A Berkefeld filter is a water filter made from diatomaceous earth (Kieselgur). It was invented in Germany in 1891 and was sold in the United Kingdom by the Berkefeld Filter Co. by 1922. The name "Berkefeld" comes from the person who owned the mine in Hanover, Germany, where the material used in the filter was mined.
The Berkefeld filter is a useful tool for removing bacteria from water. It is used in laboratories that study tiny living things, in homes, and in outdoor settings.
Design
The filter housing is made up of two cylinders stacked on top of each other. The top cylinder has a lid and is used to hold dirty water. At the bottom of the top cylinder, there are one or more holes filled with diatomaceous earth (Kieselgur) filter columns (filter candles). Gravity pulls the water through the filters, and it then flows down into the bottom cylinder, where it is stored and removed as needed.
Some filters include a carbon core to remove bad smells. These filters may also be coated with silver to stop bacteria from growing. Filters with different levels of porosity can also remove some tiny fungi and small particles. Filters that are not coated with silver are cleaned thoroughly and then sterilized using an autoclave or steam sterilizer.
Types
The filters are sorted based on the size of the pores in the earth:
- V (Viel) – Largest openings
- N (Normal) – Medium-sized openings
- W (Wenig) – Smallest openings
Usefulness
The Berkefeld filter is an inexpensive, portable, and effective tool for removing bacteria from water. However, it does not remove certain viruses, such as those that cause Hepatitis A, or specific types of bacteria, like mycoplasma. The first Berkefeld filters were used during the cholera outbreak in Hamburg in 1892.