This gave full rotation in 6600 steps. A wiper arm with
three brushes 100 mm in length and angled at 45°, swept the biosolids
towards the centre of the tank where four intake vents pulled in any
accumulated waste and removal was achieved by balanced water flow
lifting biosolids fromthe tank into the centralwaste pipe. The entire unit
was housed in a circular fibreglass tank with a planar base with an
internal diameter of 78 cm (Fig. 1). The inflow was set at 4.2 l min−1
with a water depth of 35 cm giving a tank volume of 170 l and a turnover
rate of 1.5 h.
In operation, the rotary device took 9 min 45 s to perform a
complete rotation of the 78 cm internal diameter tank and required
three rotations to move biosolids from the tank sides to the centre. A
slow operation speed allowed fish sufficient time to consume feed
pellets added to the tank. The device consumed 10.7Wh−1 of
electricity and at an estimated commercial rate of £0.21 per kWh and
would cost £0.05 to run for 24 h.