Optical sensors for on-line water quality monitoring must be durable and reliable as it is crucial to get robust data over a long period of time. To that ending, proper cleaning of sensors present in different types of water matrices is a key factor that has to be taken into account. Under this context, s::can has assessed different strategies for cleaning of the optical window under real conditions (both in river water and brackish water), such as pressured air, rotating brush in a flow cell, rotating brush in submersed mode and a rubber pet brush moving up and down for waste water complex matrices with a small optical window length. Results showed that pressurized air cleaning was more efficient than brushing and it was especially good not to have mobile parts in river water. In case there was the possibility to have power supply a compressor was used, on the other hand, in case there was no power supply, a CO2 bottle was used instead. The only case when air pressured did not perform well enough, it was when iron or manganese ions were present at high concentrations in the water matrix. The binding of these two ions with the surface of the optical window was not possible to be broken when using pressured air cleaning and the optical window remained dirty. Under these conditions, cleaning was not easy by using brushing either. Ultrasonic cleaning was also assessed but it caused massive precipitation on the surface of the optical window.To the aim to be able to minimize cleaning of the sensors in the future, s::can has been also involved in the research of new coating materials for the optical window. Experiments showed that a new artificial quartz material reported very promising results.

Overview of cleaning techniques for optical sensors and their efficiency on water quality monitoring under real conditions

248th National Meeting (2014)

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