Transcript Groundwater Quality Protection - AGW-Net

Groundwater Quality and
Protection
defining strategies and setting priorities
Learning Objectives
 To
assess and identify threats and pollution
hazards to groundwater quality
 To
discuss ways of protecting groundwater from
pollution.
Definition of common groundwater pollution terms
Term
Definition
sensitivity to contamination, determined by the natural
Aquifer
intrinsic characteristics of geological strata forming the
Pollution
overlying confining beds or vadose zone of the aquifer
Vulnerability concerned
probability that groundwater in an aquifer will become
Groundwater polluted to concentrations above WHO drinking-water
Pollution
guidelines when a given subsurface contaminant load is
generated at the land surface
Hazard
threat posed by hazard to human health due to
Groundwater pollution of a specific groundwater supply source, or to
Pollution
an ecosystem, due to pollution of a specific natural
aquifer discharge.
Risk
How do aquifers become polluted?
When contaminant load (effluent discharge
and/or leachate):

is inadequately controlled/disposed of.

exceeds
natural
attenuation
capacity
of
underlying soils and strata.
groundwater merits protection because

it provides vital source of potable water supply
Outline of Pr esenta tion
1. Rural water supply
2. Urban- and Peri-urban settlements
3. Groundwater Protection Zones
Rural Water Supply
 Currently
53 % of Africa‘s rural population is
without access to safe water (AfDB 2009)

„Safe drinking water“ is predominantly from
hand-dug-wells and drilled wells with hand
pumps
 Frequent
reports in literature indicate elevated
nitrate levels and bacterial contamination
Rural Water Supply (contd.)
High levels of nitrate and
Gyau-Boakye, P. et.
coliforms in hand-dug wells in
al. (2008)
Ghana
33 % of 2200 wells in Nigeria
Adalena, S. et. al.
have nitrate values above 45
(2008)
mg NO3/L
38 % of water from boreholes
Agyekum, W.A. et al. in a district in Ghana have
(2008)
nitrate concentrations above 45
mg/L
Contamination sources
dirty water at well head recirculating into the
well
McDonold et. al. (2005)
Contamination sources (contd.)
Pollution from animal faeces
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.)
Proper well construction
www.ualberta.ca/~xcle/img/pump.jpg
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 outbrake of water-borne diseases
(cholera).
Contamination sources
Retention of solids
Infiltration of liquids
Pathogens
Nitrates
Viruses
Source: GTZ (Werner) 2005
Polluted
groundwater
Source: Nkhuwa 2006
Strategies to improve pollution situation in Periurban areas
 Connection
to public water supply (piped water
system)
 Connection
to sewerage system
 No realistic short term solution (high investment
costs)
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
The Urban Environment
Land-use activities commonly responsible for groundwater
pollution in the Urban areas.
Contamination sources to water supply
points in Urban areas
Contamination sources to water supply
points in Urban areas
Wastewater drain – Accra, Ghana
Contamination sources to water supply
points… (contd.)
Fuel spillage from
a tanker that
overturned @ a
petrol station in
Lusaka.
Non-aqueous phase liquid contamination
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
Groundwater Protection
Common approach worldwide:
Protection of water resources by
Groundwater Protection Zones
(GPZ) – to be discussed in detail later
General aim:
To
Protect
drinking
water
resources in the groundwater
contribution zone, upstream of a
well/spring, from pollution.

What treatment is
groundwater before
consumers?
applied to the
it is piped to
Re m e d i a l
measures
Vulnerability of aquifers to pollution
Threats to groundwater pollution are a function,
among others, of:
 Thickness &
properties of overlying soil (vadose
zone)
 Depth
to water-table.
Vulnerability of aquifer to pollution (contd.)

Thin vadose zone &
shallow water-table
provides less
natural attenuation,
prone to pollution.
Vulnerability of aquifer to pollution (contd.)

Deeper and
confined aquifers
have much greater
natural protection
by the overlying
ground.
Vulnerability of aquifer to pollution (contd.)
Pollution Pathways
by Sanitation
How can groundwater pollution hazard be
assessed?

from the hydrogeological characteristics of the
overlying material.

used to produce a vulnerability index that can
be mapped

a variety of vulnerability assessment tools
may be used e.g.: DRASTIC method
How can groundwater pollution hazard be
assessed? (contd.)
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
How can groundwater pollution hazard be
assessed? (contd.)
When map of potl contaminant load overlain on aquifer vulnerability
map, it will provide a map of groundwater pollution hazard.
Groundwater protection
Its General aim:

To protect drinking water resources in the
groundwater contribution zone upstream of the
well/spring from pollution.
Common approach worldwide involves:

Protection
of
water
resources
by
Groundwater Protection Zones (GPZ)
Zone I –
 Zone II –
 Zone III –

Immediate Protection Zone
Inner Protection Zone
Outer Protection Zone
employing
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.)
Grdwater Protection Zones :
 need regulatory embedding
 need public awareness
 need Monitoring
 usually imply landuse restrictions to balance
competing user-interests.
Who should promote groundwater pollution protection?
The
ultimate
responsibility
for
groundwater
pollution protection lies with relevant government
agency......
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.
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.