The MBR Book: Principles and Applications of Membrane

TMP (Kpa)
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has been maintained between 8–12 g/L, at an SRT of �30 days, regardless of feedwater
quality and organic loading (0.46–1.5 kg COD/m 3 /day). The sludge yield is
around 0.27 kg SS/kg COD. Purification performance by the plant is very satisfactory.
Removals achieved by the MBR are 96% COD, 97% TOC, 92% TKN, 71% TN and
97% BOD5, combined with very low silt density index (SDI) of below 2. These values
equate to average values of 35.2 mg/L, 20.2 mg/L and 6.5 mg/L for permeate COD,
TOC and BOD, respectively. The RO permeate had a TOC of �2 mg/L, satisfying the
stringent requirement for water reclamation.
At capacity, the plant achieves an MBR flux of 24.5 LMH; the mean net flux is
21.5 LMH, maintained by backwashing for 30 s every 15 min and applying a recovery
clean every 3 months with sodium hypochlorite. The average TMP is 0.08–0.12 bar,
considerably below the maximum allowable value of 0.55 bar, or 55 kPa (Fig. 5.31).
The success of the Bah-Teh plant has led to other similar effluent treatment plant
being installed or planned. The TFT–LCD plant at Longtan, Taoyuan County was
commissioned in May 2003 and is designed for a peak flow of 4.2 MLD from 20 cassettes
of 20 ZeeWeed ® 500c modules in four trains, providing a total membrane
area of 8800 m 2 . The planned installed capacity for VDU fabrication effluent was
50 MLD by 2005, with a 22.5 MLD plant due for commissioning in May 2006.
Installations include two MBR-RO plants, of 5 and 1.5 MLD capacity commissioned
in 2004 and 2005, respectively, which are fitted with anaerobic pretreatment to
contend with the high COD loadings.
5.3.2 Mitsubishi Rayon Engineering
TMP
Flow rate
Maximum membrane TMP
Figure 5.31 TMP and pressure transients over winter season, Bah-Teh MBR plant
Case studies 245
5.3.2.1 Early Japanese installations
Mitsubishi Rayon has almost as many installed plant in Japan as Kubota. The plants
tend to operate at slightly lower fluxes than those of many of the other MBR technologies,
but this is countered to a large extent by the lower cost of the membrane.
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Flow rate (m 3 /h)