To coordinate funding for public water systems in North Dakota, there is established a drinking water treatment revolving loan fund to be administered by the department. The loan fund is also authorized under section 1452(a) of the federal Safe Drinking Water Act, as amended. Grants from the federal government or its agencies, including the United States environmental protection agency, allotted to the state for the capitalization of the drinking water treatment revolving loan fund, and required state matching funds must be deposited in the drinking water treatment revolving loan fund in compliance with the terms of the grants. The principal of the grants must be available in perpetuity for providing financial assistance as allowed under the Safe Drinking Water Act. To the extent amounts in the revolving loan fund are not required for current obligations or expenditures, these amounts must be invested in interest-bearing obligations.