamation Facility (WRF), handling treatment of the city’s residential, commercial and industrial wastewater. The WRF can treat 5 MGD of sewage, with a peak hydraulic capacity of 15 MGD. The cleaned water is discharged into the Cuyahoga River according to a permit issued by the Ohio Environmental Protection Agency (EPA). Along with the removal of conventional pollutants, the treatment process is also designed for the chemical removal of phosphorus and the biological removal of ammonia from the waste stream.
In addition to the potable water plant and the treatment facility, Kent also operates and maintains nine main pumping stations throughout the city, plus other associated facilities.Thoma Technologies, which provides automation systems for the City of Kent’s water/wastewater utility, began its first project with the city in 2002, implementing a telephone telemetry system for the eight remote wastewater pumping stations.
“We provided eight telemetry panels, four with 10-inch HMIs, in addition to a master panel at the WRF,” says Robert Thoma, president of Thoma Technologies. “The panel at the WRF also had alarm signals paralleled from a nearby annunciator panel. In addition to the panel, the WRF’s SCADA system had two PCs, each running LookoutDirect software from National Instruments. This was the extent of the plant SCADA system at the time.”
Spread spectrum radio
Frequent failures and lengthy repairs prompted the WRF to replace the existing SCADA telemetry system in 2004. The telephone lines used for communication were low-grade copper, limiting bandwidth and performance. The city wanted to make the switch to spread spectrum radios, so Thoma Technologies began by installing radios at the sewage lift stations. In the following year came radio telemetry for the Water Treatment Division’s potable water pump station and water tanks/towers, and soon after the remaining potable water tanks.
“由于电话线路切换到广播communications, SCADA system performance improved, downtime was reduced and third-party support issues were eliminated,” Thoma says.
The radio system now covers more than 16 square miles. Throughout the water/wastewater system, local control and monitoring is provided by AutomationDirect D205 PLC racks with D260 processors and a variety of discrete and analog I/O. These PLCs make up the remote terminal units (RTUs), the front end of the SCADA system.
Controlling a waterfall
To meet new water quality standards set by the Ohio EPA, in 2003 the city decided to bypass the Arch Dam built in 1836, rerouting the Cuyahoga River through the old canal lock to preserve the historic dam and building a small park behind the dam.
To help pump water over the dam during warm-weather months, Thoma Technologies provided a radio system for start/stop and flow control for the waterfall. The 150 hp pumps are driven by variable-frequency drives, and a weekly schedule of start/stop times enables the city to save on electricity costs.
In 2008, Thoma Technologies added radio communications to the raw water wells for the potable water treatment system. The SCADA system at the WRF was also expanded to add four AutomationDirect 15-inch C-more HMI touch panels to the two LookoutDirect PC stations. These new touch panels expanded the capability of the SCADA system to encompass the new RTUs used to help monitor and control the WRF.
The potable water treatment plant has an Iconics SCADA system with Modicon Momentum PLCs, which made for a challenging tie-in, Thoma says. “In order to work with the existing PLCs, we installed an AutomationDirect DirectLogic D0-06 PLC with dual Ethernet cards to serve as a firewall, and to scan the Modicon PLCs in the water plant,” he explains. “The PLC integrates the data into the LookoutDirect software used at the WRF. One Ethernet card is used to query plant data from the Modicon PLC via Modbus TCP, and the other card uses the city’s intranet for peer-to-peer communications with the SCADA system at the WRF.”
An additional LookoutDirect station for the Service Administration Center, located in another part of the city, created city-wide SCADA monitoring capability that covers all water/wastewater systems. “In order to add the Service Administration Center to the system, we used the same Ethernet card solution that linked the potable water treatment plant to the WRF via the city’s intranet for peer-to-peer communications,” Thoma says.
The automation provider has also worked with the city’s team to add panels for influent flow analysis, monitoring various flows, levels, pH, dissolved oxygen and temperatures, and displaying the data on local screens. “We also installed panels to monitor the performance of the anaerobic digestion tanks,” Thoma adds.
Reducing power consumption
In 2010, Thoma Technologies added an AutomationDirect D0-06 micro PLC panel to improve final clarifier operations at the WRF. The plant uses the information to control valves on influent side to balance flow and prevent short-circuiting of flow through clarifiers during low-flow conditions. Programming was also added to the panel to control aeration, since the blower controls were nearby. “Originally, we were controlling the centrifugal blowers by a very simple method of unloading motor amperage through reduced work of smaller air flows via activation of inlet valves on the blowers,” Thoma says.
Valve control resulted in better treatment and yielded a net savings of about $8,000 a year. This method worked well, but there was a limitation of minimum safe operation of the blowers and at times, especially at night, there was still excess aeration (see “Aeration Automation Improves Efficiency” for more details on the aeration automation project).
A turbo blower was added to further cover the lower spectrum of airflow. This improves speed control, and has significantly increased cost savings. In 2011, control for the new turbo blower was added to reduce airflow rates and provide further reductions in power consumption. Since project completion, the cost savings have been about $5,000 per month.
The latest project has been the installation of a D0-06 control panel at the WRF to control the aeration valves in the three mixed-liquor tanks. This system balances airflow, which provides better consistency in dissolved oxygen levels to help with biological control and water treatment.
When Kent’s water was first named “Best Tasting Municipality Water,” the city’s mayor was invited to come on the Tonight Show to share a taste with Jay Leno. With any luck, Kent will win the title again in 2014, and then perhaps the mayor will get to meet the Tonight Show’s newest host, Jimmy Fallon.
