Primary clarifier

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A primary clarifier is part of the mechanical pre-cleaning of a sewage treatment plant , on which the sewage sludge is anaerobically stabilized.

The wastewater reaches the primary clarifier via rakes , sand and fat traps (if available), where mechanical cleaning takes place. So that undissolved, organic substances or coarse substances such as ear sticks , bandages and other inorganic substances settle that were not filtered during the rake, the wastewater is passed through the primary clarifier at a low flow rate. For this purpose, the flow speed is reduced by a corresponding design of the basin. Depending on the load on the sewage treatment plant (dry or rainy weather), it is around 1.5 cm / s.

The primary sludge is pushed through a scraper into the funnel tips of the primary sludge and from there it is pumped with fresh sludge pumps for mechanical pre-thickening. Here, the primary sludge, together with the excess sludge from the activation process , is thickened to a dry matter content of around 5% with the addition of flocculants . The resulting raw sludge then enters the digestion tower , where organic matter is broken down through anaerobic processes. The wastewater from the primary clarification basin mostly flows in a free gradient into the Bio-P basin or into the activated sludge basin .

There are longitudinal and round pools. The rectangular longitudinal basins are traversed lengthwise by the waste water, with the round basins the waste water is directed from the center to the edge.

A new technology in this area is the extreme separator. A cylindrical / conical container contains an adapted diffuser which ensures a quick and precise separation of water and solids. The extreme separator requires less than 1/10 the floor space of a classic sedimentation basin and is patent pending.