WATER OPTIMIZATION IN SUSTAINABLE ENEGRY

RESIDENCES

1

Sri Lanka Sustainable Energy Authority

2

World Fresh Water Consumption Demand Variation

3

World Population Variation

• Widely believed that the nextworld war will be on waterand there will be increasingconflicts on water world overday by day.

.

4

Charges for Water supply and production Cost of water

5

To provide Pipe Born Water Supply Facility

NWSDB Spends: Rs. 175,000 - 340,000/family

NWSDB Charge: Rs. 18,000 - 25,000 / family

(Domestic)

NWSDB spends nearly Rs. 159 of Capital + O&M Cost to

produce one cubic meter ( 1000 liters or 220 gallon or 1

ton) of treated water and distribute to the door step.

6

Example: Cost of 10 Units

NWSDB Production cost for 10 units = 10 x160

= 1600LKR

Selling price of 10 units =(10X16+65)LKR

Concession = (1,600 – 225)LKR

Concession for a month is Rs 1,375 for 10m3 of consumption

Is Water expensive than Electricity ,Gas ?

7

Domestic Tariff- Non Samurdi

Single Flush Big Cistern Single Flush Small Cistern Dual Flush Small Cistern

11 LPF 6 LPF 6/3 LPF

Water conservation for sustainable Residences

•Convert your toilet to a low flush dual system(35%)

9

Conventional Faucet Low Flow Faucet

•Faucets

Low flow fixtures

•Introduce low flow fixtures for faucets (50%)

Flow rate 15-25 L/min Flow rate 8 - 10 L/min

Low flow fixtures

25-35 l/min7-15 l/min

Conventional Shower

Low Flow Shower

•Shower

•Introduce low flow fixtures for faucets (50%)

11

Best practice to reduce water consumption

13

14

It is extremely important to test the plumbing work before covering

the pipes. If left without testing the leaks can appear some time later

and it may be too late to rectify. Testing is done using test pumps

and an experienced person shall do the testing to ensure that the

system can withstand a design pressure of the system.

•Use correct pipe sizes

.Over sizing will result in additional cost and complication due to

larger pipes being buried in the walls. Under sizing will affect the

quality of service due to head losses.

Implement an effective monitoring system

•Conduct leakage test

15

•Correct Flow Rate for different fixtures

Fixtures (l/s) (l/min)

Flushing cistern 0.10 06

Wash Basin Tap 0.15 09

Shower Head 0.20 12

Sink Tap 12mm 0.15 09

Sink Tap 20mm 0.20 12

Washing Machine

0.10 06

Use correct diameters for supply and distribution

lines. Over sizing will cost more and under sizing will

cause head loss and poor water passage

16

In fact this wastewater is not the water intentionally wasted, but that is coming out of our

operations involving clean water. Clean water, once used is considered as suitable for

disposal and this is the water that is termed as wastewater.

Wastewater is primarily generated from;

a. Toilet bowl flushing (black water)

b. Bathing water (grey water)

c. Kitchen wash water from kitchen sink (grey water)

Black water shall be treated as the first priority and for residential premises the

biological treatment is the most feasible option. This is achieved through

introduction of septic tanks followed by soakage pits or soakage fields. It is

important to know that waste water can be used as a valuable resource in our

garden if managed properly. Soakage fields watered with effluent coming out

of septic tanks can be used as effective source for water required for the plants

Waste water management

17

Rain Water Harvesting-RWH

Rain water harvesting is not new to Sri Lanka. Our

great kings like Parakramabahu‟s testament that

“Not a single drop of rain touching the soil shall

be left to the sea without being used” are known

to all of us.”

18

▪Technology used for collecting and storing rainwater

for human use from rooftops, land surfaces or rock

catchments.

▪One of the world’s most important ancient water

supply techniques (practiced for more than 4,000

years), is beginning to enjoy a resurgence in

popularity.

▪Rainwater is an important water source in many

areas with significant rainfall but lacking any kind of

conventional, centralised supply system.

Introduction RWH

19

Sigiriya, Sri Lanka.

20

This reservoir cut into the rock was used centuries ago to hold

harvested rainwater.

Man Made Rain water harvesting on Rock surfaces- Sigiriya

21

Cistern of the Maya people,

called Chultun

Capacity: 45 000 Litres

Diameter: 5 m,

Catchment area: 150 m²

Source: http://www.irpaa.org.br

22

1. Roof catchments

• Simple roof water collection system for households

• Larger systems for educational institutions, stadiums, airports, and

other facilities

• Roof water collection systems for high-rise buildings in urbanised

areas

2. Ground catchments (man-made)

3. Rock catchments (natural, Man Made)

Main Types of Rainwater Harvesting Systems

23

Typical Domestic Rainwater Harvesting System

Source: http://www.eng.warwick.ac.uk/DTU/rainwaterharvesting/index.html

Water consumption demand calculation

24

Water demand of animals

25

Water consumption demand of institusions/Services

26

27

Ground Catchment System

28

Ground Catchment System

29

Rock Catchment System

Source: ENSIC (1991)

Uses, advantages & limitations

30

31

Use of Harvested Rainwater

• Non-potable purposes (mainly in urban areas)

- Gardening

- Flushing

- Washing clothes/cars

- Bathing

-Animal

-Ground charging

- Potable purpose after ensuring quality

- Drinking , Cooking etc

(mainly in rural areas)

32

▪In view of increasing migration to urban area and the emergence of

mega-cities in the next millennium, it is imperative that water supply

systems should be evolved to cater for such a development.

▪In areas with relatively high rainfall spread throughout the year, where

other water resources are scarce, RWH is an important option, for

example parts of Sri Lanka, Philippines, Indonesia, Nepal and Uganda.

▪Installation RWH system is mandatory for the construction of buildings

in some towns in India and on the Virgin Islands, USA.

▪Many government agencies and municipalities worldwide provide

grants/subsidies and technical know-how to promote RWH system.

RWH in Urban Areas

33

• Flood control - by greatly reducing urban runoff;

• Storm water drainage - by reducing the size and scale of

infrastructure requirements;

• Firefighting and disaster relief - by providing independent

household reservoirs;

• Water conservation - as less water is required from other

sources;

• Reduced groundwater exploitation and subsidence - as less

groundwater is required;

• Financial savings – where rainwater can be used in place of

water purchased from water vendors.

Advantages of RWH in Urban Areas

34

▪ The initial cost (mainly of storage tank) may prevent a

family from installing a RWH system.

▪ The water availability is limited by the rainfall intensity

and available roof area.

▪ Mineral-free rainwater has a flat taste, which may not be

liked by many.

▪ The poorer segment of the population may not have a

roof suitable for rainwater harvesting.

▪ Domestic RWH will always remain a supplement and not a

complete replacement for city-level piped supply or supply

from more ‘reliable’ sources.

Limitations of RWH

System Components and Design Considerations

35

36

• Catchment Area/Roof

- the surface upon which the rain falls

• Gutters and Downpipes

- the transport channels from catchment surface to storage

• Leaf Screens and Roofwashers

- the systems that remove contaminants and debris

• Cisterns or Storage Tanks

- where collected rainwater is stored

• Conveying

- the delivery system for the treated rainwater, either by

gravity or pump

• Water Treatment

- filters and equipment, and additives to settle, filter, and

disinfect

RWH System Components

37

• Rainfall quantity (mm/year)

• Rainfall pattern

• Collection surface area (m2)

• Runoff coefficient of collection (-)

• Storage capacity (m3)

• Daily consumption rate (litres/capita /day)

• Number of users

• Cost

• Alternative water sources

Factors affecting RWH system design

38

• The size of supply of rainwater depends on the

amount of rainfall (R), the area of the catchment (A)

and its runoff coefficient (C).

• An estimate of mean annual runoff from a given

catchment can be obtained using the equation:

S = R * A * C

Where S = Rainwater supply per annum

R = mean annual rainfall

A = Area of the catchment

C = Runoff coefficient

• The actual amount of rainwater supplied will ultimately

depend on the volume of the storage tank or reservoir.

Feasibility of Rainwater Harvesting

39

• The size of roof catchment is the

projected area of the roof or the

building’s footprint under the

roof.

• To calculate the catchment area

(A), multiply the length (L) and

width (B) of the guttered area. It

is not necessary to measure the

sloping edge of the roof.

• Note that it does not matter

whether the roof is flat or

peaked. It is the “footprint” of the

roof drip line that matters.

Catchment Area Size

40

41

Type Runoff

coefficient

Notes

GI sheets > 0.9 Excellent quality water. Surface is smooth and high temperatures help to sterilise bacteria

Tile

(glazed)

0.6 – 0.9 Good quality water from glazed tiles. Unglazed can harbour mould Contamination can exist in tile joins

Asbestos Sheets

0.8 – 0.9 New sheets give good quality water

Slightly porous so reduced runoff coefficient and older roofs harbour moulds and even moss

Organic (Thatch)

0.2 Poor quality water (>200 FC/100ml)

Little first flush effect; High turbidity due to dissolved organic material which does not settle

Characteristics of Roof Types

Source: http://www.eng.warwick.ac.uk/dtu/rwh/components2.html

42

Example 1:

For a building with a flat roof of size 10 m x 12 m in a city with the

average annual rainfall of 800 mm

Roof Area (A) = 10 x 12 = 120 m2

Average annual rainfall (R) = 800 mm = 0.80 m

Total annual volume of rainfall over the roof

= A * R = 120 m2 x 0.80 m = 96 m3 = 96,000 litres

If 70% of the total rainfall is effectively harvested,

Volume of water harvested = 96,000 x 0.7 = 67,200 litres

Average water availability = 67,200 / 365 ~ 184 litres/ day

43

• There are several options available for the storage of

rainwater. A variety of materials and different shapes of

the vessels have been used.

• In general, there can be two basic types of storage

system:

- Underground tank or storage vessel

- Ground tank or storage vessel

• The choice of the system will depend on several

technical and economic considerations like, space

availability, materials and skill available, costs of

buying a new tank or construction on site, ground

conditions, local traditions for water storage etc.

Storage System

44

• The storage tank is the most expensive part of any

RWH system and the most appropriate capacity for

any given locality is affected by its cost and amount of

water it is able to supply.

• In general, larger tanks are required in area with

marked wet and dry seasons, while relatively small

tanks may suffice in areas where rainfall is relatively

evenly spread throughout the year.

• Field experiences show that a universal ideal tank

design does not exist. Local materials, skills and

costs, personal preference and other external factors

may favour one design over another.

Storage System

45

• A solid secure cover to keep out insects, dirt and

sunshine

• A coarse inlet filter to catch leaves etc.

• A overflow pipe

• A manhole, sump and drain for cleaning

• An extraction system that does not contaminate the

water e.g. tap/pump

• A soakaway to prevent split water forming puddles

near the tank.

• Additionally features

- sediment trap or other foul flush mechanism

- device to inside water level in the tank

Requirements for Storage System

46

47

48

49

RWH Brick Jars - Uganda

Source: Rees and Whitehead (2000), DTU, University of Warwick, UK

50

Rainwater Harvesting - Kenya

Source: John Gould (Waterlines, January 2000)

51

Ferro-cement jar

for rainwater

collection -

Uganda

Source: DTU, University of

Warwick (September 2000)

52

Underground lime and bricks cistern

53

Rainwater Harvesting – Sri Lanka

54

55

56http://www.greenhouse.gov.au/yourhome/technical/pdf/fs22.pdf

57

A wooden water tank in Hawaii, USA

Source: Rainwater Harvesting And Utilisation. An Environmentally Sound Approach for

Sustainable Urban Water Management: An Introductory Guide for Decision-Makers. ITEC,

UNEP, Japan

58

http://www.arcsa-usa.org/

59

60

Source: http://www.greenhouse.gov.au

Rainwater Tanks

61

Storage tank capacity calculation

Based on rainfall and water demand pattern

• A better estimate of storage requirement can be made

using the mass curve technique based on rainfall and

water demand pattern.

• Cumulative rainfall runoff and cumulative water

demand in year is calculated and plotted on the same

curve.

• The sum of the maximum differences, on the either

side, between the rainfall curve and water demand

curve gives the size of the storage required

62

Storage capacity

Example 2

Calculate the size of the storage tank required for a school

with 65 students and 5 staff, assuming average water

consumption of 5 litres/day.

Roof area = 200 m2.

Assume runoff coefficient of 0.9.

The rainfall pattern in the area is given in the table below

Average daily demand = 70 x 5 = 350 litres

Yearly demand = 350 * 365 = 127750 litres = 127.75 m3

Average monthly demand = 127.75/12 ~ 10.65 m3

63

Storage capacity calculations

(a) Rainfall pattern - 1

Month Rainfall

mm

Jan 120

Feb 90

Mar 70

Apr 120

May 40

June 50

July 45

Aug 15

Sep

Oct 45

Nov 70

Dec 45

0

50

100

150

J F M A M J J A S O N D

Month

Rain

fall (

mm

)

64

Calculation of required storage capacity (1)

Required storage capacity = 29.4 m3 say 30 m3

Month Rainfall Rainfall Water Cum. Rainfall Cum. Water Difference

harvested Demand harvested CH Demand CD CH - CD

mm m3

m3

m3

m3

m3

J 120 21.6 10.65 21.6 10.65 10.95

F 90 16.2 10.65 37.8 21.3 16.5

M 70 12.6 10.65 50.4 31.95 18.45

A 120 21.6 10.65 72 42.6 29.4M 40 7.2 10.65 79.2 53.25 25.95

J 50 9 10.65 88.2 63.9 24.3

J 45 8.1 10.65 96.3 74.55 21.75

A 15 2.7 10.65 99 85.2 13.8

S 0 10.65 99 95.85 3.15

O 45 8.1 10.65 107.1 106.5 0.6

N 70 12.6 10.65 119.7 117.15 2.55

D 45 8.1 10.65 127.8 127.8 0

65

Mass curve for calculation of required

storage capacity

0

20

40

60

80

100

120

140

J F M A M J J A S O N D

Month

Wate

r (m

3)

Cum. Harvested Cum. Demand

66

Mass curve for calculation of required

storage capacity

0

20

40

60

80

100

120

140

J F M A M J J A S O N D

Month

Cu

mu

lati

ve (

m3)

Harvested Water demand

67

Storage capacity calculations

(b) Rainfall pattern - 2

Month Rainfall

mm

Jan 120

Feb 100

Mar 100

Apr 115

May

June

July

Aug

Sep

Oct 55

Nov 100

Dec 120

0

20

40

60

80

100

120

140

J F M A M J J A S O N D

Months

Rain

fall

(mm

)

68

Calculation of required storage capacity (2)

Required storage capacity = 35.7 + 18.3 = 54 m3

Month Rainfall Rainfall Water Cum. Rainfall Cum. Water Difference

harvested Demand harvested CH Demand CD CH - CD

mm m3

m3

m3

m3

m3

J 120 21.6 10.65 21.6 10.65 10.95

F 100 18 10.65 39.6 21.3 18.3

M 100 18 10.65 57.6 31.95 25.65

A 115 20.7 10.65 78.3 42.6 35.7M 0 10.65 78.3 53.25 25.05

J 0 10.65 78.3 63.9 14.4

J 0 10.65 78.3 74.55 3.75

A 0 10.65 78.3 85.2 -6.9

S 0 0 10.65 78.3 95.85 -17.55

O 55 9.9 10.65 88.2 106.5 -18.3N 100 18 10.65 106.2 117.15 -10.95

D 120 21.6 10.65 127.8 127.8 0

69

• Gutters are channels all around the edge of a sloping

roof to collect and transport rainwater to the storage

tank.

• A carefully designed and constructed gutter system is

essential for any roof catchment system to operate

effectively.

• When the gutters are too small considerable

quantities of runoff may be lost due to overflow during

storms.

• The size of the gutter should be according to the flow

during the highest intensity rain. It is advisable to

make them 10 to 15 per cent oversize.

Gutters

70

• A general rule of thumb is that 1 cm2 of guttering is

required for every m2 of roof area.

• Gutters can be semi-circular or rectangular and could be

made using a variety of materials:

- Locally available material such as plain galvanised

iron sheet (20 to 22 gauge), folded to required

shapes.

- Semi-circular gutters of PVC material can be

readily prepared by cutting those pipes into two

equal semi-circular channels.

- Bamboo or betel trunks cut vertically in half.

- Wood or plastic

Gutters (2)

71

• Gutters need to be supported so they do not sag or fall off

when loaded with water.

• The way in which gutters are fixed depends on the

construction of the house;

- it is possible to fix iron or timber brackets into the

walls, but for houses having wider eaves, some

method of attachment to the rafters is necessary.

• A properly fitted and maintained gutter-downpipe

system is capable of diverting more than 80% of all

runoff into the storage tank, the remainder being lost

through evaporation, leakage, rain splash and overflow.

Gutters (3)

72

Gutter configurations

Gutters - Shapes and Configurations

73

Source: www.sopac.org

Guide to sizing of gutters and downpipes for

rainwater harvesting systems in tropical regions

Roof area (m2)

served by one gutter

Gutter width

(mm)

Minimum diameter

of downpipe (mm)

17 60 40

25 70 50

34 80 50

46 90 63

66 100 63

128 125 75

208 150 90

74

Storage tank & first flush - Malaysia

75

• The quality of rainwater is relatively good but it is

not free from all impurities.

• Analysis of stored rainwater has shown some

bacteriological contamination.

• The rainwater is essentially lacking in minerals,

the presence of which is considered essential in

appropriate proportions.

• Cleanliness of roof and storage tank is critical in

maintaining good quality of rainwater.

• The storage tank requires cleaning and

disinfection when the tank is empty or at least

once in a year.

Quality of Rainwater

76

• The simple operation and maintenance of RWH

systems is one of the most attractive aspects of the

technology.

• The extent of maintenance required by a basic

privately owned household RWH system includes

- Regular cleaning of the roof tops and gutters

- Frequent cleaning of storage tanks

- Inspection of gutters and feeder pipes and valve

chambers to detect and repair leaks

• When ground catchment is used for collection and/or

ground tank is used for storage, proper fencing of both

is recommended to keep the children and animals away, thus

avoiding contamination and risks of falling into the tank.

Operation and maintenance

77Source: http://www.rainharvesting.com.au

78

Rainwater Harvesting - Australia

• In Australia the use of domestic rainwater tanks is an

established and relatively common practice, particularly in rural

and remote areas.

• Between 1994 and 2001, 16% of Australian households

used rainwater tanks, with 13% of households using tanks as

their main source of drinking water.

• 7% of the capital city households and 34% of non-capital

city households have rainwater tanks.

• In a 1996 South Australian survey, 28% of Adelaide

households used rainwater tanks as the primary source of

drinking water compared to 82% households in the rest of the

State.

Source: Guidance on use of rainwater tank. En Health, Australian Government 2004

79

80

Rainwater harvesting system, in Patan, Nepal

1 - Overhead tank

2 - Downtake PVC pipe from roof

3 - First phase storage drum

4 - Overflow goes into

underwater tank

5 - Pump to lift water to overhead

tank

6 - Sediment discharge tap

7 - 50,000 litre underground

ferrocement tank

Source: Nepali Times (16-22 August 2002)

81

Rainwater Harvesting in Tokyo

82

Rainwater Harvesting from Domed Stadium in Japan

Source: Zaizen et al. (1999)

83

Rainwater Harvesting from Domed Stadium in Japan

_________________________________________________________

Stadium Tokyo Fukuoka Nagoya

_________________________________________________________

Catchment area

for storage (m2) 16,000 25,900 35,000

Capacity of

detention tank (m3) 1000 1800 1500

Utilization Flush toilets Flush toilets, Flush toilets

watering plants watering plants

__________________________________________________________

Source: Zaizen et al. (1999)

84

Rainwater Harvesting at ChangiAirport - Singapore

• Rainfall from the runways and the surrounding green

areas is diverted to two impounding reservoirs.

• One of the reservoirs is designed to balance the flows

during the coincident high runoffs and incoming tides, and the

other reservoir is used to collect the runoff.

• The water is used primarily for non-potable functions such

as fire-fighting drills and toilet flushing.

• Such collected and treated water accounts for 28 to 33%

of the total water used, resulting in savings of approximately

S$ 390,000 per annum.

85

Rainwater Harvesting in Presidential Estate, New Delhi, India

- About 7000 residing in the estate and about 3000 visitors

every day. There is also famous “The Mughal Garden”.

- Total water demand 2 million litres per day

- 30% of demand met by Groundwater wells in the estate and

groundwater level is going down rapidly)

86

Rainwater Harvesting in Presidential Estate, New Delhi, India

• Rainwater from the northern side of the roof and

paved areas surrounding the presidential palace is

diverted to an underground storage tank of 100,000

litres capacity for low quality use (5%).

• Overflow the rainwater storage tank is diverted to

two dug wells for recharging.

• Rainwater from southern side of the roof is diverted

for recharging a dry open well. Rainfall runoff from

the staff residential area is also diverted to dry wells.

• 15 m deep recharge shafts have been constructed

for recharging.

87

• Water Supply Plant, installed at the UK's Millennium Dome

can supply around 500 m3 per day of reclaimed water to flush

all of the toilets and urinals on the site.

• Water is reclaimed from greywater produced by the hand

wash basins, rainwater from the dome's roof, and groundwater

from the chalk aquifer which is located below the site.

Water Supply at Millennium Dome, London

88

• Rainwater is collected from dome roof and adjacent

areas (100,000 m2)

• Size of collection tank is 800 m3

• Reed beds are used for treatment

Water Supply at Millennium Dome, London

89

90

• Rainwater Harvesting and Utilization. An Environmentally Sound

Approach for Sustainable Urban Water Management: An Introductory

Guide for Decision-Makers. IETC-UNEP, Japan.

• Rainwater catchment systems for Household Water Supply

(1991). Environmental Sanitation Reviews No No 32. ENSIC,

Bangkok, Thailand.

• UNEP-IETC (1999) Proceedings of the International Symposium on

Efficient Water Use in Urban Areas - Innovative Ways of Finding Water for

Cities. (8 to 10 June 1999), Kobe, Japan.

• Gould, J. and Nissen-Petersen, E. (1999) Rainwater Catchment

Systems for Domestic Supply. IT Publications, London

• Hasse, R. (1989) Rainwater Reservoirs- Above Ground Structures for

Roof Catchment. GTZ.

• NGO Forum and SDC (2001) Rain Water Harvesting System. NGO

Forum for Drinking Water Supply and Sanitation and SDC,

Bangladesh.

Bibliography

91

• International Rainwater Catchment Systems Association

http://www.eng.warwick.ac.uk/ircsa/

• American Rainwater Catchment Association

http://www.arcsa-usa.org/

• Centre for Science and Environment (CSE), India

http://www.rainwaterharvesting.org

• Development Technology Unit, School of Engineering,

University of Warwick, UK

http://www.eng.warwick.ac.uk/DTU/rwh/index.html

• Chennai Metrowater, India

http://www.chennaimetrowater.com/rainwaterfaqs.htm

• Rainwater Partnership

http://www.rainwaterpartnership.org/

Web Resources on RWH

92

• Lanka Rainwater Harvesting Forum

http://www.rainwaterharvesting.com

• Intenational Rainwater Harvesting Alliance

http://www.irha-h2o.org/

• Greater Horn of Africa Rainwater Partnership (GHARP)

http://www.gharainwater.org/

• The Web of Rain

http://www.gdrc.org/uem/water/rainwater/rain-web.html

Web Resources on RWH (2)