Sand filter bed - uses untreated and cleaned fluid in a sec. circuit to remove particles from the sand and allows a redn. in the water needed to clean the sand

摘要

In the filtering system for fluid soiled with particles, the sand of the filter bed which is loaded with the filtered particles is cleaned in a sec. circuit using a part of the dirty fluid which still has to be filtered. This is directed at the sand in a counter stream, so that clinging particles are detached from the sand and removed. Pref. the part of the untreated fluid, for use in the sec. circuit, is given a spiral flow pattern to act against the movement of the sand and particles through gravity. The vol. of untreated water used in the sec. circuit and/or the flow speed can be adjusted according to the fluid flow through the sand filter bed in the prim. circuit as the sec. circuit uses a diversion from the sand filter bed. ADVANTAGE - The operation reduces the amt. of clean water needed to clean the sand of the filter bed to a min., e.g. using 2-3% of the cleaned water.