QUALITY TESTS OF HAND PUMP WELLS
IN THE MEKONG DELTA
THOMAS NUBER1, HARRO STOLPE1, VU VAN
NAM2, TRAN VAN TY2
1U+Ö im Bauwesen, Environment+Groundwater+Ecology,
Ruhr-University Bochum, Germany
2College of Technology, Can Tho University, Viet Nam
Abstract: In Viet Nam different hand pump types are distributed designed for the
drinking water supply by drilled wells.
Simple
tests were carried out in the An Binh village (Hau Giang province, Mekong
Delta) to proof the well quality including the installed hand pumps. The power
which was necessary for a pump stroke was recorded by a spring scale. The datasets
show a clear different distribution of values for each hand pump type.
I. INTRODUCTION
1. Ground Water Hand Pumps in Viet Nam
Since the 1980s several organizations (e.g.
UNICEF) are running water and hygiene promotion campaigns in Viet Nam. Part of those
campaigns is the construction of ground water wells and the installation of
hand pumps. For instance, alone in Can Tho Province in the Mekong Delta over
50,000 wells were drilled since 1989. Those wells have diameters between 40 and
45 mm, are approx. 100 m deep and are often equipped with
suction-hand-pumps. The most widespread hand pump type is the model “VN6”, a
lighter version of the UNICEF No. 6 pump which was originally designed for the
drinking water supply in Bangladesh (see Figure 1). The UNICEF No. 6
is characterized by a stable construction and a weight of approx. 33 kg.
In Bangladesh usually one pump serves more than 100 people. In Viet Nam,
however, the user groups are much smaller. Normally, one pump serves a maximum
of 10 people. Under this condition the Bangladesh No. 6 was too heavy and
consequently too expensive for the market [4]. For that reason UNICEF
introduced the VN6 to Viet Nam. The VN6 weights 22 kg and costs approx.
300.000 VND. The Vietnamese market demands cheaper pumps. Since 1995
counterfeits of the VN6 are pushing into the market. They can be identified by
a weight below 20 kg and a fake UNICEF label. The costs for a copied VN6 hand
pump is between 80.000 and 100.000 VND.
2. Goal of the Quality Tests
The goal of the tests is the comparison of the
well quality including the installed hand pumps. Here, the focus is on the differences
between wells with original hand pumps and wells with copied hand pumps. The
results are illustrated in efficiency curves. In this first approach the
efficiency curves include well characteristics, aquifer characteristics and
hand pump characteristics.
3. Study Site
The quality tests were carried out at the village
An Binh in the Hậu Giang Province
in the centre of the Mekong Delta. Here, ground water wells are very
popular. The first wells were drilled in 1995. According to Do Tien Hung [3]
there are five major aquifers, whereas mainly the second aquifer is used for
ground water exploitation. It’s a confined aquifer (fine to coarse sand), covered
by a clay layer with a thickness of 60 m. At both sites, the ground water level
is approx. 4 m below surface. Slug and Bail Tests which were performed in
An Binh
Figure 1. Hand Pump UNICEF No. 6
(BAUMANN, 2000)
Figure 2. Experiment Set-Up and
Parameters
show a range for the
hydraulic conductivities of this aquifer between 1,9 x 10-4
and 4,1 x 10-4
m/s [2].
II. METHOD
1. Experiment Set-Up and Procedure
The experimental set-up are illustrated in Figure
2. Firstly, various geometrical data as well as the weight of the pump were documented.
Also, ground water level, depth and diameter of the borehole were measured. A
water meter was installed for the measurement of the pumping rate.
Additionally, a spring scale was attached to the handle of the hand pump.
For the actual procedure of the experiment, ground water was pumped by a
test person for about two minutes. The precise duration, amount of the pumping
strokes and the volume of the discharged ground water were measured. The power which was necessary for a pumping stroke
was recorded by the spring scale.
This procedure was carried out three times. Each time it was pumped with a
different intensity to identify a dependency between discharge rate and the
brought up power. Additional to the
tests, pump owners were asked about maintenance habits and the technical
condition of the pump was rated visually.
2. Evaluation
Besides the above listed parameters, following
figures need to be calculated for the appraisal of the hand pumps:
- discharge rate (Q)
- brought up power (P)
- efficiency factor (η)
Those figures are determined with the following
equations.
The discharge rate Q is defined as the ratio
between the measured discharge volume V and
the duration of the experiment t:
To determine the power P firstly the traction T at
the plunger needs to be calculated:
Figure 3. Efficiency curves of the
original VN6 hand pumps
Figure 4. Efficiency curves of the 15 kg hand pumps
Figure 5. Efficiency curves of the
11 kg hand pumps
The work W which was brought
up during the entire experiment is calculated by multiplying the traction T by
the length of the plunger h and the number of the piston strokes n:
Finally, the brought up
power P can be calculated by dividing the work W by the duration t of the experiment.
Additionally, the brought up power P is referred to the entire pumping height.
The efficiency factor η is defined as the ratio
between the discharge rate Q and the power P. To get a non-dimensional figure
the term needs to be multiplied by the density of water ρ and the acceleration of gravity g:
III. RESULTS AND DISCUSSION
A total of 55 wells were found in An Binh. Most of
the existing wells were equipped with electric suction pumps. Only 19 of the
wells had functioning hand pumps. Three different types of hand pumps were
identified. Beside the original VN6 pumps, hand pumps with 15 kg and
11 kg were available. Between 1995 and 1998 solely original VN6 pumps and
the 15 kg pumps were installed, whereas especially in 1997 and 1998 the
15 kg pumps were predomi nant. Since 2001 three out of six wells were
equipped with the 11 kg hand pumps (see Table 1).
In the figures 3 to 5, efficiency curves of the
wells are illustrated. The two wells with the original VN6 hand pumps which
were installed between 2001 and 2002 show the highest efficiency. The
efficiency factors of the wells with the older original VN6 hand pumps are
between 0,6 and 0,8. Wells with the 15 kg pumps show an efficiency between 0,85
and 0,25, whereas the hand pumps of the wells with an efficiency η>0,5 were in a good technical condition. According to the proprietors
of those pumps, the maintenance was carried out frequently. Against that, hand
pumps of the wells with a low factor (η<0,5) were rarely maintained. The
technical condition of those hand pumps was very poor. The efficiency curves of
wells with the 11 kg pumps show factors between 0,8 and 0,5. Nevertheless, it
can be said that the wells with the 11 kg pumps need more power to reach the
same discharge rate as the 15 kg pump and the original VN6.
Table 1. Number of installed pumps
Year of |
Orig. |
15 kg pump |
11 kg pump |
1995-1996 |
2 |
2 |
- |
1997-1998 |
1 |
8 |
- |
1999-2000 |
- |
- |
- |
2001-2002 |
2 |
1 |
2 |
2003-2004 |
- |
- |
1 |
IV. CONCLUSIONS AND OUTLOOK
Here, wells with the original UNICEF VN6 pumps are
- even after several years of intense use - more efficient than most of the
younger wells with copied VN6 hand pumps. Only the wells with very carefully
maintained 15 kg pumps show a similar efficiency than the wells with
the original VN6 pumps. The quality of the new wells with a new 11 kg hand pump
is much lower than the quality of wells with the original hand pumps and the
old 15 kg copies. Even wells with 11 kg pumps which were only three
years old could not reach the efficiency of wells with the eight-year-old
original or 15 kg hand pumps.
Overall, with this approach it is possible to quantify the quality
differences between ground water wells including the various types of hand
pumps. In a next step the influences of the various factors should be quantified.
Those factors are the characteristics of the well, the aquifer and the specific
characteristics of the hand pumps. Therefore, tests concerning the technical
conditions of the borehole, filter screens, well casings, friction of the
well-pipes, productiveness and the hydraulic conductivity of the aquifer should
be performed. At the same time, tests of the hand pumps - as described above -
could be performed under defined conditions. With this approach a general
statement about all the components and the their influences could be made and a
complete comparison of the wells even at different sites could be possible.
Environmental Engineering and Ecology
Ruhr-University Bochum
Prof. Dr. Harro Stolpe
Faculty of Civil Engineering
Tel.: +49(0)234 32 27995
Fax.: +49(0)234 32 14701
www.rub.de/ecology
thomas.nuber@rub.de
The authors would like to thank the Federal
Ministry of Education and Research of Germany (BMBF Germany) for the financial support
(Project ID 02WD0414).
REFERENCES
1. Baumann E.
2000. Series of Manuals on Drinking Water Supply. Water Lifting, Vol.7,
Skat-Foundation, St. Gallen,Switzerland.
2. Benstöm F.,
Nuber, T., Stolpe H., 2005. Determination of Hydraulic Conductivity with Slug
And Bail Tests in Small Diameter Wells in the South of Viet Nam. In this journal !!!
3. Do Tien Hung,
Nguyen Hong Bang, Pham Van Giang, 2000. Availability and quality of
ground water resources. Department of
Geology and Minerals, Division of Hydrogeology and Engineering for South Viet
Nam (DHES), Ho Chi Minh City.
4. Ikin D. &
Baumann E., 2002. Appraisal and Impact Assessment of IDE Viet Nam Hand
Pump Program. Skat-Foundation, St.
Gallen, Switzerland.