Unincorporated Community Wastewater Treatment Act of 1993 - Amends the Federal Water Pollution Control Act to authorize the Administrator of the Environmental Protection Agency to award grants for wastewater treatment to an unincorporated community that serves a population: (1) of 20,000 or fewer residents; and (2) with a median household income that is less than or equal to the median household income for non-metropolitan areas of the State in which the community is located. Sets the maximum Federal share of a grant at 75 percent of total project costs. Authorizes appropriations.