Land acquired or developed by any municipality, for which a state grant was awarded under sections 7-131d to 7-131k, inclusive, shall not be conveyed other than to another municipality or to the state for use for recreation or conservation or converted to any use other than recreation or conservation, except with the approval of the Commissioner of Energy and Environmental Protection, provided a municipality may use such land for a subsurface sewage disposal system if such system is adjacent to a municipally-owned building. If such grant was awarded for acquisition of land, such approval by said commissioner shall be conditioned on the agreement of the municipality to provide comparable land to be devoted to recreation or conservation, the full proceeds of any sale of land to be applied to such purpose and, if such proceeds exceed the amount required for such land acquisition, the balance shall revert to the state General Fund. If the municipality is unable to acquire comparable land, it shall pay to the state (1) if the land is sold, the same percentage of the proceeds of the sale as that granted by the state for the purchase of the land, or (2) if the land is not sold, such percentage of the fair market value of the land at the time of conversion to another use.