ASSESSMENT OF THE IMPACTS OF PIT LATRINES ON GROUNDWATER
QUALITY IN RURAL AREAS:
A CASE STUDY FROM MARONDERA DISTRICT, ZIMBABWE
*B.Dzwairoa, Z.Hokoa, D.Loveb,c, E.Guzhad
a
Civil Engineering Department, University of Zimbabwe hoko@eng.uz.ac.zw,
b
Geology Department, University of Zimbabwe davidlove@science.uz.ac.zw,
c
WaterNet, Zimbabwe davidlove@science.uz.ac.zw,
d
Mvuramanzi Trust, Zimbabwe eguzha@zol.co.zw
*Corresponding author. Box MP 167, MT Pleasant, Harare, Zimbabwe
Tel.: +263 4 303288; fax: +263 4 303288 dzvairo@eng.uz.ac.zw/ bdzvairo@excite.com
ABSTRACT
In resource-poor and low-population-density areas, on-site sanitation is preferred to off-site
sanitation. However, its groundwater pollution potential in such areas conflicts with IWRM
principles that advocate for sustainability of water resources in terms of both quality and
quantity. Given the widespread use of shallow groundwater for domestic purposes in rural
areas, maintaining groundwater quality is a critical livelihood intervention.
This study assessed impacts of pit latrines on groundwater quality in Kamangira Village,
Marondera District, Zimbabwe. Groundwater samples from 14 monitoring boreholes and 3
shallow-wells were analysed during 6 sampling campaigns, between February 2005 and May
2005.
Parameters analysed were total and faecal coliforms, NH3-N, NO2--N, NO3--N,
conductivity, turbidity and pH, both for boreholes and shallow-wells. Total and faecal coliforms
both ranged 0-TNTC (too-numerous-to-count), 78% of results meeting the 0 CFU/100 ml WHO
1
guidelines value. NH3-N ranged 0-2.0mg/l, with 99% of results falling below 1.5mg/l WHO
recommended value. NO2--N and NO3--N ranged 0.0-0.64 and 0.0-6.7mg/l, within 3 and 10mg/l
WHO guidelines values, respectively. Conductivity ranged 46-370s/cm while pH ranged 6.87.9. There are no guideline values for these parameters. Turbidity ranged 1-45NTU, 59% of
results meeting the 5NTU WHO guidelines limit. Water table seasonal-drop averaged 1.1-1.9m.
Soil from monitoring boreholes was characterised as sandy. The soil infiltration layer averaged
1.3-1.7m above water table for two latrines and 2-3.2m below it for one. A survey revealed the
prevalence of diarrhoea and the unsuitability of pit latrines due to structural failure.
Results indicated that pit latrines were microbiologically impacting on groundwater quality up
to 25m distance, raising fears of exposure to pathogens associated with coliforms. Nitrogen
values were of no immediate threat to health. The shallow water table increased pollution
potential from pit latrines.
Raised pit latrines and other low-cost technologies could be
considered to minimize potential of groundwater pollution.
Keywords: groundwater quality, pit latrines, rural area, sustainable sanitation
2
1. INTRODUCTION
Worldwide, water-borne diseases are a major cause of morbidity and mortality in humans
(WHO, 1996).
While water-borne pathogens infect around 250 million people per year,
resulting in 10-20 million deaths (Anon, 1996), many of these infections occur in developing
nations that have sanitation problems (Nsubuga et al., 2004). Lewis et al. (1980) also reiterates
that diseases caused by pathogens and related to the use of contaminated groundwater, are the
greatest cause of death in developing countries. In countries such as Zimbabwe and South
Africa, most of the rural communities are poverty-stricken, lack access to portable water supplies
and rely mainly on shallow-wells, rivers, streams and ponds for their daily water needs
(Nevondo and Cloete, 1991). In most cases water from these sources is used directly without
treatment and the water sources may be faecally contaminated (WHO, 1993). Simple low-cost
on-site sanitation methods have been developed to dispose faecal matter, mainly because of their
economic advantage. However, the biggest drawback is the well-recognized potential to pollute
groundwater resources (ARGOSS, 2001; Lewis et al., 1980), which conflicts with Integrated
Water Resources Management principles, some of which are to maintain water quality and
quantity and vital ecosystems. Given the widespread use of shallow groundwater for domestic
purposes in rural areas, maintaining groundwater quality is a critical livelihood intervention.
Globally, the larger part of the population lives in rural areas and in Africa it is estimated that
these people represent approximately 70 to 80% of the continent’s population. In Zimbabwe
about 70% of the population live in the rural areas and approximately the same percentage rely
on groundwater (Chenje et al., 1998).
That reliance may be higher in some districts of
Zimbabwe as noted by Hoko (2004), where rural communities like Gokwe, Nkayi, Mwenezi and
Lupane, mainly use groundwater for domestic purposes with very little reliance on surface water.
Yet there is an information gap on the levels of groundwater contamination from pit latrines in
Zimbabwe (Chenje et al., 1998; Chidavaenzi et al., 1999). Therefore the quality of groundwater,
3
which potentially can be affected by on-site sanitation systems, must be carefully assessed in
order to reduce the health and environmental risk.
This study was carried out in Kamangira Village, Marondera district, Zimbabwe. As is the case
with most rural communities in the country, the people of Kamangira Village mainly use
shallow-wells as a source of domestic water and other purposes and pit latrines for sanitation.
The geological set-up and soil type in the area, compounded by a generally high water table, are
thought to have caused several pit latrine failures such as cracking, sinking and over flooding.
According to Lewis et al. (1980), failure of on-site sanitation systems may result in serious
pollution of groundwater, the primary cause for health concerns being the excreted pathogens
and certain chemical constituents like nitrate.
The study assessed impacts of pit latrines on groundwater quality, taking levels of total and
faecal coliforms, ammonia (NH3-N), nitrite (NO2--N) and nitrate (NO3--N), conductivity,
turbidity and pH as impact indicators. The parameters chosen are those that a wide range of
studies, internationally have demonstrated to be problematic with regards to on-site sanitation.
Some of the parameters also tend to have an effect on the perceived water quality and also on
health. A disease incidence survey was carried out in order to assess the possible health impacts
of groundwater pollution.
The overall aims of the study were to contribute towards the
improvement of safe water supply and sanitation services and to recommend alternative
mitigatory and management measures where necessary.
2. STUDY AREA
Kamangira Village is in Chihota rural area, Marondera District, in Zimbabwe and the District’s
geographical location is shown in Figure 1. The village has a population of about 100 people
and the homesteads follow a linear settlement pattern. The pick rainy period for the area is
4
December to February, while June to September are the dry months, with very isolated rainy
days in June and August.
Key:
Study site
N
Marondera
Figure 1 Map of Zimbabwe and Marondera district.
(Adapted from: www.zimrelief.info/files/attachments/2002%20population%20summary.jpg)
The predominant form of sanitation is pit latrines whose impacts on groundwater quality was the
main objective of the study. The main source of domestic water is shallow-wells. Chihota rural
area is truncated by numerous faults, of which two major sets are outstanding, the north/northeast and north-east trending sets. These faults tend to have a major influence in controlling the
drainage of the area (Mukandi, 2005), with intrusive features like dykes enhancing the
groundwater potential of rocks, thereby increasing the transmission properties of the aquifer
(Maziti, 2002). At a localized scale, Kamangira Village is covered with granitic rocks and the
soils are pale-sandy.
3. MATERIALS AND METHODS.
3.1 Study site design.
Figure 2 presents the study site design. The study site was situated on a watershed, which meant
5
that the actual setup could be designed so as to exclude groundwater flow from some parts of the
drainage system. Pit latrines under investigation were marked PL1, PL2 and PL3, and the
shallow-wells close to those latrines were marked SW1, SW2, and SW3 respectively. Shallowwell (SW1) was located 44 m southeast of pit latrine (PL1), shallow-well (SW2) at 38 m north of
pit latrine (PL2), and shallow-well (SW3) was located 44 m south of pit latrine (PL3).
SW2
TW10
SW2
7990560
TW9
TW8
TW7
PL2
TW6
7990540
7990520
TW13
PL2
CONTROL
TW5
PL3
TW12
7990500
PL3
TW11
TW4
PL1
TW3
SW1
SW3
7990480
TW2
PL1
TW1
7990460SW3
SW1
300660 300680 300700 300720 300740 300760 300780 300800 300820 300840
Figure 2 Study site design.
The positions of pit latrines within the study site itself provided an ideal set-up where two pit
latrines could be joined along a transect and their impacts on groundwater quality investigated,
either individually or combined. A total of 14 monitoring boreholes were drilled upstream and
downstream of pit latrines, at positions marked in Figure 2, using a Vonder Rig. The boreholes
were cased using perforated 125 mm PVC pipe. Figure 2 also shows the location of the control
borehole at 80 m north-east of PL1 and 100 m east of PL2. The control borehole was also cased
in the same manner as the other boreholes.
3.2 Sampling and analysis methods
Six sampling campaigns were made between February 2005 and May 2005, covering the rainy
season.
Boreholes were flushed once before commencement of the sampling campaign.
6
Subsequent flushing at every sampling event could not be done because some of the parameters
which were to be tested for were sensitive to water disturbances. Furthermore, the perforation of
the casing was assumed to allow through-flow of groundwater. Groundwater samples were
collected at the water surface from the boreholes and the shallow-wells. Brickwork and heavy
concrete slabs protected the boreholes and the casings were opened only for sampling purposes.
The samples were analysed for NH3-N, NO2--N, NO3--N, conductivity, turbidity and pH,
according to standard methods as prescribed in the Water and Wastewater Examination standard
methods handbook of 1989 (APHA, 1989). Water quality data was analysed using Microsoft
Excell and Surfer 7 software packages and compared to WHO Guidelines for drinking water
(WHO, 2004).
3.2.1 Water and soil tests
For coliforms, microbiological tests were performed on duplicate 50 ml samples, after filtering
the sample portions through individual 0.45 μm membrane filter papers, as stipulated in the
Membrane Filter Technique for members of the coliform group (method number 9222). NH3-N
was determined as described in method number 4500-NH3 F.
NO2--N was determined as
described in the Palintest Nitricol Field Kit method. NO3--N was determined according to the
Ultraviolet Spectrophotometric Screening Method number 4500-NO3- B.
Conductivity was
determined by emersing the probe of a WTW Cond 340i test kit into the water samples. The
results were read off the instrument directly.
Turbidity was read off the HACH 2100N
Turbidimeter against distilled water set at zero. A microprocessor pH/ion meter pMX 3000
measured pH. The sieve test was performed on soil samples collected at varying depths along
the monitoring boreholes for soil particle size determination. The analysis was performed using
a series of B.S. sieves nested as follows: 19 mm, 9.5 mm, 4.75 mm, 236 mm, 1.18 mm, 600 μm,
300 μm, 150 μm and 75 μm. Permeability was calculated from the obtained sieve analysis data.
7
3.2.2 Disease incidence
Incidences of water-borne diseases in the study area were investigated by conducting a survey in
Kamangira Village. Direct interviews were held using semi-structured questionnaires. A total of
38 homesteads were interviewed, including the three homesteads that comprised the study site.
Information gathered included sources of water for domestic purposes, protection of the water
source, relative distances between sanitary structures and domestic water sources, awareness of
potential water contamination from pit latrines, and the most common water related diseases that
affected the villagers. Results from the survey were used to make preliminary inferences of
health impacts of groundwater pollution and contamination by pit latrines.
4. RESULTS AND DISCUSSION
4.1 Groundwater flow and water table
From Figure 2, transect 1 comprised PL1, PL2 and the boreholes TW1 to TW10, while transect 2
comprised PL3 and TW11 to TW13. Groundwater was assumed to flow along the transects as
follows: For transect 1 the flow was from TW1 towards TW4, from TW7 towards TW4 and
from TW7 towards TW10. In terms of groundwater flow, monitoring boreholes TW1 and TW7
were upstream in relation to pit latrine positions while TW2 and TW6 were downstream
boreholes. For transect 2, flow was assumed to be from TW11 towards TW13, with TW11 being
upstream and TW12 and TW13 being the downstream boreholes of pit latrine (PL3). The
contour map in Figure 2 indicated that there was a marked depression around TW4. Figure 3
highlights the relationships between pit base elevations and water tables along transect 1. It also
shows the drop in water table in boreholes along the transect and highlights the depression
around TW4. Considering boreholes close to PL1, the pit latrine generally lay above the water
tables of TW1 and TW2 throughout the sampling period. It ranged 0.2 to 1.2 m above water
tables for TW1 and 0.6 to 1.8 m above those for TW2. These ranges gave an average soil
infiltration layer range of 0.4 to 1.5 m above the water table. PL2 sat on and below the water
8
table throughout the study. It ranged 0.9 m below the water table to 0.2 m above the water table
of TW6. It also ranged 1.7 to 0.6 m below the water table of TW7. Along transect 2, according
to Figure 4, PL3 pit base sat below the water table throughout the study, ranging 3.2 to 1.2 m and
Ground
level
just after
drilling
21-Feb
1427.5
1427.0
1426.5
1426.0
1425.5
1425.0
1424.5
1424.0
1423.5
1423.0
1422.5
1422.0
7-Mar
21-Mar
tw10
tw9
tw8
tw7
tw6
tw5
tw4
tw3
tw2
4-Apr
tw1
elevation (m)
3.1 to 1.2 m below the water tables of TW11 and TW12 respectively.
w ater table elevation variation against pit base
elevation
18-Apr
5-May
PL1
PL2
Figure 3 Water table elevations for boreholes on transect 1.
The fact that there was little or no soil infiltration layer between the pit latrine base and the water
table meant that effluent could seep into the water table and contaminate groundwater. The soil
Ground
level
just after
drilling
21-Feb
1426
1425
1424
1423
1422
1421
1420
1419
7-Mar
tw13
tw12
21-Mar
tw11
elevation (m)
infiltration layer is that soil layer between the pit base and the water table.
4-Apr
18-Apr
w ater table elevation variation against pit base
elevation
5-May
PL3
Figure 4 Water table elevations for boreholes on transect 2.
9
PL3 could actually be considered as injecting raw pit latrine effluent into the surrounding
groundwater as highlighted in figure 4. Much of the results in terms of water quality tended to
depend on the depth of the soil infiltration layer allowed between the pit base and the water
table, as stated in a review of typical case studies by Lewis et al., (1980).
4.2 Soil characterization
Soil characterization was done and results showed that the soils were generally sandy and
collapsible. Soil permeability results ranged 0.02-2.7 md-1, within the range of 0.01-2.8 md-1 as
noted by (Wright, 1992) for a crystalline basement. Permeability values for soils around PL1
and PL2 were found to be lower than those for soils around PL3. This may have helped in some
of the transport mechanisms. An example was the extent and persistence of ammonia in TW12,
but whose pattern was not very distinct in TW2 and TW6, all of which were downstream
boreholes.
4.3 Coliforms
Total and faecal coliforms both ranged 0-TNTC (too-numerous-to-count), with 78 % of the total
results meeting 0 CFU/100ml WHO guidelines value. The shallow-wells were located 38-44 m
away from the nearest pit latrines, thereby placing them outside the pit latrines’ radii of influence
of 30 m as generally accepted in Zimbabwe. All of them were partially protected and they
indicated elevated levels of both total and faecal coliforms.
This could be due to water
withdrawal practices around the water point, which could have caused introduction of coliforms
by the users of the water points. Shallow-wells SW1 and SW3 served more people (5 and 7,
respectively) than SW2 (3 people), resulting in a higher demand on the former two shallowwells, with consequential soil re-suspension and a higher potential for microbiological
contamination. Variations of coliforms counts are indicated graphically in Figures 5 and 6.
10
CFU/100mL
2016.0
PL1
PL2
PL3
1516.0
1016.0
516.0
sw3
sw2
sw1
control
tw13
tw12
tw11
tw10
tw9
tw8
tw7
tw6
tw5
tw4
tw3
tw2
tw1
16.0
Sam ple point
21-Feb
7-Mar
21-Mar
4-Apr
18-Apr
5-May
Figure 5 Total coliform variation.
WHO guidelines value of 0 CFU/100 ml was not met in 100% of total and faecal coliform
results obtained for shallow-wells. The results obtained for some boreholes located within a 5 m
radius of the pit latrines indicate that a pit latrine can influence up to 5 m of its radius. Beyond 5
m the faecal coliforms are greatly reduced. The fact that TW6 had no coliforms but they were
detected in TW7 could indicate that predominantly groundwater flow was towards TW10 rather
than towards TW4. The results for TW11 and TW1, both being upstream of pit latrines,
confirmed that flow from pit latrines PL1 and PL3 was from a higher to a lower gradient.
Borehole TW10 did not show indications of impacts from the old and collapsed pit latrine that
1000
800
600
400
sw3
sw2
sw1
control
tw13
tw12
tw11
tw10
tw9
tw8
tw7
tw6
tw5
tw4
tw3
tw2
200
0
tw1
CFU/100mL
had collapsed into the ground some 5 m away from that borehole in terms of coliforms.
Sam ple point
21-Feb
7-Mar
21-Mar
4-Apr
18-Apr
5-May
Figure 6 Faecal coliform variation.
11
The presence of faecal coliform bacteria in most samples indicated that the water had been
contaminated with the faecal material of man or other animals and therefore there was a risk of
contamination by pathogens or disease producing bacteria or viruses, which could also exist in
faecal material. The presence of faecal contamination was an indicator that a potential health
risk existed for individuals exposed to that water.
4.3 Ammonia–nitrogen
Ammonia–nitrogen ranged 0-2.0 mg/l for all sampling points, with 99 % of total results falling
within 1.5 mg/l WHO recommended value. The threshold odour concentration of ammonia at
alkaline pH is approximately 1.5 mg/l, and a taste threshold of 35 mg/l has been proposed for the
ammonium cation (NH4+). Ammonia-nitrogen persisted in samples from TW12 as indicated in
Figure 7.
NH3-N (mgN/L
2.50
2.00
1.50
1.00
0.50
sw3
sw2
sw1
control
tw13
tw12
tw11
tw10
tw9
tw8
tw7
tw6
tw5
tw4
tw3
tw2
tw1
0.00
sam ple point
21-Feb
7-Mar
21-Mar
4-Apr
18-Apr
5-May
Figure 7 Ammonia–nitrogen variation.
This could have been because that monitoring borehole was located downstream of PL3, the pit
latrine that sat inside the water table throughout the study period. Diffusion processes could
have enhanced ammonia movement in water and soil matrix. Ammonia usually occurs in
drinking water at concentrations well below those at which toxic effects may occur. The pit
latrine with its base inside the water provided a continuous source of ammonia, unlike the other
boreholes that were 5 m downstream of pit latrines whose bases did not continuously interact
12
with the water table.
The collapsed and disused pit latrine could have impacted TW10.
Ammonia is not of direct relevance to health at levels generally detected in groundwater, and no
health-based guideline value has been proposed.
4.4 Nitrite-nitrogen
Overall results show that nitrite–nitrogen ranged 0.0-0.64 mg/l and this was within the 3 mg/l
WHO guidelines value. The Zimbabwean standard value of 0.001 mg/L was surpassed though,
for 26 % of the results. High levels of nitrite-nitrogen were detected at TW4 (Figure 8), which is
at the depression on transect 1, as noted in Figure 2. The borehole is also located furthest
0.70
0.60
0.50
0.40
21-Feb
7-Mar
21-Mar
4-Apr
18-Apr
sw3
sw2
sw1
control
Sam ple point
tw13
tw12
tw11
tw10
tw9
tw8
tw7
tw6
tw5
tw4
tw3
tw2
0.30
0.20
0.10
0.00
tw1
NO2-N (mgN/L)
downstream for both PL1 and PL2.
5-May
Figure 8 Nitrite–nitrogen variation.
The conversion from ammonia to nitrite with time and also with exposure to air is also noted in
TW4 where the first sampling campaign recorded lower levels of nitrite-nitrogen. The rise in
concentration in the second sampling campaign also coincided with the non-detection of
ammonia-nitrogen in that same sample at that particular sampling point. TW10 shows the
impact of old t located 5 m away from it, although it is 45 m downstream of PL2. On transect 2,
TW12 is downstream of PL3, whose base sat inside the water table continuously. Results of
nitrite confirm that this species is found usually in low levels and is usually not stable.
13
Regarding health, nitrite ion can oxidize iron in the haemoglobin molecule, from the ferrous to
the ferric ion. The resultant methaemoglobin is incapable of reversibly binging oxygen, and
consequently anoxia or death may ensue if the condition is left untreated.
4.5 Nitrate-nitrogen
Nitrate-nitrogen for all sampling points ranged 0.0-6.7 mg/l and this was within the 10 mg/l
WHO guidelines value. The tendency for nitrate-nitrogen to concentrate around the depression
NO3- -N (mg/L)
at TW4 was noted in Figure 9.
8.0
6.0
4.0
2.0
sw3
sw2
sw1
control
tw13
tw12
tw11
tw10
tw9
tw8
tw7
tw6
tw5
tw4
tw3
tw2
tw1
0.0
sam ple point
21-Feb
7-Mar
21-Mar
4-Apr
18-Apr
5-May
Figure 9 Nitrate-nitrogen variation.
TW7 showed that it was being impacted by PL2, but that nitrate movement towards TW10 was
quite slow due to the very small gradient fromTW7 to TW10. The gradient from TW6 to TW4
was much steeper and this promoted the concentration of nitrate-nitrogen at TW4. The collapsed
and disused pit latrine did not show its impacts on TW10. High levels of nitrate-nitrogen are
directly associated with methaemoglobinaemia, or "blue baby syndrome", an acute condition
which is most frequently found among bottle-fed infants of less than 3 months of age. Nitrates
and nitrites have been suggested as possible carcinogens by a number of researchers.
Researchers have also confirmed that nitrate can be used as a crude indicator of faecal pollution
where microbiological data are unavailable.
14
4.6 Conductivity
Conductivity ranged 46-370S/cm. There are no WHO guideline values for conductivity. On
transect 1 involving TW1 up to TW10, conductivity rose from TW1 towards and picked at a
location 25 m away, at TW4, before it dropped gradually towards PL2. It also rose gradually
from TW7 towards TW10, which was located 45 m away from TW7. Transect 2 involving
TW11 to TW13, showed that conductivity was lower at TW11, which was located 5 m upstream
of PL3 than at TW12, which was located 5 m downstream of that pit latrine. The significant
levels of ammonia at TW12 could possibly affect the conductivity.
Conductivity dropped
significantly at a distance 15 m downstream of PL3 to values almost similar to those for the
control borehole. The concentration of ions at TW4, TW10 and TW12 could be due to impacts
of PL1, PL2 and PL3 as well as the collapsed pit latrine 5 m away from TW10. The low values
for the shallow-wells indicated that there were very insignificant contributions of ions from the
vicinity of the shallow-wells
4.7 Turbidity
Turbidity ranged 1-45 NTU, 59 % of results meeting the 5 NTU WHO guidelines limit.
Turbidity showed a decreasing trend from TW1 to TW7 and rose again along transect 1, with a
pick at TW10. The high turbidity at TW10 could be as a result of loose soil from the collapse of
the disused pit latrine near that borehole. Since the earth acts as a filter, turbidity decrease
towards the depression at TW4 was expected. Transect 2 turbidity values were generally much
higher than those for transect 1. High turbidity values were also recorded for the shallow-wells
SW1 and SW3 and this could be due to the disturbance of the soil within the well during water
withdrawal. The depth of the shallow-wells, and in particular, the depth of the water level above
the well bottom is crucial. In this study, the deepest well was SW3 and the shallowest was SW2.
The water levels also showed the same trend for all sampling dates. The turbidity values though
were highest at SW1 and lowest at SW2, and this could be due to the fact that the base of SW2
15
was covered by a large boulder, making the soil intact, whereas the soil in SW1 and SW3 was
loose. The control borehole recorded very low values for turbidity. Solid particles suspended in
water absorb or reflect light and cause the water to appear cloudy. Turbidity affects water
aesthetics.
4.8 pH
The pH ranged 6.8 to 7.9 for both shallow-wells and boreholes. Values recorded for boreholes
along transect 1 were relatively close to those for the control, although they picked at TW10.
Transect 2 pH values rose from TW11 located 5 m upstream of the pit latrine, PL3, and picked at
TW12 that is 5 m downstream, before dropping noticeably at TW13 located 15 m downstream of
PL3. The presence of ammonia-nitrogen at TW12 could have caused the elevated pH levels at
borehole TW12. Ammonia-nitrogen presence makes the environment alkaline, thereby raising
pH. Shallow-wells recorded much lower pH values.
4.9 Survey
Thirty-eight villagers were interviewed, representing 38% of the population of Kamangira
Village. Of the respondents who owned a pit latrine, 45% of them were unusable because they
were dilapidated and unsafe (according to sentiments passed by the respondents during the
interviews) or they were now too full to be used hygienically. Those who did not have a water
point within the homestead represented 42 % of the respondents. This percentage is quite typical
of rural communities in the third world countries where half the population remain unserved with
basic water and sanitation facilities. Diarrhoea was widespread, with those having suffered from
it making up 50 % of the interviewed number. Those who did not own a water point and also
suffered from diarrhoea constituted 24 % of the respondents. There was no incidence of health
impacts from nitrate, as depicted by 0 % occurrence of “blue-baby” syndrome, whose symptoms
had been explained by the interviewer. Preference of sanitation technology revealed that 37 %
16
of the respondents would like to own eco-san which is a form of on-site sanitation, although 100
% of them sited unavailability of financial resources as the major drawback. Seven standard
cement bags were required to build the structure, besides the labour and brick requirements
according to a local Non-Governmental Organisation, which was implementing eco-san.
5. CONCLUSIONS

Total and faecal coliforms were found to be impacting negatively on groundwater
quality. Samples that gave the 0 CFU/100 ml limit represented 78 % of the total results.
Samples from pit latrines that gave positive results for coliforms counts represented 14%
of total results. Ideally, 100 % of the results should meet that figure for that water to be
declared safe for human consumption.

Ammonia-nitrogen, nitrite-nitrogen and nitrate were found to be impacting on the
groundwater quality. However their levels were not yet of health concern according to
the WHO guideline values and recommendations.

Turbidity of the water was above limit for 41 % of the results, making it aesthetically
unpleasant for domestic purposes. Although there are no WHO guideline values for
conductivity and pH, the results obtained in this study were found not to be of health
concern according to the Zimbabwean domestic water standards.

The sandy nature of the soils in the study site, compounded by the high water table, was
found to be unsuitable for pit latrine construction, resulting in several structural failures.

Generally, it may be unsafe to abstract water within 25 m distance from a pit latrine.

Although eco-san was the most preferred sanitation alternative during the survey, 100 %
of the respondents sited unavailability of funds to construct the urine separation and
composting structures.
17
6. RECOMMENDATIONS
It would be logical to treat each settlement or site on individual merit when assessing the faecal
pollution risk associated with on-site sanitation. However the economics and logistics of lowcost sanitation schemes are such as to preclude the routine use of costly hydrogeological field
investigations. Therefore the following recommendations are suggested when assessing the risk
of on-site sanitation before implementation.

The depth of the infiltration layer as well as the direction of groundwater flow were
found to be critical parameters during the assessment of the impacts of pit latrines on
groundwater and could be investigated easily before implementation of on-site sanitation.

History regarding location of collapsed pit latrines could be very important since
disregarding this factor could end up having a homestead taping domestic water close to
or from a disused pit latrine.

Raised pit latrines and other low-cost technologies could be considered as alternatives
because they minimize the risk of releasing flow across the thin infiltration layer.

The results obtained from the study are true for the study area but could also apply to areas with
similar soil, geology and rainfall pattern. An integrated approach involving geotechnology,
hydrogeology and groundwater pollution could be considered as a way forward in efforts to
solve the sanitation problems in view of structural failures within the larger Kamangira Village.
ACKNOWLEDGEMENTS
The authors would like to sincerely thank Mvuramanzi Trust and The WaterNet Regional
Capacity Building program, for funding this research. Special thanks go to the Department of
Civil Engineering and Department of Geology at the University of Zimbabwe, for their
logistical, material and moral support.
18
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