Water crisis: the importance of water treatment plants


Water is a heritage that must be protected and defended, today more than ever. In full climatic emergency due to gradual global warming, the correct management of water resources has become a priority. The lack of water resources has made the recovery of waste water, the so-called waste water, increasingly important.

These are waters whose quality has been affected by human action after use in the domestic, industrial and agricultural sectors. Their direct re-use should therefore be excluded as they are contaminated by different types of organic and inorganic substances, dangerous for health and the environment.

How a sewage treatment plant works

Urban sewage treatment consists of a series of processes in which unwanted substances are removed and concentrated in the form of sludge.

sewage treatment plant operation

The final result of purification is a flow of water of a quality that can be returned to the environment. The characteristics of this water are compatible with the self-purifying capacity of the land or river, sea or lake in which it is fed, and exclude that there are harmful consequences for the ecosystem.

What are the waste waters

The types of fluids that are managed by purification plants are:

  1. Urban waste water, ie deriving from civil waste, which includes:
    • domestic waste water: rich in urea, fats, proteins, cellulose, etc.
    • so-called runoff waters: they contain, in addition to the same substances present in domestic wastewater, a series of micro-pollutants such as hydrocarbons, pesticides, detergents, debris, etc.
    These urban wastes are biodegradable, can therefore be purified through biological treatments.

  2. Industrial waste water: it has a different composition depending on the origin. For purification, only those industrial wastewaters that can be assimilated, from the qualitative point of view, to the domestic wastewaters can be treated. The others, due to the presence of substances incompatible with the biological purification process, must be pre-treated before being discharged into the sewer.

water purification

Other ways of water purification

There are several water treatment methods used to make it drinkable, but not all of them are effective on a large scale.

Processes may exhibit slight differences based on the technology of the plant and the type of water to be treated, but the basic principles are the same. Here are some of the standard water treatment processes:

  • Coagulation: consists of adding liquid aluminum sulphate to untreated water. The resulting mixture causes the dirt particles in the water to coagulate together, forming larger particles called "flakes" that can be easily removed by filtration or sedimentation.
  • Sedimentation: when water and flakes are subjected to the treatment process, they end up in sedimentation basins. Here the water moves slowly, causing the heavy flake particles to settle on the bottom. This accumulation is called "mud" and is removed by filtration.
  • Filtration: to remove the particles of impurities, the water passes through filters composed of gravel and sand or sometimes of crushed anthracite. Filtration collects impurities that float on the water and increases the effectiveness of disinfection.
  • Disinfection: before the water enters the distribution system, it is disinfected using chlorine to eliminate bacteria, parasites and viruses that cause the disease.
  • Sludge drying: the solids that have been collected and removed from the water, through sedimentation and filtration, are transferred to the drying lagoons.
  • Fluoridation: necessary to treat community water reserves, and to regulate the concentration of free fluorine ions at an optimal level.
  • pH correction: to regulate acidity levels (pH), lime is combined with filtered water (hydrated lime). This also naturally stabilizes the fresh water in order to minimize corrosion in the water distribution system and in domestic pipes.

The use of centrifugal pumps in water treatment

In a process of purification of waste water, there is therefore a use of chemical substances that allow the removal of pollutants and the separation of the insoluble part from the aqueous one.

The centrifugal pumps used in the movement of these waters must be correctly configured in the materials, to counteract the chemical aggression of the substances present and to tolerate the presence of solids in the process. The CDR pumps that are most used in these purification treatments are the mechanical seal pumps model CCL and UCL.

CDR pumps for waste water

The CDR centrifugal pump model CCL with mechanical seal is specifically designed for water treatment. It can be fitted with different types of seals and is suitable for industrial applications that require a pump coated in polypropylene, a material suitable for not too aggressive chemicals and low temperatures.

The CDR centrifugal pump model UCL, with mechanical seal too, is instead available with a PFA or PVDF material coating, which covers a wider range of applications and in case the pumped liquid can present aggressive chemical substances and / or high temperatures.

These pumps can handle dirty fluids with small solids. If the fluids treated are clean, for the water treatment can also be used magnetic drive centrifugal pumps such as STN and ETN which have the advantage of having lower prices.

┬áContact us if you are interested in our water treatment pumps.  

purification plant