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About sludge stabilisation

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Sludge treatment in wastewater treatment. Brown liquid flowing in a concrete tank with pipes

Sludge stabilisation overview

Stabilisation processes as applied to sludge are those which reduce its:

  1. odour and putrescence (i.e. decay), and
  2. level of pathogenic organisms.

This is generally achieved either chemically or biologically.

For alkaline stabilisation, a basic chemical reagent such as lime − sometimes supplemented with a granular or powdered solid − is dosed into the sludge. Biological stabilisation employs micro-organisms which develop naturally within the sludge under the reactor conditions employed to biochemically degrade the organic material. This can be conducted under aerobic (in the presence of oxygen) or anaerobic (absence of oxygen) conditions.

Sludge stabilisation methods Credit: Judd Water & Wastewater Consultants
Sludge stabilisation methods
Sludge stabilisation hierarchy, showing alkaline and biological stabilisation methodsCredit: Judd Water & Wastewater Consultants

Sludge can also be stabilised by applying intense heat, either in the presence or absence of oxygen. These processes are normally referred to as thermochemical. They demand a substantially different system design approach.


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About this page

'About sludge stabilisation' was written by Simon Judd

This page was last updated on 19 April 2021


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