Three identical bench-scale OMBRs n

Three identical bench-scale OMBRs named OMBR1, OMBR2
and OMBR3 were operated in parallel in this study. As shown
in Fig. 1, an FOmembrane cell and a separated bioreactor with
an effective volume of 0.9 L were used in each OMBR system.
The membrane cell had two same channels (length, width and
height of 75, 45 and 40 mm) divided by a unique plate-andframe
FO membrane with an effective membrane area of
34 cm2. The cellulose triacetate (CTA) FO membranes with an
embedded polyester screen mesh (HTI, Albany, OR) were
applied in the OMBRs. Considering the fact that membrane
orientation plays a significant role in FO applications, the
“active layer facing feed ” (AL-FS) orientation was employed in
order to avoid aggravating fouling especially pore-clogging in
the support layer (Lay et al., 2011). The draw solution flew
from the upper channel to the draw tank, while the activated
sludge was recirculated from the bioreactor to the bottom
channel. As for the bioreactor, the municipal wastewater was
continuously pumped in, and the aeration of 0.5 m3 h1 was
provided through an axial perforated tube. In order to maintain
a constant water level in the bioreactor, the influent
pump was controlled by a water level sensor. In each OMBR
system, analytical grade sodium chloride (NaCl) with a concentration
of 1.0 M was used as the draw solution, which was
recirculated at a flow rate of 0.28 L min1 from a 2 L glass
reservoir through the upper channel and back to the reservoir.