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Membrane Processes for Reclamation of Municipal Wastewater 467
7.3.3. Monitoring of TOC in the Process
Figure 10.19 shows TOC (online) of the RO permeate as a function of time during
September 2003 to January 2004. It can be seen that the online TOC fluctuated significantly.
The lowest TOC was 75 ppb in October 2003, and the highest TOC was higher than 500 ppb.
High TOC was found during weekdays, probably due to high loading of organics and upset
operation of sewage treatment. However, TOC of the RO permeate was well below 500 ppb
for most of the time. It was below 200 ppb at most of the time in December 2003 before 25th
and in January 2004.
Table 10.21 shows the results of TOC retention in UF and RO processes during the study.
DOC reduction in the UF process was observed. It is because natural organic matters (NOMs)
are negatively charged and the dosage of alum into the raw feed water favors the formation of
insoluble charge-neutral products due to charge neutralization between cationic aluminum
Fig. 10.19. TOC (online) of RO permeate vs. time from September 2003 to January 2004 (46).
Table 10.21
TOC removal in UF and RO processes (46)
Date DOC of raw
feed (mg/L)
TOC of UF
permeate (mg/L)
TOC retention
in UF (%)
TOC of RO
permeate (mg/L)
19/09/03 16.8 14.6 13 0.51 96.5
07/10/03 27.8 22.8 18 1.84 90
16/10/03 34.4 24.9 28 3.54 76
17/11/03 Not measured 21.4 – 3.83 82
18/11/03 Not measured 38.6 – 3.21 92
17/12/03 56.7 37.6 34 3.11 92
24/12/03 19.6 18.1 8 0.52 97
30/12/03 33.4 29.1 13 8.50 71
08/01/04 42.0 17.8 58 1.12 94
TOC retention
in RO (%)