wash cluster – water in emergencies w w4 1 water in emergencies session 4 water sources, treatment...
TRANSCRIPT
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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
Pre-treatment
(such as roughing filtration)
Coagulation / Flocculation / Sedimentation or Slow sand filtration
Chlorination Storage Distribution
Water supply in emergency contexts may involve some or all of the above stages
Adapted form: Davies & Lambert (2002) Engineering in
Emergencies, REDR / ITDG
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Criteria for selection
Water source, treatment &
supply
Ease / ability to obtain an acceptable
quality?
Impacts of development?
• Existing users• Aquifers
• Environment
Time of set up vs urgency?
• Technical• Resource / logistical
Costs?
• Capital• O&M
Ease of O&M?
• Requirements• Resource / logistical
•Availability of trained staff
Management, legal, security, socio-
political & cultural constraints?
• Management• Land ownership
• Security• Cultural & socio-political
issues
Acceptable yield?
• Demand vs yield• Seasonal yield
• Future yield
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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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 Coagulation
& flocculation
Safety needed with chemicals…
Zaire (DRC)
S House / WEDC
Ethiopia
S House / WEDC
Pakistan
S House / OXFAM-GB
Field ‘Jar test’
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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 Cambodia
H Jones / WEDC
Moringa Oliefera
Waterlines
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Candle filter unitsOXFAM-GB
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Bulk vs Household Treatment
+ -
Bulk water treatment
• Can supply to large numbers of people
• Can supply quickly
• Can control water quality
• Can monitor changing water needs
• Not useful for dispersed populations
• High O&M inputs
• Water can be contaminated post-supply
Household water treatment
• More control for householders
• More sustainable (if appropriate to situation)
• Less risk of contamination post treatment
• Good for disperse populations
• Training needed for effective use
• More difficult to supply large numbers of people
• Limited control on effective use