Drinking water treatment chemicals at the waterworks
Drinking water has been industrially processed with drinking water treatment chemicals in large plants for around 150 years. This resulted from the recognition of a link between polluted drinking water and diseases such as typhus and cholera, and thus the need for effective drinking water treatment to prevent them.
Depending on the source of the untreated water, different processes are used to produce drinking water, since the quality and chemical composition can vary. For example, there are different types of untreated water: meteoric water (rain), surface water (lakes, rivers), spring water and groundwater.
Today, drinking water treatment includes technologies tailored to the properties of the untreated water, such as cleaning, sterilisation, removal of iron and manganese and, depending on the desired degree of hardness, desalination/softening, as well as the addition of minerals to protect the water pipes against corrosion. If necessary, drinking water disinfectant is also added to prevent re-contamination in a process known as “line protection”.
Wastewater treatment is also related to this topic, however this will not be examined in more detail here.
Treatment of drinking water: mechanical processes
The mechanical processes used to purify drinking water are among the oldest and simplest methods of drinking water treatment. For example, gravel filters and sand filters were used as early as the Middle Ages to clean rainwater before storing it in a cistern. Other mechanical methods used in drinking water treatment include rakes, sieves and filters, including both nano and osmosis filters. In addition to sand and kieselguhr, activated carbon filters are also commonly used in waterworks.
During drinking water purification, the aim is to remove turbid substances such as sand, algae, dirt, etc. from the untreated water. Flocculants are also often added to increase the efficiency of the filters. These substances ensure that small particles of dirt coalesce to form larger clumps, which then get caught in the filter meshes. The filters themselves must be backwashed regularly in order to prevent caking. When the filters are backwashed, the suspended solids are flushed out and washed away in the opposite direction.
Drinking water treatment chemicals & chemical processes
It is not possible to remove all undesirable substances from drinking water with conventional filters alone. Eliminating dissolved substances in particular requires other means. Many of these, such as iron and manganese, can be removed with oxidation. For this purpose, either oxygen, air, hydrogen peroxide or potassium permanganate based drinking water treatment chemicals are added to the water. The latter is also available in tablet form for drinking water disinfection (chlorine tablets) or for drinking water treatment during outdoor activities.
By blowing air into the water, substances can also be converted into a gaseous form and thereby “blown out” or removed, e.g. excess chlorine, hydrocarbons, sulphur compounds, etc. This process improves the water’s taste by removing unwanted odours and is known as stripping.
A hybrid form of both chemical and mechanical water treatment involves the use of absorbers. Water filters containing activated carbon have proved their worth in this field. The huge surface area of the activated carbon and the readiness with which many substances bind to it allow other undesirable substances to be extracted from the water.
Drinking water treatment-biocidal processes / disinfection
In addition to filtration, biocidal technologies are also used to disinfect drinking water. Well-known methods of biocidal water treatment include UV disinfection (UV rays kill germs very quickly), ozonisation, chlorine dioxide chlorination and special drinking water disinfectants such as Sanosil Super 25. The focus here is on killing all microbes sustainably and reliably without negatively affecting the taste of the water.
Thermal disinfection (boiling of water) is not viable in large-scale drinking water treatment plants due to the required high energy consumption, and is really only practical for outdoor pursuits and/or as an emergency measure in the household (e.g. in case of sudden microbial contamination).
In order to subsequently preserve the treated drinking water and protect it against recontamination, a process known as line protection is carried out. The effects of ozone and UV are acute, but they do not last. Therefore, a small amount of drinking water treatment chemicals in the form of a disinfectant in drinking water treatment is added to the drinking water. While this makes perfect sense from a technological point of view, it is also the subject of some criticism. Essentially, many consumers dislike the idea of a drinking water disinfectant being added to their drinking water. In addition, when using an established disinfectant for drinking water, the risk of corrosion must always be taken into account — particularly because chlorine dioxide, which is becoming increasingly popular, is highly corrosive.
Domestic service-water treatment
As mentioned above, drinking water treatment is usually managed at the municipal level. However, some consumers operate private water treatment systems for a variety of reasons. Generally speaking, this occurs on land with its own spring, spring tapping or groundwater well. The effort and expense involved depends largely on the desired quality of the untreated/drinking water.
If the water is only used only for gardening, showering, washing and toilet flushing, and the water in the collecting tank is replaced regularly, simple filtration via two successive, backwashing filter cartridges — combined with periodic cleaning of the water catchment — is generally sufficient.
Domestic drinking water treatment
On the other hand, in order to produce drinking water using your own system, additional effort is required. The easiest way to do this is with a multistage system for domestic drinking water treatment. These devices usually take the form of various modules connected in series, which combine pre-filters, ceramic filters, activated charcoal filters and UV sterilisation or pre-filters/osmosis filters. Provided they are used and maintained properly, these devices are also able to produce safe domestic drinking water from privately owned sources.
Contrary to popular belief, water disinfectants / chemical drinking water disinfection with chemicals used in drinking water treatment, is not usually necessary for domestic water treatment. In contrast, regular maintenance, inspection and, if necessary, cleaning and disinfection of the spring tapping / collection well, pumps and possibly pipelines with drinking water treatment chemicals produced by renown drinking water treatment chemicals suppliers is strongly recommended.
The Sanosil products (S015 / Super 25) can also be used directly for drinking water disinfection and emergency water conservation. They are most widely used in highly technical water treatment applications (cooling towers, cooling circuits), for combating the spread of legionellae, as well as for disinfecting wells, pipes and water treatment plants.