City of Mikkeli and Vemo project researchers of South-Eastern Finland University of Applied Sciences
approached Sensmet Oy requesting real-time analysis of heavy metals in untreated municipal wastewater.
The application is pushing the limits of current measurement technology because 

1. sampling and continuous online measurement of untreated municipal wastewater is challenging –
   you must know what you do
2. the concentrations of targeted dissolved heavy metals are in the very low µg/litre range (µg/L =
   ppb; part-per-billion) whereas the alkaline and earth alkaline metal concentrations are high
3. the municipal wastewater matrix is complex and under constant variation due to weather and
   seasonal changes. 
   So the customer request was to match the analytical performance of laboratory ICP-OES technique while
   performing record-breaking continuous online analysis of multiple heavy metals in a complex

Real-time monitoring of trace metals in municipal wastewater

To make sure that we can match customer expectations, we typically request sample liquid from our
customers. After receiving a few litres of untreated wastewater from Mikkeli, we applied Sensmet µDOES®
(Micro-discharge Optical Emission Spectroscopy) Real-time Multi-metal Analyser to investigate how well we
could detect trace metals in that water matrix.  

The µDOES® analyser is 100 % automated. The analyser automatically controls the sampling system and
finally presents the calculated analysis results in real time. The optional Sensmet cloud is helpful, especially
for research installations. Besides having the access to the analysis results anywhere and anytime, the
Sensmet cloud enables remote maintenance and automated software updates. 

The µDOES® is an extractive analyser that employs a novel measurement principle: it uses electricity to
create a discharge or microscale plasma inside the liquid. Spectrometer analyses the light emitted from the
plasma, thus building the emission spectrum of the plasma. The measurement principle is similar to ICP-
OES but is far simpler and more robust. Another benefit of µDOES® is that the measurement technology is
environmentally friendly and has low operating costs. The consumption of any hazardous chemical
reagents and expensive carrier gases such as argon is entirely avoided. 

While analysing the test samples with the newest Senspec software, we were pleased to realise that we
could see changes in copper, zinc, and nickel concentrations at the ppb level in real time. It was a great
moment to realise that we have the required ingredients to fly to the moon. The customer was impressed
with the application data and wanted to proceed to the field installation.

The next phase of the customer project took place at one of the most modern wastewater treatment plants
in the world. New Metsä-Sairila municipal wastewater treatment plant in Mikkeli, Finland has been dug and
built underground inside the bedrock. At Metsä-Sairila the µDOES® analyser produced real-time
information on copper, zinc and nickel in untreated municipal wastewater every 15 minutes at ppb
concentrations.       

“The pioneering project with the City of Mikkeli demonstrates the power and potential of Sensmet
technology. I’m sure more and more applications will appear for online trace metal analysis once the
awareness of such new measurement capabilities increases. Recently there has been a growing interest in
measuring ultralow ppb concentrations of copper and iron in industrial process streams.” says Sensmet
CEO Toni Laurila.

Transforming water analytics

Lithium production and hydrometallurgical recycling processes of battery metals are Sensmet’s main
application areas. Typical measurements include lithium, cobalt, nickel, manganese, magnesium, sodium,
potassium, rubidium, calcium, copper, iron, aluminium and zinc in different aqueous matrices. The online
measurement applications developed for battery metals include process control and quality control of the
end products.

Sensmet’s online high-end solution may currently be an overkill in municipal wastewater analysis. However,
we strongly believe in the future importance of water quality. In the next 5 to 10 years, µDOES® will likely
be used to identify the sources of heavy metal emissions into natural water bodies. 

While it’s vital to envision the long-term future of market development, Sensmet will maintain its focus on
hydrometallurgical processes of alkali and battery metals as well as impurities monitoring in ultrapure
water. However, with a breakthrough technology now available it’s worthwhile to call and ask our interest
in providing the cutting-edge technology for your moonshot. 

Interested in learning more? Download µDOES® product PDF down below!