Pham, Van ToiVan ToiPhamNguyen, Viet AnhViet AnhNguyenCHANG-PING YU2023-06-202023-06-202022-10-1825252518https://scholars.lib.ntu.edu.tw/handle/123456789/632989Sewage sludge (SS) is a by-product of the wastewater treatment plant and may cause serious environmental problems. However, SS has a lot of promise for recovering energy and resources because it is full of organic chemicals. An appealing thermos-chemical method for SS pre-treatment is the hydrothermal process (HP), which reduces big organic molecules in SS to smaller ones at higher temperatures and pressure. In this research, HP of SS was conducted in conditions: 180oC, 648.1 kPa (94 psi) during 30 to 90 min of reaction time, with nitrogen and air as working gases, to evaluate the effect of HP on the change of SS characteristics. In SS, it was discovered that HP enhanced the solubilization of organic molecules. The dissolved organic carbon (DOC) values are 2207, 2311, and 2766 mg/L after treating at 180 °C and 94 psi during the reaction times of 30, 60, and 90 min, respectively. Additionally, utilizing nitrogen or air as the working gas resulted in a rise in the value of DOC to 2207 and 2292 mg/L, respectively. The results show that the pH value decreased in HP reactions due to the formation of volatile fatty acids. The pH dropped from 6.4 (the control) to 5.89, 5.79, and 5.65 after the HP reactions were carried out at 180 °C and 94 psi for 30, 60, and 90 min, respectively. Besides, with nitrogen and air serving as the working gases in HP operations, respectively, this value dropped quickly to 5.89 and 5.75.air | hydrothermal process | nitrogen | sewage sludge | solubilizationjournal article10.15625/2525-2518/173292-s2.0-85139956962https://api.elsevier.com/content/abstract/scopus_id/85139956962