Post on 28-Mar-2018
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RAINWATER HARVESTING
Projected Water Demand
10,000
11,000
12,000
10582
Projected Water Demand
in Peninsular Malaysia
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6,000
7,000
8,000
9,000
10,000
2010 2020
Domestic
Industrial
Mil
lio
n L
itre
sp
er
da
y
Year
8184
7101
9756
Source: NPP Infrastructure and Utilities
Technical Report, 2001 in Federal Dept. of
Town and Country Planning, 2005
Uneven people-water distribution
• Development/Industrialization
• Population growth
• People migration
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RAINWATER HARVESTING
In densely populated states, demand continues to rise but river
basins have reached their limit for maximum supply
For Selangor, there are four main sources of raw water for
processing into potable water and all has been utilized
• People migration
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One of the most precious resources taken for granted
Water wastage
Average domestic water consumption in Malaysia is higher than
that of developed countries (eg. 226 litres per person per day
(LPD) in Selangor and 274 LPD in Penang) compared to best
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RAINWATER HARVESTING
Average consumption in Selangor including water used outside
the home (workplace, school, etc) is > 300 LPD. The international
standard for recommended water usage is 165 LPD1
[1] School of Humanities, USM, Malaysia
(LPD) in Selangor and 274 LPD in Penang) compared to best
practice (100 LPD - Czech Republic) and more than twice the
average of Singapore, Australia or UK
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Inte
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Inte
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RAINWATER HARVESTING
INTENT
To encourage rainwater harvesting the will lead to reduction in potable
water consumption
WHAT ARE THE ADVANTAGES?
Environmental
Inte
nt
Inte
nt
• Reduces demand on treated water
• Reduces soil erosion & flooding caused by runoff
• Reduces peak flow discharge to drainage system
• One of the purest water source
• Not exposed to contaminants in the ground
• Rainwater is soft water
Environmental
Qualitative
Rainwater harvesting from rooftop catchments for use in cistern storage is not new. It has been an important source of water supply for domestic purposes in many rural areas in the past
Fe
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Fe
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RAINWATER HARVESTING
• 3 pilot projects carried out; Government office, Mosque and a residential house
• Designing and installing RW harvesting system for several schools
In 2004 NAHRIM (National Hydraulic research Institute of Malaysia) was established to conduct research of water hydraulic and water environmentF
ea
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yFe
asi
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ity
Malaysia is endowed with far more rainfall than our water demand
when compared with other countries.
Fe
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Fe
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RAINWATER HARVESTINGFe
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Fe
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NRNC
Achieve the following percentage reduction in potable water consumption:
• 1 point: For 15% or more
GBI Water Efficiency – Rainwater Harvesting
GB
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ria
GB
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ria
RAINWATER HARVESTING
• 1 point: For 15% or more
• 2 points: For 30% or more
RNC
Achieve the following percentage reduction in potable water consumption:
• 1 point: For 10% or more
• 2 points: For 30% or more
• 3 points: For 40% or more
• 4 points: For 50% or more
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Depending on the type of buildings, potable water usage may
include the following applications:
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Potable Water
The baseline consumption refers to all treated (potable) water
taken from the water mains
RAINWATER HARVESTING
• Toilets
• Landscape irrigation
• F&B
• Cooling tower make-up
• Swimming Pools and Water Features
• Laundry
• General Washing
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Factors that affect Rainwater Harvesting Design
Str
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sS
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• Daily rainfall intensity
• Rain events distribution
- continuous rainy days
- dry spells
RAINWATER HARVESTINGS
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Str
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- dry spells
• Available catchment
• Building water usage pattern
• Storage tank size
Str
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gie
sS
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Excess/overflow from heavy downpour or continuous rainy days (affected by the size of storage tank provided)
Unaccounted potable water use during prolonged dry spells
Rainfall - uncontrollable
RAINWATER HARVESTINGS
tra
teg
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Str
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s
Source: Jabatan Pengairan dan Saliran Malaysia
Str
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gie
sS
tra
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Catchment
Site/building design – catchment area constraint
Low rise
- high catchment/usage ratio
RAINWATER HARVESTINGS
tra
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Str
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s
- high catchment/usage ratio
High rise
– low catchment/usage ratio
– RWH design more challenging
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Building Water Consumption
Building type dependent
• Residential
• Non-residential (office, shopping etc.)
RAINWATER HARVESTINGS
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Str
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- Office (5 or 6-day week)
- Residential (7-day week)
- Retail/Hotels (7-day week)
- Irrigation (daily except rain event days)
Factors to consider are hours of occupancy and days of operation
� building baseline consumption is not addressed
Effectiveness of RW Harvesting is limited if:
Str
ate
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RAINWATER HARVESTINGS
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Str
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� harvested rainwater is not effectively used
Type of usage
• Garden Irrigation
• Toilet flushing
• Others (Air conditioning make-up, etc.)
Increased Usage High RWH ratio
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nt Principles of Water Management
� Conserve water
� Reuse water
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� Reuse water
� Know where and how water is used
� Continuous evaluation of water use
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Baseline potable water consumption has to be
improved.
� Use of water efficient fittings
For an effective of RW Harvesting system:
RAINWATER HARVESTINGB
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� Use of water efficient fittings
� Improve air conditioning system
design to reduce AC make-up water
requirement
� Waste water recycling
� AC condensate water recovery
Water Closets
> 6L per flush - inefficient
< 6L per flush – good
< 4.5L per flush - excellent
Urinals
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> 2L per flush - inefficient
Water Efficient Fittings
RAINWATER HARVESTING
< 4.5L per flush - excellent
Tap Fittings
> 6 L/min – inefficient
< 6 L/min – good
< 4 L/min - excellent
Shower heads
> 9 L/min – inefficient
< 9 L/min – good
< 6 L/min - excellent
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< 2L per flush – good
< 1L per flush - excellent
Water Conservation
Select low-flow water efficient fittings
Water usage in cooling towers:
Cooling Tower water make-up
1. Evaporation
2. Bleed
3. Drift losses
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RAINWATER HARVESTING
3. Drift losses
Evaporation
• Normal process
• To remove heat from the condenser water
Drift Loss
• Water lost due to water droplets entrainment in the air stream.
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Bleeding (blow-down)
• Controlled draining of water to prevent built-up of dissolved and suspended solids (to prevent corrosion and scaling)
• Dependent on quality of make-up water and effectiveness of water treatment system.
• Based on cycle of concentration (ratio of concentration of the
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RAINWATER HARVESTING
Water Conservation
Improved air conditioning system design:
• Reduced cooling load to lower condenser water flowrate
• Select /specify low drift-loss cooling towers
• Based on cycle of concentration (ratio of concentration of the dissolved solids in the condenser water to that of the make up water)
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Water Consumption comparison between baseline and design case
RAINWATER HARVESTINGB
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Description Baseline Design
Potable Water Consumption 40,556 22,090
Greywater Recycling - 4,176
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RAINWATER HARVESTING
Greywater Recycling - 4,176
Resultant Potable Water Consumption 40,556 17,914
Rainwater Harvesting 2,910 2,910
Ratio of RWH/Potable Water Consumption (%) 7.2% . 16.2% .
Total Potable Water Consumption 37,646 15,005
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Rainwater Harvesting System Components
Pre-storage filtration
Catchment
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RAINWATER HARVESTING
Storage
Post-storage filtration
Treatment
Operation
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Catchment
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RAINWATER HARVESTING
Pitched Tile Roof Metal Roof
RC Flat Roof Block Pavement
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Pre-storage filtration
The first rainfall may contain higher than average amounts of accumulated dust, industrial pollutants, bird and animal droppings, leaves and other debris, pre-storage filtration shall be provided to prevent risk of contaminants affecting rainwater quality.
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RAINWATER HARVESTING
rainwater quality.
- Install on downpipes to remove leaf and debris
Depending on the type of catchment area and the intended use of the rainwater, filtration may be required.
Leaf and debris screen
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First Flush
- Divert minimum 1mm of initial rainfall with first flush diverter or other suitable means
- Divert higher volume
First flush diverter to improve rainwater quality.
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RAINWATER HARVESTING
Exercise
- Divert higher volume of first flush rainwater if substantial pollution expected. C
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Post-storage filtration/treatment may not be required if the rainwater is used for garden watering or car wash.
For toilet flushing, laundry or similar uses, suitable method of filtration has to be provided to safeguard against odour, sediment and discolouration that may affect appliances or clothing.
Post-storage Filtration/Treatment
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RAINWATER HARVESTING
and discolouration that may affect appliances or clothing.
Post-storage treatment includes:
- Sediment filtration (remove suspended solids)
- Activated carbon (taste/odour/colour)
- Fine micron or membrane filtration (if human contact or consumption is envisaged)
- UV light treatment (if human contact or consumption is envisaged)
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De
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Design approach:
Intended use
Rainfall data
Available/required catchment
RAINWATER HARVESTINGD
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De
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Pre-treatment (first flush diversion amount)
Above in turn determines the size of rainwater storage tank required.
Catchment type (run-off coefficient)
Available/required catchment
Rainwater Harvesting applications
Landscape Irrigation
Toilet flushing
Laundry
De
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esi
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RAINWATER HARVESTING
Laundry
Others
• pools/ponds make-up
• cooling tower make-up
• general washing
De
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esi
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Increased Usage High RWH ratio
De
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Rainfall Data
Daily rainfall data can be obtained from JabatanPengairan dan Saliran Malaysia
RAINWATER HARVESTINGD
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De
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De
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With the defined catchment area, type of catchment and the
Collectible Rainwater
Dependent on:
• Catchment area
• Type of catchment
RAINWATER HARVESTINGD
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De
sig
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With the defined catchment area, type of catchment and the rainfall data, the following Rainwater Collection Calculation formula can be used to estimate the amount of rainwater that can be captured.
Rainfall Catchment Run-off Amount Litres of
in x area x Coefficient - diverted = rainwater
(mm) (m2) (%) (L) captured