Compliance to International Standards
Sand filtration is used for the removal of suspended matter, as well as floating and sinkable particles. The wastewater flows vertically through a fine bed of sand and/or gravel. Particles are removed by way of absorption or physical encapsulation. If there is excessive pressure loss on the filter, it must be rinsed.
A distinction can be made between continuous and discontinuous filters. In continuous filters (often upward-flowing filters). the polluted sand is removed, rinsed and re-used continuously, without interrupting the filtration process. Discontinuous filters (often downward-flowing filters) are stopped, and a rinse takes place in the opposite direction. Air bubbles are blown into the sand bed to make it swirl around. Filtered water then flows through the filter bed in the opposite direction.