By Jonathan Fiedler

Wells Sanitary District
accomplishes plant refurbishment objectives

On Maine’s Southern Coast, the Wells Sanitary District (in the town of the same name) provides treatment for up to two million gallons of waste water per day. Originally constructed in the late 1970s, the treatment facility underwent a major refurbishment in 2001 to update the plant to meet all safety standards required by the U.S. Environmental Protection Agency (EPA) and Maine’s Department of Environmental Protection, to better serve the community in the years to come. The district retained Wright-Pierce, a Maine-based consulting engineering firm, to redesign many of the facility’s systems and processes to accomplish its objectives.

As part of the refurbishment, it was deemed necessary to replace the flow-meters that measured the waste throughout the treatment plant. According to Dennis Thayer, superintendent of the facility, “The existing meters had seen better days. They were worn out and needed to be replaced. Many people don’t realize that these meters operate 24/7, under demanding conditions, so they need to offer superior performance and reliability.”

Wright-Pierce recommended electromagnetic meters, or magmeters, for the refurbishment. They are now being used for three different applications at the facility, including measuring sludge recirculation, total gallons of treated effluent and sludge waste.

In the sludge recirculation area, two of the meters measure the sludge recirculation in rates from gallons-per-minute to total gallons-per-day. This is part of the facility’s inline, waste-activated sludge process. Another meter is used in the wasting sludge area to measure the flow of sludge that is removed from the system. A fourth meter is used in the treated effluent area to measure the flow of all the treated waste water that moves throughout the facility.

“The importance of accuracy and reliability in this environment cannot be overstated,” said Thayer. “Flowmeters are essential to the overall process here and at any treatment facility. Since the day that they were installed, the new magmeters have been trouble-free, accurate and reliable,” he added.

Recertifying the accuracy of the flowmeters on a regular basis is integral to helping them maintain their superior performance and ensures the accuracy of their chemical dosage. For this reason, Wells Sanitary District paired their electromagnetic meters with a portable testing and verification device. This enables complete functionality and accuracy verification of the magmeter’s flow, primary converter and cables without requiring removal from the pipeline or interruption of the treatment process.

The device can be used with most flowmeter converters as either an automatic verification instrument or a manual flow signal calibrator. After simple on-site connections, the unit verifies flowmeter performance, while creating an archived calibration record accurate within one percent of the original factory calibration. Stored verifications can be imported into an advanced PC program for easy evaluation and analysis, adding even more functionality. The verification device is directly traceable to international standards, is ISO 9001-compliant, and uses available line power at the flow tube. Thayer’s own experience with the device confirms its effectiveness.

“We recently recertified the meters, as required by both federal and state agencies on an annual basis and all of the meters were well within one percent of the original factory calibration.”
Pete Williams of Sullivan Associates, distributor of the meters and calibration devices, explains that their accuracy and reliability provides customers with a high confidence level.

“It really creates a significant comfort factor,” he said. “The figures produced (by the calibration device) are certifiable and NIST-traceable (National Institute of Testing Standards). Ultimately the device meets all government standards, including the EPA’s.”

Customers can perform annual certifications on their magmeters without any interruption of the meters’ operation. The customer will also have a history of these certifications so the results can be viewed over time.”

Thayer’s satisfaction with the performance of the meters and the ease of use of the calibration device translates to an extreme willingness to employ them again in subsequent renovations.

“In the near future, the district’s two main pump stations will undergo a major overhaul and we plan to install and use the same products. They have met— and exceeded—our expectations.”

About the author
Jonathan Fiedler joined KROHNE in 1994 and has worked in various product management and technical support roles for both flow and level instrumentation. Currently, Fiedler is the Flow and Level Product Specialist for KROHNE NAFTA. He has a bachelor of science degree in mechanical engineering from the University of Rhode Island and has more than 15 years’ experience with process control instrumentation.

KROHNE is a worldwide technological leader in the development, manufacture and distribution of accurate, reliable and cost-effective level and flow measurement instruments. KROHNE’s MagCheck, a portable testing and verification device for KROHNE electromagnetic flowmeters (EMF) is ideal for the water and waste water industries.


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