Urbanisation, industrialisation, climate change and other phenomena are placing pressure on the sources used in the production of impeccable (drinking) water. For a variety of treatment objectives, membrane processes can supplement and/or replace several – sometimes traditional – water treatment processes. This can make a positive contribution to the provision of bacteriologically safe water and the removal of harmful substances, including iron, manganese, arsenic, pesticides, endocrine disruptors, pharmaceutical products and personal care products. This project is investigating how viruses can be used to monitor the integrity of membranes.
Membrane technology is being applied with greater frequency and at an increased scale in the production of high-quality (drinking) water from a variety of sources, such as groundwater, surface water, wastewater and seawater. One of its key functions is the removal of pathogens, particularly viruses. The water sources contain a number of natural viruses, at concentrations of 1×108 to 1×1010 viruses per litre. This is 10 to 100 times more than the bacteria present. Since the size of the viruses means than they cannot pass through the membrane pores, it is technically possible to use membrane processes to produce water that is completely free of viruses. Intact membranes have a natural virus log reduction value (LRV) of 8-10. This project will study whether this LRV can be drawn on to use viruses to detect whether leaks occur in membrane installations.
Damages to membranes reduce the efficiency with which they remove viruses (as well as other contaminants in the water sources). The seals and O-rings in the membrane modules can for instance become defective. Fibre breakage can occur in hollow fibres on the membrane surface or glue lines can become damaged. Leakage can considerably reduce the virus reduction values of membrane modules. In principle, the virus LRV is therefore a potential candidate to test for leakage.
Today’s methods are only capable of determining a maximum LRV of 3, and in full-scale installations the complete virus removal capacity of membranes cannot be verified. The possibility of monitoring membrane integrity with the LRV is thus currently insufficient.
KWR has developed a new method for monitoring the integrity of membranes: Natural Virus (NV). The method makes use of viruses that are naturally present in the water. Using low sample volumes, and without having beforehand to add chemical or biological virus surrogates, NV makes it possible to very sensitively (LRV of 7 or more) monitor the virus removal, and thus to keep a finger on the pulse of the membrane integrity. Moreover, the high virus concentration in the source water makes detection possible without requiring laborious sample concentration procedures.
Thanks to the simple Natural Virus method, the integrity of full-scale membrane installations can be routinely monitored with a much higher level of sensitivity than usual. This means that an important obstacle to the application of high-pressure membranes can be removed.
The TKI research into the monitoring of membrane integrity with natural viruses is divided into five subject areas:
- (Further) development of the current test – based on PCR – that monitors the LRV of membrane installations. In addition, new metagenomic approaches are being developed for the characterisation of the properties of new marker viruses.
- Testing and further development of the NV method under different conditions, and method development for the determination of natural viruses in different water types.
- Determination of the integrity of intact and damaged ceramic microfiltration and ultrafiltration membranes based on virus removal, on laboratory, pilot and practical scale.
- Determination the integrity of intact and damaged capillary nanofiltration and reverse osmosis membranes based on virus removal, on laboratory, pilot and practical scale.
- Research into the development of a biosensor for target viruses in water systems, for rapid on-site measurement.