Membrane processes in the utilization of wastewater generated during waste gasification

Abstract

Gasification, regardless of the fuel type, is always accompanied with the generation of highly loaded wastewater. Those streams are formed during cooling and cleaning of process gas and comprise of tars, condensed water vapor and a range of organic and inorganic compounds. Nowadays, there are no treatment systems of those wastewater, especially dedicated to small and medium size gasification plants, operated with alternative fuels, ie biomass and wastes, what is the main limitation in the technology popularization and industrial commercialization. On the other hand, conventional methods proposed for the treatment characterize with the narrow spectrum of action dedicated, mainly to the removal of tar substances. In the presented paper the possibility of utilization of waste gasification wastewater by means of membrane processes is proposed. The technology was based on the two stage treatment system enabling the separation of tars by spontaneous sedimentation/floatation and low pressure drive aqueous phase filtration. Polymeric, ultrafiltration membranes of various cut off were investigated due to the contaminants removal effectiveness and capacity. It was shown, that the use of membrane processes assures the concentration of soluble organic contaminants to the rate enabling their recycle to the gasifier. The filtrate obtained during the process characterized with much decreased load of contaminants and after the proper polishing could be directly deposited to the environment.