A system for applying and recovering de-icing chemicals from a surface. The system includes a spray system for applying a de-icing chemical to the surface and draws the de-icing chemical from the surface. The de-icing chemical and contaminants are conveyed to a reservoir to form a combined solution. A recovery system includes a filter device for removing solids from the combined solution, at least one sensor for measuring a property of the combined solution, and a source of additive chemical. A controller is configured to determine a property of the combined solution based on signals provided by the at least one sensor, move a valve to an open position to cause the additive chemical to mix with the combined solution if the property is less than a predetermined minimum value, and move the valve to a closed position if the property is greater than the predetermined minimum value.