Current status and technology trends of zero liquid discharge at coal chemical industry in China

Coal chemical industry, referring to the large scale production of fuels and chemicals from coal, has been growing rapidly in China in the past decade and the trend is expected to continue in the following years. Since most large scale coal chemical plants have been built in coal rich areas lack of environmental capacity to receive wastewater discharge, Zero Liquid Discharge (ZLD) has been becoming more and more commonly used as the wastewater management strategy in the newly proposed coal chemical plants, which drives quick implementation and fast evolution of ZLD technologies in China. This paper examines the current status of ZLD practice for wastewater management and the representative ZLD processes used in the coal chemical industry in China. Additional analysis shows that major technical challenges exist in current ZLD solutions and the technology evolution trends are to further incorporate enhanced organics removal technologies, hybrid membrane and room temperature crystallization technologies, high salinity membrane concentration technologies and pure salts oriented crystallization technologies so as to achieve better system stability, lower treatment cost and beneficial recycling of pure salts.