The director shall classify all water treatment plants, water distribution systems, and waste water treatment plants affecting the public welfare with regard to the size, type, character of water and waste water to be treated and other physical conditions affecting such treatment plants and distribution systems, and according to the skill, knowledge, and experience that an operator must have to supervise the operation of the facilities to protect the public health and prevent pollution. The director may appoint advisory committees to advise the department in carrying out the requirements of this part.