The effect of blending different water qualities on distribution system water quality was
investigated in a field study. Waters produced from five different treatment systems; aeration (G1),
nanofiltration (NF0 (G4), CSF-O3-GAC (coagulation sedimentation filtration-ozone-granular activated
carbon (S1), IMS (integrated membrane system)(CSF-NF, or S2) and high pressure RO were blended and
distributed to 18 different pilot distribution systems (PDS). G1, G4, and RO source waters were taken
from the same groundwater. The RO source was augmented with salts to simulate seawater. The S1and
S2 source waters were taken from the same surface water. The PDSs consist of PVC, galvanized, lined
ductile 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 suspended
biological 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 less
than other treatments. S1 and S2 AOCs are equal. PDS biostability order is G1<G4=S1=S2<RO. During
the wet season, raw surface water TOC (total organic carbon) increased significantly, and S1 AOC was
also increased. BDOC was not correlated to HPCs and BDOC sensitivity was not adequate to assess
biostability among treatments. PDS nitrification occurred in June and July 02 as the result of a loss of
residual at 25ºC to 30ºC 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 for
hetertrophs as the system became microaerophilic. AOC and PEPA assessment of biostability indicated
HP RO (high pressure reverse osmosis) increased biostability of finished water, but NF did not improve
biostability relative to advanced surface water treatment at normal conditions. Includes 17 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 640 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 17 |
| Published : | 06/17/2005 |
