KWR has been granted a patent for a new, very sensitive method to determine how effectively a physical water treatment installation removes viruses. This DNA-based method makes use of viruses that occur naturally in (surface) water, which makes it suitable for use in membrane installations for drinking water production. KWR is now focused on further developing the method, with the aim of achieving a robust technique that can be (continuously) used in daily operations and in treatment applications for other water sources, such as seawater, groundwater and wastewater. Thanks to the great sensitivity of the new method, the use of membrane filtration as a standalone technique in drinking water production has been brought a step closer to realisation, but so too has the use of membrane filtration for the safe reuse of wastewater.
In the use of membrane filtration in water treatment, it is important to demonstrate that the membrane installation actually removes viruses. Until recently, this was only possible on a bench or pilot scale, by adding surrogate viruses into the feed water and then measuring how many of them got through the system. The addition of viruses is naturally not desirable in a full-scale membrane installation used for the production of drinking water. Furthermore, the methods typically employed were not sensitive enough to properly demonstrate a major portion of the removal.
Exploratory work under the Joint Research Programme with the water utilities has shown that it is possible to determine the removal rate of viruses by measuring the amount of DNA of specific, naturally-occurring, viruses in the feed water of an installation and then in the treated water. The high sensitivity of this new method makes it possible to show that the number of viruses in the treated water is, for example, 10 to 100 million times smaller than in the feed water. The methods currently in use can only demonstrate a drop in the virus numbers of up to a maximum of 10,000 times.
KWR has recently been granted a European patent for this new detection method, which is suitable to show the rate of virus removal for all physical water treatment methods. The further development of this method for its use in daily operations will enable an improved monitoring of the integrity of the membranes and the installation, and thereby permit a more effective application of membrane filtration. In theory, membrane filtration is capable of completely removing viruses, as long as the membranes and the installation are entirely intact. This is why sensitive monitoring methods are needed to show that the membrane installation is operating well and that no (mini) leakages exist. Since we do not yet have such methods, in the Netherlands membrane filtration is currently only used in drinking water treatment in combination with other treatment techniques.
Determining and safeguarding robustness
‘With this new measurement method,’ says Walter van der Meer, director of the Oasen water utility, ‘we can easily determine how robustly a treatment process removes viruses and bacteria, without having to add bacteriophages, which is a pretty complex method that moreover involves adding a foreign component into your production. For Oasen the new method of measuring naturally-occurring viruses is very practical and pertinent. It will allow us to precisely determine and safeguard the robustness of the One-Step-Reverse-Osmosis concept that Oasen has developed.’
Wastewater and reuse
The application of the new method in practice can also make a huge contribution to the responsible reuse of water within the circular economy. Moreover, KWR aims, together with relevant partners, to extend the method’s application possibilities by adapting it for use with other sources, such as seawater, groundwater and wastewater.