Sludge Digestion (English)Digestion des boues – RADS (système robuste de digestion aérobie) (French)Digestión de lodos  – sistema de digestión aeróbica sólida o RADS (Spanish)Schlammfaulung – Robust Aerobic Digestion System (RADS) (German)Arabic language version not availableFermentacja osadów: Trwały system fermentacji tlenowej (ang. RADS) (Polish)Aerobna stabilizacija blata (RAD) (Slovenian)Jednotky pro aerobní vyhnívání kalu (RADS) (Slovakian)Jednotky pro aerobní vyhnívání kalu (RADS) (Czech)

Sludge Digestion

RADS Sludge Digestion WastewaterNew guidelines on the disposal of sludge, such as the Landfill Directive and the ADAS safe sludge matrix, have created additional costs and challenges for commercial and industrial companies. There is now a need to significantly reduce the volume of sludge that requires transportation and final treatment – a problem that WPL’s Robust Aerobic Digestion System (RADS) was designed to address.


Typical applications:

  • Commercial or industrial wastewater solutions


WPL offers a complete treatment solution for industrial waste producers, comprising bespoke plant to meet the tightest of Regulations.


WPL’s RADS is a highly effective and cost efficient sludge treatment system that significantly reduces sludge output from any sewage treatment plant.


Utilising aerobic treatment, the RADS incorporates the unique principles of WPL’s successful Diamond sewage treatment plant and offers extended de-sludge intervals.  Analysis of data collected from existing installations has shown that installing a RADS reduces de-sludge frequencies on the plant by 75%.


The unit comes with no internal moving parts. Its shape and internal configuration ensure complete tank mixing and optimum treatment.


Why choose a RADS?

  • Increased de-sludge intervals – without placing significant RADS Sewage Treatmentbiological or hydraulic load on the rest of the plant
  • Reduced tankering costs leading to fewer vehicle emissions into the environment
  • No internal moving parts, reducing the need for operator maintenance
  • Scum skimmer option – reduces maintenance requirements
  • Low visual impact – below ground tanks
  • A significant reduction in Biological Oxygen Demand (BOD) and in total and volatile constituents
  • Minimal impact on the plant from return liquors during times of high Mixed Liquor Suspended Solids (MLSS) load within the RAD reactor
  • Minimal footprint – integrated aerobic reactor and clarifier


How it works

  • Sludge is fed to the unit through the inlet pipe to the central reactor chamber; a circular tank with a sloped, open base
  • Located in the centre of the aeration chamber is a draught tube. This contains WPL’s bespoke coarse bubble diffuser which feeds process air to the plant
  • As the diffused air rises in the draft tube a venturi effect is created, which circulates process fluid around the reactor, allowing suspended growth aerobes to stabilise the sludge and reduce its volume by endogenous respirationRADS Sewage Treatment
  • A recycling loop is generated in the reactor in which aerated sludge continuously settles to the bottom of the tank and is drawn back up through the draft tube
  • Surrounding the aeration reactor is the integrated clarifier. As sludges continue to enter the aeration chamber, liquors are displaced from the reactor to the clarifier, in which quiescent conditions allow suspended material in the effluent to settle and be re-entrained into the aeration zone
  • The clarified (treated) effluent flows up through the clarifier and over a V-notch weir, which extends around the periphery of the tank
  • The effluent collects in an outer trough where it is discharged through a 110mm (RAD 2.4) or 160mm (RAD – 3.0 & 4.0) pipe connection. A scum baffle located inside the overflow weir prevents floating solids from passing over the weir

 RADS Wastewater Treatment

The RADS unit requires minimal operator servicing beyond periodical de-sludging, provided the unit is operated within design specification. Side channel blowers supplied with the unit require periodic maintenance. It is recommended that the blower is serviced in line with the manufacturer’s guidelines.

Find out more by viewing Sludge Digestion specific case studies:

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