The MBR Book: Principles and Applications of Membrane

142 The MBR Book
Table 3.12 Feedwater quality, Bedok WRP
Parameter (mg/L) Concentration
Ammonia-N 33
BOD5 99
COD 265, of which 109 soluble
TKN 33
Total P 9.2
Table 3.13 Design and O&M data, Bedok WRP
Parameter MBR A MBR B MBR C
Membrane 0.4 �m FS, 0.8 m2 0.4 �m HF, 280 m2 0.035 �m HF, 31.5 m2 panel area element area element area
Probable technology Kubota, double deck Mitsubishi Rayon Zenon (500d)
Membrane area (m2 )
Tank sizes
480 1120 1008
Anoxic tank volume (m2 ) 30.8 37.5 25.2
Aerobic tank volume (m2 ) 11.4 – 27.9
Memb. tank volume (m2 ) 32.8 37.5 21.8
O&M
MLSS g/L 6–12 6–14 4–13
Net flux (LMH) 13–28.4 (26) 16–24 (24) 6.2–29.3 (12.4)
Initial TMP 4 17 10
Cycle (min) 9 on/1 relax 13 on/2 relax 12 on/0.5 backflush
�relax
Cleaning cycle time (day) 90 120 3.5*
Chemical cleaning reagents 0.6% NaOCl 0.3% NaOCl NaOCl
1% oxalic acid 2% citric acid (citric acid)*
Derived data
SAD p (m 3 air/m 3 ) permeate 28–50 (50) 16–24 (24) 20–30 (30)
Initial permeability (LMH/bar) 650 66 124
SAD p (m 3 air/m 3 permeate) (energy demand, kWh/m 3 )
Baseline 50 (1.4) 24 (1.3) 30 (1.7)
High flux 34 (1.2) 21 (1.0) 25 (1.3)
Low aeration 28 (1.0) 16 (0.8) 20 (1.1)
*Maintenance cleaning employed; citric acid cleaning suspended after 11 months.
The MBR plants are described in Table 3.13. The plants were all of around 75 m 3
total tank and all were submerged MBRs with a separate membrane tank. The baseline
HRT and solids retention time (SRT) values were respectively 6 h (hence 300 m 3 /day
flow) and 21 days for all tanks, and the target MLSS was 10 g/L. An ex situ clean was
only carried out once on MBR A and only due to failure of the aeration system.
Following operation for 2–3 months under baseline conditions the flux was increased
for an unspecified period and following this the aeration reduced for another
unspecified period. It is not clear whether the conditions identified were optimal.
According to the analysis conducted, MBR B (assumed to be Mitsubishi Rayon) was