Mobile screw press and decanter centrifuge

Dewatering – Why Is It Needed?

Sludge and digestate are produced continuously and therefore require efficient management. These materials can, for example, be used as fertilizers, incinerated, or composted, which means they need to be transported to their final destination. To reduce transportation costs, it is important to decrease the volume of the material, thereby reducing the number of required transports.

When water is removed, phosphorus largely remains in the solid fraction, resulting in a more concentrated nutrient content that is easier and more cost-effective to transport and apply. Nitrogen is predominantly found in the liquid fraction (reject water), which can be utilized locally, for example at anaerobic digestion facilities, or returned to a wastewater treatment plant for further upgrading through processes such as evaporation or ammonia stripping.

The use of sludge and digestate as fertilizers helps recycle valuable nutrients back into the circular economy. After dewatering, the material can be further processed through methods such as drying or pelletizing to create higher-value biofertilizer products. If the sludge is intended for incineration, it must be sufficiently dry, making effective dewatering an essential process step.

What We Offer

Our pilot-scale equipment consists of two separate units: a screw press and a decanter centrifuge.

• The screw press is a simple and robust technology that is particularly well suited for fibrous materials.
• The decanter centrifuge enables a higher degree of dewatering and is better able to handle variations in sludge quality.

The pilot setup with the decanter centrifuge (Lemitec, model MD-80) also includes peristaltic pumps for feeding sludge and polymer into the centrifuge, a mixing tank for the feed sludge, and collection tanks for the dewatered sludge and reject water. The equipment has previously been used to evaluate the dewatering of wastewater sludge and digested food waste.

The main difference between the two technologies lies in their operating principles: the screw press removes water through mechanical compression, whereas the centrifuge separates the solid and liquid phases using centrifugal force. To optimize the separation process, polymer is often added.

Using the pilot-scale equipment, companies can test and evaluate different dewatering technologies on their own sludge or digestate. This makes it possible to:

• Assess the suitability of the technology for a specific material
• Optimize process parameters
• Evaluate polymer performance and selection
• Test under real operating conditions
• Perform chemical analyses of different process streams and, where required, evaluate their suitability for use as fertilizer

Eftersom utrustningen är mobil kan den installeras direkt på anläggningen och köras med verkliga variationer i processen. Utrustningen kan hyras inklusive introduktion på plats samt löpande support från vår personal. Material kan även skickas till RISE där tester kan utföras av RISE personal.

Areas of Application

The equipment can be used to test the dewatering of, for example:

• Municipal wastewater sludge from wastewater treatment plants
• Industrial wastewater sludge from industrial treatment plants
• Digestate from biogas plants