In addition to amounts otherwise available, there is appropriated to the Secretary of Health and Human Services (in this section referred to as the “Secretary”) for fiscal year 2021, out of any amounts in the Treasury not otherwise appropriated, $500,000,000, to remain available until expended, for grants to States and Indian Tribes to assist low-income households, particularly those with the lowest incomes, that pay a high proportion of household income for drinking water and wastewater services, by providing funds to owners or operators of public water systems or treatment works to reduce arrearages of and rates charged to such households for such services.