Shaftless dewatering screw screen
To meet the growing demand for small sewage treatment plants, ANDRITZ SEPARATION has designed the AquaSpir screen, a shaftless screw screen which not only screens and conveys the solids, but also dewaters and compacts the screenings – all in a single integrated unit.
Screening takes place in the filtration zone, which comprises either a filtering wedge wire basket or a semi-circular, perforated plate, depending on the mesh size required. The solids captured in the filtration zone are conveyed automatically out of the flow by the shaftless screw. A spiral brush attached to the lower end of the screw ensures that the screening mesh is cleaned continuously. In the transportation zone, the heavy duty screw is supported by hardened steel wearing bars which are bolted to the stainless steel body of the AquaSpir screen, allowing them to be removed easily for maintenance. When the solids arrive at the compacting zone, located at the end of the screw, they pass into a stainless steel pipe which is slotted to allow the water to escape during compaction. Two spray pipes fitted with nozzles ensure that the solids plug in the compacting zone is thoroughly washed and all the excess organic material is returned to the effluent.
The AquaSpir screen can be installed quickly and easily in an existing channel for gravity flows. If there is no channel, the screen can be mounted in a tank and the effluent is usually pumped to the screen. The equipment can be installed either inside or outside, and the compacting zone can be supplied with heating elements to protect it against freezing.