In the heart of southwestern China, a zinc smelting enterprise faced a persistent challenge: how to efficiently treat and reuse wastewater while minimizing environmental impact and operational costs. The solution, as detailed in a recent study published in the Chinese journal *Industrial Water Treatment* (*Gongye shui chuli*), came from CINF Engineering Co., Ltd., where lead researcher Xia Chuan and his team reengineered the wastewater treatment process using a novel reverse osmosis (RO) concentration method.
Traditional methods often struggled with the high salinity and complex composition of zinc smelting wastewater, leading to inefficiencies and high costs. Xia and his team addressed this by implementing a two-stage RO system—medium- and high-pressure RO for concentration, followed by low-pressure RO for desalination. The wastewater first passes through multimedia filters, ultrafiltration, and resin softening to remove particulates and reduce hardness. The treated water then undergoes medium-pressure RO, with high-pressure disc-tube reverse osmosis (DTRO) further concentrating the brine. The permeate from these stages is desalinated using low-pressure RO, producing water clean enough for reuse in production. The concentrated brine, now less than 15% of the original volume, is repurposed for slag washing.
The results were striking. The system achieved a water recovery rate of over 68%—meaning nearly 70% of the wastewater was converted into reusable water—while the desalination rate exceeded 98%. The treated water met stringent quality standards, with total dissolved solids (TDS) as low as 26 mg/L, total hardness below 8 mg/L, and conductivity between 34.8 μS/cm and 78.2 μS/cm. Xia noted, “This process not only reduces freshwater demand but also cuts disposal costs by concentrating waste into a manageable brine stream.” The operational cost for wastewater resource utilization was calculated at just 7.63 yuan per cubic meter after accounting for revenue from water reuse.
For industries grappling with water scarcity and tightening environmental regulations, this case study offers a compelling blueprint. By transforming wastewater from a liability into a resource, zinc smelters—and similar heavy industries—could significantly lower their freshwater intake while reducing effluent discharge. The implications extend beyond zinc smelting; sectors like mining, chemical processing, and even thermal power plants, where water reuse is critical, could adapt this RO concentration strategy to enhance sustainability.
Xia’s work underscores a growing trend in industrial water management: the shift from linear “take-make-dispose” models to circular systems where waste streams are reimagined as inputs. As industries seek to align with global sustainability goals, innovations like these could redefine the economics of water treatment. The question now is how quickly such technologies can scale—and who will lead the charge in adopting them.