Any municipality may, by vote of its legislative body, after the formation of a district in accordance with the provisions of section 7-330, elect to apply for admission to such district and the board of such district may admit such municipality. Any constituent municipality of any district may, by vote of its legislative body, elect to withdraw from such district, but such withdrawal shall not be effective until six months after such vote, nor shall such withdrawal relieve such municipality of any liability which it incurred as a member of such district.