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