Download quantification of e. coli.bacteria in drinking water by the

International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009,
http://iraj.in
Vol-4, Iss-4, Spl. Issue-2 Dec.-2016
QUANTIFICATION OF E. COLI.BACTERIA IN DRINKING WATER
BY THE MEANS OF AMMONIA SENSING
1
ANUJ PRAJAPATI, 2JAGHADEESHWARAN R., 3MEGHANA URS, 4ESWAR SAI AVINASH M,
5
VIJAY MISHRA, 6PUNEET SHARMA
1,2,3,4
Main Author, Summer Intern, 5,6Systems Engineering Facility (SysEF), Centre for Nano Science and Engineering
(CeNSE), Indian Institute of Science (IISc), Bangalore, India
E-mail: [email protected]
Abstract – Microbial contamination of water has long been a concern to the public. All water supplies should be tested for
biological content prior to use and consumption.
E. coli is the coliform bacterial organism that is a major contaminant found in drinking water. The presence of E.coli in
water indicates recent faecal contamination and may indicate the possible presence of disease-causing pathogens, such as
bacteria, viruses, and parasites. Hence the detection of such bacteria in the drinking water has found prime importance
recently. In this study, the pathogen bacteria E. coli in drinking water was quantified by the means of Ammonia (NH3) gas
sensor and a heater which were coupled into a chamber. Bacteria were heated by the heater in air so that ammonia can be
generated by the oxidation reaction of organic components of bacteria. The NH3 gas was generated in a closed chamber and
detected by the FigaroTM TGS 826 Ammonia gas sensor mounted on the top. Bacterial concentrations up to 108 cells/ml were
quantified by this study.
Product: Using the above mechanism, a product was developed as a part that can be integrated into a typical household water
purification system.A drop is taken from a stream of water running in the purification system and placed onto the heating
surface by means of a drop dispenser.Upon integration with the water purifier assembly, this product continuously detects
the amount of E. coli.in drinking water and alerts the user of contamination if the bacterial concentration is above a set limit.
Keywords— Microbial Contamination, E.coli., Drinking Water, Ammonia Sensing.
I. INTRODUCTION
Escherichia coli (also known as E. coli) is
a bacterium of
the genus Escherichia that
is
commonly found in the lower intestine of warmblooded organisms.Most E. colistrains are harmless,
but some of them can cause serious food poisoning in
their hosts, and are occasionally responsible
for product recalls due to food contamination.E. coli
is expelled into the environment within faecal matter.
Cells are able to survive outside the body for a
limited amount of time, which makes them
potential indicator organisms to test environmental
samples for faecal contamination.
E. coli outbreaks can serve as a dangerous bioweapon for terrorism and has claimed endless lives in
the past. This calls for an effective method for
detection of E. coli bacteria which is fast and
accurate.
Conventional methods like the colony counting
technique although reliable, are laboratory based and
take a lot of time(days).
The product developed in this study can accurately
detect the bacterial concentration in drinking water
within minutes.
Values for the coefficients a, b, c and d depend on
organic
materialCaHbOcNd.
The
compound
representing bacteria is given as C5H7O2 [2][3]. Then
Eq. (1) becomes
C5H7O2+ 5O2 = 5CO2 + 2H2O + NH3 …. Eq. (2)
The aerobic reaction can be easily achieved by
heating biological cells to be oxidized in atmospheric
air containing oxygen.
Eq. (2) suggests that CO2, H2O or NH3 can be used as
the gas which indicates that an organic-free specimen
is contaminated with pathogenic bacteria. NH3 seems
to be preferable as the indexing gas among them
because CO2 and H2O are commonly found in
environmental air.
III. FLOW CHART OF PROCEDURE
II. THEORETICAL CONCEPTS
Mostly, biological tissues are decomposed due to
aerobic reactions. A general aerobic reaction
proposed by Ianneli et tal.[1]is given by
Quantification of E. coli.bacteria in Drinking Water by the Means of Ammonia Sensing
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International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009,
http://iraj.in
Vol-4, Iss-4, Spl. Issue-2 Dec.-2016
IV. SCHEMATICS
ElectronicsCircuitry
Data acquisition from the sensor and real time
plotting is an important part of this project. TGS826
fetches the concentration of ammonia and gives a
voltage as output. The output of the ammonia sensor
is given to an ADC which has higher bit resolution
such as ADS1115. This also supports I2C
communication.
Data communication between ADC and a
microcontroller which is Arduino Nano in this project
occurs via I2C interface which is also referred to as
two wire interface.
Integrated into the water purification system through
a T joint or a Y joint.
Data transferred to the Arduino I2C pins can be read
by calling few functions on Arduino platform after
installing the required libraries.
V. PRODUCTS ASSEMBLY
Devices Used
1.PolymedTMMicroFusion Set 14098 Drop Dispenser
2.TEC1-12706 Peltier Plate Heater
3.FigaroTMTGS 826 Ammonia Gas Sensor
4. Solenoid Valve & Diaphragm Pump
5. Arduino Nano
6. ADS 1115 Analog to Digital Converter
This data can be printed on serial monitor. Data goes
into serial port while printing it on serial monitor.
Python 2.7 is used to plot the live data recorded by
Arduino. Python and Arduino are interfaced by
sending the data to serial port. Data in the serial port
is accessed by python using a library called pyserial.
It is basically a voltage output of the sensor which
can be plotted in real time by using few other libraries
to append data and plot a graph accordingly.
Mechanical Design
Designing was carried out on
CreoTMelements/proTM 5.0.
Two equations weregenerated; one for calibration of
the sensor and the other gives the relation between
E.coli concentration and voltage. These relations
were manipulated and coded accordingly to get the
plots of E.coli concentration vs time, ammonia
concentration inppm vs time or E.coli vs ammonia
concentration depending on the requirement.
The ammonia sensor used is temperature sensitive;
hence a temperature sensor is used for its
compensation. Solenoid valve and pump are switched
ON and OFF after particular intervals of time. The
switching circuit is designed as well as coded
accordingly. Altium designer was a platform used for
designing of schematics and PCB of the final
circuitry used in this project.
Quantification of E. coli.bacteria in Drinking Water by the Means of Ammonia Sensing
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International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009,
http://iraj.in
Vol-4, Iss-4, Spl. Issue-2 Dec.-2016
Curve:
X axis: Bacterial concentration in cells/ml
Y axis: Sensor voltage in Volts (V)
Using the above data an equation was generated
which related the bacterial concentration (y) with the
voltage (z) generated.
z = 0.486log10(y) – 0.385
…(1).
VI. BIOLOGY EXPERIMENT
An experiment was conducted to generate a curve
which establishes the dependency of the generated
ammonia on the bacterial concentration in drinking
water.
Initially NH3 levels were recorded by heating known
concentrations of bacteria. Once the relationship
between NH3 and bacterial concentration was known,
this relation was reversibly used to determine the
unknown bacterial concentrations of water.
NH3 Sensor Calibration
The equation generated by calibration of Voltage (z)
vs. PPM (x)
z = 16.44ln(x) + 387.94
….(2)
Relation of ppm (y) vs. bacterial concentration(x)
Using equations (1) and (2), we get
y = exp{[0.486log10(x)-0.385-387.94]/16.44}
Bacteria
Escherichia coli K-12 strains were grown in LuriaBertani (LB) broth (Difco) for overnight at 37 °C.
The overnight grown culture inoculated to fresh LB
broth, kept at 25 °C, 150 rpm, until it reaches 0.6 OD
(where OD is optical density measured at 600 nm).
The 1 ml of cells (1 ml contains 1x108 cells) were
harvested by centrifugation at 6000 rpm, at 25 °C for
10 min. The cell pellet was re-suspended with 1 ml of
1X PBS.
Assuming that, 1 ml of 1xPBS contains 1x108 cells,
the experiment was carried out with drops of volume
100 µl for dilutions of 108 – 104 cells/ml and 10
cells/ml.
VII. MOVING AVERAGE MODEL
To account for the permissible inaccuracy that arises
due to some unavoidable factors like temperature,
time, which can change the bacterial concentration, a
Moving Average Model for the product is
incorporated.
• There is not a uniform distribution [3] of
bacteria over the complete volume sample.
• To tackle this, moving average model will
be incorporated for the readings observed.
X’n= ( Xn+X’n-1+…….+X’n-z )/z
X’n= Current averaged out reading
Xn= Current, true, non-averaged out reading
Z= intervals after which readings average
After the first z readings are taken by the product, the
rest are averaged out with the previous ones to
remove the inaccuracy.
Experimental Result:
The following data was generated for bacterial
concentration vs sensor voltage:
VIII. RESULT
Final test of the product were conducted based on the
following conditions:
1. 75 µl drops of tap water (unknown bacterial
concentration) were dispensed at regular intervals of
80 seconds.
2. Heater was always kept on, which evaporated the
drops in 40 seconds.
3. NH3 sensing required 60 seconds including the
time for heating.
Quantification of E. coli.bacteria in Drinking Water by the Means of Ammonia Sensing
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International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009,
http://iraj.in
4. After each reading, normal ambient ammoniacal
conditions were restored in the sensing chamber.
Vol-4, Iss-4, Spl. Issue-2 Dec.-2016
Readings can vary depending on environmental
conditions and best care has been taken to ensure any
discrepancy or inaccuracy.
As bacteria are a biological entity, they cannot be
treated as chemical contaminants and vary depending
upon the ambient conditions; hence variations are
permissible within limits.
The following plot was generated:
ACKNOWLEDGEMENT
This work was done as a part of Summer Internship at
Centre for Nano Science and Engineering, Indian
Institute of Science, Bangalore during the summer of
2016.This work was done by the main authors under
the guidance of corresponding authors. We express
our deepest gratitude to the SysEF authorities for
their tremendous support.
Y axis: E.coli. in cells/ml
X axis: Time in seconds
The E.coli readings saturated after going above 500
units.
REFERENCES
[1]
CONCLUSION
A viable product for detection of E.coli.bacteria was
developed. The product can be easily integrated into a
regular household water purification system. It will
continuously detect E.coli. bacteria and will alert the
user of contamination if the bacterial concentration
exceeds a certain set limit.
The data generated in the project is dependent on
ambient conditions i.e. temperature, humidity etc.
[2]
[3]
IANNELLI R., GIRALDI D., POLLINI M.,
RUSSOMANNO F.: ‘Effect of pure oxygen injection as an
alternative to air and oxygen enriched air in the
composting processes’. Proc. 10th Int. Waste Management
and Landfill Symposium (Sardinia 2005), Cagliari, Italy,
October 2005
POLPRASERT C.: ‘Organic waste recycling – technology
and management’ (John Wiley & Sons Ltd., 1996, 2nd
edn.), pp. 47–49
REICHEL T., HAARSTRICK A., HEMPEL D.C.:
‘Modeling long-term landfill emission – a segregated
landfill model’. Proc. 10th Int Waste Management and
Landfill Symp. (Sardinia 2005), Cagliari, Italy, October
2005.
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Quantification of E. coli.bacteria in Drinking Water by the Means of Ammonia Sensing
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