Filtration technologies and filtering methods at a glance

Activated carbon is one of the oldest and most widely used filter technologies. One cubic centimetre of activated carbon has a surface area the size of a football pitch. Pollutants accumulate on this huge surface. There are two designs. Table-top and jug filters use loose activated carbon granules, which the water merely flows around. Their performance remains limited, and the risk of bacterial contamination increases. The sintered activated carbon block is pressed into a solid block at high temperatures and achieves a significantly higher filter performance.

Reverse osmosis removes almost 99% of all dissolved substances. The process was originally used to desalinate seawater. It forces the water through a semi-permeable membrane under pressure. Depending on the substance, the efficiency is between 70% and 99%. One drawback remains: valuable minerals and trace elements are also removed. The water then tastes flatter. For household use, reverse osmosis is therefore usually oversized. It plays to its strengths in medical technology and industry.

Strictly speaking, an ion exchanger is a special case among water filters. It selectively exchanges individual ions and thus reduces a selected substance, such as nitrate, arsenic or sulphate. It can also lower water hardness, as the resin binds calcium and magnesium. All other substances remain in the water. Ion exchangers are used as central systems for the entire household.

Distillation removes around 99% of all constituents. It evaporates the water and recaptures the steam through condensation. This leaves nitrate, limescale and other substances behind. Only about 1% of dissolved substances remains. The process comes from chemistry, medicine and biology. For household use, it is very energy-intensive and therefore expensive. Distilled water is low in minerals but drinkable.

In the catalytic process, substances contained in the water are converted. Activated carbon or ion exchangers trigger the reaction, so no chemicals need to be added. One example is water hardness. The hardness minerals calcium and magnesium are converted into larger limescale clusters. Both remain dissolved in the water and are less likely to settle as limescale. In this way, the process also reduces chlorine, heavy metals, nitrate, sulphates, pesticides, arsenic and iron.

Adsorption is a physical process. Pollutants stick to the surface of the filter medium, much as they would to a magnet. This effect works regardless of pore size. Activated carbon relies mainly on adsorption. In this way, the process binds heavy metals, herbicides, pesticides, fungicides, hormones, pharmaceutical residues and substances that cause unpleasant odours and tastes.

Mechanical processes work on the principle of a sieve. Here, pore size is decisive for their effectiveness. The finer the pores, the smaller the particles the filter retains. These include microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Mechanical methods can remove sand, suspended particles, rust particles, asbestos fibres, microplastics, bacteria and viruses.

A whole-house filter sits at the water entry point in the basement. It treats all the water that flows into the house. In this way, it protects the pipes and appliances throughout the building from particles and deposits. These systems are larger and more complex to install. On their own, however, they rarely provide enough targeted protection for the drinking water in your glass.

A point-of-use filter purifies the water directly at the outlet, shortly before you drink it. This type of filter sits under the sink, directly on the tap or before the shower hose. Alb Filter's water filters belong to this category. Countertop units stand on the worktop, while built-in filters disappear elegantly under the sink. The short distance to the glass keeps the filtering effect fresh.

When most people think of a water filter, they picture a filter jug, such as those made by Brita. The cartridges in these jugs contain loose granular activated carbon. It binds chlorine and organic substances and improves taste and odour. Models with an ion exchanger also reduce water hardness. However, pollutants such as hormones or heavy metals largely remain in the water. In addition, germs can build up over longer standing times. This is why the granules are often treated with silver compounds.

Travel and outdoor models form a subcategory of their own. When camping, germ-free water is often hard to come by. Mobile filters are compact and easy to use. They can be fitted directly to the tap and use activated carbon cartridges. This allows them to purify tap water as well as lake, river and rainwater. Besides visible dirt, they also retain bacteria, viruses and toxic heavy metals.