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HUBER Coanda Grit Classifier RoSF3 Grit separation and dewatering in one unit

  • Utilisation of the Coanda effect ensures high grit removal efficiency
  • Partly reduced organic content of the grit
  • Maximum corrosion resistance and wear protection

Grit classifiers are widely used on sewage works for the removal of grit. Flow conditions ideal for maximum grit removal based on scientific definition have until now been unobtainable.

Previously designed plants based on past experience have often suffered from grit carry over due to insufficient retention time caused by undersizing of plant (consequence: deposits in digester, high wear rate of pumps) or conversely classified grit with a high organic content due to oversizing of plant. Consequence: high disposal costs, and wet grit due to insufficient dewatering.

The HUBER Coanda Grit Classifier RoSF3 was developed by HUBER in cooperation with the University of Munich, hydraulics department. Based on the Coanda-Effect, the flow into the tank can be defined exactly and simulated mathematically. When operating at optimum flow, the grit separation is up to 95 % (grain size 0.2 mm).

HUBER Grit Classifiers - grit separation and dewatering in one unit
Redundant installation of two HUBER Coanda Grit Classifiers RoSF3
HUBER Coanda Grit Classifier RoSF3
A classifying screw transports the grit from the separation room into a skip.
A classifying screw transports the grit from the separation room into a skip.
Design sketch: HUBER Coanda Grit Classifier RoSF3
Design sketch: HUBER Coanda Grit Classifier RoSF3

Design and Function

Design sketch: HUBER Coanda Grit Classifier RoSF3
Design sketch: HUBER Coanda Grit Classifier RoSF3

The difference in density between grit and other organic components can partly be taken into consideration to ensure reduced organic contamination and thus static dewatering of the classified grit. High efficiency has enabled the HUBER Coanda Grit Classifier RoSF3 to be significantly smaller than conventional classifiers.

The grit / water mixture flows either by means of a pump or by gravity into the vortex chamber where a rotary motion is induced. An automatic air intake takes place through the centrically located drilling hole on the vortex chamber.

The heart of the HUBER Coanda Grit Classifier RoSF3 is the inserted Coanda Tulip. The organically laden water flowing in from the top adheres to the tulip wall and is diverted to the horizontal below water surface by the Coanda-Effect. Reduced radial and tangential flows assist the separation process and the difference in density between organic and mineral material is partly taken into consideration.

The classifier screw transports the clean grit up an inclined plane where it is dewatered under gravity before discharge into a skip. The mineral residue from a plant operating under optimum conditions is in excess of 90% (e.g. a plant with appropriate pre-screening and grit collection facilities).

The benefits of HUBER Coanda Grit Classifier RoSF3

  • High levels of grit separation of 95 % of grain size 0.20 - 0.25 mm
  • Screw supported on both ends for minimised wear
  • High corrosion resistance
  • Encapsulated, odour-free plant
  • Option of frost-proof design


Customer Information and Documents

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Frequently Asked Questions

In order to be landfilled, the grit must be further treated before. Depending on the size of the sewage treatment plant and the amount of grit, grit classifiers or grit washers are used. The state of the art is now the grit washer.

Due to the additional washing, the organic content in the discharged grit can be guaranteed below 3%. This leads to possible lower disposal costs and volumes.

Both the grit washer and the grit classifier are fed with a grit-water mix. In the machine, the grit is separated from the water.

In contrast to the grit classifier, the grit washer is able to wash the separated grit. This means that the separated grit is freed from organic components as far as possible. The grit washer thus produces grit that is almost free of organic matter, whereas the separated grit in the grit classifier may contain a considerable amount of organic matter.

Conventional grit classifiers separate virtually all solids contained in the grit trap effluent. This classified and partly dewatered grit is usually more or less contaminated with organic particles. With further treatment in a subsequent grit washer, the organics are separated from the mineral particles.

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