Berkefeld filter

A Berkefeld filter [ [http://cancerweb.ncl.ac.uk/cgi-bin/omd?Berkefeld+filter Definition: Berkefeld filter from Online Medical Dictionary ] ] is British water filter made up of diatomaceous earth (called "Kieselguhr" [http://en.wiktionary.org/wiki/kieselguhr|] taken from the name of the mine in Hanover, Germany where it was mined) used since 1891. It was named after the owner of the mine.

It is a good bacterial water filer used in Microbiological laboratories and, home water filter, and also in the field. [Textbook of Microbiology by Prof. C P Baveja, ISBN 81-7855-266-3] [Textbook of Microbiology by Ananthanarayan and Panikar, ISBN 81-250-2808-0]

Design and mode of action

Usually these are made up of two metal or plastic cylinders sitting on top of each other. The upper one has a lid opening which, one can fill it with water. The upper cylinder communicates with the lower through a channel in the intervening guarding which sits one or more porcelain filter columns. The water, after purification trickles down to the lower chamber and gets stored. It is tapped out as and when required.

Sometimes the filters are fitted with a carbon core [http://www.britishberkefeld.com/faq.html FAQ from British Berkefeld on New Millennium Concepts ] ] to act as a deodorizing adsorbent. They may also have a silver impregnation to inhibit bacterial growth. They also remove certain microscopic fungi and particulate matter depending on its grade of porosity.

These filters act as "gravity filters." Water gravitates through the porous material from the upper to the lower container while being cleaned of particulate matter that get trapped in the porcelain. [http://www.stpaulmercantile.com/filter2.htm SafeTrek Survival Foods - Dried and Dehydrated One-Year and Four-Year Packages ] ]

It is sterilized by autoclaving or by steam sterilizer, after thorough cleaning.

Types

Depending on the diameter of the pores of the earth, these are of the following types:
#V ("Viel") - Coarsest pores
#N ("Normal") - Intermediate sized pores
#W ("Wenig") - Finest pores

Usefulness

It is cheap, portable, and a good bacterial filter in general though it is not a filter for viruses like Hepatitis A and mycoplasma. Some companies claim that they filter out from between 100% of particles above 0.9 micrometre to 98% of particles above 0.5 micrometre in diameter. These are very durable filters and the filter elements may be cleaned over 100 times before their replacement becomes necessary.

References