Notwithstanding the provisions of section 7-249, any municipal water pollution control authority which constructs any sewerage system or portion thereof, with federal financial assistance under the provisions of the federal Water Pollution Control Act Amendments of 1972, P.L. 92-500, as from time to time amended, may, in lieu of or in addition to, levying benefit assessments in accordance with the provisions of said section 7-249, assess industrial users of the portion of the sewerage system constructed with federal financial assistance for the cost of construction of such portion to the extent such cost is attributable to the treatment of such industrial users’ wastes. In determining such assessments, the municipal water pollution control authority may establish such classifications as may be approved by the administrator of the United States Environmental Protection Agency and the Commissioner of Energy and Environmental Protection.