Waterguide - Rainwater
What is rainwater?
Rain is liquid precipitation from the atmosphere in droplet form and an essential part of the water cycle on Earth. Precipitation is defined as the product that falls to earth in the form of rain, hail, or sleet because of the condensation of water vapour in the air by gravity, or product that settles on the earth's surface as snow, dew or hoar frost (ice deposits). Water is in a constant cycle, the hydrological cycle: Water evaporates from the earth's surface, water vapour rises and falls back to earth as precipitation. Lakes, streams, and rivers are formed. The water evaporates again or flows into the sea and the cycle begins anew. Thus, no water is lost, only a change of state takes place.
What are the constituents of rainwater?
Approximately 71 % of the earth's surface consists of oceans, seas, rivers, lakes, or streams. When it is hot, evaporation occurs, the water rises to the sky, condenses there, and comes back to earth as rainwater. Due to evaporation, not only pollutants but also all minerals remain in the original water, so that rainwater should come back to earth as distilled water. Unfortunately, this is hardly ever the case. On its way back, it becomes enriched again with dust particles, pollen, acids and even bacteria that are in the air. Thus, the actual rainwater quality depends on the location. In addition to sulphuric and nitric acid, the chemistry of rainwater contains all water-soluble substances - from chlorine to potassium and magnesium. In Germany, seasonal fluctuations are also registered, e.g. due to agricultural activities. During the growing season, the concentration of ammonium nitrate increases due to the spreading of liquid manure and due to higher temperatures. Much more dangerous, however, is the proportion of substances that are not very soluble in water, such as aluminium, strontium and manganese, as well as the increase in nanoparticles from industries.
Sustainability aspect: Rainwatrer as a substitute for drinking water possible?
Due to climate change, meteorologists are forecasting heavy precipitation in Germany over the next thirty years, but more rain in winter than in summer. This makes it all the more important to learn how to use this gift properly. Although the use of rainwater does not bring any advantages for arid regions, as the water balance in these countries does not change because of it, rainwater utilisation is an efficient environmental protection measure, because water consumption in the immediate vicinity as well as groundwater extraction are reduced.
Water from rain replenishes water bodies and thus contributes to their preservation. Unfortunately, the sealing of surfaces reduces the natural infiltration of rainwater and thus the natural groundwater recharge. In addition, pollutants from industry have a negative impact on water quality. A rethinking of the responsible use of precipitation is necessary to protect and preserve our environment. It is helpful to unseal areas and to manage rainwater in built-up areas in a localised manner. This often eliminates the need for expensive underground sewers and stormwater overflows. Local infiltration can contribute significantly to improving water quality. This is because rainwater infiltration on site reduces overflows from combined sewer systems into water bodies. In addition, the infiltrated water reduces the heat load of settlements.
What are the possible uses for rainwater?
According to the German Drinking Water Ordinance (TrinkwV), rainwater is not of drinking water quality. Nevertheless, it can be collected, treated, and mixed with drinking water after filtration for softening. In many regions, rainwater is the preferred source for drinking water. Since drinking water contains natural substances such as calcium, magnesium, sodium, potassium, bicarbonate, sulphate, and chloride, which are important for nutrition, rainwater must have salts added to it to be used as drinking water.
For many private purposes where drinking water quality is not required, such as watering the garden or flushing the toilet, rainwater is sometimes used. Since it is only slightly contaminated and contains neither carbonates nor other minerals compared to groundwater and surface water, it has considerable advantages for many applications. Therefore, even in regions with sufficient water supply, it can be worthwhile to collect and further use rainwater. Rainwater, for example, is just as suitable as drinking water for room air conditioning, for automatic firefighting with high-pressure fogging or for washing machines.
Rainwater as feed water for Herco units?
The use of rainwater in industry also brings economic advantages through savings in drinking water costs. Herco offers filter systems and softeners for this purpose, depending on the composition. In any case, a water analysis is necessary to ensure the right technology and the projected water quality. Ask us for more information.
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