CONSIDERATIONS FOR SIZING EQUALIZATION BASINS FOR SFBW HANDLING: CLEVELAND CASE STUDY

Due to stricter regulations governing the handling of spent filter backwash water (SFBW) by recycling, sewer discharge or surface water discharge, equalization (EQ) basin size requirements for processing SFBW at many WTPs have changed. Many states limit the allowable SFBW recycle ratio to 10 percent or less of the plant inflow, while tougher NPDES permit requirements and sewer authorities require closer monitoring of WTP waste discharges. Each of these factors has the potential to alter the rate of release (treated or untreated) of SFBW, which could directly affect the overall volume of equalization storage required to maintain filter operations. Because of these new limitations, a review of EQ sizing should be conducted to determine if addition of equalization capacity is necessary. This document provides an outline of the basic design procedure required for calculating the EQ basin storage volume required.