Many industrial plants are facing increasingly limited options for wastewater discharge. Stricter environmental regulations and rising disposal costs are making conventional treatment approaches less viable, particularly for complex industrial effluents.
Zero Liquid Discharge (ZLD) represents a consistent response to these challenges. The objective is clear: to eliminate liquid discharge entirely while recovering as much water as possible for reuse within the process. With recovery rates of up to 99%, ZLD systems transform wastewater into a valuable resource, while the remaining fraction is converted into a controlled solid product. Depending on project requirements, this residual stream is processed into slurry or dry powder, suitable either for disposal or for further use in applications such as brine mining.
UNIHA’s U-ZLD solution is based on a structured and integrated treatment approach that combines membrane and thermal processes into a single, reliable system. Following feed pretreatment, the wastewater is conditioned to ensure stable operation of all downstream stages. Under typical conditions, the pretreated feed water is characterized by a total dissolved solids content above 1 g/l, suspended solids below 1 mg/l, a total organic carbon concentration below 5 mg/l and an SDI of less than 3, providing a controlled and suitable basis for high-efficiency treatment.
The core of the process begins with reverse osmosis concentration (U-RO), where the majority of the water is separated from the dissolved salts. This is followed by a dedicated softening step (U-Soft), in which the concentrate is chemically conditioned to remove scaling components and protect the subsequent thermal systems. In the final stage, evaporation and crystallisation (U-Ev/Dec), powered either by steam or electrical energy, enable the complete separation of the remaining water from the dissolved solids.
The result is a highly efficient and robust system that minimizes liquid discharge while maximizing water reuse and creating a clearly defined solid output stream. By combining proven technologies into a fully integrated concept, U-ZLD allows industrial facilities to operate independently of external discharge routes and to significantly reduce their environmental footprint.
In this way, wastewater is no longer treated as a by-product to be disposed of, but as a resource that can be recovered, reused and reintegrated into the industrial process.
