A Collaborative Purification Device for Medical Exhaust Gas and
Wastewater based on Low Temperature Plasma Technology
Xinfei Zhangchen
1,a
, Xunchen Liu
1,b,*
, Yuan Fang
2,c
, Yuwen Shu
3,d
, Zeming Wang
1,e
and Kailin Han
1,f
1
Wuhan Institute of Technology, Wuhan, China
2
South-Central University for Nationalities, Wuhan, China
3
Wuhan University of Technology, Wuhan, China
b,
*Corresponding author: liuxunchen2021@163.com
Keywords: Medical Waste Gas and Wastewater, Collaborative Purification, Plasma, Graphite Fiber.
Abstract: With the continuous development of environmental protection and sustainable development strategy, the
traditional medical waste gas and wastewater discharge will not only pollute the environment, but also
seriously threaten human physical and mental health. It has become an urgent problem to control it
scientifically and deal with it reasonably. In this paper, an integrated device for treating medical waste gas
and waste water with low temperature plasma is designed, which uses silver-plated graphite fiber as electrode.
The device uses plasma to purify medical waste gas and wastewater, no secondary pollution, high efficiency
and environmental protection; through the atomization device is set to make waste water and waste gas
synergistic purification, improve purification efficiency; the modified graphite fiber electrode is adopted to
reduce energy consumption. This research improves the efficiency of waste water and waste gas treatment to
fill the current gap in the industry, and contributes to the sustainable development strategy.
1 INTRODUCTION
With the implementation of sustainable development
strategy in the world, people pay more and more
attention to sustainability. Under the background of
global environmental protection, how to scientifically
control and reasonably treat the organic waste gas and
medical waste water in the medical industry has
become an urgent problem (Wei, 2020).
Hospital sewage contains a large number of
pathogenic bacteria, viruses and chemical agents
(Lin, 2017), which is characterized by space
pollution, acute infection and latent infection (Yang,
2017). Medical waste gas is harmful gas produced by
combustion of medical waste (Zhang, 2019). Such
industrial waste gas contains alcohols, acids and
ketones, which will not only pollute the environment,
but also seriously threaten human physical and mental
health.
At present large hospital medical wastewater
treatment mainly using chlorine disinfectants for
disinfection, such as NaClO, ClO2, in which NaClO
in the process of using residual, easy to react with
organic matter in water generated in the process of
sterilization effect of chemicals cause cancer, birth
defects, there is a certain risk, the need of personnel
management. However, the traditional method has its
inevitable drawbacks in principle, such as high cost
of facility construction, maintenance and
management, multi-stage processing and complicated
process control.
In the processing of medical waste is the
traditional adsorption method, although adsorption
method has a very wide range of application and low
energy consumption, but if the exhaust gases contain
a variety of pollutants, the adsorption efficiency of
adsorption method would significantly reduce, and
adsorbent regeneration difficulty, easy to poisoning,
so led to the organic waste gas treatment lack of
quality assurance. So finding a new type of medical
waste gas, wastewater treatment technology is
imperative. Although there are many differences
between this research and our former study (Hua,
2022; Chen, Zhuang, 2021; Gu, 2021; Chen, Zhang,
2021), we still carry out the excellent research about
a collaborative purification device for medical
exhaust gas and wastewater based on low temperature
plasma technology.
Zhangchen, X., Liu, X., Fang, Y., Shu, Y., Wang, Z. and Han, K.
A Collaborative Purification Device for Medical Exhaust Gas and Wastewater Based on Low Temperature Plasma Technology.
DOI: 10.5220/0012011800003633
In Proceedings of the 4th International Conference on Biotechnology and Biomedicine (ICBB 2022), pages 5-11
ISBN: 978-989-758-637-8
Copyright
c
2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
5
2 DEVICE INNOVATION
With the support of the existing technology, we have
designed an integrated device for treating medical
waste gas and waste water using low-temperature
plasma with graphite fiber coated with silver as
electrode. Graphite fiber surface modification
technology was used to improve the plasma surface
discharge efficiency, and a liquid gasification device
was creatively added to the device, which could
further improve the common purification effect of
waste water and waste gas. And the plasma power and
purification rate were studied, and finally
successfully produced a set of waste water
gasification, low temperature and high efficiency
plasma water purification in one of the waste water
and waste gas treatment equipment, on the existing
basis to improve the purification rate and reduce the
energy required, the traditional purification device to
improve and upgrade.
(1) Plasma purification
Using plasma purification medical waste gas
waste water, no secondary pollution, and efficient
environmental protection: compared with the
traditional chemical precipitation method, using
plasma purification more green environmental
protection, in line with the requirements of energy
conservation and emissions reduction, oxidation and
plasma generated is strong gas efficient of
purification of bacteria, viruses and other organisms
that have slipped into the medical wastewater and
organic chemicals, achieve discharge standards.
(2) Modified graphite fiber electrode
Modified graphite fiber electrode is adopted to
reduce energy consumption. Compared with the
copper column, the surface of graphite fiber rod is
loose and porous, which is beneficial to generate
more plasma in dielectric barrier discharge and
improve the purification efficiency. Graphite fiber
itself is an excellent conductor of electricity, coating
its surface with silver can further reduce its resistivity,
but also improve its corrosion resistance, prolong the
service life. The experimental results show that the
low temperature plasma generator using modified
graphite fiber as electrode can save 20%~30% power
consumption compared with the similar device.
(3) Atomization device
Through atomizing device, waste water and waste
gas can be synergistically purified to improve
purification efficiency. The medical waste water is
mixed with the exhaust gas after pressurized
atomization, and the gas-liquid mixture phase enters
the static mixing tube at the same time with the air
after plasma treatment, and is mixed in the mixing
tube and fully reacts. This treatment method can
improve the utilization rate of plasma, reduce the
power consumption, and accelerate the reaction rate
of plasma and pollutants. Through experimental
calculation, the reaction rate is the fastest at the
interface between plasma and waste water. The
cooperative purification method of waste gas and
waste water of this device can greatly improve the
contact area of plasma air and waste water, accelerate
the reaction rate, and thus improve the purification
efficiency of the whole machine.
3 PURIFICATION PLANT
The purification device includes gas-liquid mixed
structure, plasma generator, mixed reaction structure
and condensation separation structure. Fig.1 is a
schematic diagram of the overall structure of the
device.
Figure 1: Cruise drone landing platform structure.
ICBB 2022 - International Conference on Biotechnology and Biomedicine
6
(1) Gas-liquid mixed structure
The gas-liquid mixing mechanism comprises a
gas input part and a liquid input part. Fig. 2 is a
schematic diagram of gas-liquid mixture structure.
The gas input part consists of a turbocharger, which
rotates to input the exhaust gas; The liquid input part
is composed of a water pump and a number of
atomizing nozzles arranged on the pipe wall, through
which the waste liquid is pumped into the pump, and
then the waste liquid is changed into mist through the
nozzle, and mixed with the waste gas.
Figure 2: Gas-liquid mixed structure.
(2) Plasma generator
Plasma generator by DBD low temperature
plasma generator, turbocharger, desiccant, through
the turbocharger will input air, the air through the
desiccant to remove moisture, and DBD low
temperature plasma generator to produce plasma,
input the air generator within the plasma transfer and
fresh air to produce new plasma. Fig. 3 is a schematic
diagram of plasma generator.
Figure 3: Plasma generator.
(3) Mixed reaction structure
The mixing structure consists of an input tube,
several static mixers and an output tube. Fig. 4 is a
schematic diagram of mixed reaction structure. Each
static mixer tube inlet connection by two inputs, input
contains plasma of air and waste gas and waste liquid
atomization of mixed gas, the static mixer with
multiple mixing unit, overlapping, can instantly at
very good mixing effect, including plasma air and
steam mixed fully response, the output pipe will count
all products in the static mixer.
A Collaborative Purification Device for Medical Exhaust Gas and Wastewater Based on Low Temperature Plasma Technology
7
Figure 4: Mixed reaction structure.
(4) condensation separation structure
The condensation separation structure consists of
a liquid storage tank and a condensation bend. Fig.5
is a schematic diagram of the condensation separation
structure. After treatment, the mixed steam condenses
in atomized droplets after passing through the
condensing bend and flows into the liquid storage
tank, while the gas phase continues to pass through
the bend and is finally discharged from the gas outlet.
The waste liquid in the liquid storage tank is
discharged through the liquid outlet after reaching a
certain amount. Sensors are installed on the wall of
the liquid storage tank, which can monitor the
pollution components in the waste liquid in real time
to ensure that the liquid after treatment meets the
discharge requirements.
Figure 5: Condensing separation structure.
(5) Purification process of medical waste gas and
waste liquid
The working process is as follows: the waste gas
generated after the incineration of medical appliances
will be removed through activated carbon before
entering the device, and the solid residue in the waste
liquid will be removed through coarse filtration
before entering the device to ensure that the liquid
entering the device only contains liquid phase.
Medical waste liquid by the liquid inlet through the
pump pumping unit, by several nozzle jet again in
fog, waste gas from waste gas entrance from the
turbocharger suction device, mixed with mist waste
liquid in nozzle place, and at the other side of the
device, DBD plasma plasma generator, air drawn in
by the turbocharger after drying device, mixed with
plasma plasma mixture formation, Then, the mixed
phase reacts fully with the waste gas liquid in the
mixed reaction structure, and finally separates the gas
liquid in the condensation separation structure. After
treatment, the waste liquid and waste gas are
discharged from the liquid outlet and the gas outlet
respectively. Fig. 6 is the schematic diagram of the
device.
ICBB 2022 - International Conference on Biotechnology and Biomedicine
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(Note 1: Turbocharger 2: atomizer 3: DBD plasma generator 4: Turbocharger 5: desiccants 6: water pump 7:
static mixer 8: condensing bend 9: liquid storage box 10: sensor)
Figure 6: Schematic diagram of device principle.
4 CONTROL MODULE
The control module is used to control each step of the
whole device. This module is composed of
STM32F103C8T6 single chip microcomputer and
connected high-voltage power supply, water pump,
turbocharger, voltage matching circuit, temperature
and humidity sensor, button, OLED display screen
and so on.
Power control circuit is used to realize the control
of low voltage, small current controller circuit to
power circuit, through the control of high voltage
module, water pump, turbocharger, etc., to achieve
the control of current, water flow and air.
As shown in Fig.7, the high voltage module, water
pump and turbocharger are connected with 12V
power supply and controlled by relays SR
1
, SR
2
, SR
3
and SR
4
, which are driven by triodes current amplifier
circuit.
Figure 7: Power control circuit.
A Collaborative Purification Device for Medical Exhaust Gas and Wastewater Based on Low Temperature Plasma Technology
9
When the level of GPIO port corresponding to the
single chip is 0, the base level of Q
1
is pulled down,
Q
1
is in cut-off state, and the relay is open. When the
level of GPIO port corresponding to the single chip is
1, the base level of Q
1
rises, and the control current is
generated. Q
1
turns on and the relay pulls in. When
the level of the corresponding GPIO port changes
from low to high, the relay pops open to produce a
high counter electromotive force. At this time, diode
D
1
turns on to absorb the current and avoid burning
the transistor and MCU.
5 EXPERIMENT AND TEST
RESULTS
The experimental materials were silver nitrate and
acetone, which were analytically pure. Polypropylene
(PP) emulsion (91735), solid content in 30%~33%.
Graphite fiber and deionized water are self-made by
the laboratory. The resistivity of graphite fiber is
about 13.5×10
6
Ω∙m. Epoxy sizing agent is removed
with acetone before use.
(1) Experimental process
The preparation of silver-containing slurry, PP
emulsion as the main raw material, PP/H2O emulsion
prepared for graphite fiber impregnation coating.
Then impregnated coating treatment, graphite fiber is
fixed on the bracket, put into the slurry containing
silver, through repeated impregnation to make the
slurry evenly coated on the fiber surface. Graphite
fibers were impregnated with PP/H2O emulsion
slurry with silver nitrate content of 5%. Finally, the
graphite fiber after impregnation coating treatment
was placed in high temperature tubular furnace (GSL-
1700X) for pyrolysis. The graphite fibers were fixed
at both ends on the support, and a certain tension was
applied. The temperature was heated to 500℃ at a
rate of 10 K/min in nitrogen atmosphere, and the
temperature was kept for 10min.
(2) By scanning electron microscope (SEM) test
characterization
The fibers were glued to the sample table with
conductive adhesive and observed at a constant
temperature of 50℃. Fig.8 shows SEM images of
graphite fiber GF-1 before and after treatment. As can
be seen from the figure, the surface of untreated
graphite fiber is very smooth, while many foreign
bodies can be observed on the surface of coated and
pyrolyzed graphite fiber. In this device, the polymer
in the slurry acts as a binder to make the silver nitrate
adhere to the surface of the graphite fiber. Silver
nitrate is converted to elemental silver by pyrolysis.
Figure 8: SEM photos before and after treatment (untreated on the left, silver plated on the right).
It can be seen that the silver is mainly distributed
evenly on the surface of the graphite fiber coated by
PP/H2O emulsion in the form of fine nanoparticles.
(3) Resistivity test
The self-made fiber resistivity tester and DC dual
probe method were used to test the resistivity of the
fiber sample. The test length was 10cm, and the DC
current was adjusted to 0.05a after the power was
turned on. The voltage was read and the resistivity
was calculated. The calculation formula of resistivity
is as follows:
𝜌
𝑈
𝐼
⋅
𝑌
𝐷⋅𝐿
10
Where, ρ is the resistivity (ω ∙m); U is voltage (V);
I is the current (A); Y is fiber linear density (g/1 000
m); D is fiber body density (g/cm3); L is fiber test
length (cm).
According to the resistivity test results of
untreated and silver-plated graphite fibers, compared
with the untreated graphite fiber, the resistivity of the
silver-plated graphite fiber decreased. The resistivity
of the silver-coated graphite fiber prepared by
PP/H2O emulsion coating decreased significantly,
ICBB 2022 - International Conference on Biotechnology and Biomedicine
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and the resistivity of the silver-coated graphite fiber
decreased about 40.7% compared with that before
treatment.
6 CONCLUSION
(1) The device uses the principle of dielectric barrier
discharge (DBD), which produces both low-
temperature plasma and a large amount of ozone. At
the same time, the discharge effect at the electrode
can be reduced, so that the discharge is concentrated
on the electrode surface to form a more uniform
discharge.
(2) The air containing plasma is mixed with the
waste gas liquid mixture in the mixed reaction vessel
to form activated water. The water activated by low
temperature plasma has certain bactericidal ability
and can be used in the treatment of medical
wastewater. Moreover, plasma activated water has
obvious bactericidal effect on Staphylococcus aureus,
Escherichia coli and pseudomonas aeruginosa.
(3) The power consumption of the existing
medical wastewater treatment system is 120kwh/d,
and the electricity consumption is 84 yuan /d based
on 0.7 yuan/KWH, and the daily drug consumption is
78 yuan /d, with a total cost of 162 yuan /d. The power
consumption of the low-temperature plasma
purification system is 78 yuan /d, and there is no need
to add pharmaceutical costs, and the cost is reduced
about 61%.
(4) Compared with the existing medical
wastewater treatment system, the low-temperature
plasma wastewater treatment system has a higher
removal rate of pollutants in the medical wastewater,
and can basically remove the components of COD,
BOD5 and Escherichia coli that are harmful to the
environment in the medical wastewater. The removal
of BOD5 indirectly reduces the survival rate of
microorganisms in wastewater, makes wastewater
discharge to meet national standards, and reduces the
pollution of wastewater to the environment. At the
same time, the device will be mixed with waste water
and waste gas at the same time, improve the treatment
efficiency of waste water and waste gas, with good
social benefits.
ACKNOWLEDGMENTS
The authors would like to thank Natural Science
Foundation of Hubei Province (No. 2020CFB389) for
the support given to this research.
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A Collaborative Purification Device for Medical Exhaust Gas and Wastewater Based on Low Temperature Plasma Technology
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