COLUMNS of tiny, bright-blue beads may banish harmful organic pollutants from
sewage farms and industrial effluent more effectively, say chemists at the
University of Bradford in Yorkshire. Made of silica gel, the beads make the job
of cleaning up effluent much easier.
A widely used technique for cleaning up contaminated water is to pump ozone
through it, turning pollutants into harmless substances such as carbon dioxide,
oxygen and water.
鈥淥zone will destroy any organic pollutants,鈥� says Chedly Tizaoui, leader of
the Bradford team. But because ozone dissolves sparingly in water, as little as
10 per cent of the gas is effectively available for attacking the
contaminants.
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The Bradford team鈥檚 solution is to adsorb the ozone onto silica beads around
2 millimetres in diameter, Tizaoui told a Royal Society of Chemistry meeting in
Manchester last week. This technique frees all the ozone for destroying
pollutants. Compared with bubbling ozone through water, 鈥渢he gel works out 10
times more effective,鈥� says Tizaoui. He says that the system could purge
effluent from many sources, including sewage works and oil refineries.
When freshly charged with ozone, the colourless beads turn bright blue. And
fading colour indicates when the column needs recharging. At present, the
3-metre-high lab columns need recharging every 90 minutes or so, with water
passing through at the normal rate for effluent treatment. The gel has to be
dried before recharging, which takes about an hour, although reloading with
ozone only takes 5 minutes.
Tizaoui envisages three columns working in series鈥攐ne adsorbing ozone,
one treating water and one being dried out鈥攕o one will always be in
working order. The team is now working on a secret replacement for the gel which
is even more effective.