For the more convenient management of any such municipal plant, any such municipality may vest the construction, management, control, and direction of the same in a board of commissioners to consist of three or more citizens of such municipality, such commissioners to have such powers and duties relating to the construction, management, control, and direction thereof as the municipality may prescribe. Their term of office shall be for three years and until their successors are elected and qualified. The first board of commissioners may be chosen for terms of one, two, and three years, respectively, by the legal voters of the municipality at the same meeting or election at which the provisions of this chapter are accepted, or at any special meeting or election thereafter called for that purpose, and their successors shall be elected thereafter in manner or form as the city or town may determine, provided that the term of service of the commissioners first elected shall be designated at the time of their election.