Membrane processes reverse osmosis (RO) and nanofiltration (NF) have broad industrial application in obtaining fresh water from seawater desalination and waste water treatment. One of the problems of RO and NF processes is the retentate (concentrate) disposal, which is one of the output streams. Membrane technology requires less energy than thermal technology, but in cases where the composition of the water for processing is more complex, for example, industrial waste water, the use of membrane technology is limited. Thermal technologies are expensive, use significant amounts of energy and are not suitable for high flow rates. Choosing the best available technology to reduce the volume of the retentate depends on several factors such as the composition of the water or the source of the retentate which can be a desalination plant, a waste water treatment plant or the water from mining industries. Other factors include energy use, costs and stage of technological development. Improper handling and processing of the concentrate may result in adverse effects on the environment due to high salinity and the presence of phosphorus and nitrogen, organic pollutants, including new contaminants and traces of inorganic substances. Strategies for the treatment, management and reducement of the volume of the concentrate are the subject of intensive research in order to economically apply them on an industrial scale. Contaminants in the concentrate may have an impact on the ecosystem and water quality in the vicinity of the disposal place of the concentrate. Since the properties of new organic pollutants significantly affect the efficiency of the method for purifying water, and given the high toxicity and persistence of some of them, innovative and cost-effective technologies for water treatment are needed.