Development of Greywater Recycling and its Potential ... Seminar_DrMa.pdf · Development of...
Transcript of Development of Greywater Recycling and its Potential ... Seminar_DrMa.pdf · Development of...
Development of Greywater Recycling
and its Potential Applications in HK
Environmental Management Division
Principal Consultant
Dr. Anthony Ma
15th September 2010
Overview
• Hong Kong Water Supply
June 1963-May 1964
Severe Water
Rationing
“4 hours of supply
every 4 days”
1965
Water Supply Agreement
with Guangdong
68.2 MCM/year of
Dongjiang water supply
1989
Water Supply Agreement
with Guangdong
Maximum 1,100
MCM/year of Dongjiang
water supply
2006
Flexible supply of
Dongjiang water
2008
The current agreement,
which extended the use
of a package deal
approach in 2006, was
signed in 2008 for the
supply arrangement up to
2011.
Overview
• To prepare for the declining rainfall due to climate change
and the rapidly increasing water demand in the Pearl River
Delta region, the Government has formulated a Total Water
Management (TWM) strategy.
– Water Demand Management
• To enhance public education on water conservation
• To promote use of water saving devices
• To enhance water leak control
• To extend use of seawater for toilet flushing
– Water Supply Management
• To strengthen protection of water resources
• To actively consider water reclamation (including
reuse of greywater and rainwater harvesting)
• To develop the option of seawater desalination
Total Water Management
– Wastewater from
• kitchen, bath, washing basins and/or laundry,
• generally not contain significant concentration of
excreta (Source WHO Guidelines for the Safe Use of Wastewater, Excreta and Greywater)
– Does not include wastewater from toilet or urinal
– Blackwater
• Source separated wastewater from toilets,
containing feces, urine and flushing water
Definition of Greywater
Greywater provides a
constant source for recycling
• Abundance of Greywater
• Greywater quality - less effort to recycle
• Release pressure of limited freshwater supply
• Reduce amount of wastewater discharge to the environment
Why Re-use Greywater ?
Examples of Greywater Recycling
- Japan
• Some toilet fixtures are specifically designed for greywater collected from basin for toilet flushing.
Examples of Greywater Recycling
- Japan
• Two types of reclaimed water system can be found in Japan – centralized effluent recycling system and decentralized greywater recycling system
• Piping network (中水道) has been constructed by the Government.
• The reclaimed water can only be distributed to buildings near to the treatment works.
Ochiai Water Reclamation Center
(operation started in 1964)
Examples of Greywater Recycling
- Japan
• Decentralized greywater recycling system
– Newly developed area
– Incorporated with rain harvesting system to reduce the operating cost of system
765 Yen ~
HK$70 /m3
Examples of Greywater Recycling
- China
• Beijing : Hotel Nikko New Century - a five-star joint venture luxury hotel with 712 rooms
• The greywater recycling system, with capacity of around 300 m3/day (nearly half of fresh water consumption), was constructed in the basement of the building.
Hotel Nikko New Century
(operation started in 1999)
• Operating Cost: ~RMB 0.9
– fresh water cost has risen : RMB ~1 RMB 4.6
Examples of Greywater Recycling
- China
Activated Sludge
Disinfection
Toilet Flushing Irrigation Cooling Tower
Makeup Water Car Washing
Water from
tub
Water from
basin
Hotel Nikko New Century
Code of Design of Greywater Recycling
- China
• The code of design for greywater
recycling is included in the “Code of
Design for Building Reclaimed Water
System”.
• Various technologies are
recommended.
Can Hong Kong develop greywater
recycling?
1. How much greywater available for recycling?
2. Potential uses of reclaimed water?
3. Is it financially viable?
4. How to overcome the major constraints?
– Space
– Piping alteration
– Capital investment
– Operation and maintenance requirement
Non-domestic
33%
Flushing
8%
Domestic
59%
Non-domestic
33%
Non-shower
28%
Flushing
8% Shower
31%
Quantity of Greywater in Hong Kong
Fresh Water Consumption in Hong Kong (2008)
Total: 956 million m3/year
Source: WSD Annual Report 2008-09
Shower +
laundry +
kitchen
effluent
= greywater
~40%
Reuse
Cleansing
Process water
Cooling tower
Irrigation
Seawater flushing in Hong Kong
• Nearly 85% of population supplied with seawater for flushing in Hong Kong
• Extension of the use of seawater whenever it is economically justified – Pok Fu Lam, Tuen Mun East, Yuen Long, Tin Shui Wai and Tung Chung
Potential Applications
2. Irrigation 1. Toilet Flushing (for area
without seawater flushing) 3. Makeup Water for
Cooling Tower
6. Fire Water Tank 4. Street Cleaning 5. Water Feature
Pilot Study – Reclaimed water for
Irrigation
• The reclaimed water was used to irrigate about 3 m2 of
lawn for a period of two months
• The growth condition of the lawn was satisfactory
1st Month 2nd Month
Major Potential Users of Reclaimed
Water
• Residential areas without seawater flushing
• Campsites
• University campus
• Sport centres and amenity facilities
• Commercial buildings
• Hotels
• Shopping malls
Is Greywater Recycling Financially Viable?
Source Cost (HK$ per m3)
Dongjiang Water ~ HK$ 6
Seawater (for flushing) ~ HK$ 2.4
Reclaimed water from treated sewage ~ HK$ 7-8
Water from seawater desalination ~ HK$ 10
Reclaimed water from greywater recycling
(City U Project) ~ HK$ 1.5
Money saving from greywater recycling = HK$ (4.58+1.57) – 1.5
= HK$ 4.65 /m3
• EMSD Headquarters in
Kowloon Bay
• Biological and micro-filtration
treatment
• Design flow 25 m3 per day
• Reclaimed water for toilet
flushing
• Serve 2,500 persons
Examples of Greywater Recycling in HK
• TKO Area 86 Property Development
• Rainwater and Greywater Recycling
• Development Project : 50 residential towers
Examples of Greywater Recycling in HK
• Greywater collection system collects greywater from 4 residential towers to the greywater treatment plant
• Rainwater collection system from landscape area
• A condensate water collection system from shopping mall air conditioning
• Purpose : irrigation for 8 ha (400m3 per day)
HKPC Greywater Recycling System
Greywater Recycling System in CityU
Project Start: May 2009
Operation Start: January 2010
Designed Treatment Capacity: 7 m3/hr
Aim:
Reduction of the use of city water for irrigation
so as to achieve water conservation
Design Concept
Greywater Applications
SAF + Hollow Fiber
Membrane
Submerged Aerated Filter (SAF)
– Media are installed for the attached growth of micro-organisms
– Can hold a large amount of biomass and have a higher treatment efficiency
Micro-filtration (MF)
– Hollow fibre membranes of pore size 0.1-0.4 mm to separate clean water from the SAF effluent
– No sedimentation tank, so reducing the space required
– The treated water is crystal-clear, free of germs and odour
– Membrane can be automatically backwashed
Technologies Employed
• Disinfection
– To maintain a residual chlorine level to prevent re-growth of bacteria in pipes, a certain amount of chlorine disinfectant is dosed
Technologies Employed
• The process has been
patented
– HK Short Term Patent No.:
HK1095980
Superior Treated Water Quality
Raw Greywater Quality
Recycled Water Quality
Parameter Unit Range
pH pH units 7.09.1
Chemical oxygen demand mg/L 30380
Biochemical oxygen demand mg/L 2064
Ammonia nitrogen mg/L 4.15.3
Parameter Unit Mar 09 Aug 09 Sep 09 國家回用水標準 – 城市綠化
USEPA
Guidelines
pH pH units 7.2 7.2 7.1 6.0–9.0 6–9
Colour Pt-Co Units <5 <5 <5 <30 NA
Turbidity NTU 0.1 <0.1 0.1 <10 <2
Chemical oxygen demand mg/L 22 7 7 NA NA
Biochemical oxygen demand mg/L 4 <3 5 <20 <10
Ammonia nitrogen mg/L <0.1 0.3 0.2 <20 NA
Total Phosphorus mg/L 0.32 0.04 1.0 NA NA
Conductivity μS/cm 210 140 160 NA NA
Total residual chlorine mg/L 1.8 1.3 1.4 >1.0 >1
E.Coli cfu/100 mL <1 <1 <1 NA <1
Greywater Recycling System in CityU
CityU system demonstrates that:
• Little space required – System can be housed in a 580 ft2 basement plant room
• Minimal operation & maintenance
• Greywater collection – Piping alteration to collect greywater from ~60 hand-wash basins
and condensate from AHU
• Capital Investment – System cost : less than HK$1 million
– Piping alteration cost : over HK$1.5 million
• Operation cost – ~HK$1.5/m3 resulting in a money saving of HK$4.7/m3
Thank You