13.3.- WASTEWATER TREATMENT

Water treatment focuses on human consumption, processes that occur before and after its use.

• Drinking water treatment: in the drinking water treatment plants (DWTP) water is treated to make it suitable for human consumption.
• Waste water treatment: water is treated in the waste water treatment plants (WWTP), where most of the separation of contaminants process is done.
• The first step to which waste water is subjected when entering a treatment plant is a pretreatment. Large solids, sand and grease are removed.
• Then, water is subjected to the so-called primary treatment. The suspended solids that are easily settled and part of the organic matter are removed.
• The rest of organic matter, dissolved and suspended, and the rest of solid particles that have not been removed in previous treatments are removed through the so-called Aerobic Biological Processes of Waste Water Treatment, which is the secondary treatment of the line of water.
• Sometimes a tertiary treatment is used. The purpose of these treatments is to remove the residual organic load and those other polluting substances that are not removed in secondary treatments, such as nutrients, phosphorus and nitrogen.

Water treatment is essential nowadays since it helps to:

• Protect Public Health and the Environment. If waste water is going to be discharged into a natural receiving body (sea, rivers, lakes), it is necessary to carry out a treatment to avoid diseases caused by bacteria and viruses.
• Protect the fauna and flora present in the natural receiving body (sea, rivers and lakes).
• Reuse treated water: there are activities in which it is not necessary to use drinking water, treated water can be used without any risk to health.
• Guarantee the absence of harmful effects on health.