Sand is collected in the head of works by settlement. For larger flows the most common practice is to use vortex chambers which settles the grit 4 – 6 m below ground level. Grit collected here is most effectively removed with air lift pumps. This can then be further dewatered or washed with other MEVA equipment.
The Zickert bottom sludge scraper is based on the forward and return movement of its hydrodynamically designed sections. The concave face of the scraper slowly moves the sludge towards the collection chamber. During the return, the wedge shape of the opposite side quickly slides under the sludge blanket, without disturbing the sludge layer.
Full or half bridges travelling bridge scrapers for primary or secondary sedimentation tanks. Submerged parts are manufactured from stainless steel parts while walkways can be from HDG mild steel. This greatly extends the lifespan of the bridges.