Challenge
A Peruvian refinery uses caustic treatment to rid hydrocarbon streams of undesirable contaminants such as sulfides and organic acids. This results in generation of several noxious spent caustic waste streams that are very difficult to treat with conventional wastewater treatment methods. These spent caustic waste streams are malodorous, toxic, and could contain volatile organic compounds. The refinery was interested in technology that would effectively and safely treat these high strength spent caustic waste streams.

Solution
Beginning in 2005, The Repsol YPF Refinery in La Pampilla, Peru employed Zimpro® Wet Air Oxidation (WAO). This process operates at elevated temperature and pressure in which it oxidizes dissolved or entrained contaminants. Oxidation reactions occur in the liquid phase.

Results
The WAO system proved to be an effective and reliable approach for treating the spent caustic. Sulfides and mercaptans are destroyed to below analytical detection limits. TOC and COD are greatly diminished and the oxidation products neutralized to a pH of between 8 and 10. The treated spent caustic is suitable for discharge. The gaseous and liquid effluents are no longer malodorous. The offgas is of sufficient quality that it is directed to a burner to destroy the volatile compounds.

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