Sludge Conditioning

Two sludge conditioning techniques are commonly used in the industry.

• 'Chemical conditioning', which agglomerates tiny par ticles to form larger ones by coagulation to improve liquid-solid separation. The commonly used coagu lants include Al2(SO4)3, FeCl3, lime, and organic polymers. These are also sometimes used in the pre cipitation process for the primary wastewater treatment.

• 'Heat treatment', in which the sludge is raised to high temperature (175-230 °C) under pressure (1000- 2000 kPa). This serves to improve the dewater ing characteristics ofsludge. Heat treatment is generally considered superior to chemical conditioning for dewa tering. However, compared with chemical conditioning, the process has two notable disadvantages: (1) it is more complex in operation and maintenance and (2) it gen erates highly polluted cooking liquors.

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