Water treatment -- WELCLEANING
This is the environmentally-friendly treatment of pig and cow slurry, organically-contaminated fluids as well as communal sewage with membrane filtration. The process can be used to produce industrial water, drinking water, fertilizer concentrates and special fertilization products.
atelier welter, biogas, gülle, welcleaning, manure system, motor
atelier welter, biogas, gülle, welcleaning, manure system, motor
atelier welter, biogas, gülle, welcleaning, manure system, motor

Description of the "WELCLEANING SYSTEM"

The processing of slurry and communal sewage through membrane filtration into water and fertilizer concentrates.

The use of the membrane separation techniques of ultrafiltration and reverse osmosis makes it possible and sensible to transform slurry and communal sewage into industrial or drinking water and almost completely odor-free, packable, compostable fertilization concentrates.

What's meant by ultrafiltration (UF)

Ultrafiltration is the separation of suspended or dissolved high molecular weight materials from low-molecular weight molecules in solution through the use of semi-permeable membranes made of polymers or ceramic materials that allow the passage of low-molecular weight molecules (< 5000 Dalton) and water.

The pressure difference between the top and bottom layers of the membrane is what drives ultrafiltration. In general, ultrafiltration is carried out under operating pressures of between 4 and 6 bars.

Because of the membranes' separation properties, ultrafiltration is particularly suitable for:
  • The simultaneous concentration and cleaning of high molecular weight materials.
  • The extraction of sewage contents of organic origin, such as heavy metals, but also of slurry contents.

The processes of ultrafiltration and reverse osmosis are similar in many respects. Membranes are often made from the same material and differ only in terms of pore size.

What's meant by reverse osmosis?

Applying a pressure to a solution that's higher than its osmotic pressure results in a solvent's being purified of solutes after being transferred through a semipermeable membrane.

High molecular weight materials as well as low molecular weight components such as salts are separated out of the solution during the process of reverse osmosis. The difference between the pressure applied and the osmotic pressure of the solution (between 30 and 70 bar) is what drives reverse osmosis.

How it works.

Both techniques are carried out as cross-flow-procedures, that is, the flow across the membranes is at such a high speed that a clogging of the pores such as that seen in static filtration, is largely avoided.

For the process of ultrafiltration, previously separated fertilization slurry or communal sewage that contains materials of less than 0.5mm is fed into the ultrafiltration plant and run over the ultrafiltration membranes at a high speed. At a pressure of about 5 bars, suspended solid materials and the macro-molecular components (carbohydrates, proteins) are concentrated out with a dry matter concentration of 12-14% to a maximum of 18%.

At the same time, the solution (ultrafiltration-filtrate) that contains the salts and the low molecular-weight components is drained off with a dry matter concentration of 0,6-1,5%.

Through optimal technical conditions such as overflow rates, operating pressure and temperature, operation of the plant at almost constant filtrate flow is guaranteed over a long period of time without the need for cleaning.

Slurry contents such as urea have a cleaning effect that fight against clogging.

With reverse osmosis, the solution crosses through the membrane at a high flow rate and at about 40 bars. This leads to a concentration of the salts including low molecular weight molecules and a separation from now nearly salt-free water. However, because the membranes only achieve salt retention of between 95-99%, some of the salts still wind up in the "raw water."

This water doesn't yet meet the conditions for drinking water but can always be used as valuable industrial water or as water for cultivated plants.
If this water (the first reverse osmosis permeate) is processed in a second reverse osmosis step, drinking water is produced.



Ultrafiltration is a process that uses pressure effects to separate and concentrate colloid and high molecular weight components out of solution. A selective, semi-permeable membrane makes this separation process possible.

High molecular weight components are held back by the membrane's surface while low molecular weight components and solute are able to pass through the membrane. Contrary to usual filtration methods, the medium being filtered flows parallel to the membrane's surface.

The retained high molecular weight components don't therefore block the surface of the filter membrane but are rather washed away by the turbulent flow. This allows for high filtration capacity.


Pre-filtered slurry with particle sizes of less than 0,5mm (through use of mechanical separators, centrifuge or similar), is introduced into the ultrafiltration plant.

This can easily separate solid and fluid components of the material that has been introduced. The membrane constitutes a safe retaining wall that not only separates these two components, but also blocks the passage of bacteria and viruses. Membrane filtration uses the natural physical principal of molecule transport through a semi-permeable membrane due to pressure difference (trans-membrane pressure). Molecules or particles are held back by the membrane because of size, weight or structure. The membrane is characterized by its pore size, the distribution of pores on the surface, by the number of pores per square meter of membrane surface, by their charge and through their chemical composition.

The fluid being treated is pumped by a supply pump over an uptake pipe into the circulation container. The cross-flow filtration flows in a circuit that includes a circulation pump, membrane unit and working tank. The fluid that flows through the circuit enriches itself continuously with the solids that are being separated out from the permeate moving across the membrane. The working tank must therefore be emptied periodically, after it reaches a corresponding end concentration (UF and reverse osmosis concentrations). The circulation pump is set up so that a sufficient velocity is achieved along the membrane. This high velocity creates significant sheer forces that prevent the build-up of filter crust on the membrane's surface and so guarantees high permeate through-put over a long time period.

The part of the fluid that crosses through the membrane is purified permeate that has been cleared of solids and viruses. This permeate is fed into a downstream osmosis step.

Plant construction for osmosis is similar to that of ultrafiltration. The modular set-up is different however because of the function and construction of the membrane/units.

The permeate produced by the reverse osmosis is fed into a carbon filter and this produces drinking water. The concentrate is then fed into the circulation tank of the ultrafiltration system and fertilizing concentrate is what's left at the end of the process.

Steuerschrank Separator Welcleaning System