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The effect of blending different water qualities on distribution system water quality wasinvestigated in a field study. Waters produced from five different treatment systems; aeration (G1),nanofiltration (NF0 (G4), CSF-O3-GAC (coagulation sedimentation filtration-ozone-granular activatedcarbon (S1), IMS (integrated membrane system)(CSF-NF, or S2) and high pressure RO were blended anddistributed to 18 different pilot distribution systems (PDS). G1, G4, and RO source waters were takenfrom the same groundwater. The RO source was augmented with salts to simulate seawater. The S1andS2 source waters were taken from the same surface water. The PDSs consist of PVC, galvanized, linedductile iron and cast iron pipes taken from existing distribution systems and had a 5-day HRT.Chloramines were added to meet CT and residual requirements. AOC (assimilable organic carbon),BDOC (biological dissolved organic carbon), HPC (heterotrophic plate count)are measures of suspendedbiological activity. PEPA (potential of exoproteolytic activity) measures attached film bioactivity.The S2 and G4 AOC are essentially equal, but the RO (reverse osmosis) AOC is reduced and lessthan other treatments. S1 and S2 AOCs are equal. PDS biostability order is G1G4=S1=S2RO. Duringthe wet season, raw surface water TOC (total organic carbon) increased significantly, and S1 AOC wasalso increased. BDOC was not correlated to HPCs and BDOC sensitivity was not adequate to assessbiostability among treatments. PDS nitrification occurred in June and July 02 as the result of a loss ofresidual at 25C to 30C and pH 7.8 to 8.3. During nitrification, the HPC values increased significantly,DO (dissolved oxygen) decreased; nitrification was nearly complete, which provided a carbon source forhetertrophs as the system became microaerophilic. AOC and PEPA assessment of biostability indicatedHP RO (high pressure reverse osmosis) increased biostability of finished water, but NF did not improvebiostability relative to advanced surface water treatment at normal conditions. Includes 17 references, tables, figures.

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Edition: Vol. - No. Published: 06/17/2005 Number of Pages: 17 File Size: 1 file , 640 KB