S.C. Code Ann. § 40-23-305

A person employed as an operator of a public wastewater treatment plant must hold a wastewater treatment operator license issued by the board in the certification class required by this section and the regulations of the board. The required certification class must be determined by the treatment group of the public wastewater treatment plant where the operator is employed, as established by the Department of Health and Environmental Control pursuant to Section 48-1-110. The board shall establish in regulations the certification class required for each treatment group of public wastewater treatment plants defined in Section 40-23-20.