Our AquaCritox® unit continues to run successfully at a site in Rabigh, Saudi Arabia, proving the concept of treating industrial quantities of spent caustic at source using AquaCritox NC advanced hydrothermal oxidation technology. Spent caustic waste streams containing approximately 8 – 17 g/l of COD (predominantly sulphides and mercaptans with 30 – 35% organic COD) were treated by the unit, resulting in COD reduction in excess of 98%.
The Application
Sulphidic spent caustic is generated at a number of refineries in Saudi Arabia. Spent caustic is a noxious and hazardous waste stream, which must be treated prior to disposal. The site in Rabigh currently processes various types of spent caustic.
Site Operations
Trial results were obtained during an initial 3-week operating window in May 2020. The daily testing process allowed operation for 6 hours; this was more than sufficient to process 160 litres of sulphidic spent caustic on each run. The plant was operated and
monitored by local staff and remotely by the specialist SCFI team based in Cork, Ireland. The fully integrated stand-alone control system minimised site intervention while allowing remote start-up and shutdown. Analysis of the feed and effluent waste sample was undertaken by the on-site laboratory and verified by a certified laboratory in the United Kingdom.
The Success
Thanks to the fully automated unit, the plant ran without issues for the duration of testing. Laboratory results confirm that efficient destruction of both inorganic COD (mainly sulphides and mercaptans) and organic COD was achieved. The treated spent caustic is therefore suitable for disposal or further treatment in a biological system.
