No abstract

Stricter environmental regulation policies and freshwater as an increasingly valuable resource are leading to global growth of zero liquid discharge (ZLD) processes in recent years. During this development, in addition to water, the recovery of recyclable materials, e.g. salts, from industrial wastewater and brines is considered more frequently. Within the framework of the HighCon research project, the subject of this study, a new ZLD process with the goal of pure single-salt recovery from industrial wastewater has been developed and investigated in a demonstrational setup at an industrial site. With regard to pure salts recovery, separating organic components is of great importance during the treatment of the concentrate arising from used water recycling. The removal of COD and of ions responsible for scaling worked very well using nanofiltration. The nanofiltration permeate containing the monovalent ions was pre-concentrated using electrodialysis and membrane distillation before selective crystallization for single-salt recovery was performed. An example economic case study for the newly developed ZLD process – based on demonstration results and considering optimization measures for a full-scale design – indicates that the costs are equal to those of a conventional ZLD process, which, however, does not provide inter alia the aforementioned benefit of single-salt recovery.

Pharmaceutical and diagnostic substances like antibiotics, cytostatics and iodised X-ray contrast media (XRC) are well-known for not being metabolised and are excreted soon after application. As a result, these preparations are difficult to biodegrade and their adsorption behaviour is rather poor. Finally, the refractory properties of these substances are leading to an accumulation in the natural waterbody depending on the hydrological situation. The elimination of contrast media from urine and diluted urine solutions by ozonation was investigated using a bubble column reactor to remove and recover the formed elemental iodine from the solution by gas stripping and down stream absorption. The experiments showed that the destruction of XRCs from concentrated solutions like urine is feasible and a recycling of elemental iodine from the exhaust gas is technically and economically possible.

No abstract