Gravel and Sand Industry

Due to increasing demands on the purity of building materials, it is necessary to wash and recycle gravel, sand, grit and other building materials.

Therefore, water is used, which is soiled during the washing process. To be able to reuse it, the water has to be cleaned.

Often, large amounts of freshwater are used for the washing process. Afterwards, the soiled water flows into a tailing pond, where coarse particles are sedimented and a proportion of the roughly cleaned water is reused, the rest is effluent. The tailing pond has to be dredged regularly with great effort.

Advantages of the water treatment:

  • compact design, little space required
  • reduces freshwater consumption and costs
  • through sludge drainage by press or decanter a compact sludge can be achieved
  • dewatered sludge can be transported and used as bulk material
  • if enough space is available, rinsing ponds can be used as well
  • low maintenance-, operation- and cleaning-effort
  • trouble-free operation, great washing performance due to clean washing water
  • low energy input required
  • less flocculants required
  • low wear and tear
  • possibility to additionally separate fine sand, extraction of additional reusable material

The main assembly for the treatment of effluent is the lamella separator. As the effluent flows through the lamellas, particles settle onto the lamellas (sedimentation) and slide down into the sludge funnel and can be exported. The purified water flows into the clean water tank by passing a weir and gets pumped to the washer.

There are several methods for a further dewatering of the sludge, depending on the particular application.

Methods for sludge dewatering

The first method is the use of a rinsing pond. The investment costs are pretty low as the pond can be excavated by existing machines (e.g. earthmover). Rinsing ponds take up a lot of space, as several ponds are necessary to get well dewatered sludge. The majority of the water seeps away and cannot be reused, the sludge has to be removed by an earthmover.

The second method is dewatering by decanter centrifuge. The centrifuge runs automatically and generally, no supervision is needed. The dewatered sludge is compact to gel-like. A disadvantage of the decanter is its high power consumption, and costs for maintenance and replacement-parts that should not be underestimated.

The third method is dewatering by belt press. The belt filter press runs automatically, the compact sludge is exported to a tip and can be cart away with an earthmover from time to time. An optimal flocculation is of vital importance when belt filter presses are used. The flocculation has to be adjusted if the feed material or solids content changes. Therefore, a certain effort for supervision is necessary.

The fourth method is dewatering by chamber filter press. With the chamber filter press, the highest solids content can be achieved. The press works batchwise. At the beginning of the feeding process the volume flow is very high but decreases to the end, whereas the pressure rises. If the maximum pressure is reached, the feeding process is stopped and the press opened. The filter-cakes fall out onto a tip. In the best case flocculant may not be necessary when using a chamber filter press and the energy consumption is moderate. The press works automatically, but may need a certain effort for supervision, as the filter-cakes do not always come off the fleece perfectly.

Sludge dewatering with products of Leiblein GmbH

Leiblein GmbH manufactures the assemblies, necessary for the treatment of effluent, in-house, as for example the lamella separator. Assemblies for the sludge dewatering are not manufactured by Leiblein GmbH. Therefore, we can offer independent consultation and help you to find the most appropriate and a customised solution for your individual application. For example, only the core components (e.g. lamella separator) are delivered by us and additional components are added on site. Alternatively, we can also deliver the complete plant for the water- and sludge-treatment.

Our references

In the following, we would like to give you an overview of projects we have implemented in the metal processing industry. If you require any further information or explanation, please do not hesitate to contact us.

Leiblein GmbH – solutions for the gravel and sand industry

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