Flocculation in wastewater

The floc is the ecological and structural unit of the active sludge from which the biological purification process is carried out, which is part of the secondary treatment of WWTPs.
One of the most important phases of urban wastewater treatment happens in the biological reactor, where the active sludge process takes place.

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The effluent that reaches the reactor carries with it organic matter, bacteria and protozoa that, due to the change of the conditions due to the supply of oxygen, give rise to the formation of flocs. Flocs are suspended solids that can be easily removed.

What does flocculation mean?

The water flocculation process, in the secondary treatment of wastewater, is a chemical process that aims to agglutinate the colloidal substances in the water forming thicker flakes called flocs.

The objective of the formation of these flocs or aggregates of particles is to facilitate their later elimination, either by filtration, sedimentation or flotation.

To favor the formation of flocs there should be added chemicals called flocculants.

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Some of the most used flocculants for water treatment are salt iron and aluminum.
Wastewater treatment: Biological process
This wastewater treatment plant applies a biological process of activated sludge under the modality of oxidation ditch, with sludge treatment by aerobic digestion and dehydration with filters and band of polishing systems with multimedia filter.

The treatment station (WWTP) works in five stages: pretreatment (grids, sand trap, regulator), primary treatment, secondary treatment (biological), polishing with multimedia filters and disinfection, in addition to the stabilization of the generated sludge.

At agrohydr, you will find innovative environmental solutions that adapt effectively to the needs of different industries, as well as the requirements of each project of your company. If you wish to obtain more information about our services, do not hesitate to reach us through our contact information on this webpage.

Water Treatment Plants, Sytems and Types

There are mainly 3 types of wastewater treatment: Primary Treatment, Secondary Treatment and Tertiary Treatment, some consider a fourth type before the primary treatment: Preliminary treatment. The treatment of wastewater is a practice that, although it has been carried out since ancient times, today is something fundamental to maintain our quality of life. There are many wastewater treatment techniques with a long tradition and, evidently, much has been improved in the knowledge and design of the same over the years to the point of classifying the systems basically in three types of wastewater treatment. The increasingly demanding regulations that must be met have opened the way for the application of new water treatment technologies, many of them even allow their recovery and important value is given to the waste generated. Here are some waterwaster treatment and solution according to their function (type):


It consists in the elimination of coarse solids, resulting in a reduction of the pollutant load in its wastewater. Depending on the required quality of your final effluents you may need either a filter, a flotation system or a flocculation and flotation system. If you discharge your water to a sewer system, a primary treatment may be sufficient to meet the requirements of the final effluent.


Primary filter systems are used to separate large particles from wastewater. The removal of these particles prevents the plugging of “downstream” pipes and the protection of “upstream” equipment. The following types are available:
  • Fixed grids.
  • Channel filters, including Aquarake (motorized grille) and screw filters for channel.
  • Parabolic filters, including static and vibratory types.
  • Rotary filters, internal and external power.
  • Fabric filters.


They are used to remove heavy solids and floating particles, as oil from wastewater, without the need to add chemicals. The following systems are available:
  • Sedimentation units.
  • Screw conveyor for sand.
  • Oil and water separators API / CPI / TPI.
  • Cross flow separators.
  • Counter-current separators.
  • PPA modules.
  • Hydrocyclones


Flotation systems are used to separate undissolved materials by flotation by air or dissolved gas. Spena Group provides a dissolved air flotation system based on the intelligent aeration system owned by Nijhuis. Where the formation of fine bubbles of air promotes and increases the separation of the particles. The following systems are available:
  • IAF induced air flotation.
  • Flotation by IGF induced gas.
  • Floating by dissolved air DAF (with and without packets of sheets).
  • Dissolved gas flotation DGF (with and without packets of sheets).


Coagulation and flocculation systems are used to remove emulsions, dispersions and heavy metals from wastewater by the addition of coagulants, flocculants or precipitants. The following are coagulation – flocculation systems available:
  • Tubular flocculator.
  • Reaction tank
  • Electroagulation
  • Chemical dosing equipment.