In recent years, refinery and petrochemical producer is forced by more stringent environmental regulations to better monitor and control their wastewater. One of the key contributors to relatively high chemical oxygen demand (COD) and biological oxygen demand (BOD) is from the acid gas (both CO2 and H2S) and mercaptan removal system (s) typically using dilute caustic soda (NaOH) as the active reagent. The resultant waste stream is otherwise known as spent caustic. It’s difficult to clean up and dispose of due to its toxic properties. Today’s various methods are used for treating spent caustic, such as wet air oxidation and direct acid neutralization. In this review, these methods were studied in detail and were compared together

Sodium hydroxide (caustic) scrubbing solutions are commonly used in petrochemical and gas/petroleum refineries for the removal of acid components such as hydrogen sulfide, cresylic acids, mercaptan and naphthenic acids from the refined product streams [1]. Due to being hazardous, odorous, and/or corrosive components of spent caustic, handle and dispose of them, can be a challenge. Spent caustic streams may also have other characteristics that can create issues with conventional biological processes such as noxious odors, pH swings, foaming, or poor settling of biological solids [1]. Effluent requirements may be difficult to achieve because some spent caustic contaminants are not readily biodegradable. Typically, the material is disposed of by high dilution with bio treatment, acid neutralization, deep well injection, incineration, wet air/catalytic/Humid Peroxide Oxidation or other specialty processes [2]. The two basic methods for treating spent caustic solutions are wet air oxidation (WAO) and direct acid neutralization (DAN), respectively. In this paper, first spent caustics and then treatment methods were discussed in detail

Treatment, Wastewater, Spent Caustic, Sodium Carbonate, Recovery , Wastewater treatment

Evaluation of the Different Methods of Spent Caustic Treatment