WASH Cluster – Water in Emergencies
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Water in Emergencies
Session 4
Water Sources, Treatment &
Implications
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Water Supply
Stages
Water
abstraction
Raw
water
storage
Pretreatment
(such as
roughing
filtration)
Coagulation /
Flocculation /
Sedimentation
or Slow sand
filtration
Adapted form: Davies &
Lambert (2002) Engineering in
Emergencies, REDR / ITDG
Chlorination
Storage
Distribution
Water supply in emergency contexts may involve some or all of the above stages
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Acceptable yield?
Ease / ability to
obtain an acceptable
quality?
Management, legal,
security, sociopolitical & cultural
constraints?
• Management
• Land ownership
• Security
• Cultural & socio-political
issues
• Demand vs yield
• Seasonal yield
• Future yield
Criteria for
selection
Water source,
treatment &
supply
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• Existing users
• Aquifers
• Environment
Time of set up vs
urgency?
Costs?
Ease of O&M?
• Capital
• Requirements
• O&M
• Resource / logistical
•Availability of trained staff
Impacts of
development?
• Technical
• Resource / logistical
Adapted form: House & Reed (1997)
Emergency Water Sources, WEDC
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Shallow & Medium Depth Groundwater
Shallow well, Lao PDR
S House / ACF
Handpump on shallow
borehole, Liberia
S House / ACF
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Springs
Piped Supplies
Piped supply from motorised borehole, IDP camp, northern
Uganda
S House / MSF-OCBA
Spring being protected, Zaire
S House / WEDC
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Deep Groundwater
Surface Water
Submersible pump
S House / WaterAid
Surface water sources supplying
refugee camps, Zaire
S House / MSF-OCBA
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Rainwater
Roof collected
Ground collected
Health facility in an IDP camp, northern Uganda
S House / MSF-OCBA
Birkad underground rainwater collection tank, northern
Kenya
S House / AAH-US
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Implications of selection of
Water Source and Supply
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Scenarios
1. Spring located above an IDP camp, used by the local community, sited
on a private landowners land
2. Shallow wells developed in a wooded area outside an IDP camp for
people displaced by a conflict
3. Water is being tankered from one part of a city which is under control of
one armed group and has to pass through the area of another armed
group before reaching its point of supply to a group of displaced people
4. Water is being piped from a seasonal stream being fed from a spring in
a mountainous area following a major earthquake, aftershocks are still
being felt
5. 100,000 displaced persons due to conflict arrive in a semi-arid area
and new boreholes are drilled to supply the camps
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Implications of Selection of
Source & Supply
Exercise - Consider the particular scenario
provided to you and consider the following:
1.What are the risks / potential negative
implications apparent in the scenario and to what
or whom?
2.How could you reduce the risk?
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Water Treatment
• Most common water treatment = chlorination
• Chlorination works most effectively with low turbidity
of 1 NTU (or max 20 NTU)
• Guidelines for chlorination given for pH<8, turbidity
<5 NTU, temperature approx 20oC, 30 min retention
time
• If pH higher, temp lower or turbidity higher then
adjust processes
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Pre-Treatment
Pre-treatment:
– Roughing filtration
– Coagulation, flocculation & sedimentation
– Rapid sand filtration
Other treatment:
– Slow sand filters - but also need pre-treatment to
reduce turbidity
– Water treatment kits - various methods
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Bulk Water Treatment
Safety
needed with
chemicals…
Coagulation
&
flocculation
Ethiopia
S House / WEDC
Zaire (DRC)
S House / WEDC
Field
‘Jar test’
Pakistan
S House / OXFAM-GB
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Chlorination
Practical handout on chlorination provided
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Household water treatment
• Candle filters
• Ceramic pot filters
• Biosand household
filters
• Chlorination
• Boiling
• Sodis – using UV light
& plastic bottles
• Local natural
coagulants
Moringa Oliefera
Waterlines
Cambodia
H Jones / WEDC
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Candle filter units
OXFAM-GB
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Bulk vs Household Treatment
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Bulk water
treatment
• Can supply to large numbers
of people
• Not useful for dispersed
populations
• Can supply quickly
• High O&M inputs
• Can control water quality
• Water can be contaminated
post-supply
• Can monitor changing water
needs
Household
water treatment
-
• More control for householders
• More sustainable (if
appropriate to situation)
• Less risk of contamination
post treatment
• Training needed for effective
use
• More difficult to supply large
numbers of people
• Limited control on effective use
• Good for disperse populations
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