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In nature Water is the only substance that can be present in its three different states at room temperature, which is why the water present in the hydrosphere is not stationary, as large water masses are continuously being transferred from one area to another. This is what is known as the hydrological cycle or water cycle. It is the continual movement of water which evaporates from the sea, condenses and then falls back to earth in the form of rain, which may later return to the atmosphere through evaporation or transpiration, or return to the ocean through surface or underground rivers. Collection. Crude water is collected from the water stored in the reservoirs, , wells (underground waters), rivers and lakes (surface water) and through desalting (still not a commonly used method). Collection consists of extracting and pumping the water, which is then treated and taken to the purifying plants. Purification. Surface and underground water are exposed to processes of contamination and for this reason it is necessary to have strict water quality controls to ensure it is fit for human consumption when supplying water to centers of population. This water is purified in the Potable water treatment plants. In simple terms, the EEC requires that water destined for human consumption must be clean, colorless, and odorless, have a pleasant taste and not contain an excessive amount of dissolved material. The water undergoes periodic quality controls to ensure it is of good quality and has been correctly treated. Distribution. Despite the fact that water covers 79% of the Earth’s surface, only 2.7% of this is fresh water, and of this amount, only 28% is available to sustain life, as the rest is frozen as perennial snows and glaciers. Therefore, water would appear to be a scarce asset requiring great care. Water is distributed to customers through supply networks. This distribution includes pumping and the creation of the pressure necessary to ensure the water reaches the consumer. Consumption. Water is far from abundant and we must learn not to waste it. Water consumption in the home or garden decreases considerably when very simple measures, such as turning off the tap while washing our teeth or using a drip irrigation system in the garden, are adopted. End users must collaborate to ensure water is not wasted. Water in the home. Tips for consuming less water. Sewer system. The wastewater leaving or homes, businesses and industries runs into sewers, and here used, dirty water mixes with the rain water and garbage that can be found in the sewers. This sewer system flows into the Sewer treatment plants. The water that comes from the purification network in our cities has undergone profound changes and differs from its initial state to such an extent that returning it to the environment may have an enormous impact. These spillages have a direct effect on the natural conditions of the ecosystems as well as on the economic flows and social factors affected by a deterioration of the resources. This is why it is essential treatment plants be built. Treatment. Wastewater carries foreign elements known as pollutants and water treatment basically consists of removing these elements. The aim of sewage treatment is to reduce contamination and its effects as much as possible, ensure the environment and the living beings inhabiting this are protected and predict urban and industrial development. In order to achieve these objectives many different technologies have been developed to partially or totally remove these pollutants. Final spillage. The correctly treated wastewater that is not reused is emptied into the seas, rivers or lakes. This dumping is generally carried out through underwater outfalls so that this water does not cause the quality of the bathing water at the beaches close to towns and cities to deteriorate.
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