This paper is devoted to the development and operation of specialized water treatment and water purification systems, based on the principle of reverse-osmosis filtration of water, for the operation of bench nuclear power systems at the A. P. Aleksandrov Scientific-Research and Technological Institute. Reverse-osmosis filters permit softening the process water, improving its quality, and greatly decrease the load on the ion-exchange filters when desalinating water. Ultimately, the contamination of drain waters with dissolved salts is also greatly decreased. The drain waters can also be purified by a combination of reverse-osmosis and ion-exchange filters. A modular membrane-sorption system whose capacity reaches 0.5 m3/h is presented.