S.D. Codified Laws § 9-48-29
Any funds, fees, rentals, charges, or rates collected under the authority of §§ 9-48-26 to 9-48-28, inclusive, shall be remitted to the finance officer by the officer charged with their collection at least once each month and shall be kept in a separate fund to be known as the sewer rental fund. Such fund shall be used for the purpose of paying the cost of financing the operation, maintenance or construction of the sewer utilities. However, no part of such fund may be used to meet the cost of construction of lateral sewers serving local territory or the portion of the cost of sewer utilities which have been financed by special assessment against benefited properties. Surplus funds may be transferred in the manner described in chapter 9-21.
SDCL 9-48-29