Effect of varying hydrothermal temperature, time, and sludge pH on sludge solubilisation

•Hydrothermal treatment to release valuable organic components into aqueous phase.•Hydrothermal conditions of 200 °C, pH 12, 1 h yielded highest concentration of COD 1743 mg/g, carbohydrates 131 mg/g.•The best hydrothermal conditions correspond to a severity factor of 9.7.•Compounds for applications in adhesives, polymer industry, and levulinic acid are among the identified molecules.