Microbubbles clean up Chinese lakeside

’It’s very gratifying to see our technology at work in the field,’ said professor of civil and environmental engineering Andy Hong, who developed the system at the university.

The microbubble system works by infusing water or soil with pressurised ozone gas microbubbles, making it possible to expose pollutants and make them easier to remove. The process is called heightened ozonation treatment, or HOT.

Until recently, heightened ozonation had not been demonstrated outside of Hong’s lab. But now, the University of Utah has partnered with Honde − a large Chinese environmental cleanup company − and the Chinese government to remediate the industrial site at the large lake, which is adjacent to Wuxi − a major Chinese city west of Shanghai.

‘Lake Taihu is polluted by numerous contaminants. Wuxi is an industrial city in a region dotted with polluted factory sites. The lake receives runoff from across the region, which causes nutrients to collect in the lake and feed harmful algae,’ said Hong.

’The lake requires extensive environmental cleanup after years of neglect,’ Hong added. ’We are fortunate that the Chinese government is aggressively cleaning up this area and willing to tackle challenging issues with new techniques that haven’t been used anywhere else.’

The demonstration project began in September and is expected to last three months. The focus is removing heavy metals and other contaminants from the soil. The centrepiece of equipment is a HOT reactor, which is a pressurised metal vessel that produces ozone microbubbles. The reactor is currently being used to treat soil, but it can also be used to treat water, algae or sewage waste.

The HOT reactor is filled with contaminated soil, which is excavated from the site. Organic contaminants (hydrocarbons) are removed first by repeatedly pressurising and depressurising the reactor with ozone gas, creating microbubbles that degrade the hydrocarbons. Metal contaminants are then removed by adding a chelating agent to extract them, then adding lime to precipitate the contaminants so that they can be filtered out and then disposed of.

’The clean soil will be used for tree planting on public lands, and the water is recycled and reused in subsequent batches of soil cleanup,’ Hong said.

If the demonstration is successful, Hong expects the project to be replicated at other sites for different types of contaminants around Lake Taihu, in work that Honde will manage.

In addition to Honde, 7Revolutions Energy Technology Fund − an investment company based in Salt Lake City and a University of Utah startup − has licensed the technology and started a company to explore uses in the US and elsewhere.