Zimpro wet air oxidation technology from Siemens will be used to treat sulfidic spent caustic wastewater streams generated in the production of ethylene. The wet air oxidation systems will destroy odorous sulfide pollutants, break down complex organic contaminants, such as phenols, to either carbon dioxide and water, or biodegradable organics. The system will generate a biodegradable effluent that can be discharged to conventional biological wastewater treatment.