Microbiological contamination of groundwater.pdf


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Microbiological contamination of groundwater by Cryptosporidium oocysts in Haiti. Health risk assessment for population

to evaluate risks to human health linked to the
consumption of water from groundwater; and (ii) the
results of its application on groundwater from Les
Cayes.

2.2. Presentation of study site

Les Cayes is a city located in Haiti’s Southern region.
Its population is currently 137,952 habitants (IHSI,
2009). The city is located at 18o34’00’’ Northern
Latitude and 72o21’00” West Longitude on the
Caribbean coast, on a coastal plain with high rainfall
2. Methodology
(over 2,000 mm/yr), The average temperature varies
2.1 General approach of health risks evaluation
from 24°C to 28°C. There are two rainy seasons:
The National Research Council (1983) defines the
from April to May and August to October.
assessment of risks as the activity that evaluates
There are several types of groundwater, among
Les
Cayes
is a city located
in Haiti’s
Southern
Its population is currently 137,952 habitants (IHSI,
the toxic
properties
of a chemical
product
and region.
the
o
o
them:
alluvial
aquifers,
aquifers,
34’00’’
Northern
Latitude
and unconfined
72 21’00” West
Longitude
on karst
the Caribbean
2009).
The
city
is
located
at
18
conditions of human exposure to this product, in
giving
rise
to
a
variety
of
resurgences
and
coast,
a coastal
with
rainfall
(over and
2,000 mm/yr), The average temperature varies from flows
24°C
order toonobserve
theplain
reality
of high
human
exposure
(PNUD,
1991a).
The groundwater resources are
to
28°C.
There
are
two
rainy
seasons:
from
April
to
May
and
August
to
October.
characte­rize the nature of the effects that may result.
used for drinking water. From an ecological point
The general
approach
of of
health
risk assessment
is
There
are several
types
groundwater,
among them:
aquifers,
karst aquifers,
giving
ofunconfined
view, theyalluvial
represent
a considerable
amount
of
based
steps:
the and
hazard,
studying
rise
to on
a four
variety
of identifying
resurgences
flows
(PNUD, 1991a).
The
groundwater
resources
are
used
reserve water and play a major role in the feedingfor
of
the dose-response
relationship,
estimating
exposure
drinking
water. From
an ecological
point of
view, they many
represent
considerable
of supply
reserveiswater
lakesa and
rivers. Theamount
mode of
from
and characte­
rizing role
the risk
(NRC,
1983).
and
play a major
in the
feeding
of many lakes and
rivers. Theextraction
mode of supply
from groundwater
groundwater
with theisinstallation
of wells
extraction
the installation
of wells and boreholes,
and
spring
catchments.
Distribution
via private
In the field with
of chemical
risks, methodological
guides
and boreholes, and spring catchments.is Distribution
networks
and
connections,
and public
to Balthazard-Accou
(2011), the and
municipal
refer to the
available
tools, whether
it isstandpipes.
models or According
is via private
networks and connections,
public
water
system
istoxi­
supplied
byand
two physico-chemical
wells with a flow rate
of
66
L/s
and
an
average
production
of(2011),
about
c
ological
databases
of
standpipes.
According
to
Balthazard-Accou
3
10,134
m the
/day.
data. On
contrary, the biological risk has many
the municipal water system is supplied by two wells
a simpleoftransposition
characteris­
withthe
a flow
rate oflatrines
66 L/s are
and easily
an average
production
In
addition,tics
duethat
to prevent
the topography
this coastal city,
existing
in contact
with
of the methodology
thethechemical
to the
of about
m3/day.
groundwater;
especiallyfrom
during
rainy season,
facilitating
the10,134
movement
of microorganisms. Moreover,
biological
Thetodifference
methodology
the
city is field
very area.
sensitive
flooding. in
A brief
description In
of the
urban due
environment
of the city is
in
addition,
to the topography
of presented
this coastal
between
the
estimate
of
a
chemical
risk
andimplementation
that of a
the scenario (Figure 1) developed for the
this existing
biological
risk assessment.
city,of the
latrines
are easily in contact with
microbiological risk lies in the identification of dosegroundwater; especially during the rainy season,
The
scenario
highlights
existenceinofthe
a dumpsite
leachates are not collected or treated. They
ponse
res­
functions
and the
particularly
choice where
facilitating the movement of microorganisms.
are
in model
direct contact
with the soil
and they(Gofti,
follow the transfer mechanisms toward the groundwater.
of the
of dose-response
relationship
Moreover, the city is very sensitive to flooding. A brief
Latrines
and septic
tanks,
into
the unsaturated geological matrix area, are also noted. Other
reservoirs
1999). Human,
animal,
and discharging
envi­ronmental
description of the urban environment of the city is
utilities
such as boreholes
wells and
feeding
a family or group of families with water, an urban water
are notoriously
difficult to and
control
quantify
presented
in the
scenario
(Figure
supply
and an individual
sanitation network are also presented
in this
scenario
(Figure
1).1) developed for
(Zmirou-Navier
et al., 2006).
the implementation of this biological risk assessment.

Septic tank
& infiltration wells
Wild
discharge

Domestic
wells

Water
tower

Human
inhabitants

River

Latrine

Unsaturated zone : semiperméable
Saturated zone : groundwater
Figure 1. Graphic representation of the scenario studied
Fig.1. Graphic representation of the scenario studied

The scenario reproduces the supply mode of drinking water and wastewater management in Les Cayes.
53
Aqua-LAC
- Vol. 9 - Nº.
- Mar. 2017operation of the effluents generated
Percolation of leachates from uncontrolled
discharge,
the1 hydraulic
by latrines and septic tanks, contamination of surface water and the interactions between these aquatic
ecosystems and groundwater reflect the existence of a risk to human health that may result from the