There may be a department of public welfare which shall be under the supervision of a director of public welfare, who may be the city manager or a person appointed by the city manager with the approval of the council. The director of public welfare shall constitute the local board of public welfare of the city. The director of public welfare shall appoint the superintendent of public welfare and such other employees of the department as may be necessary. The superintendent of public welfare of an adjacent county or counties may be appointed superintendent of public welfare of the city. The department of public welfare shall be responsible for carrying out the duties and functions imposed on local boards and superintendents of public welfare by general law and such other duties as may be assigned by council.