This study investigated the efficacy of alkaline pretreatment using potassium hydroxide (KOH) as an agent for waste activated sludge (WAS) under ambient conditions to enhance subsequent anaerobic digestion. Gravity-thickened WAS was treated with KOH dosages ranging from 0 to 0.15 g/g volatile solids (VS) for 3 hour at 25 ± 2 °C. Pretreatment rapidly elevated and stabilized sludge pH at approximately 12, inducing extensive disruption of extracellular polymeric substances (EPS) while essentially preserving microbial cell integrity. Soluble chemical oxygen demand (sCOD) increased from 1.42÷1.68 g/L to a maximum of 6.65 g/L, raising the sCOD/TCOD ratio from 14÷16% to 44÷50%. The degree of COD solubilization (DS) reached nearly 50% at the highest dosage, with a strong linear correlation to KOH dose (R2 = 0.8). Concurrently, mixed liquor suspended solids (MLSS) decreased by up to 18.5%, whereas the sludge volume index (SVI30) rose from 88 to 187 mL/g, reflecting significant deflocculation and impaired settleability. Scanning electron microscopy confirmed severe degradation of the EPS matrix and exposure of microbial aggregates. These results demonstrate that KOH is a highly effective, low-energy pretreatment reagent capable of achieving comparable or superior organic solubilization to NaOH, while offering potential advantages in ionic mobility and reduced methanogenic inhibition. Optimal performance was observed at 0.09 ÷ 0.12 g KOH/gVS, providing a practical basis for enhancing biogas recovery from municipal WAS. KEYWORDS: Waste activated sludge, alkaline pretreatment, potassium hydroxide, COD solubilization, EPS disruption, anaerobic digestion.