Ozonation with micro-nanobubble technology for algae and PFAS reduction, UniSA

The study examines whether ozone nanobubbles could provide a practical alternative or supplementary treatment for contaminated surface waters. The researchers used the City of Salisbury as their case-study area and compared its available water-quality data with results from published ozone and nanobubble treatment studies.

The central idea is that ozone is already a powerful oxidant, but conventional ozone has relatively short contact time in water. Nanobubbles can remain suspended much longer and provide improved gas-to-water mass transfer. Combining the two therefore has the potential to increase ozone utilisation, extend treatment activity and improve contaminant degradation.

This study is a review of published work. Every figure below comes from the literature the thesis surveyed.

The literature reviewed in the thesis found conventional ozonation achieving algae reductions generally above 90%. When ozone was combined with micro and nanobubbles, the reported performance was particularly strong. In studies with water-quality parameters considered comparable with Salisbury, conventional ozone achieved approximately 93 to 95.9% algae reduction, ozone with micro-nanobubble technology achieved approximately 96 to 100% algae reduction, and other nanobubble studies demonstrated substantial improvements in dissolved oxygen.

One laboratory study reported 100% algal mortality after four hours, while another achieved approximately 96% reduction. The technology may therefore offer more than simple oxygenation: ozone carried within nanobubbles provides a powerful oxidation mechanism capable of directly attacking algae and associated contaminants.

The thesis found encouraging evidence for ozonation of PFAS, with relevant studies reporting reductions above 76%, including results around 95% under certain treatment conditions.

The thesis's conclusion that ozone nanobubbles could improve PFAS treatment is an informed hypothesis rather than a directly demonstrated result. The authors reason that because nanobubbles can increase oxidation efficiency, ozone residence time and contaminant contact while potentially requiring lower ozone concentrations, they could enhance PFAS treatment. But this needs laboratory and field validation.

The study also considered whether the technology could realistically be deployed across multiple surface water bodies. Of 135 Salisbury water bodies considered, only three were larger than the largest water body identified in the literature as having been treated using micro-nanobubble technology.

On the study's assumptions, this suggests that the great majority were potentially within the demonstrated treatment scale, and many of the smaller water bodies could be treated by a mobile treatment system. Rather than waiting for an algal bloom and then applying emergency chemical treatment, ozone nanobubble systems could potentially be deployed proactively to maintain healthier water conditions and reduce bloom formation.