Mineral scaling and biological fouling processes decrease the efficiency of reverse osmosis (RO) desalination and often require costly measures to mitigate, such as the introduction of chemical antiscalants, biocides, or physical pretreatment by microfiltration (MF) or ultrafiltration (UF) membranes.
A number of electromagnetic based non-chemical water treatment technologies have been commercialised but their main application has not been in the prevention of RO membrane fouling. Many of these technologies have not been embraced by the membrane desalination industry due in part to inconsistent results in early trials, exaggerated claims and the lack of scientific transparency regarding mechanisms of action.
The anti-scaling and anti-biofouling activities are incompletely understood but presumed to derive from an applied electromagnetic field (EMF) that varies in amplitude and frequency. It is hypothesised that the secondary EMF changes the surface electrical potential of suspended colloids and also causes damage to the cytoplasmic membranes of bacteria.
Investigate the EMF method of action by examining the effects of two commercial pulsed EMF units on bacterial growth, mineral scaling and on “magnetic memory” (or water structure).
Two commercial units were characterised in terms of their frequencies and waveforms and static operation, which was adopted to give a worst case scenario and to maximise the sensitivity of the experiments. The results demonstrate that exposure to EMF radiation can both stimulate and inhibit bacterial growth depending upon the time of exposure and the specific waveform used. However, it was found that the observed inhibition of growth, whilst significant, is minimal and is not sufficient to justify the claims of the manufacturers. Studies looking at manufacturers’ claims that EMF effect reduces chemical scaling in a RO feed stream revealed no convincing evidence.
The baseline effects of the two commercial EMF units have now been determined and the team will continue this work by building an EMF device and repeating the experiments to confirm the findings. Further investigation into the water structure/clustering studies are needed to compare the effects of different durations of EMF treatment. Different impurities, such as iron, will also be tested to determine the effects of various compounds on “water memory”.
Total Value: $328,900 (cash and in-kind contributions)
Principal Investigator: Dr Thomas Yeager
Title: Evaluation of non-chemical pulsed power technology as an antifouling pretreatment for reverse osmosis desalination membranes
Length: 31 months
Personnel: 6 collaborators contributing 1.4 FTE
- 2016. Piyadasa, C. Evaluation of pulsed electromagnetic field technology as an anti-biofouling pre-treatment for reverse osmosis membranes. PhD thesis, Victoria University.
- 2015. Piyadasa, C., et al. The effect of electromagnetic fields, from two commercially available water-treatment devices, on bacterial culturability. Water Science and Technology.
- 2014. 4th Membrane Society of Australasia Early Career Researcher Symposium.. Geelong, Victoria.
- 2014. 10th International Congress on Membranes and Membrane Processes. Suzhou, China.