An integrated membrane- and thermal-based system for coal chemical wastewater treatment with near-zero liquid discharge

The coal chemical industry consumes and discharges huge volumes of water, with the subsequent treatment and use of this wastewater presenting a great challenge. Near-zero liquid discharge (Near-ZLD) is an efficient technology that supports wastewater reuse and helps to manage shortages in freshwater resources. Near-ZLD is an integrated process combing scaling ion removal, filtration/concentration and evaporation/drying, with the feasibility of this system verified in an engineering case-study (500 m3/h) in China. A combination of coagulation and ion exchange can effectively remove Mg2+and Ca2+ from wastewater, achieving total removal rates of 99.96% and 99.97%, respectively. A combined process of filtration and ultrafiltration can effectively reduce the final turbidity of treated wastewater to below 0.1 NTU. Coupled nanofiltration and evaporation units can achieve effectively terminal wastewater treatment, separating and removing NaCl. Reclaimed water can be recycled with the integrated process, thus achieving near-ZLD, demonstrating high stability and providing an environmentally friendly and sustainable approach for the treatment and reuse of hypersaline coal chemical wastewater.