Treatment of sand
and gravel washing water

The washing water to be recycled flows from the wet preparation into the lamella or oblique clarifier.  The sludge deposited there is pumped directly into the decanter centrifuge for sludge dewatering. As the centrifuge can process large quantities, interim storage in a stacking tank is generally not necessary.

The treatment of sand and gravel requires a lot of water. Water is a scarce resource in many regions of the world, which makes groundwater extraction increasingly more regulated and expensive. Sand and gravel mills can save further by using recycled water to reduce their need for fresh water, but lagoons are not the most efficient way to recycle. The large water surface of lagoons allows for evaporation of the water being stored there, which must be replaced by fresh water.

Flottweg systems drain the sludge from wet treatment very efficiently. The clarified water is available to the washing plant again. Depending on the process, over 90 percent of the process water can be recovered. This means that valuable groundwater hardly needs to be used for cleaning.  As it is a closed circuit, no process water is returned to the environment. Settling basins or lagoons for the used washing water are reduced or can be partially omitted.

Flottweg decanter centrifuges can continuously process high sludge quantities. Sand and gravel can thus be fully automatically processed in parallel operation. Designed for mining work, the machine has highly efficient wear protection on the screw and rotor. The centrifuge works as a closed system and separates even the finest solids from the washing water. Thanks to the Simp Drive® drive system, it automatically adjusts to different feed volumes and, if necessary, to fluctuating solids concentrations in the incoming sludge. A high dry matter content in the discharged solids enables  the material to be conveniently conveyed or loaded. At the same time, recycled water is clean and virtually free of solids.

The sludge separated in wet treatment is often temporarily stored in lagoons or ponds. Over time, the solid sediments and settles on the bottom of the pond. Gradually, more and more sediment accumulates on the bottom of the pond reducing its usable volume for water storage. To increase its capacity to store water, the pond has to be excavated regularly at a high cost. Decanter centrifuges separate the fine solids from the water, eliminating the need to maintain sedimentation ponds for sludge dewatering. 

The compact design of the Flottweg decanter centrifuge makes the construction of additional buildings or infrastructure for gravel and sand mills unnecessary. This significantly reduces investment costs. As decanter centrifuges use centrifugal force, there is no need for consumables such as filter cloths.

Flottweg decanter centrifuges are designed for use around the clock. Fully automatic operation is easy with the sensor-based Motice condition monitoring system, the intelligent screw drive Simp Drive ® and the new Ingo user interface. Hardly any personnel are required to operate the system. In addition, the cleaning cycle is omitted during the operating phase. This saves time and costs.

Whether you need to expand your existing sand and gravel treatment system or need a complete turnkey solution for water treatment: We can handle the entire project on request. Depending on the process, we integrate our decanter centrifuge into existing processes or supply further equipment, such as fresh water storage tanks, conveyor belts, etc. After consultation, we act as the sole contact for our customers and take care of all necessary construction and mechanical measures. Our engineers have many years of experience in designing machines and systems for the treatment of sand and gravel. We are there to support you as a reliable partner throughout the entire project and beyond.

The Reithelshöfer GmbH sand distribution and management company has been relying on Flottweg since June 2003. The decanter centrifuge is used in the treatment of sand washing water.