Pretreatment solution for WWTP

Inlet Works Package

The inlet works package SPIRAC designed for this council is designed to remove solids and grit from the incoming sewage, at a capacity of 200L/second, or 12,000L/minute.

The pretreatment area is using several materials handling products supported on galvanised steel beams, making for an easy installation process and minimised maintenance requirements. By constructing the system on support beams, the need for complex civil works was eliminated, making the entire process much more efficient and cost-effective.

Scope of Work

Sewage is pumped into one of three SPIROGUARD® units with press heads - working in a duty/assist/assist configuration. The SPIROGUARD® combines screening, including the removal of solids larger than 2.0 mm from the effluent stream, conveying, washing and dewatering. Once wastewater has passed through the perforated screen, the collected solids are transported up the shaftless screw conveyor to a press head. Within the press head, the screenings enter the wash zone first where remaining organics are removed and the wash water flows back into the wastewater stream. The flush water system in the press head ensures dewatering efficiency. Screenings are compressed against a pressure plate for dewatering before being discharged. Typically, the weight reductions of the screenings can be 65 per cent or over depending on the quality of captured screenings. Meanwhile, screened flow passes through an effluent outlet, on its way downstream. The wastewater enters the Grit Vortex from SPIRAC, which is designed to separate high-density grit particles from lower-density organics. The screened sewage then enters the Grit Vortex where a slowly rotating impeller spirals lower-density organic particles upwards to the chamber outlet. Any high-density grit particles settle at the bottom and are put through a fluidising cycle, enabling them to be pumped to the SANDWASH grit washer.

Utilising a multi-stage cleaning process, the SANDWASH is designed for applications where all visible organics must be removed from the grit. Organics and other larger, lower-density objects are then returned to the downstream biological treatment. The grit and water stream from the Grit Vortex is transferred into the SANDWASH, where agitator paddles ensure that any remaining organics are removed from the grit. After separation from mineral particles, material is removed via the organics outlet. The clean grit is then transferred up a shaftless screw conveyor, where it passes through another phase of dewatering and is discharged into a bin. Should the Mirani plant need to prevent odour in the future, it could simply add a SPIROTAINER® to their system with a retractable chute. The SPIROTAINER® is an autofilling containment and road transport system, designed for the hygienic and automatic handling of foul or objectionable waste materials.

Features and Benefits:

Complete pre-treatment package: including screening and grit capture, washing and dewatering.

  • Galvanised steel beam construction reduces civil works, resulting in lower capital cost.
  • Low power consumption and wash water usage.
  • Custom design and layout to suit client-specific requirements.
  • Prefabricated - reduced installation time on site.
  • Easy access and few moving parts for low maintenance.
  • Simple and reliable operation, with automatic control for great flexibility.

SPIRAC products used:

  • SPIROGUARD® Shaftless Spiral Screen
  • Grit Vortex from SPIRAC
  • SANDWASH Grit washing unnit
  • Manual Bar Screen
  • SPIROLINE® and SPIROLIFT® shaftless spiral conveyor systems 


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