When it comes to basic sanitation, we immediately imagine water supply and sanitary sewage. However, we rarely ask ourselves how, in fact, water treatment works so that it gets clear in our homes.
Several stages of treatment are adopted, enabling the water to become potable and healthy for consumption, since it is extremely important for human life.
Therefore, understand what is the path adopted for water treatment, allowing this element to reach homes with maximum quality.
Why is water treatment so important?
Despite the fact that the planet is formed by about 2/3 of water, only 0.008% of the total of this resource is actually drinkable. To make matters worse, a large part of our sources, such as rivers, seas and lakes, are being contaminated by the action of man.
For this reason, saving water must be a priority issue, which depends on all of us. But treating it is just as important, since, once ingested without proper treatment, we run the risk of being affected by various diseases.
Thus, the proper water and sewage treatments represent fundamental actions for the quality of life of the population.
In cities that have an adequate supply network, water is captured in the springs and subjected to various filtering and disinfection procedures, only then to be distributed, as we will see below.
Before it is offered to the population, the water is subjected to a series of appropriate treatments, which will reduce the concentration of pollutants until they no longer present health risks.
Thus, the following steps are taken during water treatment:
The first stage of water treatment is the capture of this element for consumption. It is usually removed from water sources and reservoirs. At this point, the water passes through a railing system, which prevents the entry of solid elements into the treatment plant, such as leaves, branches and trunks.
After that, the water proceeds to the desarenation, where the sand is removed by sedimentation, improving the pretreatment process. Finally, it is pumped to the treatment plant (ETA).
In this stage there is the transport of water for treatment or treated water to the distribution system. This process is normally carried out by means of pumps that take the collected water to the ETA.
In the water to be treated there are impurities, the particles of which are small and do not settle under the action of gravity.
To solve this challenge, it is necessary to add chemical coagulants to the water. Here in Brazil, the commonly used coagulant is aluminum sulfate (Al2 (SO4) 3).
It favors the union of particles and impurities, facilitating removal via decantation. These coagulants are insoluble in water and generate positive ions (cations) that attract negatively charged impurities.
In this stage of water treatment, the liquid will be stirred strongly by a mechanical stirrer for about 30 seconds, in order to increase the dispersion of the coagulant.
Then the system is stirred slowly, allowing contact between the particles.
The decantation process is basically the act of separating, by gravity, the sedimentable solids that are contained in the liquid solution. The solids settle at the bottom of the decanter, being removed as sludge, while the effluent passes through the spillway.
After being decanted, the water is then sent to the filtering units, where the filtration process takes place, which consists of passing the water through filters formed by several layers, such as coarse sand, fine sand, gravel, gravel and coal.
These layers are able to retain the flakes that pass without settling or other impurities.
In disinfection, it is the time when the dosing pump makes the addition of chlorine before the water leaves the treatment plant. This process ensures that the water supplied arrives free from bacteria and viruses to consumers’ homes. At this stage, there is still control of the PH.
At the end of the process, the water will be stored in reservoirs, with two purposes:
- Maintain regular supply;
- Meet excessive demands, such as those that occur during periods of intense heat or when, during the day, a lot of water is used at the same time.
Finally, it is worth mentioning that each citizen has a duty to contribute to the sustainable consumption of this good, allowing the supply of treated water to be available to all.
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