(a) Unless designed for advanced nutrient removal, an aeration basin must be designed to maintain a minimum dissolved oxygen concentration of 2.0 milligrams per liter (mg/l) throughout the aeration basin at the maximum diurnal organic loading rate determined in §217.32(a)(3) and Figure: 30 TAC §217.32(a)(3) of this title (relating to Organic Loading and Flows for New Wastewater Treatment Facilities).(b) The volume of aerated influent wastewater channels and aerated mixed liquor transfer channels of an activated sludge system may be used to meet aeration basin volume requirements, provided the activated sludge system uses aeration by diffused air and the diffuser depth conforms to the requirements of §217.155(b)(5)(A) of this title (relating to Aeration Equipment Sizing).(c) The use of a contact stabilization system for nitrification is prohibited.