What are black waters and what are they correct treatment?

What are black waters?

Black waters refer to waters whose composition has been specifically altered.

Unfortunately, these waters are a frequent source of diseases in underdeveloped countries due to insufficient water treatment facilities, affecting more than 2 billion people, as reflected by organizations like the World Health Organization.

However, proper treatment of these waters can be a source of sustainability, as expressed by the UN. Therefore, in this article, we explain what black waters are, what causes them, and how they can be treated to beneficially reverse their impact on hygiene, health, and the environment.


  1. What are Black Waters
  2. 1 What They Contain
  3. Microorganisms
  4. Risks of Consumption
  5. Treatment


The term “Black Water” is used to refer to wastewater or sewage, i.e. water that has undergone human intervention in such a way that its composition has been altered, either by the discharge of chemical elements (such as those resulting from certain industries) or organic elements (such as faeces).

It is important not to confuse them with greywater, which is water from domestic use.


As mentioned above, the composition of sewage is altered by materials that can be both organic and inorganic. These can be found in water in different forms:

  • In suspension
  • In solution
  • In a colloidal state

These substances can be either solid (such as sandy particles) or liquid (such as fats like oil), and can lead to microscopic bacterial activity resulting in foul odours and colonies of micro-organisms.


Now that we know what Black water is, where do these microscopic bacteria and pathogens come from? In general, from the faeces and digestive tract of people whose waste has come into contact with the water.

Among the micro-organisms that can appear in Black Water, which in many cases is consumed in less developed countries, are those that cause the following diseases:

  • Dysentery
  • Cholera
  • Hepatitis
  • Typhoid fever

And, in general, any disease where faeces are a source of transmission. But it is not only pollution from human waste that can contaminate Black Water; industry is also responsible for this type of process.

Particulate water discharges from animal production plants, slaughterhouses, farms or the chemical industry, such as the detergent industry, can result in waste that affects the composition of Black Water.

This is why in developed countries such discharges are completely illegal, and the septic tanks through which sewage passes must also follow specific treatment regulations.


The action of the particles that form part of Black Water, as well as the transmission and growth of colonies of micro-organisms in the Black Water, can give rise to various risks from the consumption or use of Black Water:

  • Infectivity: Many of the microscopic components of sewage can cause diseases, but while these can attack human consumers, they can also affect the health of animals and plants, as well as impoverish and damage the health of the environment.
  • Foul odour: Due to the chemical elements as well as organic reactions taking place in sewage, sewage can be a source of foul odours.
  • Toxicity: Although the components of sewage are not infectious in nature, in other words, they do not generate a bacterial disease in humans or animals, they may be molecules that, due to their structure, organisms cannot process, causing damage and harmful intoxication.
  • Thermal alterations: mainly some chemical residues can contaminate water at a thermal level, causing damage to the natural processes that usually take place in its environment.

All of these dangers are compounded by the fact that the appearance of the water is affected, as it tends to become darker and also causes aesthetic damage to the areas into which it is discharged.


Black Water began to be treated hundreds of years ago in the Roman Empire, which was the first civilisation to incorporate a sewage system.

However, the treatment and purification of sewage today, in specialised plants, has brought about a revolution that allows for the total reuse of Black Waters.

This process is carried out in wastewater treatment plants that subject the water to a series of physical mechanisms (such as filters) and chemical reactions (such as the emulsification of fats), which allow the water to return to its original composition.

This purification treatment consists mainly of 3 phases:

  1. Separation and sedimentation of solid particles, such as sand.
  2. Biological transformation of organic matter into solid waste, in a similar way as in septic tanks.
  3. Through a series of pools, different processes are carried out, including microscopic filtration or disinfection, among others.

Once these processes have been completed, the water has been treated and can be reused in the applications deemed appropriate.

Sewage treatment plants are therefore a basic and fundamental infrastructure to ensure the health of people and the environment, and one of the challenges of the present time is to ensure that the entire world population can count on these facilities to put an end to the consumption of Black Waters.

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