NAMS 2002 Workshop - ICOM 2008

MBR systems typically operate with a MLSS concentration ranging between
5,000 to 30,000 mg/L, a turbidity range of 3,500 to 20,000 NTU (eqn. 1).
Membrane directly filters such mixed liquor and produce clean permeate with a
turbidity of around 0.1 NTU, achieving LRV>4.5. The resolution of standard
turbidimeter is about 0.01 NTU, therefore with the meter it is easy to measure
LRV of 5.
Integrity monitoring in MBR
An integral membrane module consisting of 2000 fibers was used in MBR to filter
mixed liquor with a SS of 12,500 mg/L. The baseline turbidity was recorded as
0.06 NTU. Then 1, 2 and 5 fibers were cut respectively at the top end. The
results of this test are shown in the table below. From the PDT results, poor
permeate turbidity and fecal coliform results were expected. However, on-line
turbidity meter recording shows an initial surge in turbidity, but turbidity of
permeate rapidly dropped back to less than 0.2 NTU.
Number of cut fibers at top end 1 2 5 Loss of pressure in PDT (kPa/min) 30 60
~120 Peak turbidity(NTU) 1.993 1.349 2.4 Average turbidity 24h (NTU) 0.136
0.147 0.196 Fecal coliforms in permeate(cfu/100 mL)