Clarifier Mechanism

Primary Clarifier

Primary Clarifier: The flocculated effluent will enter into the circular primary clarifier made of RCC construction through centre feed pipe. The clarifier has circular geometry and has drive mechanism, access platform, rake arm mechanism mounted on it. From the centre feed pipe, effluent will entered into the settling zone of clarifier. The clarifier will be designed based on the settling velocity particle. In settling zone, flocculated particle will be settled down and formed sludge at the bottom of clarifier. The clarifier will have two scrapper rake arms settled sludge. The settled sludge shall be transferred into the sludge holding tank by gravity. The clarified water will rise at the top of clarifier and will be collected into the outlet weir. From the weir it will be collected into the clarified water storage tank by gravity.

Secondary Clarifier

The function of the secondary clarifier is to separate the activated sludge solids from the mixed liquor that is generated in Aeration tank. These solids represent the colloidal and dissolved solids that were originally present in the wastewater. In the aeration unit they were incorporated into the activated sludge floc, which are settleable solids. The separation of these solids, a critical step in the activated sludge process, is accomplished in the secondary clarifier. The excess sludge production from secondary clarifier is pumped to sludge holding tank by a tapping from RAS pump. The purpose of return sludge is to maintain MLSS concentration of activated sludge in the aeration tank sufficient for the desired degree of treatment.

High Rate Solid Contact Clarifier

HIGH RATE SOLID CONTACT CLARIFICATION (HRSCC) Water clarification is the process of removing suspended solids, turbidity, colloids from water. The HRSCC has been designed such that coagulation, flocculation, setting and sludge remove are combined in a single tank. HRSCC are designed to treat different type of water for a various application for solid settling and separation. These units are tailor - made to suit various flow rates and can design for very large flows. For optimum operation effective solid separation HRSCC employs use of flash mixer, and stilling chamber prior to clarifier. Typically chemical treatment using Alum, Zinc and polyelectrolyte are used to aid coagulation &flocculation and enhance removal of solids.

HRSCC comprises of the following:

  • Draft Tube
  • Reaction Well
  • Central Reaction Turbine
  • Sludge Blanket zone
  • Rake arm.

There are two drives in the HRSCC: one drives the sludge disposal rake and the other drives the turbine mixer which re circulates the sludge.

Coagulation, flocculation, setting and sludge removal is combined into a single tank. Concentrated solids, which have earlier settled in the clarifier, are recirculated to the mixing zone by the turbine and mixes with the incoming influent which has a relatively low concentration of suspended solids. The rate of flocculation is directly dependent on the solids concentration (by volume). Therefore by recirculating the settled floe, the amount of solids increases, thereby improving flocculation and hence the name Solids Contact Clarifier. This also results in lower requirement of coagulation chemicals since contact of this floc which has been formed earlier with new floc results in good growth of the same. This water then flows into the reaction well where the solids coagulate and settle. The flow passes through the sludge blanket at the bottom of the reaction well and this further removes suspended particles. The rotating rake arm moves the settled solids or sludge to the center of the clarifier for r emoval. The flow rises upward in the clarification zone and water is removed by the redial collection troughs on the surface. A portion of the settled sludge is periodically drawn off by opening the blow down valve. The recirculation of sludge result in the HRSCC producing water of very low turbidity for a wide range of inlet suspended solids level and even in conditions of low inlet turbidity.

Salient Features

  • Extensively used for continuous mechanical removal of settleable solids from wastes.
  • Both bridge and center column support available.
  • Sludge removal mechanism with 2 or 4 arms equipped scrappers.
  • Uniform distribution of flow in all directions.
  • Can also be equipped with scum removal system.
  • Both fixed & travel type bridges available.
  • Various MOC of wetted parts available for various application.
  • Capacity 2m dia to 24m dia & SWD 3 & 3.5m


  • Pre treatment
  • Solid recovery
  • Potable water treatment
Model Dia(m) Swd(m) Area(m2) Flow(m3) Motor RPM Launder Position
CL02FB25 2 3 25 9 750 Inside/Outside
CL03FB25 3 3 42 21 750 Inside/Outside
CL04FB25 4 3 63 38 750 Inside/Outside
CL05FB25 5 3 86 59 750 Inside/Outside
CL06FB25 6 3 113 85 750 Inside/Outside
CL07FB25 7 3 143 115 750 Inside/Outside
CL08FB25 8 3 176 151 750 Inside/Outside
CL09FB25 9 3 212 191 750 Inside/Outside
CL10FB25* 10 3 251 236 750 Inside/Outside
CL12FB25* 12 3 339 339 750 Inside/Outside
CL14FB25* 14 3 440 462 750 Inside/Outside
CL16FB25* 16 3 553 603 750 Inside/Outside
CL18FB25* 18 3 678 763 750 Inside/Outside
CL20FB25* 20 3 816 942 750 Inside/Outside
CL22FB25* 22 3 967 1140 750 Inside/Outside
CL24FB25* 24 3 1130 1356 750 Inside/Outside
* Half Bridge Traction Type Available


  • All Dimensions are in Meter.
  • Free board is around 0.3 to 0.5m.
  • Skimming arrangement & scum box can be added as per client's requirement.
  • Gear Box ratio is 70:1
  • Both Central driven and traction type mechanism available.
  • MOC is available in MSEP/MSFRP for both Shell and mechanism.