The board shall classify all wastewater treatment plants. Cesspool and septic tank facilities connected to an individual household shall be exempt from classification. Industrial facilities for treatment of process water from oil refineries and sugar mills shall be exempt from classification provided such waste streams contain no domestic component and further provided that they do not discharge to a municipal collection, treatment, or disposal system. Application for exemption from classification of other industrial wastewater treatment facilities may be made to the director. In classifying or exempting from classification wastewater treatment, the board shall consider the applicable provisions in chapter 38 of the department of health regulations regarding wastewater treatment facilities and any rules and regulations of the department of health pertaining to the control of underground injection of wastewater. The classification shall take due regard to size and type, character of wastewater to be treated, other physical conditions affecting such wastewater treatment plants, and the skill, knowledge and experience required of an operator.