Except as otherwise provided in § 48-9-1220, the term of office of each commissioner is four years, except that in newly created districts the elected commissioners’ terms of office are until the next regular election is held under the provisions of § 48-9-1220 and the first appointed commissioners must be designated to serve for terms of one and two years, respectively, from the date of their appointment. A commissioner shall hold office until his successor has been elected or appointed and has qualified. Vacancies must be filled for the unexpired term. The selection of successors to fill an unexpired term, or for a full term, must be made in the same manner in which the retiring commissioners shall, respectively, have been selected, except that in the case of a vacancy in the unexpired term of an elected commissioner a successor may be appointed by the board upon the unanimous recommendation of the remaining commissioners. Any commissioner may be removed by the board upon notice and hearing for neglect of duty or malfeasance in office, but for no other reason.