A process for cooling a heated coolant, said process comprising: (a) passing a heated coolant to an evaporative cooling apparatus wherein the coolant is cooled by evaporation; (b) heating at least a portion of the coolant from step (a) to provide a heated coolant; (c) recycling at least a portion of the heated coolant from step (b) to step (a) to form a circuit; wherein the process further comprises passing at least a portion of the coolant to a reverse osmosis unit to form a retentate solution and a permeate solution; introducing at least a portion of the permeate solution into the circuit; and removing the retentate solution.