RapiSand™ Ballasted Flocculation

RapiSand Ballasted Flocculation

RapiSand™ Ballasted Flocculation Overview:

The WesTech RapiSand™ Ballasted Flocculation System is a high rate clarification process using rapid mixing and multi-stage flocculation, followed by sedimentation.

RapiSand™ sedimentation is extremely fast and can be applied in a wide variety of suspended solids removal applications. The typical uses of RapiSand™ include expanding plant capacity, minimizing plant footprint, providing fast startup capabilities, and providing great performance characteristics. RapiSand™ can be the answer to your suspended solids process needs.

Need a fast and efficient solution for clarification and sedimentation? Our mobile RapiSand units can be on site at your location within weeks. They’re available for lease, so you can contract them for only as long as you need. To learn more, use the Contact Us form to submit more information about your project or application. 

How It Works:

RapiSand ballasted flocculation is a four-step process:

1. Coagulation: Raw water is mixed with coagulant in the first tank.

2. Flocculation: Coagulated water is mixed with polymer and recycled micro-sand in each of two flocculation tanks.

3. Clarification: The flocculated water flows into the clarification tank.  There, the floc settles and clarified water passes up through tube settlers and enters the outlet launder to leave the system.

4. Separation: Settled floc and sand are raked and pumped to the hydrocyclone where the sand is separated from the solids. The solids are sent to waste and the separated sand is returned to the first flocculation tank.

The micro sand has a specific gravity of 2.6. The sand acts as ballast when attached to the floc via the polymer. Thus the term "ballasted floc". The ballasted floc settles at rates 15 to 35 times higher than conventional clarification. The resulting high rise rates allow the RapiSand system to fit into a fraction of the space required for conventional treatment systems.

RapiSand Ballasted Flocculation Rendering


  • Hydrofoil Mixers
  • Circular Rake System
  • Industrial Recirculation Pump
  • Hydrocyclone
  • Chemical Feed Systems


  • Ensures uniform mixing in all three mixing chambers.
  • Guarantees rapid transport of settled sand/solids to a centrally located hopper, allowing for rapid process startup.
  • Provides reliable recirculation of the clarifier underflow to the hydrocyclone.
  • Provides separation of the sand and coagulated solids.
  • Coagulant and polymer feed systems are designed for optimum performance and efficient chemical deployment.


  • NTU/TSS Removal
  • Tertiary Phosphorus Removal
  • TOC Removal
  • Color Removal
  • CSO Treatment
  • Algae Removal