How does a slurry separator work?

A slurry separator divides the slurry into two components: a solid phase and a liquid phase. By applying pressure, the substrate is separated into two fractions: a homogeneous, pumpable press water and a dry, stackable solid. For many agricultural, municipal and industrial operations, separation is now a central component of modern slurry and digestate management. It reduces storage space requirements, improves application and supports biogas technology by stabilising the fermentation process and increasing gas yield.

Below, you will learn how a slurry separator works technically, how the process unfolds step by step, and how Paulmichl separators prove their worth in practice.

How a slurry separator works, explained simply

A modern slurry separator operates using a mechanical separation process and is pressure-controlled: the slurry is drawn in by a pump and pumped to the separator. Inside the separator, the substrate is conveyed by a screw conveyor fitted within a screen basket. As the screw conveyor moves the substrate through the screen basket, it is separated into solid and liquid components. The aim is to achieve a stable, consistent and economical separation process.

The process consists of several steps:

1. Suction of the slurry: Feeding is usually carried out via a self-priming eccentric screw pump, which conveys the substrate directly from the pit or pre-tank into the separator. Foreign objects such as stones are separated beforehand to protect the pumps and screens. Furthermore, the substrate should be sufficiently homogenised beforehand.

2. Conveying and pre-pressing: Inside the separator, a rotating screw conveyor transports the slurry towards the screen. During this process, the pressure increases continuously – the basis of the separation.

3. Separation at the screen basket: The liquid medium flows through the stainless steel screen, whilst the solids are conveyed further towards the discharge. The screw continuously cleans the screen through friction, ensuring reliable operation. Fibrous material located in the screen gap is reliably cut off by the sharp-edged design of the screw and conveyed out of the screen gap by the pressure of the screw.

4. Control of dry matter content: The desired dry matter content of the solid phase can be set using weights via a pressure flap or another back-pressure system – important for bedding, composting or biogas substrate management. The correct selection of the gap width, as well as the geometry of the screen basket and the press screw, are also decisive factors here.

5. Discharge of solids & removal of press water: The solids fall out of the separator as a plug and can be discharged directly. In mobile units, the solids can be transferred to a conveyor belt or a discharge screw. The press water drains via a free outlet or, optionally, via an additional press water pump.

The result: a stackable solid phase and a highly homogeneous, free-flowing liquid phase that is easier to pump and can be distributed more evenly.

Find out more right here in the case study from the Müller dairy farm

Advantages of separation at a glance

✓ Targeted and precise application of nutrients for optimal fertilisation
✓ Quickly absorbed thin slurry with significantly less plant contamination
✓ Versatile solids for use as bedding, compost or biogas
✓ Up to 20% additional storage volume in the slurry tank
✓ Improved operational nutrient balance through targeted release of surpluses
✓ Reduced environmental and odour pollution through treated slurry fractions
✓ Higher yields through more efficient and crop-oriented nutrient utilisation
✓ Reduced mineral fertiliser requirements and long-term cost savings
✓ Homogeneous, pumpable press water for precise application technology
✓ Stackable solid phase for easy recycling and transport