A COMPREHENSIVE BENCH SCALE STUDY TO EVALUATE CHLORAMINE STABILITY AND DBP FORMATION IN DISTRIBUTION SYSTEM CARRYING BLENDED STREAM OF DESALINATED AND TREATED SURFACE WATERS

摘要

The San Diego County Water Authority (Water Authority) is planning to accept desalinatedseawater (DSW) from Poseidon's proposed 50 mgd seawater desalination plant in Carlsbad,California, at some point in the future. Water Authority intends to blend disinfected DSW withTwin Oaks Valley Water Treatment Plant (TOVWTP) treated surface water (TSW) in theTOVWTP's Clearwells. In the short term, DSW may also be blended with treated water from theMetropolitan Water District (MWD) in one of the Water Authority's distribution pipelines.While DSW will provide an important new source of drinking water for San Diego Countyresidents, several factors must be considered to ensure that the introduction of DSW into theWater Authority's system will not adversely impact water quality. A comprehensive bench-scalestudy was conducted to evaluate the impact of DSW bromide level on chloramines decay anddisinfection stability, quantify the amount of chlorine boosting necessary to maintain a targetchloramine level after blending, determine boosting location(s) to minimize operating cost andevaluate disinfection byproduct formation potential for blended streams of DSW and TSWs. Thispaper presents testing methodology and outcomes of the study. The information presented in thispaper will provide a great value for agencies and consultants who are considering use ofseawater desalination as a means to supplement current water supplies and plan to introducedesalinated seawater into their existing distribution system.