Membrane and Desalination Technologies - TCE Moodle Website

Membrane Processes for Reclamation of Municipal Wastewater 457
Figure 10.12 shows conductivities of RO feed and permeate at the plant throughout the
study. The conductivity of RO feed was in the range of 780–2,310 mS/cm while the
corresponding conductivity of RO permeate was 12.1–49.3 mS/cm. The results indicated
that the RO membrane performance in terms of salt rejection was stable in the range of
98.1–98.8% throughout the 5-month study.
6.3.2. Online Monitoring of RO Permeate TOC
Figure 10.13 shows the online TOC of RO permeate during 16 May–26 June 2004 when
the permeate from MBR-A was used as the RO feed. It can be seen that TOC was in the range
of 23–32 ppb during 16 May–10 June. A high peak of TOC over 60 ppb appeared on 27 May,
which was probably because the wastewater influent received a spike of nonbiodegradable
organic that was capable of passing through the RO membrane. Then, TOC level slightly
increased at 26–37 ppb during 11–23 June, which might be due to change of the feed TOC.
Figure 10.13 also illustrates that the peak valley of TOC appeared daily. It might be due to
high and low loading of influent to the wastewater treatment works. Also, it is well understood
that the pattern of the TOC peak valley is consistent with the daily life of human beings
as the raw sewage is from domestic sources.
6.3.3. RO Permeate Quality at Different Fluxes
Table 10.16 shows analytical result of RO permeates at different fluxes of the RO
membrane, where the operating pressure was adjusted while the RO system recovery was
remained as 50%. At the flux of 17 L/m 2 h, RO permeate quality in terms of total dissolved
solids (TDS), B, Ca, Na, Cl, F, NO3, and SiO2 were relatively high. With an increase in the
membrane flux, RO permeate quality became better than that at 17 L/m 2 h. Higher operating
Fig. 10.12. Conductivities of RO feed and permeate vs. time (33).