Screening device for use in coarse matter screening wells of a waste water treatment plant

A screening system for a wastewater treatment plant comprising:

• a solids settling chamber (1);
• a pumping chamber (2);
• a wall separating the settling chamber (1) and the pumping chamber (2)
• an opening (3) extending through the wall placing the settling chamber (1) and the pumping chamber (2) in fluid communication;
• a first movable retention grating (4) for covering the opening (3) comprising a series of vertical bars spaced apart from one another;
• a second movable grating (4) identical to the first movable retention grating (4), capable of being situated above the first movable retention grating (4) and of being vertically positioned in an upper rest position, above a top of the wall;
• respective movement mechanisms for interchangeably moving the first and second movable retention gratings (4) from the upper rest position to an operating position opposite the opening (3);
• a vertical frame (9) disposed within the solids chamber (1);
• a vertically movable rake (6) disposed within the settling chamber (1) and movably supported by the vertical frame (9) and capable of placement adjacent the vertical bars of the first or second movable retention grating (4) such that teeth of the vertically movable rake (6) fit between the spaces between the vertical bars, and waste adhered to the surface of the bars becomes detached as the rake (6) moves past the first retention grating (4);
• a vertical movement mechanism for the rake (6);
• and
• a rotatable cleaning brush mechanism (5) for cleaning the first or second removable retention grating (4) when positioned in the upper position at rest;
• wherein, the vertically movable rake (6) and the rotatable cleaning brush mechanism (5) are configured for sequential operation.