Ahead of the 250th anniversary of the Declaration of Independence in the US, an ozone nanobubble system has been used to keep the Lincoln Memorial Reflecting Pool clear.

Months before the celebrations a massive clean up of the pool had taken place, but despite this an algae bloom had turned the water bright green. To deal with this a US$1.7 million (£1.27 million) ozone “nanobubbler” injected microscopic bubbles into the pool.

Nanobubbles are extremely small gas bubbles, often made with oxygen, air or ozone, that can remain in water far longer than ordinary bubbles. In a pool, ozone nanobubbles can act as a strong oxidising treatment, attacking algae and organic matter.

But the more important question is whether this state-of-the-art technology can help solve one of the hardest problems in aquatic restoration: getting oxygen to places where lakes, reservoirs and coastal seas are dying from the bottom up.

Clearing the Lincoln Memorial reflecting pool

The famous Lincoln Memorial reflecting pool in Washington DC is shallow, hard bottomed and man-made. It has no natural sediment bed like that of a natural lake, and its primary goal is to look clear. In this context, ozone nanobubbles can be useful, provided the water is circulated artificially and the treatment is maintained.

This is much easier than restoring a natural body of water, where the main problem is often not obvious, and can be complex to resolve.

In a eutrophic lake or sea, one that has become overloaded with........

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