Optimization of Physical Parameters affecting Disinfection of Water by Copper

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Journal of Civil and Construction Engineering
Volume 3 Issue 2
Optimization of Physical Parameters affecting Disinfection of
Water by Copper
Sonal Garg1*
, Dr. D.J.Killedar1
, Dr. Pawan Labhasetwar2
, Dr. Pranav Nagarnaik2
Department of Civil Engineering & Applied Mechanics, S.G.S.I.T.S, Indore (M.P), India
Water Technology & Management Division, CSIR-National Environmental Engineering Research
Institute, Nagpur, 440020, Maharashtra, India
sonalgarg1992@gmail.com
Abstract
Disinfection of water is the most essential step which can prevent endemic and/or epidemics
of water borne diseases. Recently, USEPA has registered copper as the first solid
antimicrobial material due to its continuous antimicrobial properties. Therefore, the
objective of this study was to optimize the physical parameters (i.e. ratio of Surface Area of
Copper to Volume of Water in Contact) which have a great effect on disinfection using
copper. The optimization study was carried out on copper vessels of different configurations
such as cylindrical copper jug and rectangular copper plates against important
diarrhoeagenic bacteria, including, Escherichia coli, Salmonella typhimurium, and
Pseudomonas aureofaciens. In the study, the prepared test sample was stored in copper
vessel for about 8 hrs at room temperature (around 25o
C) and its microbial examination was
done after every 1hr time interval by passing 1 ml of sample through membrane filtration
technique and plating on selective media for all three strains and incubated for 24 hrs at
37o
C for Escherichia coli and Salmonella typhimurium, while at 30o
C for Pseudomonas
aureofaciens. It was observed that as the ratio of surface area of copper in contact to volume
of sample in contact decreases, the time taken for disinfection increases.
Keywords- Antimicrobial, Bacteria, Copper, Drinking-water, Disinfection, Escherichia coli,
Pseudomonas aureofaciens and Salmonella typhimurium, ratio of surface area to volume.
INTRODUCTION
Microbially safe drinking water is essential
for good health and well-being of humans.
In recent years, the water is being polluted
mainly due to anthropogenic activities.
Contaminants present in drinking water
include microbial pathogens, trace
organics, inorganics and radioactive
elements.
Consumable water quality occurs when
there are especially no bacteria of faecal
origin present that may cause human
diarrhoea and other life threatening
diseases (e.g. typhoid fever). Improper
disinfection or insufficient residual
disinfection of water in the supplied water
might not eradicate microorganisms and
other germs completely which results in
growth of microorganism in water due to
availability of inorganic and organic
nutrients in water. There is also concern on
faecal contamination that might build up
near pipes and surface soil. Faecally
contaminated material tends to enter the
water supply through leakages and cracks
in the system due to negative hydraulic
pressure.
WHO estimated that 94% of these
diarrheal diseases are preventable through
clean drinking water and improved
sanitation and hygiene (WHO.,2007a).
Many of the ongoing efforts to decrease
diarrheal disease have stemmed from the
Millennium Development Goals (MDGs)
regarding drinking water and sanitation.
Although the MDGs had a significant

Volume 3 Issue 2
impact on worldwide access to improved
drinking water sources, there are several
areas that are still unaddressed or are
lacking access to safe drinking water.
Researchers have repeatedly observed that
the microbiological quality of water in
transportation and drinking vessels in the
home is lower than that at the source,
suggesting that contamination may occur
at different stages during the process from
collection of water to consumption (Pruss
et al., 2002; Gundry et al., 2006). Even
though, storage of water has been
recommended as a method of water
purification, contamination of treated or
disinfected water can also occur during
storage due to improper handling. Hence it
is important from a safety point of view to
maintain the quality of drinking water
during storage. Certain heavy metals (like
Silver, Copper, Zinc) are thought to be
antimicrobial and they have great potential
to be used as disinfectant in the treatment
of drinking water. The disinfection using
these metal ions have been studied in
different configuration. The sensitivity of
metals to human and microbial tissues is
different.
MATERIAL & METHODS
Preparation of bacterial culture
Bacterial culture containing E.coli,
Salmonella typhimurium and
Pseudomonas aureofaciens was prepared
by inoculating specific bacteria into
Nutrient Broth (HIMEDIA, Mumbai) from
their respective selective media plates and
incubating for 24 hours in bacteriological
incubator at specific temperatures.
Preparation of test water
In order to prepare sample for testing
appropriate quantity of prepared bacterial
culture was spiked in normal saline
solution (NaCl, 0.85% w/v) which was
autoclaved at 121o
C temperature.
Detection of pH and Copper ion
concentration
pH of the test sample was tested before
and after treatment and was found to rise
by 1 unit[1-20]. Leaching of copper in
treated sample was also tested by
Inductively Coupled Plasma-Optical
Emission Spectroscopy and it was found to
be within the BIS permissible limit.
Optimization of physical parameters
With cylindrical copper jug of 1 L.
capacity
A cylindrical jug of 1L. Capacity as shown
in Fig. 1 and a glass beaker as shown in
Fig. 2 were taken. Copper vessel was
wiped with 100% ethanol and then 2-3
times with hot boiling water to remove any
organic or inorganic impurities, if present.
Similar and equal amount of test sample,
say 100 ml (containing E.coli species in it)
was placed in both the copper vessel and
the glass vessel respectively. The glass
vessel was used as negative control. The
depth (d1) upto which test sample was in
contact with copper jug was measured.
Raw sample was withdrawn from both the
containers to determine the initial bacterial
count[21-35]. The sample in both the
containers was stirred with a stirrer for 5
mins and then with a sterile pipette for 10
to 15 seconds, each time before taking the
sample. Sample time points like t=1, t=2,
t=3, t=4, t=5, t=6, t=7 and t=8 hrs were
selected and the sample so taken was
passed from Membrane filtration apparatus
(0.45µm pore size membrane) after desired
serial dilution. The membrane was then
placed on EMB agar petri plates. The plate
was then placed in bacteriological
incubator at 37o
C in inverted position for
24 hours. The bacterial counts were noted
by counting the no. of purple coloured
colonies on plate indicative of E.coli. This
determined the bacterial reduction. The
above set of experiment was repeated by
adding 300 mL of test sample to each
copper jug and the glass beaker
respectively and the depth (d2) upto which

Volume 3 Issue 2
test sample was in contact with copper jug
was noted down. Similarly, by adding 600
ml of sample the experiment was carried
out and the depth (d3) was measured. It can
be stated that by changing the volume of
sample in contact, the area of copper jug in
contact with the sample also changes.
Hence, the ratio of surface area of copper
jug in contact to volume of sample in
contact also changes (2.1, 0.92, 0.65). The
details of the same have been presented in
Table 1.
Fig. 1 Cylindrical Copper Jug Fig. 2 Glass beaker used as negative control
Table 1 Calculation of ratio of Surface area of copper in contact to Volume of sample in
contact with cylindrical copper jug
S. No. Volume of
sample in
contact with
copper jug
Radius of
copper jug
Depth of
sample in
copper jug
Area of
copper jug in
contact with
sample
2πr(r+ h)
Ratio pH of sample
(in mL) (in cm.) (in cm.) (in cm2
) (in cm-1
) Initial Final
1 100 5.2 d1 (1.2) 210 2.1 6.5 7.0
2 300 5.2 d2 (3.2) 275 0.92 6.5 7.5
3 600 5.2 d3 (6.8) 392 0.65 6.5 7.5
With rectangular plates of 18 cm x 10
cm
The glass beakers of capacity 2L. were
taken. Test sample of quantity 2L.
(containing E.coli bacterium in it) was
added in each glass beaker. Copper plates
of 99% purity and dimensions 18cm x
10cm (total surface area of 360 cm2
) were
used[36-40]. The plates were wiped with
ethanol and hot boiling water. The
experiment was carried out in batches,
since, the number of plates were limited.
Half copper plate was dipped in 1st
beaker,
1 full plate in 2nd
beaker, 2 full plates in 3rd
beaker, 3 full plates in 4rth
beaker, 4 full
plates in 5th
beaker and no copper plate in
last 6th
beaker which was used as a
negative control. All the beakers were
placed on magnetic stirrer at low stiring as
shown in Fig. 3. Raw sample was

Volume 3 Issue 2
withdrawn from the containers to
determine the initial bacterial count. The
sample in the containers was stirred with a
sterile pipette for 10-15 seconds, each time
before taking the sample. Sample
timepoints like t=0.5, t=1.0, t=1.5, t=2.0,
t=2.5, t=3.0, t=3.5, t=4.0, t=4.5 and t=5.0
hrs were selected and the sample so taken
was passed from Membrane filteration
apparatus (0.45µm pore size membrane)
after desired serial dilution[41-47]. The
membrane was then placed on EMB agar
petri plates. The plate was then placed in
bacteriological incubator at 37o
C for 24
hours. The bacterial counts were noted by
counting the no. of purple coloured
colonies on plate indicative of E.coli. This
determined the bacterial reduction.
In this experiment the volume of sample
have been kept constant while the surface
area of copper in contact with sample was
varied by increasing the number of plates
being dipped in beakers. Hence, the ratio
of surface area of copper in contact to
volume of sample in contact varied (0.09,
0.18, 0.36, 0.54 and 0.72). The details of
the same have been presented in Table 2.
Table 2 Calculation of ratio of Surface area of copper plates in contact to Volume of sample
in contact with rectangular copper plates
S. No. Volume of sample
(in cm3
)
Surface Area of copper plate in
contact with sample
(in cm2
)
Ratio
(in cm-1
)
1 2000 180 0.09
2 2000 360 0.18
4 2000 720 0.36
5 2000 1080 0.54
6 2000 1440 0.72
Fig. 3 Beaker with rectangular copper plates & Beaker with negative control

Volume 3 Issue 2
RESULTS & DISCUSSION
The results of log10 (No/Nt) reduction
values for E.Coli in different experimental
trials performed by varying the surface
area of copper in contact and volume of
sample in contact (2.1, 0.92, 0.65) with a
cylindrical copper jug of 1L. capacity of
known dimensions have been presented in
the form of graph as shown in Fig. 4.
Fig. 4 E.coli evaluation for surface area and volume variation
It could be observed from Fig. 4 that when
the SA/V ratio was 2.1 then the time taken
for complete 5 log10 reduction was 11 hrs
which indicated very slow disinfection.
There was a sharp decrease in the
concentration of E.coli in 5th
hr of contact
and then the decrease was gradual[48-57].
When the SA/V ratio decreased to 0.92
then the disinfection time reduced to 4 hrs
for the same concentration of E.coli. When
the SA/V ratio was further decreased to
0.65, then 4 log10 reduction took place in
only 1 hr of contact time. Thus, it can be
stated that as the ratio of surface area of
copper in contact to volume of sample in
contact decreases the time taken for
disinfection increases.
Optimization of physical parameters
using rectangular copper plates (18cm x
10cm)
Optimization study was carried out by
varying the ratio of surface area of copper
in contact to the volume of sample in
contact (0.09, 0.18, 0.36 and 0.54). Surface
area was varied by dipping half, one, two
and three plates in the 2L sample and the
bacterial reduction was noted. It is
presented in the form of graphs.

Volume 3 Issue 2
Fig. 5 Optimization using rectangular copper plates (18cm x 10cm)
From the graph it is clear that time taken
for complete 6 to 7 log10 reduction of
E.coli was minimum (3 hrs) when the ratio
SA/V ratio was 0.36. As the ratio increases
the time for disinfection decreases. Thus,
the SA/V = 0.36 ratio was considered as
the optimum ratio for complete 6 to 7 log10
reduction of bacteria.
DISCUSSION
Copper pots have been used for storage of
drinking water and many experimental
researches have proved that the copper has
antimicrobial activity mainly on the water
borne pathogens. In this study the physical
parameter i.e. ratio of surface area of
copper in contact to volume of sample in
contact was optimized with cylindrical
copper vessel and with rectangular copper
plates (18cm x 10cm), the two being of
different configurations. None of the
bacteria were recovered when tested
periodically upto 8 hrs of storage. Another
study also reported that none of the test
pathogens were recovered from drinking-
water stored in copper pots even after
enrichment culture (Sudha et al., 2009).
This indicated that the bacteria in the test
samples was completely killed or had lost
their culturability on the medium under the
observed test conditions. Functioning of
disinfection through copper is not
dependent on fuel, electricity, replaceable
filters/ membranes, intensity of sunlight,
etc. to operate or maintain it.
CONCLUSIONS
The results of bacterial examination
performed on copper vessels of different
configuration such as copper jug and
copper rectangular plates in the laboratory
proved to be very effective in removing all
test micr-organisms upto 5log10
concentration under observed test
conditions. From the optimization study
carried out on test micro-organisms under
observed test conditions, ratio of SA/V =
0.36 was considered optimum for complete
6 to 7 log10 reduction of bacteria. It can be
concluded from the experiments that as the
ratio of surface area of copper in contact to
volume of sample in contact decreases, the
time taken for disinfection increases.
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