Method for denitrification of wastewater in a sewage treatment plant

摘要

The method comprises recirculating optionally the nitrified wastewater, optionally biomass or excess sludge (3a, 3b) from a biological clarification stage or a final clarification tank (8) of a clarification plant and the sludge mixture from a preliminary clarification tank (2) of the clarification plant into the preliminary clarification tank or an inlet (1) of the preliminary clarification tank. When the wastewater inlet exceeds a dry-weather intake, then only a part of the wastewater inlet is branched off above the preliminary tank and is again supplied below the preliminary tank. The method comprises recirculating optionally the nitrified wastewater, optionally biomass or excess sludge (3a, 3b) from a biological clarification stage or a final clarification tank (8) of a clarification plant and the sludge mixture from a preliminary clarification tank (2) of the clarification plant into the preliminary clarification tank or an inlet (1) of the preliminary clarification tank. When the wastewater inlet exceeds a dry-weather intake, then only a part of the wastewater inlet is branched off above the preliminary clarification tank and is again supplied below the preliminary clarification tank. Above the preliminary clarification tank, 30-100% of the wastewater inlet coming out over the dry-weather intake (Qt) is branched off. The part of the wastewater inlet branched off above the preliminary clarification tank is directly guided into the biological clarification stage or into the inlet. The biological clarification stage is parallely arranged as sprinkling filter. The part of the wastewater inlet supplied to the preliminary clarification tank i.e. the part not branched off above the preliminary clarification tank lies from 1-times to 2-times of the dry-weather intake. The part of the increased wastewater inlet is branched off above the preliminary clarification tank. The recirculated amount of the nitrified wastewater is 400% of the wastewater inlet quantity. The sludge level in the preliminary clarification tank is adjusted to 20-100 cm. The wastewater inlet quantity lies over the dry-weather intake, which redirects a portion of the wastewater inlet exceeding the dry-weather intake only partially around the preliminary clarification tank i.e. a certain portion of the wastewater inlet is directly introduced into the preliminary clarification tank. An independent claim is included for a clarification plant.