Nepal Journal of Science and Technology 2 (2000) 27-30
Oligodynamic Action of Traditional Nepalese Water Pots
against E. Coli [ATCC 259221
R. R. Shahil, R. Adhikari2, M. P. Barall and T. M. Pradhanangal
I Royal Nr,pcrl Academy of Science cG Teclznolo,q~,GPO Box 3323, K ~ ~ I ~ r ~ z ( i 1 ~ 1 i i
Cerztrd Dr~par~rnerzt
of Microhiolog~:Tril~I~rl~wl
Urliversiry, Kirtipiir
Received October 1999; accepted January 2000
Abstract
Five types of traditional Nepalese pots were tested for their bactericidal action against E. coli..
Copper, silver and brass pots were found to be very effective for their bactericidal action. Steel and aluminium
pots were found to be less effective whereas earthen pot was found to be ineffective against E. coli. Copper.
silver and brass pots decreased the original bacterial load from 10"' cells/mL to 101 cells/mL within 4 hours.
After 8 hours the bacterial load were found to be nil in those three pots. Whereas, in steel and aluminium pots,
the bacterial counts were found to be decreased from 10"' to 1 0 cellsImL at the end of 24 hours. No change in
bacterial load was found in earthern pot within 24 hours storage.
Kejwords: Oligodynnmic, Water Pots, E. Coli
Introduction
Water is a part of the human environment, and it
is an absolute necessity for life. However, water can
also be the carrier of suffering and the cause of
health hazard. Human beings are common host for a
variety of pathogenic microorganisms and water has
been found to be the medium for the transmission.
Most of the water samples from Kathmandu
water supply system show fecal contamination as
reported by ENPHO/DISVI( I99 I - I992), Sharma
(1978), Adhikari et al. (I986), Bottino et al. (1991)
Thapa et rrl .(1993) and Pradhananga(l994). A
detailed study on pollution in water supply system of
Kathmandu City was made by Bottino et (11. (1991).
Their study shows that though the total coliform
count is nil at some reservoirs and treatment plants, it
is high in most of the areas of Kathmandu city. This
indicates contamination in the distribution system.
In some areas, peoples of Kathmandu are still using
stone taps (Dhungedhara) as a source of water for
drinking and other domestic purposes. The
study made by
Thapa et al .(1993) on the
pollution of waters of stone taps shows that most of
stone taps water were polluted in t e r m of total
coliform count. All these mentioned reports indicate
the necessity ot treatment of water before household
consumption.
There are various ways for the
treatment of water in household level some of them
are traditional and others are modern. One of the
most easiest and effective way for desinfection is the
boiling. As Nepal is one of the poorest countries,
most of the people cannot afford to use expensive
fuels for boiling the water. It is not necessary to
mention that advanced water treatments are beyond
their capacity. Thus it is worthwhile to use some low
cost traditional methods for the treatment of water in
countries like Nepal.
From ancient time metallic water pots have been
i n common use i n most parts of Nepal and India.
The tradition of storing drinking water overnight in
silver vessels and offering it in silver goblets is still
maintained in wealthier Hindu families. Jahn(1981).
Even today, Nepalese village people fetch water in
copper, brass, steel, aluminium and rarely in silver
vessels. They use these pots for fetching water from
distance water source and also for water storage.
These metallic vessels are beleived to have antiseptic
qualities. The ability of silver and copper vessels to
purify water has been reported by Nadkarni(l976)
WHO( 1993 ). Concerning bactericidal action of
silver, Clark(l956) has reported that filter candles
coated wlth silver has germicidal action.
There are limited knowledge regarding the ability
of metal pots to act as a bactericidal agent with
known water bacteria like E. coli. The objective of
present study is to examine the quantitative bacterial
effects in water stored in different metallic and other
pots used by the Nepalese people.
R. R. Shahi er al.lNepal Journal of Science and Technology 2 (2000) 27-30
Materials and Methods
Microorganism used in this study was E. coli
[ATCC 252991 received from t h e Central
Department of Microbiology, T.U., Kathmandu. The
0
culture was maintained in lactose broth at 37 C for
18 hours.
The initial number of bacteria in the original
suspension was measured by counting the total
bacterial number in the lactose broth after 18 hours
incubation at 3 7 O ~by serial dilution method. The
viable count of each dilution was carried out by
membrane filter (MF) method,WHO (1993) . The
method used for the analysis were followed from the
Standard Method for the Examination of Water and
Wastewater ( 1989).
Five metallic pots (silver, copper, brass, steel and
aluminium) and an earthern pot of same size and
shape were utilized for the study. The capacity of
each pot was about 700 mL. The volume of distilled
water taken in each pot was 495 mL. The pots were
0
autoclaved tor 30 rninutes at 121 C, while wrapping
their mouth with aluminium foil. Then 5 mL of
\tandard bacterial suspension was transfered to each
pot aseptically. After shaking well, all the pots were
kept at r o o m t e m p e r a t u r e . Average room
temperature during the experiment was between 10
to 2 0 ' ~ . After every 4 hours, three samples form
each pot were taken and measured for E. coli by MF
method. The observation was carried out upto 28
hours form the time of the first inoculation. The data
presented in the tabular form were the mean of three
replications per pot at a particular time.
Concentration of the residual Ag+ in water stored
in silver coated pot was analyzed by AAS by using
Standard method( 1989) .
Results and Discussion
The initial mumber of E. coli was determined by
serial dilution method. Five mililiter of bacterrial
suspension of known concentration were added in
the previously autoclaved pots each containing 495
mL of water. In every four hours interval time, three
samples were taken from each pot and measured for
number of E. coli by M F method. The obtained
data were tabulated and the reduction of bacterial
number and time are given in the Table 1. The
reduction of log number of E. Coli with time in
different pots is shown in Figure I .
As mentioned in the Tablel, there is a significant
decrease i n E. c:oli count with tirne i n water stored i n
the metallic pots, particularly in silver coated copper,
copper and brass. Water in these pots become free of
E. coli after 20 IIULII-s of storage. However. water in
metallic p o t s like steel a n d a l u m i n i u m h a v e
significant number of E.coli even after 28 hours of
storage.
It is observed form this study that bactericidal
action is effective among coinage metals like copper
and silver. As shown in F i g u r e I , there is a
significant decrease in E. coli count with tirne i n the
copper, brass and silver coated copper pots. The
decrease in E. coli concentration was found to be
sharp up to the first four hours of storage. Between 4
to 8 hours of storage there was also decreased in E.
coli counts with tirne but it was not as significant as
compared to previous one. However, the bacterial
counts become zero upto the 20 hours of storage.
But water stored in aluminium and steel pots had
almost equal number of bacteria ever after 24 hours
of storage. It means steel and aluminium pots do not
have germicidal action against E. coli .
The germicidal action of metallic pots is due to
oligodyniunic characterstic imparted by metals. The
term oligodynamic came form Greek word, oligas
meaning few and dynamic meaning power. It is
caused by small or minute forces. functioning in
minute quantities. It is generally refered to the
bactericidal action exerted by certain metals in
elemental form. i.e., silver and copper.
Besides oligodynamic properties shown by
elemental silver and copper, the ions of these metals
have germicidal action at high concentration. The
ability of vessels made of metal like silver and
copper to purify water was known from ancient
time. The toxicity of certain metallic ions to bacteria
and fungi was exploited in the use of mercury,
copper and silver derivatives as disinfectants and
antiseptics. A solution of copper sulfate with
concentration of 1 mg/L has been recommended to
kill taste and o d o u r p r o d u c i n g f r e e f l o a t i n g
microorganism "plankton" in modern water
reservoirs. Copper ion concentration in drinking
water above 3 mg/L cause acute gastric irritation in
some individuals. High concentration of copper ion
can give rlse to taste problems. In human beings,
higher oral closes of copper ions will have hepato
toxic effect (WHO 1993).
Silver ions added to tap water as stlver nitrate are
efficient germicide. As reported by Fisher ( 1957)
water with up t o 22000 E. coli /mL was free after 20
minutes when A g + had been added in a
concentration of 100 pg/L. However. the presence
ot silver ions in drinking water I S not condusive to
human health with respect to argyria, a conditwn in
which skin & hair are heavily discoloured by silver
in the tissues (WHO 1993). It has been reported that
high concentration of salts of heavy metals like
R. R. Shahi et aLINepal Journal of Science and Technology 2 (2000) 27-30
Table 1 Reduction in Number of E.coli with Time in Differnt pots
No. of E. coli at
Types of
Pots
Initial No. of
E.coli
CountImL
1.10 x 10l0
4 hrs
8 hrs
20 hrs
24 hrs
9.93x109
6.54~
lo9
3.40 x 101°
6.53 x lo9
Steel
1 o8
10.89~
[9.03]
5.81x109
[8.76]
6.40x108
[8.80]
5.53x108
[8.74]
Aluminium
12.21~10~
[9.08]
Copper
10 . 0 0 ~lo4
[5.00]
8.00~10~
[8.90]
Nil
1 2 . 7 0 ~ 1 0 ~ 5.10~108
[9.10]
[8.70]
Nil
Nil
Si l ver,coated
copper
1 0 . 0 0 ~1 o3
(4.00)
Brass
8.00x104
[4.90]
6 . 0 3 lo8
~
[8.78]
4 . 0 0 lo3
~
l3.W
I .oox103
[3.W
3 . 0 0 ~lo3
[3.47]
Earthen
28 hrs
3 . 2 3 lo8
~
[8.5 11
Number in Parenthesis: log no. of E.coIi
Nil :no growth
------ :no observation war made
mercury, copper and silver coagulate cytoplesmic
proteins resulting in damage of death of the cell.
The residual concentration of silver ions in water
stored in silver coated pot was found to be not
significant as examined by AAS in Bureau of
Standard, HMG, Nepal. Since the concentration of
silver ions i n water pot is insignificant so the
bactericidal action in silver coated copper, copper
and brass pots may be purely oligodynamic
properties imparted by these metals. This shows that
storing of water in metallic pots is more safer than
treatment by addition of chemicals whereas the study
of the residual concentration of other metal ions on
different other metallic pots are recommended. Due
to ililteracy and ignorance, the use of chemicals as
disinfection of water is dangerous of overdose or
underdose.
Steel
Aluminum
copper
Silver
Brass
.
0
4
,
8
20
24
IncubationTime (Hn)
28
Figure 1. Reduction in log number of E.coli with time in
diffrent pots
Brass is the alloy of copper and zinc. The
presence of copper in the brass may have shown
potentiality for the decrease in bacterial count. The
bactericidal properties of brass may be considered as
similiar to silver and copper.
Steel and aluminium pots do not show effective
germicidal action against E. coli . According to the
result shown in Table 1. The E. coli count is still
high even after 28 hours of storage. The
oligodynamic characterstic of heavy metals for
purification of water is well documented. But there
is lack of literatures concerning germicidal action of
steel and aluminium against E. coli . It may be due
to the fact that oligodynamic properties imparted by
steel and aluminium pots are less than silver, copper
and brass.
The earthen pots are used by majority of the
Nepalese villagers for fetching and storing water.
The main reason is that the earthern pot is cheaper in
comparison to brass and copper pots. Another
advantage of earthern pot is that it helps in keeping
water cool for several hours but it has been found
that earthen pots do not have bactericidal action
against E. coli at all. As shown in Table 1, there are
too many counts (TMC) of E. coli even after 28
hours of storage. There was no decrease in E. coli
number from the begining to the end of experiment.
Albala and Taylor-Ide (1985) reported positive
correlation between use of earthen vessels and
diarrhoea i n a rural community of eastern Nepal.
R. R. Shahi et a1.lNcpal Journal of Science and Technology 2 (2000) 27-30
According t o their studies, there is almost 5 fold
increase (9%-38%) in the prevalance of diarrhoea in
f a m i l i e s using e a r t h e n p o t s f o r water s t o r a g e a s
cornpared to brass pots. This may be related to the
ability of earthen vessels to harbor bacterial colonies
and to act as seeding source while copper, brass and
silver lack this capability, Albala and Taylor(1985).
Conclusion
Water stored in copper, brass and silver coated
c o p p e r p o t s a r e f o u n d to b e b e t t e r t o kill
microorganisms than water stored in aluminium,
steel and earthen pots. It is due to the ologodynamic
action of metals against bacteria.
Acknowledgements
T h e authors express their gratitude to RONAST
and Central Department of Microbiology, T U for
providing the laboratory facility and microorganisms
for this study. Our special thank goes to Dr. Uttam
K u w a r o f Bureau of Standard, HMGIMinistry of
Industry for analyzing the silver ions in the studied
samples.
References
Adhikari, R.K., S.K. Rai, B.M. Pokheral, and J.B. Khadka
1986. Bacterial Study of Drinking Water of
Kathmandu Vallery. Journal of Institute of Medicine. 8:
313-316.
Albala, D.M. and D.T. Idc 1985. Water Quality and
Diarrhoea1 Rural Community of Eastren Nepal,
Jour~iciloflnstitu~eoJ'Mrclicines, 7:35-42.
Bottino, A,, A. Thapa. A. Scatolini. B. Ferino. S. Sharma.
and T. M. Pradhananga 1991. Pollution in the Water
Supply System of Kathmandu City, Journal o f Nc,pcrl
Chernicd Socic,ry 10: 33-44.
Clark, R.N 1956. The Purification of Water on a Small
Scale , B~rlletinWHO, 14 820-826.
ENPHOIDISVI 1991-92, Monitoring Of The Kathmandu
City Water Supply with Rcfcrcnce to Chlorination B
Microbiological Quality. Kathmandu.
Fischer. M. 1957. Der derzeitige Slander Anchauung uher
die hakterizide Wirkung von Silber Bcr. 26. Tapung
Dtsch. Gesscllsch. f. Hygiene and Mihrohiolo2ie
Bcrlin , 190-206.
Jahn, S.A.A. 198 1. Trarlitiorzul Wutcr Purifi'cariolr in
Tropical Dovt~lopingcorcntric~s,Exisiting Mt~tl~ods
n~ul
GTZ.
Potentid Ap/~/it:~lliolz,
Nadkarni. K.M. 1976. lnrlir~~~
Mutc>riuMoe1ic.c~3rd Edition.
Bombay.
Pradhananga, T.M. 1994. Supply and Quality ol' Water in
A Cornpc,ndirtri~o n tlic Environrnentol Srtiri.stitrs of
Nepul: 1.ss~rc.scrnd Fncts, National Planning
Commission Sccretariat. Central Bureau of Statistics.
Kathmandu. Ncpa1.p. 153.
Sharma, A.P. 1978. The Quality of Drinking Water in
Kathmandu. Jo~rrnalof flnsrirufr~OJ'SCI'CI~CP
1 : 15-22.
Stundart1 Mcf11orl.stor. [he Exunrir~otion01' Wurrr &
Wastewtrtrr 1989. 17th Edition, Lcnores Clcsceri.
Arnold E. Greenerg & R. Rhodes Trussell.
Thapa. A,, U. Shnrma. R.R. Shahi, S. Shrcsthn, and T.M.
Pradhananga 1993. Water Quality Monitoring of Stone
Taps of Pashupati Area, Journal of N ~ p dCl~en~ical
Socrc~ty12: 55-62.
WHO 1993. G~ritlelinesfor Drinking Wutc~rQuulity.
Rrco~n~i~c~nrlrr~ions,
1 , Second Edition, Geneva.