New area for distillation: wastewater treatment

Abstract

The protection of our environment is an actual and global problem in our time and the wastewater treatment is its important part. It is based on biological treatment. In certain cases, however, due to special regulations, the biological tools are not allowed and other options should be considered and selected. The incineration is an alternative but impact assessment studies show that it can make a serious burden upon the environment as well as it might be an expensive solution. Physico-chemical tools can mean a realistic alternative in such cases. In case of wastewater containing organic solvents (ethanol, ethyl-acetate, toluene, halogenated solvents, etc.), that is typical for wastewaters of medicine and fine chemical industries, the distillation is a powerful tool to remove the volatile polluting compounds. These volatile organic compounds (VOC) can contribute significantly to the chemical oxygen demand (COD) of the wastewater. This contribution we call VOC-COD. The Adsorbable Organically Bound Halogens (AO X) can be removed also with distillation. Industrial case studies show that the distillation offers a realistic alternative and the recovered solvents can be also utilised. The COD can be reduced in certain cases below the emission limit (1000 mg/lit) and the AOX, after the physico-chemical treatment, is less than 8 mg/lit.