Air blast washing system GW

watersand

Definitive Ecology’s GW grit classifier with washing stage separates/classifies and washes grit to remove the organic matter that it always contains. The grit slurry is transferred to a helical chamber which imparts rotary motion to the particles: the water changes direction of rotation as it enters the tank. Due to the increase in volume, the effluent undergoes a significant velocity reduction in the tank. The combination of these two factors allows the heavier particles to settle so that they form a bed at the bottom of the tank, while the lighter particles remain in suspension. Water is injected into the bottom of the tank to provide counter-current washing of the grit bed: the lighter particles are ejected with the cleared water or through a valve located on the tank. The washed grit reaches the pit supplying the lifting screw conveyor. Before reaching the outlet, the extracted grit is dewatered. An arm rotating at reduced speed in the tank optimises separation of organic matter from the grit. In the case of high organic matter contents the tank may be equipped with an aeration system in which air is injected through dedicated nozzles.