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Metso solution increases capacity in wastewater treatment plants

Metso has developed an online measurement technology with which municipal and industrial wastewater plants are able to improve their performance and reduce the amount of chemicals used in sludge drying process by even up to one third.

The new Metso Low Solids Measurement is the first online measurement technology for municipal and industrial wastewater treatment plants that enables measurement of a media with very low solids contents in difficult applications like centrifuge centrate.

The technology claims to offer significant savings per centrifuge in polymer and centrifuge usage. Until now, there has not been any online measurement technology available that would enable reliable measurement of a media with very low solids contents in this measurement position.

“The new technology developed by Metso offers the world’s water treatment plants an opportunity to improve their performance and thus gain major cost savings. A large North American wastewater treatment plant has calculated that it saves even up to 30% in its annual US$ 2.5 million chemical costs.

"In addition, a municipal plant in Finland using Metso LS estimates that they will achieve annually EUR 15,000 savings in polymer and centrifuge usage only by keeping reject water total suspended solids lower that 1000mg/l,” says Timo Rantala, Product Manager, Metso’s Automation business line.

The Metso Low Solids Measurement system is based on LED and laser technology. It dearates, filters, and measures the process solids along with possessing self-cleaning capabilities to keep the measurement optics clean for continued accurate measurement.

It complements Metso’s measurement product portfolio to the wastewater processes. Earlier Metso has launched Metso TS, total solid measurement to the waste water treatment processes. Metso TS is based on microwave technology.

Key benefits

With Metso LS measurement it is possible to control polymer usage and thus improve throughput and function of the centrifuge. A higher solids content of concentrated sludge results in higher thermal energy in the subsequent incineration process, or alternatively reduces transportation costs when shipping to a landfill.

Furthermore, Metso LS reduces conventional sampling and laboratory work due to its reliable and accurate operation. The small investment in an online solids measurement system gives significant operational savings and correspondingly a very short payback time.

Typical applications

Metso LS is specially developed for municipal or industrial wastewater treatment processes to measure low solids in difficult applications. Typical such application is centrifuge centrate water solids.

The device gives accurate information about centrate water quality, enabling the process to be controlled in the most cost-efficient way. A too high solids rate in centrate water would cause the excess solids to be repeatedly treated and centrifuged.

Reliable information about the centrate water quality is very important for choosing the right polymer and to determine the right polymer dosage.

Operation principle in a nutshell

The Metso LS device can be connected online to the process and is able to measure continuous sample flow through the system by utilising an integrated centrifugal pump.

The device has two light sources, LED and laser, that measure absorption, scattering and depolarization of these sources as they pass through the flowing media. The measurement cell has an extremely strong sapphire glass with high optical properties.

The cell and sample lines are automatically cleaned at given intervals. Metso LS continuously measures the suspended solids content within the range of zero to 5000 mg/l and also the entrained air index, which indicates overdosing of polymer.

The Metso LS measurement system dearates, filters and measures the process solids along with possessing self-cleaning capabilities to keep the measurement optics clean.

Global potential

“In the first phase, the new technology will most probably interest especially large wastewater plants in Western Europe and North America, where the level of automation is already high. It is these plants that often have major capacity issues and are under pressure to save costs. Interest in these kinds of solutions is growing in Asia, too,” Rantala comments.

In the past five years, Metso has strengthened its role as an expert in wastewater treatment, and now considers itself to be a market leader in microwave technology measurements used in treatment processes.

[Pictured above: The Metso Kappa Analyzer.]

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