BAC Filtration Examples in Full-Scale Drinking Water Treatment Plants - Activated Carbon for Water and Wastewater Treatment - page 319

range of 0.40-0.48mg L -1 . BDOC was composed of 4-13% of readily biodegrad-
able substrate, 53-80% rapidly hydrolyzable substrate, and 16-33% of slowly
hydrolyzable substrate [8]. In BAC filtration the EBCT varied in the range from 10
to 30 min. The carbon grade Picabiol GAC (Pica Company, France) was used in
the operation. BAC filtration decreased the BDOC by about 0.19-0.27mg L -1 .
However, BAC filtration did not modify the refractory DOC that was present at
about 1.34-1.81mg L -1 in ozonated waters. This indicated that organic matter was
no longer adsorbed in filters that had been functioning for several years without
GAC regeneration [8].

10.2.4
Ste Rose Plant in Quebec, Canada

In BAC filtration in the Ste Rose treatment plant (Quebec, Canada), where river
water (Milles Iles River) is treated by flocculation, settling, rapid sand filtration,
ozonation, BAC filtration, and final disinfection with chlorine dioxide, the tem-
perature was shown to affect the performance significantly. For temperatures
between 1 and 10.0 1 C, average BDOC was 0.32mg L -1 in the inlet water before
ozonation and 0.20mg L -1 in the outlet water. BDOC levels showed seasonal
variability. For temperatures between 10.0 1 C and 25.5 1 C, average BDOC was
0.54mg L -1 in the inlet water and 0.21mg L -1 in the outlet water [8].

10.2.5
Plant in Z¨rich-Lengg, Switzerland

The full-scale treatment plant at the water works Lengg comprises preozonation,
rapid sand filtration, ozonation, GAC filtration, and slow sand filtration.
Figure 10.3 shows the seasonal changes in the raw water fed to this plant. The
major part of the organic carbon in the raw water stems from humic material. As
Lake Zurich water is relatively clean, the highest DOC concentration during the
whole pilot study was 1323 m gL -1 . In the same plant, after preozonation, AOC
increased about threefold to an average concentration of 171 7 57 m gCL 1 and
decreased almost to the original level after sand filtration [9].
The pilot plant which simulated the full-plant operation includes prefiltration of
raw water, ozonation, GAC filtration, and ultrafiltration steps. It was shown that
prefiltration had no influence on NOM fractions. LC-OCD chromatograms of raw
water and ozonated water showed that ozonation transformed higher-molecular-
weight compounds (humics) to lower-molecular-weight compounds (building
blocks, LMW humics). The SUVA of humics was about 40% lower in the ozonated
sample than that in the raw water. Except for the biopolymers, there was a
decrease in all NOM fractions from the top to the bottom of the GAC filter in the
flow direction. However, the biopolymer fraction was not removed during startup
or after 5 months of GAC filtration in spite of development of biological activity.
Therefore, this fraction was regarded as nonbiodegradable and nonadsorbable [10].
However, this fraction was generally less than 10% in the raw water.