RO/NF

UF

MBR

ChemicalsC A S E S T U DY
RO | UF | MBR |Wastewater Treatment
Hong Kong, China

Wastewater Treatment Upgrade with Toray MBR
at Mui Wo Sewage Treatment WorksPROJECT BACKGROUND

Mui Wo is a rural town located in Lantau Island,Hong Kong, with one of its main attractions being
Silver Mine Bay and Beach. Rises in population andtourism to this region have resulted in an increased
volume of sewage and the need to upgrade theexisting wastewater treatment system.
Mui Wo Sewage Treatment Works (MWSTW) wascommissioned in 1985 to treat sewage water via
conventional secondary treatment consisting ofscreening and de-gritting facilities, an oxidation
ditch, and ultraviolet (UV) disinfection. With acapacity of 1,190 cubic meters per day, MWSTW
treats wastewater from Mui Wo's sewerage
network, septic waste collected by private
contractors and the Food and Environmental
Hygiene Department, and sludge from other
Drainage and Ser vices Depar tment (DSD)
treatment works. The plant would not have theextra capacity to treat the increasing volume ofwastewater, increasing the risk of poor effluent
quality that would contaminate nearby beaches.

Figure 1: Mui Wo Sewage Treatment Facility
Table 1 — Quick Facts
Plant design

4 trains with 7 modules per train

Model

TMR140-400DW

Start-up

March 2016
Avg. dry weather flow: 3,700 m3/day

Design capacity

Peak wet weather flow: 7,400 m3/day

Design influent
quality

BOD
COD
TSS
NH3-N
TKN

629 kg/day
1,332 kg/day
666 kg/day
85 kg/day
170 kg/day

Design effluent
quality

BOD
SSTN
E. coli count/100 mL<20 mg/L<30 mg/L<10 mg/L (annual average)<100 (monthly average)

Actual effluent
quality

BOD
COD
TSS:<3 mg/L
<10 mg/L<3 mg/LOEM
Consultant

03-HK-MB2-MuiWo-202108

Biwater Man Lee

Hong Kong's Special Administrative Region (SAR) government
expanded the existing wastewater treatment plant to provide publicsewerage services to Mui Wo and surrounding villages and protect
the water quality of Silver Mine Bay.
PROJECT DETAILSToray partnered with Biwater Man Lee, a local E&M contractor
approved by the DSD of Hong Kong SAR. Biwater won thecontract for the upgrade needed at MWSTW with Sum Kee CEC
Joint Venture, the main contractor. The improvement would
replace the existing oxidation ditch with a membrane bioreactor(MBR) system and significantly reduce the system footprint while
producing higher quality effluent. The MBR system would use
Toray's flat-sheet MBR technology for the final design.
MEMBRANE BIOREACTOR
The MBR system is designed to handle a peak flow of 0.086 cubic
meters per second. The system incorporates pre-treatment using a3-millimeter punch-hole drum screen (2 duty, 1 standby), four MBR
trains (3 duty, 1 standby), and ancillary equipment. Each of the trains
has an anoxic and aeration tank that houses the MBR modules.

AECOM

1 of 2Wastewater Treatment Upgrade with Toray MBRat Mui Wo Sewage Treatment WorksC A S E S T U DY
RO | UF | MBR |Listed below are some of the key characteristics
and advantages of Toray MBR model TMR140400DW at MWSTW:•Toray's proprietary polyvinylidene fluoride(PVDF) microfiltration membrane provides
high resistance to chemicals and superiormechanical strength;•The membrane pores, with a nominal size of
0.08 micrometers, are uniformly distributed
along the surface, delivering high quality andvolume of filtrate;•One unit consists of four element blocks ina double-deck arrangement for a total of560 square meters of membrane area permodule;•The double-deck arrangement helps increase
the aeration efficiency and was integral tosaving system footprint with the given limited
space at the plant;•Less chemical cleaning is required. Membrane performance can be restored byallowing the membranes to relax for one minute in every 10-minute cycle, further
reducing operational costs.

Figure 2: Mui Wo Sewage Treatment Works with Toray MBR

START-UP AND OPERATIONThe operation of the membrane modules started up in 2016. Due to the ongoing
construction and because the sewage treatment plant was built along the water,
the plant experienced seawater intrusion. Salinity levels in the feed increased to ashigh as 18,000 ppm causing corrosion of some stainless steel SS316 components
throughout the plant, including the manifolds on some of the MBR modules.
Eventually, sludge leaked into the permeate side and resulted in high turbidity
levels. In response, Toray provided replacement parts made of polypropylene andbrought the MBR system online without interrupting operations for an extended
amount of time.
Toray MBR modules allowed the trains to run independently and efficiently and treat
the plant's anticipated increase of influent flow.
When the DSD took over operations in 2019, the Mui Wo Sewage Treatment Works was thelargest active MBR plant in Hong Kong.

Figure 3: Double-deckarrangement of TMR140-400DW.

TORAY INDUSTRIES, INC.
Head Office: Nihonbashi Mitsui Tower 24th Floor, 1-1, Nihonbashi-Muromachi 2 chome, Chuo-ku,Tokyo, 103-8666, JAPANwww.water.toray+81 3 3245-4542

LinkedInYouTube

Marks designated with a ™ or ® are trademarks of Toray Industries, Inc.
All information presented herein is believed reliable and in accordance with accepted engineering practices. Toray makes nowarranties as to the completeness of this information. Users are responsible for evaluating individual product suitability forspecific applications. Toray assumes no liability whatsoever for any special, indirect or consequential damages arising from thesale, resale or misuse of its products. © 2021 Toray Industries, Inc. Subject to change without notice.
03-HK-MB2-MuiWo-202108

2 of 2