Fan sifts the sewage

A sewage-separation system that works by imitating a tornado has been
invented by Mark Youds and Colin Jarrett (GB 2354232). Raw sewage is fed into a
sloping conical tube beneath a high-speed fan that creates a downdraught. The
inventors say that the angle of the tube is critical. When the angle is just
right, the airflow created by the fan reverses—just like a tornado hitting
the ground—which sends water out of the top of the tube, leaving dry
solids at the bottom. The inventors say their system can deal with 4 tonnes of
sewage an hour.