The SpiraSnail® is a highly efficient screw-type grit dewatering system that delivers 95% removal of all particles 106 μm and larger and 75% of 75-106 μm particles, without the need for washwater - cutting plant solids handling and disposal costs.

Designed to provide dedicated dewatering for high-performance Hydro International grit washing units such as the GritCup®, the SpiraSnail® provides effective, affordable grit dewatering that is ideal for smaller plants with peak flows of up to 430 L/s.

Its unique clarifier design, low loading rates, and slow screw speeds mean that the SpiraSnail® provides high capture efficiency while minimising re-suspension of captured materials, and its low number of wear parts, easy access for maintenance and washwater-free operation keeps operating and maintenance costs to a minimum. 


  • Grit dewatering at smaller wastewater treatment plants
  • Treatment plant retrofits

Only SpiraSnail® 

  • Is optimised for use with the GritCup® grit washing system

Designed for

Coarse particles
Fine particles


Get efficient grit dewatering optimised for smaller plants

Having been designed specifically to address flows of up to 430 L/s peak, the SpiraSnail® is optimised for use at smaller plants - meaning that it is able to provide efficient, economical dewatering while maintaining the standards of performance that wastewater treatment plant operators demand. 

Get operator-friendly dewatering

The SpiraSnail® is designed with the operator in mind. Its minimal number of wear parts and easy access for maintenance reduce operating costs, maximised internal clearances prevent clogging, and a unique clarifier design allows the auger trough to be rotated away from the clarifier, allowing maintenance even while the unit remains full of water. 

Prevent odour

The SpiraSnail® is a fully enclosed system with easy access when you want it open and secure closures to minimise odour issues. 

Minimise maintenance costs

The SpiraSnail®'s shafted screw design prevents the need for difficult to replace liners or steel wear bars, and the four-bolt external bearing can be accessed from outside the trough, saving both time and money when it comes to inspection and maintenance. 

How it works

How it works

  1. Flow from the GritCup® is introduced tangentially into the SpiraSnail® clarifier. This tangential entry forces the grit to the outside of the clarifier cone.

  2. From the outside of the clarifier cone grit settles into the SpiraSnail® conveyor trough.

  3. The slowly rotating shafted screw conveys the captured grit and dewaters it as it moves towards the discharge chute and into the grit receptacle ready for landfilling.

  4. Clarified water passes over the perimeter weir before being sent back to the plant for further treatment.

Unlike conventional screw classifier systems, the SpiraSnail® is only used for dewatering and not grit washing. This reduces the speed at which the screw needs to rotate, thereby minimising the turbulence that would otherwise release captured fine grit particles.

Technical Information

Technical information


  • 95% removal of grit 106 μm and larger
  • 75% removal of grit 75-106 μm
  • >60% total solids in output grit at design flow
  • <20% volatile solids in output grit at design flow

Conveying capacity 

  • 0.57 m3 / hour 

Design Notes 

  • Variable frequency drive in the control panel provides flexibility, allowing screw speed adjustment to match changing local operating conditions
  • Optional explosion proof motor allows the system to operate in classified environments
  • Standard 304 stainless steel construction (316 SS optional) 
  • Standard odour cover 


Case Studies

Case Studies