ral areas. The surveil-
lance methodology included a check-list of hazards (Text
Box 1) to assess the sanitary conditions of water supplies
as part of a sanitary survey form, together with the as-
sessment of the microbial water quality using 44˚C
thermo-tolerant FC counts.
Lloyd and Helmer [8] (in Peru, Indonesia [Java] and
Zambia), and Lloyd and Boonyakarnkul [10] (in Thai-
land), showed that the combined risk analysis of the
sanitary survey results and the FC counts was an efficient
means of identifying and prioritizing water supply ha-
zards for remedial action. The effectiveness of the reme-
dial action was assessed with a follow up survey. This
surveillance methodology, which was later published in
Text Box 1. A checklist of hazards.
Observable sanitary hazards of open dug wells [8,11]
1) Is there a latrine within 10 m of the well?
2) Is the nearest latrine on higher ground than the well?
3) Is there any other source of pollution (e.g. animal excreta, rub-
bish) within 10 m of the well?
4) Is the plinth drainage poor, causing stagnant water within 2 m of
the well?
5) Is there a faulty drainage channel? Is it broken, permitting pond-
ing?
6) Is the wall (parapet) around the well inadequate, allowing surface
water to enter the well?
7) Is the concrete floor less than 1m wide around the well?
8) Are the walls of the well inadequately sealed at any point for 3 m
below ground?
9) Are there any cracks in the concrete floor around the well which
could permit water to enter the well?
10) Are the rope and bucket left in such a position that they may
become contaminated?
11) Does the installation require fencing?
WHO Guidelines for Drinking Water Quality [11], is
relatively simple, yet robust, in identifying the potential
sources of microbial health risks associated with drinking
water supply. This methodology is useful in the context
of developing countries which often lack advanced tech-
nology and financial resources.
4. Study Area
The Maldives Islands
The Republic of Maldives is a group of 1200 islets
spread approximately over a distance of 868 km in the
Indian Ocean. Of those, only 200 Maldivian islands are
officially classified as inhabited. The Maldives islands
spread over the equator between latitudes 7˚0630′′N and
0˚4148′′S and Longitudes 72˚3230′′E and 73˚4554′′E.
Seven study islands; Vilufushi, Thimarafushi, Vey-
mandoo, Burunee, Fenfushi, Thoddoo and Daravandhoo,
were chosen for the study by the director of the Maldives
Water and Sanitation Authority (MWSA). The study
islands were selected based on the history of water qua-
lity issues. Tables 1 and 2 summarize some information
about the study islands. According to the best informa-
tion available to the lead author there was no previous
systematic well surveillance study carried out in the Mal-
dives islands to assess the health risks associated with
open dug wells.
5. Project Outline and Methods
This study involved a field based surveillance program-
mme carried out in the selected islands of the Maldives
to systematically collect data about sanitary hazards of
abstraction wells and the quality, including thermo-tol-
erant (faecal) coliform (FC) counts, of groundwater.
Sanitary survey and well water sampling for FC counts
were carried out during day time. The surveillance work
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL.
Copyright © 2012 SciRes. JWARP
476
Table 1. Some fundamental characteristics of the Ma ldive s study islands.
Study Area Vilufushi ThimarafushiVeymandooBuruneeFenfushi Thoddoo Daravandhoo
Area (ha) 61 14.5 40.8 30.5 24.2 173.8 56.1
Resident Population 0 2408 1018 566 795 1475 966
Internally Displaced Population
(IDP) by the 2004 Tsunami 0 -
** - 2018 - - -
Population
Reconstruction Workers 425 0 0 0 - - -
Population Density (/ha) 7 166 25 85 33 9 18
Approximate Well/Latrine Density* (/ha) 2 28 5 15 6 2 3
*Every house in the remote Maldives islands has an individual household well and an on-site sanitation system and average number of people in a dwelling is
assumed to be 6; **Exact number not known (could be around 100).
Table 2. Summary of borehole permeability test results from three islands in the Maldives.
Borehole Code & Island Depth of Test Zone (m) Number of Falling Head
Tests in Zone
Average Permeability for
Test Zone (m/day) Source of Data
H2, Hithadhoo 3.0 - 4.0 3 4 Falkland, December 2000
HOA2 Hoarafushi 3.0 - 4.0 4 2.1
HAN1 Hanimaadhoo 3.0 - 4.0 3 30.9
Falkland, August 2001
Sources: [2,12].
in the Maldives was carried out from November 2007 to
January 2009. Random sampling of the well water was
carried out in each study island. The sampling locations
in each study island were selected such that the observa-
tions present a representative picture of the current
groundwater quality condition in each island studied.
The published sanitary survey form to assess the sani-
tary conditions of open dug wells [8,11] was used as a
tool to assess the sanitary conditions of open dug wells in
the Maldives islands. When a hazard, likely to cause
faecal contamination of the well, is observed, the rele-
vant survey question was marked as “Yes”. Then, at the
end of the survey all the questions with “Yes” answers
are added to get the Sanitary Hazard Score (SHS) for
graphical display against FC counts and grades for each
well. The FC grades are explained in Table 3.
To present surveillance data for collections of wells,
Lloyd & Helmer [8] proposed that, as a preliminary as-
sessment, equal weighting be given to every observed
sanitary hazard present in the operational courtyard and
well head area of each well. This was done with a view
to adding together all recorded hazards to provide a SHS
which could be plotted against FC grades for each well in
an administrative area. The principal reason for this
combined hazard/FC assessment plot was to identify the
worst wells, with most hazards and highest FC counts, in
most urgent need of rehabilitation. The graphs could also
be used to investigate a simple hypothesis, that the
greater the number of hazards, the greater the probability
of increased faecal contamination. There proved to be
only weak positive correlations in well studies in Java
and Thailand [8,10], indicating that some hazards were
Table 3. E. col i/faecal coliform classification scheme for wa-
ter supplies.
Grade Faecal coliform
counts (cfu/100ml) Risk
A 0 No risk
B 1 - 10 Low risk
C 11 - 100 Intermediate to high risk
D 101 - 1000 Gross pollution; high risk
E > 1000 Gross pollution; very high risk
Sources: [8].
more important than others. The combined analysis, of
hazards and FC counts, was subsequently analyzed by a
simple multivariate method by Lloyd and Boonyakarnkul
[10], to identify the relative importance (weighting) of
different sanitary hazards in contributing to the intensity
of faecal contamination. They produced a sanitary hazard
index to place in rank order all recorded hazards, and
assessed the impact of remedial measures (removing spe-
cific hazards) on tube wells in Thailand.
In this project the FC counts of the dug well water was
assessed using the DelAgua field test kit and the Interna-
tional Standards Organization membrane filtration tech-
nique [13]. At each study location duplicate well water
samples were processed to assess the reproducibility of
the method by the lead author, whilst a MWSA field of-
ficer collected the duplicate water samples.
Considering the statistical confidence level for FC co-
lony counts, the homogeneity levels of the FC grades
A-E (Table 4) obtained for each set of duplicate samples
demonstrated the satisfactory reproducibility (levels 1
S. BARTHIBAN ET AL. 477
Table 4. Comparison of the homogeneity of the observed faecal coliform grades between duplicate well water samples 1 and 2,
by study islands in the Maldives.
Homogeneity levels Level 1 (%) Level 2 (%) Level 3 (%) Level 4
(%)
Level 5
(%)
Study area Period AA BB CC DD EEABBCCDDEACBDCEAD BE AE
No. of
samples
Jan-08 0 0 0 2 1 0 1 1 0 0 0 0 0 0 0
Vilufushi
Total 3 (60.0) 2 (40.0) 0 (0.0) 0 (0.0) 0 (0.0)
5
Jan-08 0 3 1 6 3 1 1 4 2 0 0 1 0 0 0
Thimarafushi
Total 13 (59.1) 8 (36.4) 1 (4.5) 0 (0.0) 0 (0.0)
22
Jan-08 0 2 4 5 5 1 0 3 1 0 0 0 0 0 0
Veymandoo
Total 16 (76.2) 5 (23.8) 0 (0.0) 0 (0.0) 0
21
Jan-08 0 2 2 8 2 1 1 0 0 0 0 0 0 0 0
Burunee
Total 14 (87.5) 2 (12.5) 0 (0.0) 0 (0.0) 0 (0.0)
16
Feb-08 0 6 1 0 4 4 1 0 0 0 0 0 0 0 0
Fenfushi
Total 11 (68.8) 5 (31.3) 0 (0.0) 0 (0.0) 0 (0.0)
16
May-08 1 0 5 11 6 0 0 0 0 0 0 0 0 0 0
Thimarafushi
Total 23 (100.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)
23
May-08 1 1 2 6 4 4 1 2 0 0 0 0 0 0 0
Veymandoo
Total 14 (66.7) 7 (33.3) 0 (0.0) 0 (0.0) 0 (0.0)
21
May-08 0 1 6 3 4 0 1 1 0 0 0 0 0 0 0
Burunee
Total 14 (87.5) 2 (12.5) 0 (0.0) 0 (0.0) 0 (0.0)
16
May-08 6 0 1 2 3 0 0 1 1 0 0 2 0 0 0
Thoddoo
Total 12 (75.0) 2 (12.5) 2 (12.5) 0 (0.0) 0 (0.0)
16
Oct-08 2 3 2 0 0 1 0 0 0 0 0 0 0 0 0
Daravandhoo
Total 7 (87.5) 1 (12.5) 0 (0.0) 0 (0.0) 0 (0.0)
8
Dec-08 1 1 0 4 0 0 0 1 0 0 0 0 0 0 0
Daravandhoo
Total 6 (85.7) 1 (14.3) 0 (0.0) 0 (0.0) 0 (0.0)
7
Overall 11 19 24 47 32126 134 0 0 3 0 0 0
Overall Total 133 (77.8) 35 (20.5) 3 (1.8) 0 (0.0) 0 (0.0)171
and 2) of results by the sampling team alongside control
blank samples. Hence the mean of the duplicate data sets
(samples 1 and 2) was used in the combined analysis.
In addition to the first batch of well survey (with sam-
ples 1 & 2), a second batch of well water quality and
sanitary surveys of the same wells were undertaken in
four numbers of islands. These two surveys were sepa-
rated by two (in Daravandhoo island) to four (in Thima-
rafushi, Veymandoo and Burunee islands) months dura-
tion. The time between the two surveys was dependent
on the MWSA logistics to arrange the field work.
The second batch of surveys in the Maldives study is-
lands were carried out to:
Assess the reproducibility of the sanitary hazard me-
thodology and data;
Attempt to determine whether any changes had occu-
rred in quality characteristics.
6. Results and Discussion
6.1. Faecal Coliform (FC) Grades
The percentage occurrence of the observed FC grades,
arranged by study islands and surveys, is presented in
Table 5. Overall results showed that only 6.4% of the
samples satisfied the WHO Drinking Water Quality Gui-
deline value (zero counts/100ml of sample). FC grade
“D” (101 - 1000 cfu/100ml) was the most frequently
(35.8%) observed well water faecal contamination level
in the Maldives. Overall 78% of the wells showed FC
grades equal to, or greater than, C-grade (11 - 100
cfu/100ml). That is, a high proportion of the studied
wells in the Maldives is grossly polluted and is at high
risk.
Unlike duplicate sample sets, the observed FC grades
of the first and the second batch of surveys of the same
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL.
478
Table 5. Frequency (percentage) of occurrence of thermo-tolerant (faecal) coliform grades, arranged by sampling periods.
Frequency (percentage) occurrence of FC Grade
Study islands Period A (0) B (1 - 10) C (11 - 100) D (101 - 1000) E (>1000)
No. of
samples
Vilufushi Jan-08 0 (0.0) 0 (0.0) 1 (20.0) 3 (60.0) 1 (20.0) 5
Thimarafushi Jan-08 0 (0.0) 1 (4.5) 5 (22.7) 12 (54.5) 4 (18.2) 22
Veymandoo Jan-08 0 (0.0) 3 (14.3) 5 (23.8) 8 (38.1) 5 (23.8) 21
Burunee Jan-08 0 (0.0) 2 (12.5) 4 (25.0) 8 (50.0) 2 (12.5) 16
0 (0.0) 6 (9.4) 15 (23.4) 31 (48.4) 12 (18.8) 64
Overall Jan-08 C grade = 58 (90.6)
Fenfushi Feb-08 0 (0.0) 10 (62.5) 2 (12.5) 0 (0.0) 4 (25.0) 16
0 (0.0) 10 (62.5) 2 (12.5) 0 (0.0) 4 (25.0) 16
Overall Feb-08 C grade = 6 (37.5)
Thoddoo May-08 6 (37.5) 0 (0.0) 2 (12.5) 2 (12.5) 6 (37.5) 16
Thimarafushi May-08 1 (4.3) 0 (0.0) 5 (21.7) 13 (56.5) 4 (17.4) 23
Veymandoo May-08 1 (4.8) 5 (23.8) 3 (14.3) 8 (38.1) 4 (19.0) 21
Burunee May-08 0 (0.0) 1 (6.3) 8 (50.0) 3 (18.8) 4 (25.0) 16
8 (10.5) 6 (7.9) 18 (23.7) 26 (34.2) 18 (23,7) 76
Overall May-08 C grade = 62 (81.6)
Daravandhoo Oct-08 2 (25.0) 4 (50.0) 2 (25.0) 0 (0.0) 0 (0.0) 8
2 (25.0) 4 (50.0) 2 (25.0) 0 (0.0) 0 (0.0) 8
Overall Oct-08 C grade = 2 (25.0)
Daravandhoo Dec-08 1 (11.1) 1 (11.1) 2 (22.2) 5 (55.6) 0 (0.0) 9
1 (11.1) 1 (11.1) 2 (22.2) 5 (55.6) 0 (0.0) 9
Overall Dec-08 C grade = 7 (77.8)
11 (6.4) 27 (15.6) 39 (22.5) 62 (35.8) 34 (19.7) 173
Overall
C grade = 135 (78.0)
wells (separated by 2 - 4 months) did not show good
homogeneity levels (Table 6) which could be a result of
many factors, such as rainfall events and time of sam-
pling during a single day (Table 7).
Rainfall can increase bacterial contamination with the
onset of rainfall, because the matrix force between the
bacteria (including pathogens) and the soil particles are
broken. With continuing rainfall the quality improves,
because of dilution of contaminants with rainfall re-
charge. Flushing out of the contaminants from the
groundwater system may also occur at the coastline.
However, dramatic daytime variation in FC counts in a
single well (Ve03), across the full range of FC grades
A-E, is recorded in Table 7. The peak FC count was very
strongly (and almost instantaneously) linked to very re-
cent latrine contamination of well water by the user in
the same household. This provides the best confirmation
of the source-pathway-receptor principle.
6.2. Sanitary Surveys
This section discusses the relevance of the sanitary ha-
zards listed in the published sanitary survey form for
open dug wells, in the context of the observations spe-
cific to the Maldives.
Q1: Is there a latrine within 10 m of the well?
This question checks whether the open dug well is lo-
cated at less than a safe separation distance from an on-
site sanitation system. Here, 10 m safe separation dis-
tance was used as a general guideline value. What could
be the safe separation distance in the context of the Mal-
dives study islands where the aquifers are classed as ex-
tremely vulnerable and there is virtually no soil layer?
The British Geological Survey guidelines for Assess-
ing the Risk to Groundwater from On-Site Sanitation
(ARGOSS) defines the groundwater abstraction system
as being at significant risk when it is located at a distance
less than 25 day groundwater travel time from an on-site
sanitation system [4]. This corresponds to a much
greater distance th an 10 m in the Maldivian aquifer con-
text.
The summary of borehole test results carried out by
Falkland [2,12] is presented in Table 2. According to
Table 2 the average permeability at a depth of 3.0 to 4.0
m varied from 2.1 m/day to 30.9 m/day in different study
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL. 479
Table 6. Comparison of the observed faecal coliform grades between the preliminary and follow up surveys arranged by
study islands in the Maldives.
Level 1 (%) Level 2 (%) Level 3 (%) Level 4 (%) Level 5 (%)
Homogeneity
levels AA BB CC DD EE ABBCCDDEAC BDCE AD BE AE
Total
no. of
samples
0 0 2 8 2 0 0 3 3 1 1 2 0 0 0
Thimarafushi
island 12 (54.5) 6 (27.3) 4 (18.2) 0 (0.0) 0 (0.0) 22
0 2 2 2 2 0 0 4 4 0 3 0 1 1 0
Veymandoo island 8 (38.1) 8 (38.1) 3 (14.3) 2 (9.52) 0 (0.0) 21
0 0 2 0 0 0 0 6 3 0 2 2 0 1 0
Burunee island 2 (12.5) 9 (56.3) 4 (25.0) 1 (6.25) 0 (0.0) 16
1 1 0 0 0 0 1 3 0 0 1 0 0 0 0
Daravandhoo
island 2 (28.6) 4 (57.1) 1 (14.3) 0 (0.0) 0 (0.0) 7
Table 7. Daytime FC counts profile showing considerable
variation with sampling time observed at Ve03 in the Vey-
mandoo island.
Date Time (hrs)
Average FC counts
(cfu/100ml)
7:40:00 4
9:05:00 12
11:00:00 0
13:05:00* 1049
15:15:00 41
25.05.2008
17:03:00 8
*The land lady had just finished using the bathroom (had a bath for sure, and
had also used the toilet).
islands in the Maldives.
Assuming a minimum permeability value of 2.1 m/day
at the specific depth among those summarized in Table 2 ,
the distance of 25 day groundwater travel time will be at
least 52.5 m. Therefore, if the separation distance be-
tween a dug well and an on-site sanitation system in the
Maldives islands is less than 52.5 m, then the dug well is
at high risk of microbiological contamination. Therefore
Q1 of the survey form needs to be modified according to
the hydro-geological setting e.g., Q1: Is there a latrine
within 52.5 m of the well? In the context of the Maldives
islands.
It is common practice in the Maldives islands to build
the latrine facility next to the well, or within the wash
room, which is also shared by the domestic well. How-
ever, the latrine pit (septic tank) is located further away
from the latrine, but within the compound. Therefore
question 1 in the sanitary survey form should be con-
cerned with the latrine pit (septic tank), rather than the
location of the latrine in the context of the Maldives, be-
cause, unless the latrine plate and waste pipe are dam-
aged, it is the leachate from the latrine pit which causes
the great majority of the faecal contamination of ground-
water. A latrine pit located within the safe separation
distance of a well will be treated as a hazard only when
the latrine has the potential to contaminate the well water.
Dry, on-site, sanitation systems do not pose a threat to
the microbial groundwater quality (unless it is directly
contaminated), because there will not be leachate coming
out of the pit. However, as in the case of the Maldives
islands, wet on-site sanitation systems are likely to be the
major source of faecal contamination of groundwater and
well water.
In the context of the Maldives islands, question one
should be modified as, Q1: Is there a latrine within 52.5
m of the well?
Now, the maximum possible separation distance be-
tween two latrines located within an area of 1 ha can be
39.9 m (2 times the area of a circle with a radius of 39.9
m is equal to 1 ha). All individual houses in the Maldives
study islands own a well and an on-site sanitation system.
Hence the feasible separation distance between a well
and an on-site sanitation system will be less than 39.9 m;
this is less than the separation distance of significant risk
(52.5 m in the context of the Maldives islands) as defined
in BGS ARGOSS guidelines [4] The overall maximum
and the minimum observed separation distances between
a well and a latrine observed in the Maldives study is-
lands were 36.1 m and 1.0 m respectively, with an aver-
age value of 8.1 m. Also, the latrine density in the Mal-
dives study islands were above 2 no./ha. Therefore all the
latrine effluents in this Maldives study were located
within the safe separation distance of the well!
The maximum feasible separation distance between
two wells, in the Maldives islands, is 39.9 m. Therefore,
depending on the rate of well water abstraction, the
natural groundwater flow direction can be altered in the
vicinity of the well for some time until the cone of de-
pression caused by the groundwater abstraction fully
recovered to the level of groundwater table. Considering
the high density of on-site sanitation systems and open
dug wells, every individual well is surrounded by more
than one on-site sanitation system. This situation pro-
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL.
480
vides more opportunities for the leachates from any on-
site sanitation system to reach one or more wells rapidly.
Therefore the answer to this altered question (Q1) will
always be “Yes” in the case of the Maldives islands stud-
ied, and thus becomes both the commonest and the most
important hazard. Considering these facts (and based on
the BGS ARGOSS guidelines [4]), it is concluded that
maintaining a safe separation distance between an open
dug well and an on-site sanitation system is not possible
in most of the Maldives islands.
Q2: Is the nearest latrine on higher ground than the
well?
The second question in the published survey form is
intended to reinforce Q1 where groundwater flow direc-
tion is likely to increase the risk of faecal contamination
from latrines. However, since the topography of the Mal-
dives is almost flat there is virtually no down-gradient
flow, Question 2 can therefore be excluded. Furthermore,
it is not possible to deduce the potential for the leachate
from the latrine to reach the well water without tracer
study information about the groundwater flow direction.
However, this information was not available for the Mal-
dives.
Q2: Is the nearest latrine on higher ground than the
well? Of the published survey form is redundant and will
not be considered further.
Q3: Is there any other source of pollution (e.g. animal
excreta, rubbish) within 10 m of the well?
This question checks the possibility of microbial con-
tamination of well water from other localized sources of
contamination. It is not a common practice in the Mal-
dives to keep live stock, or pets due to the religious be-
liefs. However, breeding birds including hens were seen
in several houses in the study islands. Open disposal of
rubbish within the house plot near domestic dug wells
was observed frequently in the Maldives islands. As dis-
cussed in the case of Q1, the distance checked in Q3
might be modified to 52.5 m in the context of the Mal-
dives islands. However, at this distance (52.5 m) this
hazard is most unlikely to represent hazard. Therefore the
Q3 need not be modified in the case of the Maldives is-
lands.
Q4: Is the drainage poor, causing stagnant water
within 2 m of the well? AND,
Q5: Is there a faulty drainage channel? Is it broken,
permitting ponding?
These questions check whether the wasted well water
and other surface water, which potentially carries patho-
gens, could drain back into the well through preferential
pathways. Even though the wells were built inside the
washroom most of the time, the drainage was directed
out of the wash room towards the garden, or garbage
dumping area, or sometimes into the soakage pits of the
latrines. The washrooms were either marbled or ce-
mented. However, cracks on the floor of the washroom
were witnessed. Therefore, in the context of the Maldives
islands, these questions, Q4 and Q5 are valid and don’t
need to be modified, but become Q3 and Q4 respectively.
Q6: Is the wall (parapet) around the well inadequate,
allowing surface wa ter to enter the well?
Question 6 checks whether any contaminated surface
water, can potentially enter into the well due to an in-
adequate, damaged parapet wall. Only in very rare oc-
currences was the parapet wall around the well observed
to be inadequate in the Maldives study islands. However,
this can be a potential hazard in the context of the Mal-
dives and thus remains a valid question as Q5.
Q7: Is the concrete floor less than 1 m wide around the
well?
As in the case of questions four and five, question
seven checks whether any potentially contaminated sur-
face water can enter into the well water through prefer-
ential pathways, in the absence of 1 m wide plinth around
the well. This could be another potential observable
sanitary hazard in the Maldives islands. Yet, it is a com-
mon practice observed in the Maldives islands, to build
the domestic well within the wash room (next to the la-
trine)! Since, the wells are located within the washroom,
most of the time the plinth around the well happens to be
wider than 1 m (with floor tiles or concrete paving). Con-
sequently, this remains a major concern and the question
is retained as Q6.
Q8: Are the walls of the well inadequately sealed at
any point for 3 m below ground?
This question checks the availability of preferential
pathways for the polluted water interflow to enter into
the well. Since the groundwater table in the Maldives
islands is very shallow (about 2 to 3 m), this question can
be an important potential hazard identification question
in the Maldives islands’ context. It is therefore valid in
the Maldives and becomes Q7.
Q9: Are there any cracks in the concrete floor around
the well which could permit water to enter the well?
Once again question 9 checks the presence of prefer-
ential pathways for the polluted water to reach the well
water. Even though most of the wells in the Maldives
islands are located within the wash room with a wide
plinth present around the well, still the floor can have
cracks. Therefore question 9 is valid in the Maldives is-
lands’ context and becomes Q8.
Q10: Are the rope and bucket left in such a position
that they may become contaminated?
A metal or plastic container attached to a pole, called a
“Dhani”, is the means of manual abstraction used in the
Maldives islands to abstract groundwater. However, in-
creasing usage of demand driven pressure pumps are also
observed in the study islands for flushing the toilets and
in the kitchens. When the “dhani” was used for well wa-
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL.
Copyright © 2012 SciRes. JWARP
481
ter abstraction, often it was left in an unsanitary position.
Therefore, question ten is a valid question in the case of
the Maldives islands and can be modified as Q9: Is the
groundwater abstraction means (“Dhani”) left in such a
position that it may become contam inated?
Q11: Does the installation require fencing?
Question 11 checks whether any animals can reach the
well head and cause contamination of the surface water
(by excreting) which can then reach the well water
through preferential pathways. Pet breeding is unusual in
the Maldives islands except for a few cases of birds
breeding. Birds cannot be restrained from reaching the
well using a fence. Hence this question is not useful in
the case of the Maldives islands and is removed.
Therefore, in the context of the Maldives islands, the
sanitary survey form for open dug wells was modified as
follows:
Q1: Is there a latrine within 52.5 m of the well? Is it on
higher ground than the well?
Q2: Is there any other source of pollution (e.g. animal
excreta, rubbish) within 10 m of the well?
Q3: Is the drainage poor, causing stagnant water
within 2 m of the well?
Q4: Is there a faulty drainage channel? Is it broken,
permitting ponding?
Q5: Is the wall (parapet) around the well inadequate,
allowing surface wa ter to enter the well?
Q6: Is the concrete floor less than 1m wid e around the
well?
Q7: Are the walls of the well inadequately sealed at
any point for 3 m below ground?
Q8: Are there any cracks in the concrete floor around
the well which could permit water to enter the well?
Q9: Is the groundwater abstraction means (“Dhani”)
left in such a position that it may become contaminated?
The answers to the first sanitary survey question in the
modified list are all “Yes” for all study wells except in
Vilufushi island in the Maldives islands. Vilufushi Island
was under complete reconstruction of the infrastructure
and residential buildings after the complete inundation by
the Year 2004 tsunami brought sea water, during the
study period. Hence only 425 construction workers and
officials were occupying the Vilufushi Island at that time.
Hence the island had couple of on-site sanitation systems
built next the residences of the workers and officials. The
answers to the rest of the questions are the same as those
observed using the sanitary survey form for open dug
wells published by WHO [11]. Therefore the frequency
of occurrence of the sanitary hazards of the modified
sanitary survey form is summarized in Table 8.
6.3. Faecal Coliform Counts vs. Sanitary Hazard
Score
To understand the strength of correlation between the FC
counts and the SHS, the FC observations were plotted
against the SHS for each study area. This will test the
hypothesis that increasing number of hazard points are
broadly correlated with increasing level of groundwater
faecal contamination.
The FC count observations varied from zero/100ml to
Too Numerous to Count (TNTC). In order to accom-
modate this wide range of FC counts, the base ten loga-
rithmic FC counts (Log10FC) are plotted against the ob-
served SHS of each studied groundwater source in the
following graphs. To avoid Log0 issues 0.1 is added to
each FC count. Counts as high as 30,000 FC cfu/100ml
sample are assigned to FC count observations denoted as
TNTC and CG (Confluent Growth).
The correlation coefficient value of the curves (Table
9) is the square root of the R2 value. It is a tool used to
express the level of correlation between the two parame-
ters studied. The correlation coefficient values suggest
the following relationships between the parameters:
0 to 0.3: weak correlations;
0.3 to 0.7: moderate correlation e.g. Daravandhoo
(logarithmic correlation, Graph 1);
0.7 to 1: good correlations.
Table 8. Frequency (percentage) of occurrences of the sanitary hazards listed in the modified sanitary survey form in the
Maldives islands.
Sanitary hazard points (Yes: 1, No: 0)
Island 1 2 3 4 5 6 7 8 9
Number
of well
surveys
Vilufushi 1 (16.7) 4 (66.7) 6 (100.0) 6 (100.0) 4 (66.7) 5 (83.3)4 (88.7) 6 (100.0) 1 (16.7) 6
Thimarafushi 22 (100.0) 17 (77.3) 4 (18.2) 1 (4.55) 0 (0.0) 2 (9.09)4 (18.2) 11 (50.0) 19 (86.4)22
Veymandoo 16 (100.0) 15 (93.8) 10 (62.5) 9 (56.3) 1 (6.25) 13 (81.3)0 (0) 15 (93.8) 10 (62.5)15
Burunee 16 (100.0) 14 (87.5) 3 (18.8) 1 (6.25) 0 (0.0) 12 (75.0)3 (18.8) 14 (87.5) 11 (68.8)16
Fenfushi 15 (100.0) 8 (53.3) 8 (53.3) 7 (46.7) 2 (13.3) 8 (53.3)2 (13.3) 10 (66.7) 9 (60.0) 15
Thoddoo 15 (100.0) 11 (73.3) 12 (80.0) 11 (73.3) 3 (20.0) 14 (93.3)3 (20.0) 14 (93.3) 11 (73.3)15
Daravandhoo 10 (100.0) 7 (70.0) 6 (60.0) 7 (70.0) 0 (0.0) 6 (60.0)0 (0.0) 7 (70.0) 6 (60.0) 10
Overall 95 (96.0) 76 (76.0) 49 (49.5) 42 (42.4) 10 (10.1)60 (60.6)16 (16.2)77 (77.8) 67 (67.7)99
S. BARTHIBAN ET AL.
482
Table 9. Summary of linear correlation coefficient (R2) values of Log10FC counts vs. SHS curves.
Study island Study period Linear correlation coefficient Study period Linear correlation coefficient
Vilufushi Jan-08 0.0204 - -
Thimarafushi Jan-08 0.0928 May-08 0.0604
Veymandoo Jan-08 0.0241 May-08 0.0139
Burunee Jan-08 0.0902 May-08 0.0379
Fenfushi Feb-08 0.0043 - -
Thoddoo May-08 0.0378 - -
Daravandhoo Oct-08 0.3564 Dec-08 0.4624
Graph 1. Plot of the Log10FC counts vs. Sanitary Hazard Score observed in Daravandhoo Island during October and
December 2008.
The correlation coefficient values summarized in Ta-
ble 9 indicates that the correlation between the observed
FC counts and the SHS’s are generally weak. Only Da-
ravandhoo Island shows moderate correlations (Graph
1).
However in both of the scenarios the observed fre-
quency of the sanitary hazards (Table 8) did not show
any noticeable trend. Therefore the reasons for the dif-
fering correlations observed could be that most of the
hazards present in the study islands, other than Dara-
vandhoo island, are not significantly contributing to fae-
cal contamination of well water compared with the pro-
ximity of well to latrine effluent. Otherwise there may be
other contributory factors such as rainfall or population
density influencing the FC counts and the correlations
between the LogFC counts and the SHS. Therefore there
is a fundamental need to assess the relative weight of
each observable sanitary hazard listed in the survey form.
The population density can be an important factor in
the context of the Maldives islands, because of the very
small size of the study islands and the lack of safe sepa-
ration distance between the open dug well and the latrine
pits. However, the impact of the population density can
be underwhelmed by strictly following the standards of
(water sealed) septic tank construction together with a
tile field for further treatment of septic tank effluent be-
fore it reaches the groundwater body. In other words by
efficiently containing the contaminants at the source the
impact of the population density on the microbial well
water quality can be reduced.
The population density is not the major contributor for
the observed higher levels of faecal contamination (above
D grade) in the Maldives setting, as it shows a weak cor-
relation (Table 10 and Graph 2) with higher levels fae-
cal contamination.
The rainfall impact during the survey in May-08 in
Veymandoo Island and during both October and Decem-
ber 2008 in Daravandhoo island (Ta bl e 1 1 ) were insensi-
tive to the observed FC counts (Graph 3). That is heavy
rainfall event (Table 12) showed least correlation with
the observed FC counts while light rain showed no sig-
nificance. Having observed least correlation between
heavy rainfall event and observed faecal coliform counts
implies that the impact from rainfall is not significant in
the Maldives islands.
6.4. Combined Risk Analysis
Lloyd and Helmer [8] used the criteria in Table 13 to
assess the relative risk of water supplies using the com-
bined analysis of FC grades and the sanitary hazard score
classification, and to prioritize the water supplies for re-
medial action. The faecal grade and the sanitary risk
grades used in Table 13 are presented in Tables 3 and 14.
However, Lloyd and Boonyakarnkul [10] used a slightly
different sanitary inspection risk score classification sche-
me for tube wells (Table 14).
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL. 483
Table 10. Population density in the Maldives study islands.
Study island Period Population
density (/ha)
Samples with
above FC grade
D (%)
No. of
samples
Vilufushi Jan-08 7 80 5
Thimarafushi Jan-08 166 72.7 22
Veymandoo Jan-08 25 61.9 21
Burunee Jan-08 85 62.5 16
Fenfushi Feb-08 33 25 16
Thoddoo May-08 9 50 16
Daravandhoo Oct-08 18 0 8
Table 11. Daily rainfall in Veymandoo and Daravandhoo
islands during two batches of surveys.
Island Veymandoo Dharavandhoo
Survey type Date Rainfall (mm) Day Rainfall (mm)
12-Jan-08 36.8
13-Jan-08 0
1st survey
14-Jan-08 0
17-Oct-08 0
24-May-08 0
2nd survey
25-May-08 0
16-Dec-08 Trace
Source: [14].
Table 12. Classification of rainfall intensity.
American meteorological society UK meteorological office
Rainfall intensity
(mm/hr) Classification Rainfall intensity
(mm/hr) Classification
Trace to 2.5 Light rain Less than 0.5 Slight rain
2.6 to 7.6 Moderate rainfall0.5 to 4 Moderate rain
over 7.6 Heavy rainfall Greater than 4 Heavy rain
Sources: [15,16].
Table 13. Lloyd and Helmer’s [8] combined risk analysis of
sanitary inspection and faecal coliform contamination.
Faecal grade + Sanitary hazard gradeAction priority
A + No Risk No Action
B + Low Risk Low Priority
C + Intermediate to high risk Higher Priority; As soon as
the resources permit
D/E + Very high Risk Highest Priority; Most
urgent action
Table 14. Sanitary inspection risk score classifications.
Lloyd and Helmer (1991) Lloyd and Boonyakarnkul (1992)
Hazard scoreRisk Hazard score Risk
0 No risk 0 - 2 Low risk
1 - 3 Low risk 3 - 5 Intermediate risk
4 - 6 Intermediate to
high risk 6 - 8 High risk
7 - >10 Very high risk9 - 10 Very high risk
Sources: [8,10].
Graph 2. Plot of the population density in the study islands
vs. the percentage occurrence of above-D grade faecal con-
tamination levels.
Graph 3. Plot of the rainfall intensity vs. the observed FC
counts in Veymandoo island, during January and May
2008.
The sanitary inspection form used in this study for dug
wells, lists all the observable sanitary hazard points that
are attached to a particular groundwater point source. A
zero sanitary inspection score indicates that there is no
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL.
484
observable risk attached to the studied open dug well.
The aim of the combined sanitary risk analysis (Table 13)
is to prioritize remedial action in large collections of
wells, by identifying and removing observable hazards.
However, the vulnerability (and level of contamination)
of a point groundwater source is also dependent on the
hydrogeology of the aquifer from which the groundwater
is tapped. In shallow, highly porous or fissured aquifers
such as limestone aquifers with large solution cavities,
contaminated groundwater originating from remote loca-
tions, distances much greater than the required safe se-
paration distance between a sanitation system and the
groundwater point source, can easily reach the well water.
In this scenario, even with a zero observable sanitary
hazard score the groundwater point source could be at
considerable risk. Hence, in this hydro-geological setting,
the inclusion of zero sanitary hazard score within the
“low risk” group is a more logical approach. Because of
this the slightly modified form of the Lloyd and Boon-
yakarnkul’s [10] sanitary hazard inspection risk classifi-
cation scheme (Table 15) is used in this paper as the ba-
sis for the combined risk analysis.
Similarly, because of the observed large variation in
FC counts during a few hours (Table 6), a single (or
even duplicate) zero thermo-tolerant FC observation may
not mean zero risk, but low risk [4]. Therefore the E.
coli/FC classification in Table 16 is used in the com-
bined risk analysis of sanitary conditions and FC con
tamination (Table 17) in this paper.
According to Table 18, less than 7.2% of the wells in
the study areas are at low risk and hence of low action
priority. Unfortunately, above 57.7% of the wells in the
study are at very high risk of microbial contamination
and require urgent action.
The idea of combined risk analysis was used [8]
Table 15. Sanitary inspection risk score classification.
Hazard score Risk
0 - 2 Low risk
3 - 5 Intermediate risk
6 - 8 High risk
9 Very high risk
Table 16. E. coli/faecal coliform classification scheme for
water supplies.
Grade Faecal coliform
counts/100ml Risk
A 0 Low risk
B 1 - 10 Low risk
C 11 - 100 Intermediate to high risk
D 101 - 1000 Gross pollution; high risk
E >1000 Gross pollution; very high risk
Table 17. Combined risk analysis of sanitary inspection and
faecal coliform contamination.
Faecal grade + Sanitary Hazard grade Action priority
A/B + Low risk Low Priority
C + Intermediate to high risk Higher Priority; As soon as
the resources permit
D/E + Very high Risk Highest Priority; Most
urgent action
mainly to group the study wells according to the relative
risk of faecal contamination and to prioritize remedial
action. Since a majority of the wells in Table 18 are ca-
tegorized as at very high risk and require urgent action,
there is a need for further prioritization among the “very
high risk” group of wells to cope with the limited re-
sources. Elsewhere [10] assessing the relative signifi-
cance of individual hazards helped to prioritize remedial
actions, but in the Maldives all wells need protection
from direct gross contamination of the aquifer by septic
tank effluents.
7. Conclusions
The list of sanitary hazards occurring in open dug wells,
which was published by Lloyd & Helmer [8] and WHO
[11], required revision under the naturally high vulner-
ability hydro-geological setting of the Maldives islands.
A modified list of sanitary hazards was developed with
justifications and applied here. It can be used in future
sanitary surveys in the Maldives and similar small island
scenarios.
As a preliminary approach using plots of graphs of
combined risk assessments, proposed equal weighting for
all the observable sanitary hazards with open dug wells
was proposed [8], even though the relative weighting will
vary in reality [10]. However, the combined risk assess-
ment revealed that more than 50% of the wells studied in
the Maldives islands are at high risk, requiring urgent
action to reduce faecal microbial contamination. Im-
proving all identified wells with respect to all the ob-
served sanitary hazards would involve substantial capital
costs which are not readily available in developing coun-
tries such as the Maldives islands. Consequently the ob-
servable sanitary hazards need to be weighted using a
multivariate analysis [10], to prioritize and economize on
rehabilitation work. Pilot remedial action projects are
required to demonstrate that sanitary hazards with the
highest weighting are carried out first to demonstrate
significant water quality improvements.
It has been shown that faecal contamination of aqui-
fers in the Maldives is almost ubiquitous. This is due, in
large part, to the proximity of septic tanks to the wells.
The generally weak correlations between the total of
sanitary hazards and FC counts reflect the dominance of
Copyright © 2012 SciRes. JWARP
S. BARTHIBAN ET AL.
Copyright © 2012 SciRes. JWARP
485
Table 18. Grouping of open dug wells according to the associated risk of faecal contamination, arranged by study areas.
Survey type Study area No. of wells Low risk: Low action
priority (No.)
Intermediate to high risk: Higher
action priority (No.)
Very high risk: Urgent
action (No.)
Vilufushi 5 0 1 4
Thimarafushi 21 0 5 16
Veymandoo 17 0 4 13
Burunee 16 0 6 10
Fenfushi 15 3 8 4
Thoddoo 16 1 5 9
Daravandhoo 8 3 5 0
Total 97 3 38 57
1st batch of
surveys
% occurrence 7.20% 35.10% 57.70%
Thimarafushi 22 0 5 17
Veymandoo 17 0 6 11
Burunee 16 0 9 7
Daravandhoo 9 2 2 5
Total 64 2 22 40
2nd batch of
surveys
% occurrence 3.10% 34.40% 62.50%
one or two hazards, principally the influence of septic
tanks on groundwater contamination. The potential influ-
ence of other contributory factors to the faecal contami-
nation of well water such as rainfall (to a lesser degree)
and, notably, population density, appears to be much less
significant.
Considering all the facts discussed earlier (and based
on the BGS ARGOSS [4]), it is explicit that maintaining
a safe separation distance between an open dug well and
an on-site sanitation system is not possible in most of the
Maldives islands. Consequently, the top priority should
be the improvement of septic tank design and perform-
ance. This will enhance the effective containment of the
pollutants at the source level (in the source-pathway-
receptor relationship). Once the overwhelming influence
from the septic tanks on groundwater contamination is
significantly reduced/eliminated, a follow-up surveil-
lance study will help to evaluate the efficacy of the septic
tank improvement programme in improving the well wa-
ter quality, and to judge the impact from the other ob-
servable sanitary hazards listed in the sanitary survey
form.
8. Acknowledgements
This project was carried out with the practical support of
the Director and staff of the Maldives Water and Sanita-
tion Authority (MWSA), Republic of Maldives, and with
the financial support of the Mayor of Karlsruhe’s post-
tsunami charitable fund managed by Stadtwerke Karl-
sruhe, Germany.
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Abbreviations
ARGOSS: Assessing Risk to Groundwater from On-site
Sanitation;
MWSA: Maldives Water and Sanitation Authority;
GoM: Government of Maldives;
UNICEF: United Nations Children’s fund.
Copyright © 2012 SciRes. JWARP