Wherever any assessment or installment thereof shall become delinquent, the city treasurer shall enforce the collection thereof in the same manner as provided in chapter 9, Laws of 1933 [as codified in chapter 35.50 RCW], or such other laws as may be hereafter enacted for the foreclosure of delinquent local (physical) improvement assessments. All assessments or installments unpaid at the expiration of the time fixed herein for the payment of the same, shall bear interest at the rate of ten percent per annum, from said date until paid.