Transcript Groundwater Quality and Protection - AGW-Net

Groundwater Quality and
Protection for Sanitation and
Hygiene
defining strategies and setting
priorities
Groundwater Quality
• What does groundwater quality mean to you?
Learning Objectives
 To
assess and identify threats and pollution
hazards to groundwater quality
 To
discuss ways of protecting groundwater from
pollution.
How does Aquifer Pollution occur?
• Waste disposal and contaminant load is uncontrolled
• It exceeds attenuation capacity of the ground
• Soil in the vadose actively attenuates many pollutants esp.
domestic wastewater, and increases the time available for
contaminant elimination processes
• Groundwater pollution threat is primarily to shallow aquifers
• Deep and confined aquifers can become polluted in highly
fractured media and when pollution persists over a long time.
• Sharply-focused pollution control measures can produce major
benefits for relatively modest cost.
Assessment of Pollution
• Groundwater pollution hazard assessment is needed to appreciate the
actions required to protect groundwater quality; it should be an
essential component of environmental best-practice
• Groundwater pollution hazard is the interaction between the aquifer
pollution vulnerability and the contaminant load
• Aquifer vulnerability is essentially fixed by the natural hydrogeological
setting but contaminant load varies
• Aquifer pollution vulnerability can be assessed from the
hydrogeological characteristics of the overlying material which can be
mapped (Eg. DRASTIC)
• Potential contaminant load can also be mapped and overlaid on the
aquifer vulnerability map => groundwater pollution hazard.
Definition of common groundwater pollution terms
Term
Aquifer
Pollution
Vulnerability
Groundwater
Pollution
Hazard
Definition
sensitivity to contamination, determined by the
natural intrinsic characteristics of the unsaturated or
vadose zone overlying the aquifer concerned
probability that groundwater in an aquifer will
become polluted to concentrations above WHO
drinking-water guidelines when a given subsurface
contaminant load is generated at the land surface
threat posed by pollution of a specific
Groundwater groundwater supply source to human health or to
Pollution Risk an ecosystem due to natural aquifer (polluted)
discharge.
Vulnerability of aquifer to pollution
Thin vadose zone &
shallow water-table
provides less natural
attenuation
prone to pollution.
Vulnerability of aquifer to pollution
Deeper and
confined aquifers
have much greater
natural protection
by the overlying
ground.
Vulnerability of water well to pollution
Pollution Pathways
by Sanitation
Aquifer
Vulnerability
Mapping
G Groundwater hydraulic confinement
O Overlying strata
D Depth to groundwater
=> Vulnerability Index
Groundwater Vulnerability Map
DRASTIC
 D - depth to water
 R - net recharge
 A - aquifer media
 S - soil media
 T - topography
 I - impact of vadose zone
 C - hydraulic conductivity
Pollution Hazard Assessment
Groundwater Pollution Hazard Map
Map of potential contaminant load overlain on aquifer
vulnerability map => groundwater pollution hazard map
Contaminant Load – Pollution Hazard
Groundwater Pollution Sources
Acid Mine Drainage (AMD)
1
1111
Common grdwater contaminants and associated pollution sources
Pollution source
Type of contaminant
Agricultural Activity
nitrates; ammonium; pesticides; faecal organisms
In-situ Sanitation
nitrates; faecal organisms; trace synthetic hydrocarbons
Gasoline Filling
Stations & Garages
benzene; other aromatic hydrocarbons; phenols
Solid Waste Disposal
ammonium; salinity; some halogenated hydro-carbons;
heavy metals
Dry Cleaning
trichloroethylene; tetrachloroethylene
Sewage Sludge
Disposal
nitrates; various halogenated hydrocarbons; lead; zinc
Leather Tanneries
chromium; various halogenated hydrocarbons; phenols
Mining
Acidity, iron, heavy metals, sulphate
Rural Water Supply
Gyau-Boakye, P. et. al.
(2008)
High levels of nitrate and coliforms in
hand-dug wells in Ghana
Adalena, S. et. al. (2008) 33 % of 2200 wells in Nigeria with
nitrate values above 45 mg NO3/L
Agyekum, W.A. et al.
(2008)
38 % of water from boreholes in one
district in Ghana nitrate concentrations
above 45 mg/L
Contamination sources
dirty water at well head recirculating into the well
McDonold et. al. (2005)
Protection measures
 Proper
well construction can significantly
improve water quality
 Well location upstream/away from pit latrines,
waste dumps and cemeteries
 Concrete
platforms around well with proper
drainage
 Animals
must be kept away by a fence
Protection measures (contd.)
www.ualberta.ca/~xcle/img/pump.jpg
Proper well construction
www.wateraid.org/images/cm_images/pump-web.jpg
Concrete platforms
around the well
Fencing to keep away animals
http://rehydrate.org/dd/img2/su312.jpg
Peri-urban settlements
Present situation in Peri-urban settlements in Africa:
 Uncontrolled settlement
 Predominant use of on site-sanitation
 Uncontrolled waste dumping
 Water supply predominantly from dug wells or
water ponds
 Extensive
contamination by nitrate, nitrite,
ammonia, and faecal bacteria
 Frequent outbreaks of water-borne diseases
(cholera).
Contamination sources
Retention of solids
Infiltration of liquids
Pathogens
Polluted
groundwater
Nitrates
Viruses
Source: GTZ (Werner) 2005
Source: Nkhuwa 2006
Systems of Human Waste Disposal
Toilet
Well
Choice of location of
Pit latrines in highdensity settlements
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Strategies to improve pollution situation in
peri-urban areas

Connection to public water supply (piped water
system)

Connection to sewerage system

These are very expensive options
 Alternative systems: Ecosan Toilets / Constructed
wetlands
Str a tegies to impr ove pollution situa tion
in Peri-urban areas (contd.)
 Improvement of on-site sanitation through reuse
of faecal matter (dry toilets – ecosan).
Dehydrating toilets
Source: CSIR 2004
Str a tegies to impr ove pollution situa tion
in Peri-urban areas (contd.)
 Improvement
of on-site sanitation through use
of low cost wastewater treatment.
Wastewater treatment
Source: BGR 2008
Contamination sources to water supply
points in Urban areas
What is the
impact of
such waste
on water....?
Contamination sources to water supply
points… (contd.)
Fuel spillage from
a tanker that
overturned at a
petrol station in
Lusaka.
Non-aqueous phase liquid contamination
Pollution Risk to Human Health
•
High nitrates and bacterial contamination are common.
•
Poor sanitation and informal sewage disposals are the major contributors
to groundwater quality degradation.
•
Pollution of underlying groundwater sources mainly from pit-latrines and
broken septic tanks has reached critical levels, leading to typhoid
outbreaks.
•
Increasing contamination from industrial, agricultural and mining
activities
Delineation of Groundwater Protection Area (GPA)
simple powerful
concept readily
understood by
planners:
designed to provide
special vigilance for
groundwater destined
for public supply
GPAs also need:
- regulatory embedding
- public awareness
- monitoring
Groundwater protection (contd.)
Zone 1 – Protects
well/spring from
direct contamination
Well
I
II
Zone II – Protects drinking water
source against pathogenic
microbiological constituents
bacteria, viruses, parasites.
III
Groundwater
Flow Direction
Zone III – Protects against
contamination affecting drinking
water source over long distances
(for chemical substances, which
are non- or hardly degradable)
Groundwater protection (contd.)
Groundwater Protection Zones :
 need regulatory embedding
 need public awareness
 need hydrogeological data and monitoring
 usually imply landuse restrictions to balance
competing user-interests.
How to protect against contamination?
• Separation – keep waste materials and groundwater far apart
• Containment – secure waste in impermeable ponds / land fill
facilities
• Waste management
– sorting & separation
– waste recycling / reuse
– treatment of toxic waste
• Remediation – treat polluted aquifers – better to prevent
than to treat.
• Well head delineation and protection
How to protect against contamination?
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Well field protection
Well spacing, pumping restriction
Land use planning/regulation
Agrochemical (fertilizer/pesticide) use regulations
Proper solid waste disposal facilities
Proper sanitation and waste water treatment
facilities
Polluter-pay-principle or economic incentives
Monitoring, early warning, trend analysis
Public awareness raising
• Maintaining quality groundwater supply is key to ensuring
good health for all.
• The level of protection in the catchment strongly
influences the quality of the well water.
• Sanitation must not be delinked from Groundwater
Protection.
• There is need for new sanitation and water protection
initiatives in Africa’s urban centers.
Overall Groundwater Remediation Strategy
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Restriction on GW use
Development of alternative (water supply) sources
Dilution with clean water
Remediation/clean-up technologies
Groundwater Remediation Technology
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Containment
Ex-situ treatment
In-situ treatment
Natural clean-up/attenuation
Groundwater Purification
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Aeration
Filtration
Mixing/dilution
Desalinization
Adsorption/ion exchange
Chemical precipitation
Thank you for your attention
Exercise – Waste Management Role Play
 You
are required to improve waste management / effluent
disposal in the capital city in your country. Participants divide
into stakeholders: Water/Groundwater managers; Waste
Disposal companies; Industry discharging effluent; Citizen
Groups; Politicians.
 The water managers must propose sweeping reforms to
improve all aspects of waste management in the city for the
purpose of protecting quality of groundwater (& surface water).
The other stakeholders should raise queries about the impact of
the changes on them, & make objections/suggestions to the
water managers.
 Preparation: 20 minutes
 Debate: 40 minutes.
Group Activity.
Characterisation of groundwater systems
Purpose: To appreciate the link between understanding
groundwater systems and strategies for management
Duration: 60 Minutes
Scenario : 2 groups: City managers and NGO’s / User
communities. The city wants to establish a solid waste disposal
site on top of an important aquifer that is widely used for
domestic water supply. NGO’s / Users oppose this proposal,
saying that aquifer pollution is likely to occur.
Activity – Role Play: City defends its position with reference to
specific aquifer and hydrological characteristics, explaining why
the plan is safe, and the groundwater management activities to
be introduced. NGO’s / Users question the plan, referring to
aquifer vulnerability and pollution remediation issues etc. and
querying the aquifer management proposals.
EXERCISE
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Purpose: To share experience of groundwater quality problems.
Activity: Break into groups of 4 or 5. 1 hour.
Each group to Identify a common groundwater quality problem in
one of your countries.
Discuss the nature & scale of the problem – is it anthropogenic or
natural?
How is the problem being managed and who is responsible for the
management?
What have been the aims of the management and how successful has
it been?
What would you need to change to improve the situation?
Report back: 15 minutes per group.