Water Treatment Process

Water is a vital resource for life it self and a variety of other uses. But unfortunately water doesn’t always come in abundant so it needs to be produced; its quality isn’t always suitable for its required use so it needs to be treated; after we use it for various needs it needs to be disposed of properly or reused after treatment. Water pollution is a serious issue for many parts of the world. All these reasons and factors make water treatment processes vital.

A water treatment process can be done domesticaly, as part of household water treatment; it can be in large scale treatment plants that serve entire cities or it can be individually to purify water and drink it while travelling. Here we will go over the water treatment process mainly in regards to wastewater treatment and drinking water.

Drinking water treatment process

Naturally, drinking water requires much less treatment and generally a simpler process than wastewater of any kind – especially opposed to sewage or industrial wastewater. Drinking water may require different treatment methods in different areas, or even no treatment at all. The water treatment process type depends on water quality from the source – groundwater, lakes, rivers, streams, rain collection etc. We are talking about drinking water from a fresh potable source and not desalination water for example which are produced in a completely separate treatment process.

A water treatment process for drinking water can include all or some of the following stages:

  • Coagulation: This part of the water treatment process removes dirt and grit from the water coming into the plant, a coagulation agent such as Alum is added to the water and this creates sticky particles known as “Floc” – This makes dirt, grit and other solids come together and settle to the bottom of the tank/pool. Also called flocculation.
  • Sedimentation: simply, most of the solid and other heavy substances sink to the bottom and then the clear water can move on to the next stage.
  • Filtration: There are different types of water filters used, they can be physical, chemical or biological. A common filtration method is filters made from layers of sand, gravel and charcoal (activated carbon).
  • Disinfection: Mostly done using chemical agents, Chlorine or compounds of it is very common. The disinfection kills bacteria and micro-organisms left in the water. The chemical is residual and normally stays in the water when it reaches consumers.

Now the drinking water can be sent to storage or to consumers via pipes.

Wastewater treatment process

This water treatment process is relevant to sewage purification and general wastewater treatment. The treated water is reused in agriculture or industrial uses or it is flowed back into water bodies in nature.

  • Initial screening: meant to catch and remove large debris from the water system – Using simple metal bars.
  • Grit removal / Coagulation: using either gravity alone or by coagulation chemicals, large and heavy particles come together and sink to the bottom.
  • Sedimentation: in large tanks or lagoons, other heavy particles settle to the bottom creating sludge that is removed.
  • Sludge treatment / Biosolids: the sludge from the bottom of the sedimentation pools can be “eaten by bacteria to some extent or mainly removed and treated further to usually become fertilizer.
  • Filtration: similar to the water treatment process in drinking water, may involve more “heavy duty” filters and more stages.
  • Aeration: adding oxygen to the water by mixing it, adding chemicals and other methods (activated sludge). This helps purify the water further.
  • Lagoons: an optional stage, similar to the disinfection stage of drinking water treatment process. Also encourages aeration.
  • Advanced treatment / Tertiary treatment: achieves high purification levels. Removing remained harmful nutrients and contaminants.  

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