Integrated unit for intake and pretreatment with local backwashing

A local backwashing apparatus for a filtering system comprising:

• an enclosure having an open lower end and being positionable above a surface of filter media of the filtering system, the filter media supported by a drainage layer,
• a pneumatic system in fluid communication with an upper part of the enclosure and configured to determine an air pressure in an upper part, the pneumatic system comprising an air pump,
• a pipe system connecting an upper part of the enclosure with the pneumatic system and with a discharge structure, and
• a control unit connected to the pneumatic system, the control unit configured to conduct local backwashing of consecutive partial volumes of the filter media by sinking the enclosure into the filter media until the enclosure is supported on the drainage layer by reducing the air pressure in the upper part of the enclosure through the pneumatic system once the open lower end of the enclosure is immersed in filter media, to enclose the partial volume of filter media within the enclosure and generating local backwashing of the partial volume of the filter media enclosed in the enclosure, during continued operation of global filtering through filter media outside the enclosure in the filtering system, by generating suction through the pneumatic system that initiates a water flow from the upper part of the enclosure through the pipe system to the discharge structure, wherein the water flow introduces into the lower end of the enclosed partial volume of filter media filtered water from the drainage layer which expands the enclosed filter media and releases sludge therefrom to the water flow that flows to the discharge structure, and raising the enclosure above the surface of the filter media to release the backwashed enclosed volume of filter media, by injecting air and increasing air pressure in the upper part of the enclosure through the pneumatic system to float the enclosure above the filter media;
• wherein the enclosure comprises side walls with a roof, the free ends of the side walls forming the open lower end of the enclosure, the free ends are connected to the side walls at connection points having a cross-sectional area identical to the cross-sectional area of the upper part of the enclosure, the free ends converging directly from the connection points to provide an open lower end with a smaller cross-sectional area than the upper part of the enclosure.