Practical and theoretical guidelines for implementing the extended terminal subfluidization wash (ETSW) backwashing procedure

Extended terminal subfluidization wash (ETSW) is an advanced granular media filter backwashing strategy that can be employed for reducing or even eliminating the filter ripening turbidity spikes commonly encountered immediately after restarting a backwashed filter. ETSW is based on sound scientific principles, but there is not yet sufficient data and experience for making precise a priori predictions of the optimum ETSW rates under the varying conditions found in practice. ETSW is like many other water treatment strategies in the sense that it must be tailored to a treatment plant's unique operating conditions, and the technique may also need to be adjusted periodically to accommodate changes in the treatment process. The purpose of the following correspondence is to inform current and future users of the ETSW backwashing process of the underlying scientific principles and of a rational procedure that can be used in the implementation and optimization of this technique for use in any water treatment plant. Future experiences with the ETSW approach could provide more insight into how to most efficiently and effectively apply this technique.