Operation and diagram of a waste water treatment plant

Operation and diagram of a waste water treatment plant

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Waste water treatment

How does a waste water treatment plant work? Giving back clean water to the environment is a social duty other than a specific obligation regulated by law. But we often know so little about the operation of plants that bring us water at home and especially about what happens after using it. A greater awareness of the required treatments for waste water can also help us understand problems and risks of pollution, therefore push us towards a sustainable use of water. Let’s see then which are the necessary treatments to clean water from human use “effects”.


Water facilities. Screening, sand trap, oil separation

Chiariflus® lamella pack oil separators by Allegri Ecologia.

Waste water way starts with the waste coming from buildings and goes on through sewer system. Before being given back to environment, durty water is collected by manifolds that lead it to water treatment plants. The first step is usually water lifting: water is pushed up towards the different stages of treatment. The first real treatment is screening: water passes through special grids that retain the more or less coarse polluting substances. Water contains sand and oils . During sand trap process, sand settles down naturally by gravity inside tanks, from which it is then withdrawn.
Oil separation is water cleaning form fats and oils : air is blown into tanks to make oils and fats emerge. Right in this stage Chiariflus® lamella oil separators by Allegri Ecologia can be installed.


Water facilities: sedimentation and biological oxidation

Chiariflus® lamella pack settlers by Allegri Ecologia

Lamella pack settlers – like Chiariflus® model by Allegri Ecologia – are used in the primary sedimentation tanks to help sedimentable solids settling.

RBD® disk biological rotors by Allegri Ecologia

Afterwards water goes to the biological oxidation treatment. Air is blown into the tank, oxygen feeds the bacteria present in water with organic compounds. Bacteria aggregation creates sludge flakes that fall to the bottom because heavier.
One way to make oxidation treatment is using RBD® disk biological rotors by Allegri Ecologia.

At this point we are at the end of water facilities, that have given us back clean water. But a final step is required. Very often in fact water needs a further treatment: disinfection. Water is disinfected to remove any harmful residue, before being fed back – finally clean– into environment.


Sludge facility of a water treatment plant

After water line, the water treatment plant has not completed its work yet, as sludge is left. Sludge is retrieved off the bottom of sedimentation tanks and treated again. It goes through thickening and dehydration processes in order to be disposed more easily.
Water anthropic cycle has finished: from environment to houses, towns, factories and back in nature.