The MBR Book: Principles and Applications of Membrane

212 The MBR Book
Whilst the projected capital costs of the MBR plant were higher because of the
lower flux, this was more than offset by the additional capability offered by the MBR.
It is noteworthy that whilst Aberporth remains the only UK site where microfiltration
of sewage is employed abiotically, there were at least 44 MBRs for sewage treatment
operating in the UK by June 2005, 75–80% of these being Kubota and all but
two based on the single-deck membrane (Section 4.2.1).
Plant design and operation The stipulations regarding the Porlock plant were that it
should be a small-footprint plant, and able to disinfect substantially the sewage
whilst imposing little visible impact. The plant therefore had to be housed in a stonefaced
building identical in appearance to an adjacent farmhouse (Fig. 5.2). It comprises
four aeration tanks (Fig. 5.3), 89 m 3 in liquid volume size and having
dimension 3.3 m wide � 7.4 m long � 4.5 m deep. The actual liquid depth is
�3.8 m, the dimension allowing for future expansion to seven modules per tank.
The tank volume allows for the volume displaced by the membrane units, about
Permeate
lift pumps
Crude effluent
inlet
Blowers
4.
3.
Washing tank
Figure 5.2 A view of the MBR plant at Porlock
Fine screens
3 mm
Membrane units
Tidal storage
Figure 5.3 A schematic of the MBR plant at Porlock
2.
1.
Aeration tanks
1–4
Final effluent
out
Anoxic recycle
tank