Abstract: A process and system for treating excess sludge produced from a biological treatment system. The process includes biologically treating water or wastewater and producing excess sludge. The excess sludge is directed to a solubilizer where the sludge is solubilized. The solubilized sludge is directed to a liquid/solid separator, which separates the solubilized sludge into a liquid fraction and a solid fraction. The process further includes at least partially digesting the liquid fraction and directing the partially digested liquid fraction to the biological treatment system where the liquid fraction is subjected to further treatment. Finally, the solid fraction is subject to further solubilization.

Abstract: The invention provides a method for the treatment of excess sludge derived from at least one effluent biological purification treatment facility producing excess sludge, whereby said method comprises at least one solubilization stage (4) and at least one sludge digestion stage (5). Said method is characterised in that it comprises at least one solubilized sludge liquid/solid separation stage (6), at the end of which the liquid fraction at least partially undergoes a digestion stage (5) before being directed upstream of said sludge biological treatment, whereas the solid fraction of said solubilized sludge is redirected to said solubilization stage (4).