The MBR Book: Principles and Applications of Membrane

Table 3.11 Cleaning protocols for the four MBR technologies, PLWTP
Kubota Mitsubishi Rayon Zenon Memcor
carbon (TOC) and chemical oxygen demand (COD) concentrations were respectively
�2 mg/L, �9 mg/L and �31 mg/L. Silt density index (SDI) values measured for the
Kubota MBR effluent during Phase I ranged from 0.9 to 1.1. Effluent from the Kubota
MBR was treated downstream using Saehan BL and Hydranautics LFC3 reverse osmosis
membranes. These were operated with minimal fouling during operation on raw
wastewater and advanced primary effluent. The average net operating pressure of
the Saehan 4040 BL (low-pressure) RO membranes measured during testing was 3.
1 bar, and that of the Hydranautics LFC3 (fouling resistant) RO membranes measured
during testing was 8.3 bar. A 1–2 mg/L dose of chloramine in the RO feed was
effective at mitigating membrane biofouling.
3.2.4 Bedok Water Reclamation Plant, Singapore
Design 141
Recovery
Reagents NaOCl, 0.5% NaOCl, 0.3% NaOCl, 0.2% NaOCl,
used Oxalic acid, 1% Citric acid, 0.2% Citric acid,
0.2–0.3%
(pH 2–3)
100 mg/L as Cl2 Protocol CIP by soaking CIP by flushing Tank drained and Tank drained and
for 2 h; reagents through for 2 h membranes hosed membranes rinsed
applied and soaking for down with water; with water for
consecutively 2 more hours membranes 10 min; membranes
backpulsed with flushed through
reagent until with reagent then
flux stable soaked for 4 min
Maintenance
Reagent Concentration Duration
Zenon NaOCl 250 mg/L 10–15 s � 3
backpulses at
55 LMH, 30 s
relaxation
between pulses
This trial arose from the Singapore NEWater project under the auspices of the Centre
for Advanced Water Technology of the Singapore Utilities International Private
Limited, a wholly owned subsidiary of Singapore Public Utilities Board. The work is
intended to produce high grade water of drinking water standards, called NEWater,
from municipal effluent to ensure a diversified and sustainable water supply. The
project began in 2000 with the installation of ultrafiltration/microfiltration (UF/MF)
plants for polishing secondary sewage prior to RO treatment. The MBR/RO option
has been explored with trials of three MBR pilot plants operating simultaneously.
The three technologies are unspecified in the report produced (Tao et al., 2005) but
have membrane properties similar to those of the Kubota, Zenon and Mitsubishi
Rayon products. The plants were commissioned in March 2003 and fed throughout
with primary settled sewage (Table 3.12).