The MBR Book: Principles and Applications of Membrane

Tensile elongation
retention (%)
100
80
60
40
20
Figure 4.25 A train of five PURON ® modules
0
0 500 1000 1500 2000
Ozone dose (mg/L day)
Commercial technologies 185
High-crystalline PVDF
Low-crystalline PVDF
Figure 4.26 Tensile strength against ozone loading, Microza ® fibre
(rated 0.1 �m), as determined by rejection of uniform latex (Fig. 2.4), and the high
tolerance to oxidative chemicals (Fig. 4.26). Tests conducted against both 0.5 wt%
sodium hypochlorite and 4 wt% sodium hydroxide have shown no significant decrease
in tensile strength over a 60-day period. This has been attributed by the suppliers to
the high crystallinity of the PVDF.
The MBR membrane module has been under development since 1999 and was
launched in June 2004. The rack comprises a number of vertical elements mounted
onto a steel frame (Fig. 4.27a), each module providing a membrane area of 25 m 2
and having dimensions of 150 mm diameter � 2 m. The fibres are potted at both
ends and gathered into bundles at the top of the element (Fig. 4.27b) to encourage
the escape of suspended matter. Air is introduced via a separate aerator and directed
into the element by a skirt fitted to the element base (Fig. 4.27c). A four-element