Aquaculture Engineering

Rotary screens - Axial flow rotary screens

Unit 12 - Management of ponds

Filtration

Classification according to form of materials - Mechanical filters

Rotary screens

Axial flow rotary screens
Fluid enters from the left-most chamber and passes through the screen in an axial direction. Screen rotation causes the partially clogged screen to pass in front of the backwash unit, where high pressure water sprayed against the down stream screen face forces particles out of the screen. The contaminated backwash water is captured by a trough on the upstream screen face and conducted to a disposal area.

Axial screens are relatively in expensive and easily operated and do not require much labour for maintenance. They are more or less automatically cleaned and will take a much higher concentration of particulate materials in the influent stream than stationary screen. The maximum size particle the screen will pass is determined by the screen mesh selected. Mesh size ranges available for rotary screens are comparable to that of stationary screens. Flow rate is determined by the screen mesh size, head loss across the screen, cleaning efficiency, amount and characteristics of particulate materials in the influent stream and cross–sectional area of the screen. Mesh size selection is based on the maximum particle size that can be allowed in the effluent.