Which substance can filter water immediately?

Household water treatment: water filters and filter systems

Mechanical particle filters that are located directly behind the water meter system are mandatory and make sense. These filters are expressly not meant in the following explanations. On the other hand, we are taking a closer look at different types of water treatment, the by table water filter or by under-table devices he follows.

The market for both variants is flourishing. With misleading advertising promises and sales methods, consumers are often to be persuaded to buy the mostly expensive systems. So it is good to know the advantages and disadvantages of water treatment in the household.

Different methods of treatment

Basically, water filters and filter systems in the household only make sense if the water is actually contaminated with undesirable substances. But then the filter method must be selected to match the substance. Nevertheless: When used in the household, the risks often outweigh the promised benefits:

Activated carbon filter

Activated carbon can hold back some large, non-polar, organic substances in water, e.g. B. chlorinated hydrocarbons, plant treatment products or medicines. But heavy metal ions (e.g. lead), nitrate and calcium / magnesium (lime) cannot be filtered out with this process.

Disadvantage: If the filter is fully loaded, the accumulated substances can "break through" back into the water in a concentrated manner. Activated charcoal provides an excellent breeding ground for microorganisms. That is why the filters often contain germicidal silver, which is washed out. If the devices are not operated for a long time or if there is water in the container, there is still a risk that germs will multiply in the water.

Ion exchange

Ion exchangers remove inorganic, polar particles (ions) from drinking water and exchange them for others. For example, calcium or magnesium ions (lime) can be removed from hard water and exchanged for sodium ions.

Disadvantage: If the exchanger is full, it can suddenly release the retained ions into the water in a concentrated manner. This can go unnoticed as the devices only show a pressure increase or a certain flow rate. If devices are not used for a long time or if there is water in the container, germs can multiply. Loaded filter cartridges in table-top units cannot be regenerated, but must be replaced. Permanently installed systems must be regularly regenerated with exchanger solution.

A word about lead and nitrate:
Lead and nitrate could also be replaced by cations or anion exchangers with sodium or chloride ions. But be careful: a filter weighs in with a false sense of security. The danger of absorbing a concentrated load of the substances unnoticed is great when the filter is full. Boiling also does not remove lead and nitrate.

Membrane / reverse osmosis process

Reverse osmosis processes use electric pumps to force water through a membrane that is only permeable in one direction. This skin only lets through very small molecules like water. Larger substances such as nitrate, phosphate, heavy metals, but also minerals are retained. In this way, "ultrapure water" is also created for laboratories and space travel.

Disadvantage: To prevent the fine membrane from clogging, it has to be rinsed using a lot of water. To obtain 1 liter of filtered water, for example, 3 liters of drinking water are needed. The result: high energy and water costs. The membrane is susceptible to contamination because suspended matter collects there. Constant consumption of this water can deprive the body of minerals and lead to an undersupply.


Distillers heat the drinking water to 100 degrees Celsius. It evaporates and drips over a cooler "bridge" into another vessel. Any pollutants with a higher boiling point and minerals remain. Distillation devices are used, for example, for the "desalination" of water in the laboratory. However, volatile substances with a low boiling point, such as solvents, are not retained.

Disadvantage: High energy consumption. The distillation removes minerals from the water. Long-term consumption can lead to undersupply and functional disorders in the body.


Microporous hollow fiber membranes with pore sizes of 0.2 micrometers (i.e. 0.2 thousandths of a millimeter) hold back bacteria. Connected to the tap, they can be useful in motorhomes, boats and developing countries.

Disadvantage: Nitrate, pesticides and chlorine are not retained. A water pressure of at least two bar is required to operate the filter.

A word about bacteria:Germs can multiply where water is standing for a long time. Therefore, always use fresh water as possible. You should heat up your boiler at least once every three months.

Esoteric water treatment

Caution is advised with devices that promise "harmonization", "vitalization", "levitation", "energizing" or "transformation" of the water. The improvement of drinking water quality through such procedures cannot be proven. Expert opinions from dubious, pseudoscientific sources are often cited as evidence of the alleged success.