Primary Clarification

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Clarification processes are commonly used in as the first stage of solids separation in water, sewage and industrial treatment systems. Hydroflux Epco have provided over 330 clarifier units throughout Australasia, Middle East and UK with installations dating back to 1962.

Hydroflux Epco have extensive expertise in the design and construction of primary clarifiers for:

  • Primary sedimentation for sewage treatment.
  • Primary clarification for water treatment (river water, dam water, desalination).
  • Primary clarification for industrial water treatment (mining, food & beverage, tunneling, construction and power industries).

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Key Advantages
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Principle of Operation
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  • Proven robust mechanical design with over 330 installations.
  • Heavy duty high torque drive systems.
  • Proven effective bottom sludge removal systems.
  • Elimination of dead zones.
  • Elimination of denitrification.
  • All the weight of the scrapers is suspended from the bridge, therefore there is less risk of breakdowns and there is nothing wearing on the concrete floor in the bottom of the tank.
  • Stainless Steel chain and bolting underwater, which gives longer design life and less breakdowns.
  • Proven commissioning success drawing on 52 years of experience installing over 200 clarifiers.
  • Submerged feedwell is self-cleaning so it doesn’t grow vegetable matter such as pumpkins and tomatoes.
A number of designs and configurations are available, these include:
    • Centre Drive
    • Peripheral Drive
    • Full bridge
    • Half bridge

A clarifier is essentially a gravity process which separates suspended solids from the liquid. The clarifier mechanism collects both the sludge (heavier material), and scum (lighter material) by physical means. There is one flow inlet to the tank and multiple outlets.


In operation, the influent enters the clarifier tank through the ports in the centre column. High radial inflow currents are suppressed by the EdiGate® energy dissipation inlet (optional) which redirects self cancelling tangential flows to the outer FlocWell™ feedwell, which in turn, directs the flow downward toward the bottom of the tank.

The major concentration of heavier material settles below the EdiGate® and FlocWell™ flocculation skirt, with lighter material settling in the tank extremities.

The sludge is collected by the scraper blades due to their rotation, and is moved across the floor to the sludge pocket in the centre of the tank, by the floor slope and the spiral blade pattern. The sludge is then removed from the centre pocket via pumps or gravity.

Scum on the water surface is removed from the tank via the radial scum scraper, the hinged skimming mechanism and scum boxes. The scum boxes have a bottom dump valve which is actuated every revolution by a striker mounted onto the underside of the bridge.

The inside of the peripheral scum baffle is wiped continuously every revolution, by a rubber wiper attached to the hinged skimmer.

Clarified effluent leaves the tank via the peripheral vee notched weir plates and launder channel.