Review on treatment technology of salt wastewater in coal chemical industry of China

Reducing salt wastewater emissions to the outside world is significant for the “zero discharge” requirement of coal chemical industry. This review is mainly about the treatment technologies of salt-containing wastewater and high-salt wastewater in coal chemical industry of China. In the treatment of high-salt wastewater, coal chemical industry projects in China mostly use the “double membrane” reuse technology of “ultrafiltration + reverse osmosis”. Reverse osmosis is the core and main technology of reuse treatment, while ultrafiltration is the pretreatment and protection process. High-salt wastewater refers to the concentrated reverse osmosis wastewater of the reuse system. Evaporation crystallization technology can achieve “zero discharge” of wastewater by transforming high-salt wastewater into solid crystal mixed salt. It is a mature and recognized process at present stage, but the disposal of mixed salt is an urgent problem to be solved. Cooling crystallization and nanofiltration membrane can realize separation of mixed salt, but these technologies have not been applied to actual coal chemical project, and further research is needed.