Clarifiers/Tube Settler

Clarification is a process whereby liquid is separated from solid matter. Solids settle due to the pull of gravity.

The clarification stage is usually preceded by coagulation and flocculation, during which colloids are destabilized in order that they gather together into flocs of a large enough size to settle. A clarifier (a hydraulic process) is then used to encourage these very light flocs to settle in a tank, from which they can be easily removed.

Clarification takes place in a state of continuous flux. There are several types of flux :

  • Horizontal Flux (generally used in parallelepiped clarifiers)
  • Vertical Flux (generally used in cylindroconical clarifiers with the settling zone in the cylindrical section)
  • Tilting Flux in a countercurrent or co-current lamella clarifier


DEWTEX Solids contact reactor which uses a propeller for internal solids recirculation and a variable settling area for solids separation. There are more than ten (10) design variations. Unit dependent on basin design (i.e. inlet location, mechanism support and flow rate). Process applications include surface water clarification, iron and manganese removal, cold lime softening and heavy metals precipitation. The units can be installed in round or square, steel or concrete basins. Multiple units are used for higher clarification flow rates.

Water enters tangential to the base of the unit and spirals upward to the effluent collection trough at the top of the basin.


Flocculation Clarifier are mainly applied for surface water clarification of supplies with moderate turbidities. Turbine flocculators are positioned inside of a flocculation well sized to promote floc formation. Sludge collection of settled solids are provided by rotating scraper arms. Center or bridge supported units are available.


Sludge Extractor is a sedimentation removal system with rectangular settling basins. Typical applications include surface water treatment with light floc formation such as alum sludge. The units consist of a sludge removal header which is mounted on the floor of the basin The removal header is moved along the basin floor by a drive cable connected to the drive system. Underwater components are constructed entirely ofss-316.


Sludge Thickener is commonly used to thicken backwash water waste from filters and sludge blow down from clarifiers. The thickeners can be designed for intermittent or continuous operation. High torque, open gear drives are used for collection of settled sludge.


Tube settlers use multiple tubular channels sloped at an angle and adjacent to each other, which combine to form an increased effective settling area. This provides for a particle settling depth that is significantly less than the settling depth of a conventional clarifier, reducing settling times.

Tube settlers capture the flocs that escapes the clarification zone beneath the tube settlers and allows the larger floc to travel to the tank bottom in a more settleable form. The tube settler’s channel collects solids into a compact mass which promotes the solids to slide down the tube channel.

Tube settlers offer an inexpensive method of upgrading existing water treatment plant clarifiers and sedimentation basins to improve performance.

They can also reduce the tankage/footprint required in new installations or improve the performance of existing settling basins by reducing the solids loading on downstream filters.

Made of lightweight PVC, tube settlers can be easily supported with minimal structures that often incorporate the effluent trough supports.

They are available in a variety of module sizes and tube lengths to fit any tank geometry, with custom design and engineering.

Advantages of Tube Settlers

Tube Settler can operate at 6 times the normal rate of clarifiers.

  • It is possible to cut coagulant dosage by up to half while maintaining a lower influent turbidity to the treatment plant filters.
  • Less filter backwashing equates to significant operating cost savings for both water and electricity.
  • New installations using tube settlers can be designed smaller because of increased flow capability.
  • Flow of existing water treatment plants can be increased through the addition of tube settlers.
  • Tube settlers increase allowable flow capacity by expanding settling capacity and increasing the solids removal rate in settling tanks.