Analytical filtration bacterial analysis water membrane filtration drinking pollution testing

Apparatus for Analytical Filtration of Water Samples - the FiltrABut



The "FiltrABut" can be used for water sample membrane filtering in bacterial analysis of water.


Useful distinctions from the analogues.

Direct filtration of water sample from the sampler-bottle; without pouring the sample from the sampler-bottle into the filter funnel.

Possibility to interrupt the sample filtration and change the filter at any moment.

Second sample contamination probability is minimal, because of the water - apparatus contact area is very small.

Working pose is sitting (More comfortable for the operator).


Principle of operation

The membrane filter 1 is set on the base 2 (with a support screen), pressed to it by bottle holder 3 by means of the captive nut 4 (which is not shown on the other plans for visibility advance) and the taper joint 5 is locked with the ball cock 6. The complete filtering head FH is turned upside-down and set on the neck of sampler-bottle 7. The resulting assembly is turned upside-down and taper joint 8 is locked with the filtrate collector 9, which is connected to a suction device and equipped with a vacuum-gauge 10 and a rarefaction regulator 11.

Some quantity of liquid flows out from the bottle-sampler 7 into the space over filter 1 in holder 3 . As a result the pressure above liquid in the bottle-sampler 7 decreases and the difference between the one and atmosphere pressure holds the liquid column in the sampler-bottle 7.

The cock 6 is opened and liquid filters from the space over filter 1 through it under the action of rarefaction in the collector 9. Liquid level in the space over filter 1 comes down uncovering the rim of sampler-bottle neck and an air bubble enters the sampler-bottle 7, replacing a liquid portion in it, which again shuts down air inlet in the sample-bottle. This phenomenon repeats then.

When the required volume has been filtered, the cock 6 is closed and the assembly of sampler-bottle 7 together with filtering head FH is overturned back. At that the liquid, placed above the filter 1, flows down inversely into the sampler-bottle 7, but the particles are retained on the filter 1 owing to differential pressure remaining on the filter 1 due to closed cock 6 and to impermeability of the wet membrane filter for air.

The filtering head FH is pulled off the sampler-bottle neck, disassembled, the filter 1 is changed by a new one and the next portion of liquid is filtered.


Performance attributes

Filter diameter, mm 35 or 47

Sterilization of the base 2, holder 3 and bottle neck by flaming

Suction by any appropriate device.

Contact area of sample with the bottle holder 4 sm2.

Sampler-bottle is in preference the hospital volumetric glass bottle for dropper.