The study focuses on the chemical pretreatment of the aqueous phase formed during the hydrothermal liquefaction of excess activated sludge. This study aims to find the most efficient method of chemical pretreatment of the aqueous phase. The purification methods used are: oxidation with Fenton's reagent, oxidation with sodium persulfate, precipitation of organic doi: 10.48047/AFJBS.6.15.2024.7556-7569 Introduction substances with polyaluminum chloride, sorption. COD, BOD5, dry residue and calcined residue values were determined in the sample to evaluate the efficiency of the aqueous phase treatment. The best results in water phase purification were achieved by sorption with BAU-A industrial carbon (COD value decreased by 1.8 times, BOD5 by 20 times, dry residue amount by 1.1 times, calcined residue by 2.7 times). The purified sample showed a 1.9-fold reduction in toxicity in terms of dehydrogenase activity level and a 3.5-fold reduction in inhibition. Based on the data obtained, sorption pretreatment can be recommended as a pretreatment method for HTL-AP.