22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Application of pulsed Streamer plasma in bacterial disinfection and dye
degradation
R.K. Singh1, L. Philip1 and S. Ramanujam2
1
2
Department of civil engineering, Indian Institute of Technology, Madras, 600036 Chennai, India
Department of electrical engineering, Indian Institute of Technology, Madras, 600036 Chennai, India
Abstract: The present study dealt with the application of pulsed streamer plasma for
disinfection of water and dye degradation. Different initial cell concentrations were used
for the disinfection study. Effect of voltage magnitude, initial dye concentration and
volume of contaminated water were also studied. Rate constants for disinfection and dye
degradation were different with the variation of concentration, voltage magnitude and
reactor volume.
Keywords: pulsed, streamer, disinfection, dye degradation, rate constant
1. Introduction
With the current water scarcity and waste disposal in
water bodies, it is estimated that the 11% of world
population are lacking safe drinking water and
approximately 3000 children are dying due to water borne
diseases [1]. Plethora of microbial diversity and organic
pollutants in water leads to many water borne diseases
and sometimes are even responsible for death. The
organic dye like Methylene blue (MB) is widely being
used in textiles industries and it plays the role of a robust
staining material in biology and chemistry. Every year
around 70,000 – 100000 tons of dye is being released
directly as wastewater into the water bodies [2] and these
dyes are carcinogenic, allergic and mutagenic in nature
and can have significant adverse effect on humans, plants
and on aquatic species [3]. To disinfect water many
tertiary treatment technologies like chlorination,
ozonation and UV treatment are in practise. Along with
bacterial disinfection, some disinfection by-products
(DBPs) such as trihalomethane and haloacetic acids etc
also forms during chlorination [4] and disinfection and
these DBPs are carcinogenic in nature [5]. This is one of
the biggest demerits of the above said technologies. Also
the control of UV dose is difficult and many times
bacteria tend to revive back by their DNA repair
mechanism [6]. Presently advanced oxidation processes
(AOPs) such as fenton, photo-fenton, UV/O 3 , H 2 O 2 /O 3 ,
sonolysis, photo-catalysis etc. are gaining importance as
these processes can produce hydroxyl radicals (OH*).
OH*, having a high oxidation potential, gives the biggest
advantage of reduction of the volume of the reactor and
treatment time, which is not possible with the existing
conventional treatment technologies. However most of
these processes require high input of energy and high
treatment cost [7]. Plasma technology in water
purification, one of the latest technologies for water
treatment is gaining attention because of its superior
potential to kill pathogens without the production of any
toxic by-products [9]. Pulsed streamer discharge in air
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and/or water produces different reactive oxygen species
like OH*, H 2 O 2 , O 3 and O 2 -* along with UV and intense
wave. This synergetic effect results in the effective
oxidation of organic pollutants and/ or microbial
decontamination. The present study discusses the
application of pulsed streamer plasma technology in
disinfection of water and dye degradation. By using
pulsed high voltage, plasma in the form of streamer was
produced in air and propagated to water to form different
reactive species and these species in turn were responsible
for the ultimate water treatment.
2. Methodology
Experimental set up and electrode configuration
For the high voltage power supply a 100 kVA
transformer was used. A half wave rectifier circuit was
designed with the help of a diode rating 140 kV, 20 mA,
100 kΩ, and a capacitor of rating 140 kv and 10000 pF. A
rotating spark gap was used as a pulse generator (Fig. 1).
In the present study, a self-built reactor was used. The
reactor contains a multiple needle type tungsten (Alfa
Aesar, India) electrode for generating the high voltage
pulsed streamer discharge for a fluid capacity of 100 mL.
The reactor was placed in a water jacket and cooling
water at 15-20 °C was allowed to flow through the jacket
to maintain isothermal conditions in the reactor. The top
of the reactor had a sampling port and also a port to insert
high voltage electrode into the reactor. Square pulses with
a rise time of 0.4 µs and pulse width of 20 ms were used.
Bacterial culture and chemicals
Pure culture of E. coli bacteria was isolated from
Tryptone bile glucuronic agar (Himedia, India) plate, resuspended in Luria Bertani (Himedia, India) liquid media
and incubated overnight in an orbital shaker of 120 rpm at
room temperature. Culture were centrifuged at 5000 x g
for 10 min and washed with physiological saline prior to
experiment. Quantification of bacterial concentration was
performed using plate count method. 500 mg/L stock
1
a
b
Fig. 2. Effect of initial E. coli concentration on
disinfection rate at 23 kV input voltage.
Table 1. Deactivation rate constant at different cell conc.
Initial E. coli conc. as
log(cfu/mL)
1.00
2.19
3.30
5.60
6.73
Fig. 1. Diagrammatic representation of pulsed streamer
discharge system (a) circuit for high voltage source (b)
reactor with tungsten electrode.
solution of methylene blue was prepared in Millipore
water and different concentrations of dye 10 – 50 mg/L,
was prepared by using stock solution. Different dye
concentrations were quantified by measuring the
absorbance at 668 nm wavelength in spectrophotometer
(Shimadzu, Japan).
Deactivation rate constant
(log(cfu/mL)/min)
0.50
0.71
0.74
1.17
1.37
3.2. Dye degradation using pulsed streamer plasma
3.2.1. Effect of voltage magnitude on dye degradation
For the MB degradation three input voltage of 17 kV,
20 kV and 23 kV was applied. From the Fig. 3, it can be
observed that the dye degradation efficiency increases
with the voltage magnitude because the reactive species
such as OH*, H 2 O 2 and O 3 increases with voltage
magnitude [10]. Total time required to complete
decolourization of MB dye was 8 min for 50 mg/L dye
concentration at 23 kV. Approximately 60 % of total
organic carbon (TOC) removal was obtained at the end of
10 min of treatment. It shows a good agreement with
reported value of Wang et al. [11].
3. Results and discussion
For the disinfection and dye degradation, a voltage
magnitude of 23 kV and frequency of 25 Hz was applied.
3.1. Effect of initial cell concentration on disinfection
Different bacterial cell concentrations in order of
10 cfu/mL, 102 cfu/mL, 103 cfu/mL, 104 cfu/mL,
105 cfu/mL and 107 cfu/mL were used to observe the
variation in deactivation constant.
The variation in deactivation rate using pulsed streamer
is shown in Fig. 2. For the complete disinfection, 2 min to
6 min of treatment time was required and the rate constant
for deactivation at different cell concentration is presented
in Table 1. The rate of bacterial deactivation decreases
with decrease in initial cell concentration of E. coli.
Therefore initial cell concentration is also an important
factor for deciding the rate of degradation.
2
Fig. 3. Effect of voltage on dye degradation for initial
dye concentration of 50 mg/L
3.2.2. Effect of initial dye concentration and reactor
volume
Initial pollutant concentration and volume tends to
affect the rate of degradation. Dye degradation efficiency
of streamer discharge for different dye concentration is
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shown in Fig. 4. Similarly dye degradation efficiency of
streamer plasma for different reactor volume is shown in
Fig. 5. From the study it was found that, the MB follows
first order kinetics for the degradation and it can be
represented by Eq. 1.
𝐶
log � � = −𝑘𝑘
𝐶0
(1)
where, C 0 = Initial dye concentration, C = Concentration
of dye at time‘t’ and k = First order rate constant.
The rate constant for dye degradation (Figs. 4 and 5)
was calculated by Eq. 1 and is presented in Table 2. From
the result it can be concluded that the concentration of dye
and reactor volume also decides the rate of dye
degradation.
Table 2. Rate constant of dye degradation for different
initial concentration of dye and reactor volume.
Parameters
Fig. 5. Dye degradation with respect to time for different
reactor volume at 23 kV input voltage
4. Conclusion
The current study demonstrated the applicability of
pulsed streamer technique for the treatment of pollutants
like bacteria and organic dye present in water. From the
current study complete disinfection was achieved in 6 min
of streamer discharge at 23 kV input voltage for a
bacterial reduction of 7 orders of magnitude (107 cfu/mL).
And complete dye decolourization was achieved in 8 min
of treatment time for a dye concentration of 50 mg/L. It is
shown that the operating parameter like voltage
magnitude enhances the rate of treatment process
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R2
Initial dye concentration (mg/L)
10
20
30
40
50
0.57
0.56
0.52
0.45
0.44
0.99
0.99
0.98
0.99
0.96
Initial reactor volume (mL)
10
20
30
40
50
Fig. 4. Dye degradation with respect to time for different
initial concentration of methylene blue at 23 kV input
voltage
Rate constant
(min-1)
0.58
0.48
0.34
0.25
0.24
0.91
0.93
0.98
0.99
0.92
significantly and initial pollutant concentration has also
got an effect on degradation rate. It is thus proved, that
the treatment time and reactor size for water treatment can
be significantly reduced by adapting pulsed streamer
technique. Studies of this kind enable to develop pilot
scale studies for the water treatment in industries.
5. Acknowledgement
The authors acknowledge the financial support from
department of science and technology (DST), India
throughout the study.
6. References
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