Envites - Clarification

Main fields of use
Basic parts of clarifiers
Principle of clarification
ENVITES products for clarification
Additional chemicals
Advantages of ENVITES solutions

The main task of sedimentation is to separate solid substances from the liquid. Simple sedimentation is insufficient in most cases (the particles do not settle, or settle very slowly) and the liquid must be treated chemically. In such a case, a physical-chemical method of water clarification is used – the so-called clarification.


  • Increased speed of sedimentation – compared to the simple sedimentation it is possible to work with significantly higher suspension flow rates
  • Smaller dimensions of the equipment – compared to the simple sedimentation it is sufficient to use tanks with smaller volumes at the same performance (flow rate)
  • Reduced capital costs and area needed for the installation
  • Separation of non-settling, or poorly settling substances – by dosing suitable chemicals it is possible to form clusters of flocs out of the solid phase and the flocs can settle.

Main fields of use:

  • Treatment of service water (power engineering)
  • Industrial wastewater treatment
  • Municipal wastewater treatment
  • Production and treatment of drinking water
  • Processing of raw materials and minerals
  • Metallurgical industry
  • Food-processing industry

Basic parts of the clarifier:

  • Coagulation tank
  • Flocculation tank (flocculator)
  • Sedimentation tank

Coagulation, flocculation and sedimentation tanks can be combined as required by the specific applications.

The clarification system includes tanks for storing, preparing and dosing of additional chemicals.

Principle of clarification

Some solid particles in suspension do not form larger clusters spontaneously, on the contrary, they repel. The reason is their identical electric charge. When dosing a destabilisation agent (coagulant), the electric charge of the particles is disturbed which results in the formation of primary clusters of particles. Subsequently, flocculating agent is dosed into the suspension, which accelerates formation of the particle clusters – settling flocs.

Course of the process:

Coagulation agents are usually dosed into reactors (homogenisation tanks). In some cases it is possible to dose directly into pipes (using pipe mixers) and thus it is not necessary to use the homogenisation tank.

Perikinetic phase (coagulation): The mixture of suspension and coagulant is thoroughly mixed in the coagulation tank. By doing so, the solid particle charge is neutralized and the particles gather in larger clusters.

Orthokinetic phase (flocculation): The suspension is fed into the flocculation tank or a part of the clarifier (flocculator), where flocs are formed at slow-speed mixing. The mixing speed must be adjusted to the character of the suspension – the flocs must not be broken and at the same time it is necessary to ensure that the clusters of particles are combined into larger clusters.

The suspension is conveyed from the flocculation tank into the sedimentation tank where the flocs settle. Clarified water flows out of the clarifier, the settled slurry is drained by water overpressure or by using a pump; for further treatment.

Proper dosing of additional chemicals has a crucial importance for the whole process. The chemicals differ based on the types of suspensions and it is usually necessary to verify their application through a sedimentation tests.

In order to achieve higher weight proportion of the suspended solids in slurry, thickening is performed using slurry thickening.
Additional thickening is very important for the following slurry dewatering.

The clarified water is usually returned to the treatment process.

ENVITES products for clarification systems:

Preparation and dosing of chemicals:

  • Flocculant mixing tanks
  • Lime mixing tanks
  • Chemicals storage tanks


  • Homogenisation tanks

Sedimentation tanks:

  • Lamella primary sedimentation tanks
  • Lamella separator
  • Primary flocculation tank with lamella partitions
  • Clarifier CF (compact combined equipment)
  • Clarifier CVL (set of a coagulation and flocculation reactor and lamella primary tank)

Division of additional chemicals:

  • Inorganic compounds – e.g. FeCl3, Al2(SO4)3, whitewash
  • Organic compounds - polymers – based on the character they are subdivided into polyelectrolytes (anion-active, cationic, non-ionic)

Benefits of ENVITES solutions:

  • Conduct of laboratory tests
  • Optimum design of the whole clarification process from the technological point of view– suitable selected type, size and material of the tanks, type and volume of flocculants, retention periods, mixing speeds, types of pumps etc.

We produce and supply individual products as well as complete technological units.