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Sludge Screening

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Sludge Screening

The Problem

Rag and grit are major problems in wastewater sludges causing blockages, wear and inefficiencies throughout the wastewater treatment works. When sludges are used in downstream processes such as anaerobic digestion, rag and grit cause even greater problems. These problems include but aren’t limited to reduced tank capacity, further wear on dewatering centrifuges, and a significant reduction in biogas yield as a result of lost digester volume and increased downtime when maintaining and cleaning digester vessels. The first stage of sewage treatment in a wastewater treatment works (WWTW) is the removal of rag and grit from the energy bearing liquid effluent.

The Solution

Originally screening took place in order to protect downstream assets from blockage and wear. With the advent of energy generation from sludge, the protection of these valuable assets has never been so important. Our S:MAX screening technology successfully removes both grit and rag from sewage sludges, sewage screenings and tank cleaning residues, creating segregated, washed stockpiles of grit and rag for reuse or disposal.

These solutions bring the following benefits to the sludge screening process:

  • Elimination of blockages- The screen’s simple design means that whatever type of material is pumped onto the screen, it will process it. There is nowhere for rag to block within the screening system.
  • High processing rate- Due to high-frequency vibrations, our screens can operate up to 77L/s at a dry solids content of 6% and can comfortably work on high thickness sludge. The result is that our screens can process directly from inter-site tankers, avoiding the need for buffer storage tanks.
  • High screenings retention rate- The screening size (i.e. the separation size) can be easily modified depending on the application in which it is being used. The vigorous nature of the screen ensures it is virtually impossible for particles larger than the screening size to pass through the screen.


The Result

With our S:MAX sludge screening solution, our customers are now sending 50% less waste to landfill than was previously the case.

We are also recovering a range of materials from the waste and converting them into commercial products which have uses in a variety of applications.

  • Reduce downtime and maintenance requirements
  • Maximise tank capacity and improve biogas yield 
  • Reduce transport and disposal costs
  • Reduce waste sent to landfill
  • Produce high quality sludge for use in biosolids applications and energy generation processes

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