Veolia Water Technologies & Solutions

Densadeg XRC* Extreme-rate Clarifier

Extreme-rate clarifier

The Densadeg XRC is a unique combination of solids contact, ballast addition and solids recirculation principles providing enhanced, rapid treatment.


Densadeg XRC Technology

The Densadeg XRC is a high-rate settling clarifier process combining solids contact, ballast addition and solids recirculation to provide enhanced, high-rate settling of solids.

The clarifier process consists of 

  1. Rapid Mix / Coagulation Stage: Raw water flows into the rapid (flash) mix zone where a coagulant is added. Coagulation is the destabilization of colloidal particles, which facilitates their aggregation and is achieved by the injection of a coagulant such as alum or ferric chloride. 

  2. Flocculation Zone: Coagulated water then flows to the flocculation zone where, with a lower energy vertical turbine mixer, a continuous ballast media recirculation feed and a low dose of a flocculating agent (polymer) are added to begin the process of agglomerating the coagulated water into floc particles. 

  3. Maturation Zone: Flocculated particles are then developed and grown into large, very dense mature particles. This is achieved with optimized mixing energy and detention time. The result is a floc which settles at extremely high rates. 

  4. Settling & Clarification Zone: Flocculated solids enter the settling zone, over a submerged weir wall, where dense, suspended matter settles to the bottom of the clarifier. Clarified water is displaced upward from the downward moving slurry, through inclined tube settlers. The tube modules act as a polishing step for lighter, low density solids. 

  5. Hydrocyclone and ballast recovery: Settled sludge is continuously recycled via a recirculation pump to the hydrocyclone where the ballast media is separated from the waste stream. Ballast is returned to the flocculation zone and the waste stream is sent to sludge handling. 

  6. Effluent collection: Uniform collection of clarified water is accomplished in effluent launders above the settling plate assembly.

Features & Applications

DensaDeg XRC Features & Applications

Main Features

  • Extreme-rate yields compact footprint 
  • Enhanced TSS & BOD removal 
  • Fully automated 
  • High density ballast 


  • Combined Sewer Overflows (CSO) 
  • Sanitary Sewer Overflow (SSO) 
  • Storm water treatment 
  • Dual-purpose enhanced primary/CSO 
  • Dual-purpose tertiary/CSO 
  • Industrial Treatment 
  • Tertiary phosphorous treatment

The Densadeg XRC™ process is explained in this video animation


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