Membrane and Desalination Technologies - TCE Moodle Website

466 J. Qin and K.A. Kekre
Fig. 10.17. Conductivity of RO feed and permeate vs. time from November 2003 to February 2004 (46).
Fig. 10.18. pH of RO feed and permeate vs. time from November 2003 to February 2004 (46).
was replaced and CIP on the RO membranes was conducted on 6 January 2004, the permeate
conductivity recovered to 35–75 mS/cm. At the end of the study, the salt rejection of RO
membrane remained 96%, indicating that the RO membrane had performed well and tolerated
organics from industrial wastewater.
Figure 10.18 shows pH (online) of the RO feed and permeate as a function of time from
November 2003 to February 2004. It can be seen that the RO feed pH was generally in the
range of 6.8–7.6. The RO permeate pH ranged of 5.5–6.6, which was 1.0–1.3 unit lower than
that of the RO feed. The situation of a lower permeate pH than the feed pH in an RO process
appears to be quite a common occurrence in water and wastewater treatment (18, 48–51),
which has been explained by the influence of HCO 3 elsewhere (50–51).