(a) The purpose of this subchapter is to establish minimum requirements that define the acceptable management of water treatment residuals. These requirements apply as specified in §312.2 of this title (relating to Applicability).(b) The following term, when used in this subchapter, shall have the following meaning, unless the context clearly indicates otherwise. Land application unit is an area where water treatment residuals are applied onto or incorporated into the soil surface for disposal, where the disposal occurs within five feet of the land surface.(c) When water treatment residuals are mixed with sewage sludge, biosolids, or domestic septage or when water treatment residuals are placed on land for disposal along with sewage sludge, biosolids, or domestic septage, it is subject to all applicable requirements of sewage sludge, biosolids, or domestic septage, as specified in this chapter.