The treatment of effluents consists of a series of physical, chemical and biological processes to eliminate the contaminants present in the water, be they effluents of human origin or other sources.

Most of the effluent contamination elimination process is carried out in specialized treatment plants and the rest is completed by the natural processes that occur in the receiving body (rivers, lakes, land, etc.)

The receiving body is one of the variables in this process, as its self-purification capacity depends on factors such as its flow rate, oxygen content and its ability to reoxygenate itself in the case of water and reabsorption in the case of soil. .

Therefore, the objective of effluent treatment is to produce an effluent suitable for nature to continue purifying and a solid residue or sludge suitable for disposal or reuse.

Origin of wastewater

Wastewater is generated in homes, institutions and commercial, industrial or agricultural facilities. These can be treated at the site where they are generated (eg with septic tanks, biodigesters or other purification means) or they can be collected and taken through a network of pipes – and possibly pumps – to a municipal treatment plant.

Wastewater comes from bathrooms, showers, kitchens, etc.; and discharged into sewers or sewers. In developed countries, gray water from sinks and bathtubs is often separated from black water, which is from bathrooms, urinals and kitchens.

Gray water can be used with minimal treatment to water plants and recycled for use in bathrooms, for example.

While black water is very cloudy and contains a lot of solids. They constitute one of the most serious causes of water pollution due to their content of organic matter, pathogenic microorganisms, detergents, etc. The evacuation of these waters to water courses without previous treatment can cause serious damage, mainly the decomposition of organic matter by bacterial action, which produces a decrease in dissolved oxygen, and can even leave the receiving body lifeless.

The treatment process

The treatment process usually has three steps or more:

  • Primary treatment (separation and settlement of solids).
  • Secondary treatment (biological treatment of suspended organic matter to biologically degrade it and reduce the levels of COD, BOD and consumed oxygen it has)
  • Tertiary treatment (additional steps such as microfiltration or disinfection).

Effluent treatment begins with the physical separation of large solids (waste) from the stream, using a grid system (mesh). or similar treatment) that separates suspended solids in wastewater.

To remove dissolved metals, precipitation reactions are used, which are mainly used to remove lead and phosphorus. This is followed by the progressive conversion of the dissolved biological material into solid biological mass using suitable bacteria, generally present in these waters.

Once the biological mass is separated (process called secondary sedimentation), the treated water can undergo additional processes (tertiary treatment) such as disinfection, filtration, etc.

Thus, the final effluent can be released or reintroduced into a natural body of water (stream, river or bay) or into another environment (surface, subsoil, etc).

Physical treatment of contaminants

To carry out an effluent treatment process, it is necessary to homogenize some of the contaminants found in them.

There are several procedures to achieve the homogenization of contaminants in effluents, one of which uses specific agitators. The function of these agitators is to group the residues so that it is easier and faster to remove them.

Wastewater Agitators

As explained on the website Timsa.es, a company specialized in agitation, dosing and pumping equipment, the equipment used for the homogenization of effluents is composed of a motor and propellers that are responsible for agitating the water. The propellers have a special hydrodynamic design so that they generate a flow of water to produce the flow of water necessary to achieve homogenization and suspension of contaminants.

While the engine must be strong enough as it will be subjected to strong water pressure. In addition, it must have the necessary power to generate the water flow necessary to achieve homogenization.

This flow must agitate the water with sufficient intensity to generate inertia in the movement of the polluting particles until they collide with each other and cluster together. Subsequently, these particles will be pushed from the bottom to the top, driven by the flow of water itself.

Once the homogenized residue remains in suspension forming a solid crust in the liquid phase, decanters can be applied or removed by specialized machinery to complete the effluent purification process.

Other uses of waste water agitators

Wastewater mixers can also be used in:

  • Homogenization tanks
  • Municipal wastewater treatment
  • paint mix
  • sludge agitation
  • Industrial processes
  • rain water tanks
  • Chemical industry
  • paper industry

Importance and necessity of effluent treatment

All over the world, wastewater treatment is inefficient, especially in developing countries. This is a serious environmental problem that also impacts the health of the population.

This lack of an adequate process to decontaminate water is a product of overpopulation, the water crisis and the high cost of building treatment systems.

The contaminants present in the effluents are suspended and dissolved solids, such as organic and inorganic materials, nutrients, oils and fats, toxic substances and pathogenic microorganisms.

These residues without proper treatment, discarded at their point of origin or collected and transported, represent a danger to the health of the population. These untreated or poorly treated waters mainly cause parasitic infections (by direct contact with faecal matter), hepatitis, and various gastrointestinal diseases, including cholera and typhoid fever (by contamination of the water and food source).

Environmentally, when untreated or poorly treated water is discharged into receiving waters, it poses a danger to the habitat of aquatic and marine life. Solids accumulate, oxygen decreases due to decomposition of organic matter; and aquatic and marine organisms can be further harmed by toxic substances, which can spread to higher organisms by bioaccumulating in food chains.

If the discharge enters closed water systems, such as a lake or a bay, its nutrient content can cause eutrophication, with an exacerbated growth of vegetation that also affects the life of that habitat. In addition, it can impact economic activities such as fishing and tourism.

Wastewater treatment projects aim to prevent or mitigate the effects of pollutants on the health of the population and the natural environment. When executed correctly, their total impact on the environment is positive.

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