(a) A submerged biological contactor (SBC) may be used in conjunction with other treatment systems.(b) An SBC may be used as a roughing unit, as described in §217.182(b)(1) of this title (relating to Trickling Filters--General Requirements), in series with activated sludge.(c) SBC units may be installed in existing activated sludge basins to create a combination of fixed and suspended growth processes.(d) If a dual treatment system employs an SBC, the engineering report must include supporting data, calculations, process descriptions, and vendor information to describe how the proposed dual treatment system will provide the required treatment levels.(e) These designs may be subject to the requirements of §217.7(b)(2) of this title (relating to Types of Plans and Specifications Approvals).