The possibility of using the seeded calcium carbonate precipitation technology developed previously by the author for the utilization of concentrates of existing reverse osmosis units has been explored. In modern reverse osmosis plants, scale inhibitors are used to prevent calcium carbonate scaling of membranes; the role of antiscalants consists of adsorption on the surface of forming crystals and slowing down their growth. The presence of antiscalants in the concentrate decreases the growth rate of the "seed" crystals and hampers the utilization of the concentrate. To increase the rate of crystallization, it is necessary to increase the supersaturation of the solution or increase the amount of seed crystals to be introduced. The dependence of the calcium carbonate growth rate in the antiscalant-containing concentrate on the added "seed" dose, recovery, and the pH has been studied. Various antiscalants have been compared in terms of performance, and their type most suitable for the process has been chosen. The results of comparison of the operating costs of a reverse osmosis plant involving concentrate utilization, depending on the antiscalant type used, are presented.