The MBR Book: Principles and Applications of Membrane

184 The MBR Book
Sealed end
Membranes
Central
aeration
Germs
Bacteria
Filtrate
Filtrate
Backwashing
Braid
Membrane
of the fibres only at the base, with the membrane filaments individually sealed at the
top (Fig. 4.24a). Scouring air is injected between the filaments intermittently by
means of a central air nozzle at the module base so as to limit the degree of clogging
at the module base. The free movement of filaments at the top of the module is
designed to allow gross solids, such as hair and agglomerated cellulose fibres, to
escape without causing clogging in this region. The fibres are strengthened by an
inner braid, since the lateral movement of the filaments subjects them to a certain
degree of mechanical stress. In the normal operational mode, aeration is applied for
between 25% and 50% of the operation at a SAD m of 0.15–0.35 Nm 3 hairperm 3
permeate.
Filtrate is withdrawn from the manifold at the base of the cylindrical element
which also houses the aerator (Fig. 4.24a). The individual fibre bundles are 2 m high
and currently provide a membrane area of ~3.3 m 2 . In a commercial system these
bundles are connected in rows (see Fig. 4.24b). Several of these rows are mounted
into a stainless steel frame forming a membrane module (see Fig. 4.25). The
PURON ® module is available in standard sizes of 500, 235 and 30 m 2 membrane
area. The footprint of the 500 m 2 module is approximately 2 m 2 .
4.3.5 Asahi Kasei Chemicals Corporation
Filtrate
Membrane
bundle
Filtrate
Air Air
(a) (b)
Fibre support
Figure 4.24 PURON ® membrane (a) element and (b) row
Asahi Kasei Chemicals Corporation is part of the Asahi Kasei group in Japan. The
company has been manufacturing HF UF/MF membranes and modules for various
industrial applications since the 1970s. The Microza ® PVDF MF membrane for
water treatment applications was introduced in 1998, and Asahi Kasei Chemicals
currently produces a million square metres of MF membrane each year, mainly for
drinking water treatment. The Microza ® membrane module has been used as a
classic pressurised module by Pall Corporation in their industrial and municipal
water treatment systems, providing about 500 MLD potable water capacity from
over 50 membrane filtration plants in the USA alone, as of May 2005. Key features
of the 1.3 mm o.d. Microza ® membrane fibre are the narrow pore size distribution