Machine Parameter

Design dimension characteristic for the geometry of the separation apparatus that influence the process directly. Examples for machine parameters are the cake formation angle at drum filters, or the drum length of a decanter centrifuge.

Magnetic Fishing

Method to separate low concentrated active substances, i.e. proteins from a multicomponent mixture. The slurry, i.e. a fermentation broth is mixed with magnetisable particles in the μm-range, which are coated with ligands to bind special molecules selectively. The loaded particles are separated in a magnetic field whereas the rest of the slurry is discharged. In the following steps the concentrated product is washed, eluted and separated from the magnetic beads, which are recycled.

Magnetic Separation

Method to deposit magnetisable particles from a slurry to the surface of a collector under the influence of a magnetic field. Electromagnets or permanent magnets can be used. Due to the geometrical configuration of the collector and the deformation of the magnetic stream lines high gradient magnetic separation or open gradient magnetic separation is realized. An additional positive effect for separation arises, if the particles to be separated are flocculating in the magnetic field. If nonmagnetizable particles are caught by the magnetic flocs one speaks about heterocoagulation.


The mixing of a particular dry solid into a liquid to produce a suspension. For example, the suspension prepared for alcoholic fermentation during the wine or beer making is called mash.

Mass Concentration

The mass concentration states the solids content in a suspension. Commonly, the mass concentration is quoted in [g/ISusp.], and can be readily determined gravimetrically, but causes problems when comparing suspensions made from different compounds whose densities do not correspond. For these cases the volume concentration is better suited.

Mass Throughput

Mass transported or separated in a separation apparatus per time unit. The mass throughput refers mostly to the solids mass throughput. It is often correlated to a filter area. The area-specific solids mass throughput is stated in [kg/m h].

Material Feeder

The purpose of a material feeder is the even distribution across the separating surface of the suspension to be separated. Material feeders can be a diffuser like distribution metal plate, groove like distribution facilities with a paddle discharge, and distribution or floating dam plates, respectively. Applications for such devices can be found e.g. in strongly flocculated suspensions in the straining zone of double belt presses.

Mechanical Demoisturing

In the solid-liquid separation technology one generally differentiates between mechanical and thermal demoisturing. While at the thermal demoisturing a phase transition of the liquid into the gaseous state is always included, the mechanical demoisturing is achieved by displacement of the liquid at constant temperature. The mechanical demoisturing occurs under the influence of either the earth‘s gravitational or a centrifugal field, a hydrostatic head, a hydraulic or mechanical pressure, or a gas difference pressure.

Mechanical Demoisturing Boundary

The mechanical demoisturing of porous solids systems is subject to certain limits. In the demoisturing of bulk solids, the mechanical demoisturing boundary is reached when the coarse capillary liquid is removed due to exceeding the capillary pressure by the differential gas pressure. Then the liquid in the bulk exists only in form of interstitial liquid, adhesive liquid, inner liquid, and isolated liquid regions. In the centrifugal field one can still remove certain portions of these liquids by the acting mass force. In the demoisturing by mechanical pressing, a limit is reached when the solid particles get destroyed by the compacting pressure.


(Latin: membrana = skin). Membranes are used in solid-liquid separation in two different manners. For one, impermeable rubber or plastic membranes are employed in the mechanical press demoisturing of sludges in membrane filter presses. Alternatively, permeable membranes are used as porous filter medium in microfiltration and ultrafiltration. The pore size is generally located in the sub-μm region. Filtration membranes are offered in a large variety of materials and have to be carefully adjusted to the product to be filtered, in order not to clog too early and thus become inoperable.

Membrane Filter Cloth

A microporous membrane for cake filtration integrated in a technical weave or a fleece (patent of the BOKELA company). Aside from producing particle- free filtrates, the membrane filter cloth has the special advantage of complete suppression of the gas breakthrough during the demoisturing phase which is unavoidable in conventional cake filtration. The principle of this semi-permeability lies in the fact that hydrophilic membranes have to have such small pores that their capillary pressure cannot be surpassed by the acting gas pressure difference (e.g. vacuum with 0.8 bar). The filter cake on the other hand has to be capable of being demoistured at this pressure difference. Membrane filter cloths display pore sizes between 0.2 μm and up to about 1 μm. Cake formation performance and final residual moisture correspond in general to those attained in conventional filtration with a common filter cloth.

Membrane Filter Plates

Special filter plate for a membrane filter press, which is equipped with press membranes. These membranes can be hydraulically stretched to the outside to push out the filter cake from the filter chambers.

Membrane Filter Press

Further development of a chamber filter press. In membrane filter presses the filter cake can be squeezed in the filter chamber from one side by a press membrane. Filter- and membrane plates alternate with each other. Advantages of this design are that the feed pressure of the suspension can be kept low and for this a high pressure pump is not needed anymore, that a residual volume filtration can be achieved without difficulties, and,last, the filter cake can be uniformly compressed.

Membrane Fouling
Mercury Intrusion
Mercury Porosimetry
Mercury Porosimetry

A technique for measuring the pore size distribution in porous systems. First, the evacuated voids of a porous system are filled under pressure with mercury. This procedure is also called mercury intrusion. The filling of the pores is performed with continuously stepwise increasing pressure. Following each pressure increase one waits until the equilibrium of the mercury-absorption in the specimen is reached. Then, according to the Laplace-equation a pore diameter can be assigned to each pressure level. The distribution results from the respective quantity of the intruded mercury.


Number of openings per linear inch in filter weaves. So, for example 5 Mesh corresponds to a pore size of 4000 μm; 50 Mesh correspond to 297 μm, and 5000 Mesh correspond to 2.5 μm.

Mesh Width

Opening cross section of pores in a filter weave. The term mesh width is not clearly defined. Mostly, it is perceived as the diameter of a sphere capable of passing through a medium sized mesh. Mesh widths in a technical weave are principally size distributed, aspiring a pore size distribution as narrow as possible.


Molecular aggregates of for example a tenside that form on the surface of a liquid which had been prior saturated upon further addition of tenside. If the surface is capable of adsorbing more tensides again, for instance, through area enlargement, the micelles disappear. The tenside concentration in a liquid at which a micelle formation begins is called the „critical micelle concentration“ (cmc).


A type of surface filtration where porous membranes, generally with a pore diameter of less than 5 μm, are employed either in crossflow filtration or dead end filtration. Microfiltration is applied in polishing and concentrating of suspensions, that contain a large amount of submicron size particles.


Pore structure with pore sizes of 5 μm and smaller.

Residual Moisture
Moisture Measurement
Residual Moisture Measurement

Weave, which is woven from endlessly spun individual threads. Monofil weaves are extremely adjustable in pore size, and are often applied in the cake filtration. A lower pore size limit is around 5 μm.

Monolayer Filter

Apparatus of the deep bed filtration type with a homogeneous bed structure operated as quick filter with a highly porous layer of filter aid. The layer is supported on a perforated horizontal filter floor onto which the feed flows in the direction of gravity. The filter is regenerated by changing the layer or by a momentary flow reversal and back flushing (backflush). Their main application is the field of water purification.

Monoplate Filter
Leaf Filter
Mother Liquor

A liquid originally contained in the suspension to be separated that remains in the bulk following the filter cake formation. This mother liquor, however, can be displaced or diluted in a following process step with a wash liquid.

Multi-Pass Test

This test was developed in the first place for the examination of hydraulic liquid filters similar to the single-pass test. Here the suspension is recirculated through the tested filter medium in a large number of passes. A particle measuring device registers the amount and size of the particles before and after the filter during the test period.


Weave woven from endlessly spun threads and twisted into a twine. Multifilament weaves due to the thread structure, display a certain deep bed filter characteristic which can lead to blockage, but they are more stable against thread breakage than a monofilament weave.

Multilayer Cartridge Filter

Candle shaped filter element flowing from the outside to the inside and working as a deep bed filter. A multilayer cartridge works like a bulk multilayer filter, but with a filter layer made up of several layers of differently fine porous filter media (e.g. fleeces) instead of bulk material. Again the pore size decreases in the direction of the flow. Multilayer cartridge filters are used in the purification of liquids with extremely low solids contents (pulp colloids).


Description for the filtration efficiency in ultrafiltration. Molecular Weight Cut Off is quoted in [Dalton].

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