Support collections, in cases in which an assignment has been made to the department and after the support payment has been made to the appropriate collection agent pursuant to this article, shall be paid directly to the state department and distribution shall be made by the state department in accordance with the provisions of the Social Security Act and amendments thereto. Support collections in cases where there is not an assignment to the department but services are otherwise being provided pursuant to the requirements of Title IV-D shall be accounted for and distributed by the state department in accordance with rules published and provided by the department. When an obligor is subject to more than one support order being enforced by the department and the amount received from the obligor for distribution is not sufficient to satisfy the total amount due under all of the orders, distribution of current support shall have priority over any past due support. Where two or more orders for current support against an obligor are being enforced by the department and the amount received from the obligor is not sufficient to satisfy all current support due, the state department shall allocate a pro rata share of the total amount received to each family for whom support is being enforced by the department. When two or more support orders are being enforced against an obligor by the department, more than one of which has an accumulated arrearage, and the total amount collected is in excess of the amount sufficient to satisfy current support due under all of the orders, but is insufficient to satisfy all arrearages due, the department shall allocate a pro rata share of the amount collected, over and above the amount needed to satisfy the current support, to each family for whom support is being enforced and to whom an arrearage is owed. Distribution shall be made based upon the percentage of the total amount required to satisfy all of the respective support orders multiplied by the total amount available for distribution. The State Treasurer shall deposit collections of support received by the state department into a separate interest-bearing account. The State Treasurer shall at the end of each quarter credit any and all interest accruing on the interest-bearing account to the Public Welfare Trust Fund. The interest shall be used for general welfare purposes and is appropriated for those purposes.