Spent Caustic Treatment Using Advanced Oxidation Processes

Abstract

Mixed refinery spent caustic is an industrial wastewater that is generated from oil refineries. Spent caustic undergo two treatment steps, chemical oxidation followed by biological post treatment step. The goal of chemical oxidation is to drop the contamination concentration to a level that biological treatment can take place. The maximum contaminants concentration, which can be measured by chemical oxygen demand, that biological treatment can be applied, is 1,000 ppm. Advanced oxidation processes, in specific, fenton's reaction is tested to check if the method can be applied to spent caustic treatment. The research is divided into two parts, bench scale study followed by pilot plant study. The goal of bench scale study is to treat spent caustic to achieve a final chemical oxygen demand of 1,000 ppm with minimum hydrogen peroxide to chemical oxygen demand ratio possible by manipulating other factors affecting chemical oxygen demand removal. It was found out that the highest chemical oxygen demand removal achieved is 97% at optimum hydrogen peroxide to ferrous sulfate to chemical oxygen demand mass ratio of 3.8/2.1/1. Moving on to the pilot plant study, the objective of the pilot plant study is to check if fenton's process can be applied in large scale. The best result obtained is a final chemical oxygen demand of 525 ppm while operating at hydrogen peroxide to ferrous sulfate to chemical oxygen demand mass ratio of 3.5/1.6/1.