In recent years, the tightening of environmental regulations has compelled refineries and petrochemical plants to exercise stricter supervision and control over their effluent streams. A principal contributor to the observed increase in chemical oxygen demand (COD) and biochemical oxygen demand (BOD) is the deployment of acid gas (H₂S and CO₂) and mercaptan removal units, which conventionally employ dilute caustic soda (NaOH) as the scrubbing reagent. The resultant by-product, commonly referred to as "spent caustic," poses considerable challenges in terms of treatment and disposal, owing to its unfavorable physicochemical properties and pronounced toxicity to the environment. The present study undertakes a detailed characterization of the chemical attributes of this waste material. A multitude of treatment strategies has been developed for spent caustic management to date, and the present review offers a comprehensive and up-to-date survey of these approaches, with particular emphasis on their underlying mechanisms and comparative performance.