A method for reducing sludge viscosity of a sewage sludge having a solids
concentration of at least 10% (w/w). The method comprises the steps of
increasing the pH of the sludge to 9.5-12.5%, at least one step selected
from subjecting the sludge to a holding step of at least one day and
adding inorganic or organic chemicals to facilitate viscosity reduction,
followed by incubating the sludge at temperature up to 100.degree. C., and
subjecting the sludge to a shearing or disintegration step. The method
provides sludge, especially concentrated sludge, that is more readily
pumped or transported.
