Membrane and Desalination Technologies - TCE Moodle Website

464 J. Qin and K.A. Kekre
Table 10.19
Operating conditions of the plant (46)
Parameter Sep 03 Oct 03 Nov 03 Dec 03 Jan 04 Feb 04
UF unit
Dosage of NaOCl in UF feed (mg/L) 6 6 6 6 6 6
Dosage of alum in UF feed (mg/L) 3.5 3.5 3.5 3.5 3.5 3.5
UF feed flow (m 3 /h) 2.25 2.0 1.9 1.9 1.7 1.7
UF permeate flow (m 3 /h) 1.8 1.5 1.4 1.4 1.2 1.2
UF recovery (%)
RO unit
80 75 74 74 71 71
Dosage of NaOCl in RO feed (mg/L) 2 2 2 2 2 2
Dosage of PT-191 in RO feed (mg/L) 2 2 2 2 2 2
RO feed flow (m 3 /h) 1.3 1.1 1.1 1.0 1.0 1.0
RO permeate flow (m 3 /h) 0.52 0.44 0.44 0.39 0.38 0.38
RO water recovery (%) 40 40 40 39 38 38
RO operating pressure (psi) 55 60 100 100 100 100
Normalized flux ( 10 6 Lm 2 h Pa) 29.4 22.8 20.5 18.0 17.5 17.5
7.3. Plant Performance
7.3.1. Characteristics of the Raw Feed Water
Raw feeds for hourly samples on different days and for composite sample of 24 hourly
samples on each day were characterized during March–August 2003. Overall ranges of the
analytical results are summarized in Table 10.20. Comparing the analytical results for hourly
samples with that of daily composite samples, the overall range of the composite samples for
each parameter was narrower than that of hourly samples. It indicated that the fluctuation of
raw water quality was wider with the time of the day than the daily average of different days.
Overall range of the analytical results for daily composite samples shows that levels of
ammonia, TOC, suspended solids, and conductivity as well as heavy metals, such as iron
and strontium of the raw feed were high.
7.3.2. Monitoring of Conductivity and pH Values in the Process
Figures 10.16 and 10.17 show conductivity of RO feed and permeate as a function of time
during the study. It can be seen that conductivity of the RO feed was in the range of
1,300–2,100 mS/cm and most of the time between 1,400 and 1,700 mS/cm. The RO permeate
conductivity ranged of 60–80 mS/cm when operating pressure was 55–60 psi during September–October
2003 as shown in Fig. 10.16. In Fig. 10.17, after the operating pressure was
increased to 100 psi, the permeate conductivity was better and ranged of 30–50 mS/cm in
November 2003, and then 35–75 mS/cm in December 2003. However, the permeate conductivity
suddenly increased to 120 mS/cm since 24 December, which was probably due to
serious fouling of the RO membranes. Later, integrity check on UF modules was conducted,
and a few broken fibers from one of the modules were found. After the damaged UF module