Summary of Environmental Technique Doctoral thesis: Research improving the process preparing superoxidized sulution and application in disifecting hospital wastewater

MINISTRY OF EDUCATION AND
VIETNAM ACADEMY OF
TRAINING
SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY
……..….***…………

NGUYEN THỊ THANH HAI

RESEARCH IMPROVING THE PROCESS PREPARING
SUPEROXIDIZED SULUTION AND APPLICATION IN
DISIFECTING HOSPITAL WASTEWATER
Major: Environmental Technique
Code: 62 52 03 20

SUMMARY OF ENVIRONMENTAL TECHNIQUE
DOCTORAL THESIS

Hanoi, 2018
1


The work was completed at: Graduate University of Science and
Technology – Vietnam Academy of Science and Technology

Science instructor 1: Assoc. Professor, Dr. Nguyen Hoai Chau
Science instructor 2: Assoc. Professor, Sc.D. Ngo Quoc Bưu

Reviewer 1:
Reviewer 2:
Reviewer 3:

The dissertation will be protected at the Council for Ph.D. thesis, meeting at
the Graduate University of Science and Technology – Vietnam Academy of
Science and Technology at ... hour ... ', date ... month ... 201 ... .

The dissertation can be found out at:
- Library of the Graduate University of Science and Technology
- National Library of Vietnam

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INTRODUCTION
1. Statement
The electrochemical activation phenomena were discovered by Russian
engineer Bakhir in 1975. Then the electrochemical activation (ECA)
technology has been widespreading in Russian Federation and many other
countries in the world, including Vietnam.
In Vietnam, since 2005 a researcher group of Institute of Environmental
Technology, VAST, has began to study and fabricate the ECA divices by
using imported from RF different electrochemical chambers suchs as FEM-3,
FEM-7, MB-26, especially the latter model MB-11, which seemed to be the
most suitable in work under tropical climate of Vietnam. However, after
operating in real weather conditions our ECA device based on an
electrolytical chamber MB-11 has exhibited some disadvantages such as ECA
chamber’s temperature increasing, rapid deposition on the catode etc...,
resulting in worsening product’s quality as well as decreasing equipment’s
lifespan.
The need to improve the ECA solutions produced on the MB-11 - based
ECA devices has become urgent since 2011. The research group of the

Institute of Environmental Technology, among which author of this thesis has
played an important role, have found out the solution to constrain the
temperature increasing effect of the electrolytical process by changing the
hydraulitic scheme of the device. The success of the improved designing of
the ECA equipment using MB-11 module will open new possibilities to solve
the problems of disinfection of hospital waste water which the Institute of
Environmental Technology is dealing with for 15 years.
2. Objectives of the thesis
To investigate and improve the technological process of producing
superoxidation solutions in order to produce ECA device suitable for
Vietnamese climatical conditions and apply the solutions of this device for
disinfection of hospital wastewater.
3. Main contents of the thesis
- Improvement of the technological process of producing superoxidation
solutions suitable for the real tropical conditions in Vietnam;
- Application of superoxidation solution to disinfect hospital wastewater.
4. New contributions of the thesis
The thesis has successfully investigated and set up a new hydraulytic
diagram of the superoxidation water (SUPOWA) device producing
superoxidation solution (SOS) with a capacity of 500 ± 5 g of oxidants/day in
Vietnam. The improved hydrolytic diagram was based on the non-circulating
catholite flow instead of the original circulating one. This operational mode
was done by setting up the relationship between the number of catholite turns
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and the quality of the supowa solution produced and the MB-11’s lifespan.
Due to this improvement the temperature of the module could be kept below
39oC during operation of the device, which resulted in the increased longevity
and stable operation of the electrolytic module in tropical climates, meeting

the requirements of the small hospitals wastewater stations or healthcare
centers with a capacity of about 150 beds. In addition, the results of the thesis
also demonstrated the possibility of localization of the supowa devices except
for the imported ECA electrolytic modules.
Results of the thesis have opened a new direction in application of high
technology to disinfect drinking and waste water. The improved ECA
technology is friendly with environment and able to reduce significantly the
risk of chlorine gas poisoning for operating workers. The SOS produced on
the improved ECA devices are cost-effective, safe and powerful disinfectant
for treatment of hospital waste water.
CHAPTER 1. OVERVIEW
1.1. Super oxidation solution and its general characteristics
1.1.1. Introduction tot superoxidation sollution (SOS)
1.1.1.1. Electrochemical activation solution
Electrochemical activation is a combination of electrochemical effects
on the dilute aqueous solution of ions and molecules in the space near the
electrode surface (anode or cathode) in a flow-through electrolytic module
(FEM) with a semipermeable membrane separating the anodic and cathodic
spaces. Under the electrochemical impact some part of the polarisation energy
is transformed into inner potential energy. As a result of the electrochemical
activation the near-electrode medium comes into a metastable state
characterized by anomal activity of electrons and other physico-chemical
parameters. Simultaneously changing in time, these perturbed parameters of
the near-electrode medium gradually attain equilibrium values during
relaxation process. This phenomenon is called electrochemical activation,
while solution produced by the technology based on these phenomena is
called electrochemical activation solution
[19]. Whilst superoxidation
solution or superoxidatin water (supowa) is electrochemical activation
solution with highly oxidizing activity while mineralization is extremely low

[22].
Characteristics of “coventional” ECA solution and superoxidation solution
are shown in Table 1.1.

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Table 1.1. Characteristics of nomal electrochemical activation solution and
superoxidizing solution
No.
Technical parameters
Conventional
Superoxidation
ECA solution
solution
1 Mineralization
(TDS), ~4500 ÷ 5000
~ 1000 ÷ 1500
mg/L)
2 Oxidants
concentration,
~300
~500
mg/L
3 Oxidation
Reduction
> +800
> +800
Potential (ORP), mV
4 pH

6,5 ÷ 7,5
6,5 ÷ 7,5
Superoxidation solution used in the
experiments below was made by an ECA
device with MB-11 module (an improved
module of electrochemical activation
technology with a little diffirence in
structure and technical characteristics Figure 1.4. Electrochemical
compared with the previous module type.
module MB-11
MB-11 module has more stable anode
coatings, higher polarization voltage ( 3000 mV), allowing the activation of
solutions with much lower mineralization. The supowa solution consisted of a
series of high active oxidants such as HClO, H2O2, Cl, HO, HO2, O3, 1O2,
O, Cl2, ClO2, O3, etc. [21]. It was well known that all these substances present
in living organisms (in cytochromes), so that supowa solution posseses a
broad spectrum capacity for killing pathogenic microorganisms, including
bacteria, viruses, and fungi, while it doesn’t damage human cells and other
higher organisms. The difference is due to the difference in the cell structure
[25].
Except for the Russian researchers, there are many others in the world who
have studied the SOS, which are essentially ECA solutions under various
trade names
such as Sterilox®, Sterisol®, Medilox®, Dermacyn®,
Microcyn®, Varul®, Esterilife® and Estericide® QX, ... Each of them has
different components [30]. Most opinions suggest that superoxidant water
(SOW) has a great potential for disinfection in all fields of life, but it requires
an in-depth research into applications for each field.
1.1.2 Some methods for production of SOS
1.1.2.1 Principles of anolyte production technology

5


Fingure 1.5 Diagram of FEM-3 Fingure 1.6. Digram of MB-11
priciples to produce catalytic newtral principles to produce supowa
anolyte ANK solution [Error! solution based on receiving the
Reference source not found.]
wet oxidants gas mixture [21].
Operation principle of the SOS technology using MB-11 module is as
follows: Pure water is supplied to the cathode chamber of the MB-11module,
while sodium chloride solution is directed to the anode chamber. Under
conditions of transmembrane pressure PA (anode chamber) is greater than the
PC transmembrane pressure (cathode chamber). Na+ ions along with water
will travel from the anode chamber to the cathode chamber to form catholyte.
After the catholyte solution passes through the gas separation chamber to
discharge H2 gas and metal hydroxides, it is drawn to absorb the wet gas
mixture of oxidants outgoing from the anodic space [19].
1.1.2.2. Some supowa modulation technologies have been applied

NaCl
10-20 g/L

Figure
1.9.
Some anolit
Fingure
1.8.
Diagram
of modulation schemes of Russia [62]

the improved process
allows for the generation
of ANK high oxidant
content on the improved
STEL-30-ECO-C
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1.1.3. Studies on superoxidation solutions (abbreviated as SOS) in Vietnam
In Vietnam, 2000, a research group in the National Center for Natural
Science and Technology (now: Vietnam Academy of Science and
Technology) was formed to manufacture equipments producing anolyte
according to the technological model STEL-10H-120-01 by using PEM-3
module imported from Russia. Researchers at Institute of Environmental
Technology (IET) have conducted research, design and production ECA
equipments. The aim of these studies was to clarify the differences in
different technological diagrams, the stability in time of ECA solutions as
well as the characteristics of their disinfection capability in specific tropical
conditions of Vietnam to improve the effectiveness of ECA technology in our
country. Based on the use of FEM-3 modules imported from Russia, IET has
successfully fabricated the classic equipments "STEL-ANK" called ECAWA
with a capacity of 20 ÷ 500 L/h, ORP of 800 ÷ 900 mV and oxidants
concentration of 300 ÷ 350 mg/L.
Since 2002, ECAWA has been used widely throughout the country for
medical and water disinfection [23,40], environmental pollution treatment
[23,100], shrimp seed production [101], seafood processing [100,102], animal
husbandry [103] and poultry slaughter and farming [104].
Since 2011, IET has received STEL 2nd and 3th generation equipments
delivered by Russian [23] for research and evaluation. After a period of
testing in Vietnam, these equipments have revealed some drawbacks that need

to be overcome: unstable operation, frequent clogging of the membrane,
electrode damage, increasing temperature of electrochemical chamber, etc.
that directly affect the products quality and equipment’s lifespan
1.2. Hospital wastewater and pollution characteristics
Hospital wastewater contains not only conventional pollutants but also a
lot of pathogens such as bacteria, viruses, hamful protozoa, worm eggs, etc.,
especially wastewater from infectious hospitals, tuberculosis hospitals and
other infection areas. Specific types of bacteria presenting in hospital
wastewater are: Vibrio cholerae, coliforms, Salmonella, Shigella etc.
Coliforms are considered as a sanitary indicator. These species are usually
resistant to antibiotics.
1.3. Methods of hospital wastewater disinfection
Current agents used for hospital wastewater disinfection are mainly
chlorine compounds, ozone and ultraviolet light. popularly,among which
chlorine compounds are more commonly used. The disadvantages of these
agents are high corrosion, toxic byproducts, poor disinfection efficiency,
unsafe for producers and users.

7


The hospital wastewater disinfection method using ECA solutions is a
solution to improve the effectiveness of chlorine-containing disinfectants.
Although there have been initial studies confirmed the strong antiseptic
activity and safety, environmental friendly but there is no yet comprehensive
research on medical wastewater disinfection
In summary, based on the results of the improvement in design of
technological SOS diagrams to suit for tropical conditions in Vietnam, this
thesis proposes the application of SOS for medical waste water disinfection.
This will address the shortcomings of traditional wastewater disinfection

methods and open new directions for application of the advanced ECA
technology to disinfect water in general and in particular hospital wastewater.
CHAPTER 2. CONDITIONS AND METHODS OF EXPERIMENT
2.1. Research Subjects
+
Receiving
SOS
with
low
mineral
concentration,
using improved process technology, fabrication and perfect the device
producing low-mineral SOW.
+ Wastewater from Huu Nghi and Quan Y 354 hospitals.
2.2. Methods of improvement of the technology for preparing SOS
2.2.1. Methods of studying the absorption technology of wet-gas oxidants
mixture for the supowa preparation.
2.2.1.1. Design a pilot scheme for the preparation of supowa
2.2.1.2. Operating conditions
2.2.1.3. Operating parameters to be achieved
2.2.2. Studies on storage capacity and oxidation loss during storage of SOS
2.2.3. Manufacturing equipment producing SOS
2.2.3.1. Equipment requirement
2.2.3.2. Select the technological diagram of the device and the related details
2.2.3.3. Design, manufacture and commissioning
2.2.3.4. Perfect the equipment, set up the operating procedures to achieve
basic SOS parameters
2.2.3. Methods of determining the SOS parameters
2.3. Studies on the application of the SOS for hospital wastewater
disinfection

2.3.1. Evaluation method of sterilization effect of the superoxidizing
solution
2.3.2. Method of evaluating the effect of pH, ammonium, COD and BOD5
in wastewater on disinfection effect of SOS
2.3.3. Comparing the formation of THMs in supowa solution with other
disinfectants
2.3.4. Study of the application of SOS for hospital wastewater disinfection
2.4. Materials used
8


- Disinfectants;
- International bacterial strains;
- Other materials and chemicals.
- Other materials and chemicals.
2.5. Techniques used: All measurements, breeding techniques, methods of
identification of indicators, preparation of test solutions, sampling, etc. are in
accordance with the current international and Vietnamese standards.
CHAPTER 3. RESULTS AND DISCUSSIONS
3.1. Preparation of superoxidation solution (SOS)
3.1.1. Preparation of low-mineralization SOS using circulating catholyte
method
3.1.1.1. Set up diagram and production process
The supowa superoxidized water
is obtained at a flow rate of 15 L/
h with oxidants concentration of
approximately 500 mg /L , ORP
~ 905mV, neutral pH and TDS ~
1000 mg/L. equivalent to the
product obtained from STELANK-PRO-01

of
Delphin Figure 3.1. Schematic diagram of the
(Russia).
oxidation solution with revolving
catholyte
3.1.1.2. Influence of catholyte flow on the SOS parameters
The larger the catholyte flow, the lower the concentration of oxxidants,
TDS (Fig.3.2) and temperature of the reaction chamber.

Figure 3.2. Effect of circulating
catholyte
flow
on
oxidant
concentration and mineralization in
the superoxidizing solution

Figure 3.3. Effect of revolving
catholyte flow on activated
electrochemical chamber
temperature

However, continuing to increase catholyte flow would reduce the
concentration of oxidants in supowa to less than 500 mg/L. Therefore,
catholyte flow from 20 L/h to 25 L/h was chosen .

9


3.1.1.3. Effects of the voltage applied to the electrodes of MB-11 on the SOS

parameters

(a)

(b)

Figure 3.4. Influence of electrolytic potential on oxidants concentration
and oxidants capacity
Increasing the electrolytic potential facilitated the increase of oxidants
concentration and the decrease of TDS concentrations of the products.
However, the supowa capacity (Figure 3.4b) increases linearly only when
the electric potential is 6.6 V ÷ 6.8 V, then the increase slows down due to the
competition of the water electrolytic reaction, which increases the electricity
cost. Increased voltage also increases the electrochemical chamber
temperature, leading to reduced electrode life. Thus the applied voltage
ranged between 6.6 and 6.8 volts. This value is within the manufacturer's
guide range (6 ÷ 8 V). This is very valuable because in order to achieve the
same product parameters, the lower the voltage, the lower the cost of
electricity.
3.1.1.4.
Influence of the salt quantity used on the supowa parameters
Consumption of salt has a great influence on the quality of the products.
The high consumption of salt results in increase of oxidants concentration, but
TDS content in the product also increased, leading to a decrease in the SOS
activity. The results showed that the appropriate salt levels ranged from 18 ÷
24 g/h.

Fingure 3.6. Effect of supplied
salt on oxidants productivity

Fingure 3.5. Effect of supplied salt
quantity on SOS quality

10


3.1.1.5. Operation in optimal mode as shown in Table 3.1
It can be seen that preparation SOS with low-mineralization and
catholyte-circulating scheme allows to apply a lower voltage (6.7 ÷ 6.8V).
The experimental data presented in tabl 3.1 showed that operation conditions
and product parameters are similar to those of the same type of ECA device
manufactured by Russia. However, the electrochemical chamber temperature
(measured outside the chamber) rapidly increased to a high level (39 oC ÷
40oC) in a short time. Within 72 hours of operation, a decrease in the amount
of oxidant in the product was recorded due to the deposition of metal
hydroxide precipitates on the membrane .
Table 3. 1. Optimal operating mode of the circulating catholyte diagram
Thông số
Unit Value attained
Oxidants concentration of superoxidizing mg/L
 500
anolyte
Oxidants capacity
g/h
≤ 7,5
pH of anolyte
6,5÷7,5
Electrolytic potential applied
V
6,6÷6,8

Catholyte flow rate
L/h
20÷25
Sodium chloride supplied
g/h
18÷24
Electricity power consumption
W.h/g
7,0 ÷ 7,2
Quantity of NaCl required for obtaining 1 g
g/g
2,26 ÷ 2,91
of oxidants
O
Cathode chamber’s temperature
C
39 - 40
Practical operation of the device has shown that the catolit turn-over
mode increases the temperature, pH and conductivity of the catolite. These
three quantities depend on several factors that can be described as follows:
toC, EC, pH = f (n)
toC - electrolyte chamber temperature (on cathode surface);
EC - conductivity of catolite solution
pH - pH of the catolite solution
n - number of catolit turns
However, the dependence on the number of catolit turns is best
demonstrated by the conductivity of the catolite solution. The relation
between the conductivity of the catolite solution and the number of cycles of
catolit turn is:
y = 0.4773x + 350.79

(3.1)
2
(with R = 0.7603)
The greater the number of catolite cycles, the greater the electrical
conductivity (or TDS) of the catolite solution, the higher the mineral content
in the catolite, the greater the deposition potential on the electrode and the

11


diaphragm. In other words, to reduce these negative effects, the maximum
number of catolit turns must be reduced.
A modification for the hydraulic diagram has been performed, in
which the catholyte does not circulate but goes straight forward into the gas
separation chamber, extracted in part into the supowa output to adjust the pH,
and the rest is flushed out. This scheme is expected to avoid scale formation
due to the formation of hard carbonates and hard salts of metals in the cathode
compartment and excessive overheating of the electrochemical reaction
chamber during operation.
3.1.2. Preparation of low-mineralization SOS using non-circulating
catholyte method
3.1.2.1. Set up the diagram and the producing process
3.1.2.2. Effects the catholyte flow on the supowa parameters
SOS Supowa is obtained with a flow
rate of 16 L/h, oxidants concentrations of
approximately 500 mg/L, ORP ~ +910
mV, neutral pH and TDS ~ 950 mg/L.
The parameters of the supowa prepared
by non-circulating catholyte scheme are
similar to the supowa that prepared by

circulating catholyte scheme, and to the Figure 3.9. Schematic diagram of
product prepared by the manufacturer’s the oxidation solution with nonscheme (Delphin Corporation - Russia). circulating catholyte

Figure 3.10. Influence of the noncirculating catholyte flow on the
supowa parameters

Figure 3.11. Influence of the noncirculating catholyte flow on the
cathlyte chamber’s temperature
It can be seen that the larger the catholyte flow, the lower oxidants
concentration, the lower mineralization of the supowa and the lower
temperature of the reaction chamber. Appropriate catholyte flow was chosen
to be about 2.0 L/h, much smaller than the catholyte prepared by the
revolving catholyte modulation scheme (Figure 3.1).

12


3.1.2.3. Dependence of the supowa parameters on the electrolytic potential

(b)

(a)

Figure 3.12. Effects of electrolytic potential on the supowa parameters
Appropriate voltage values are chosen between 7.5 and 8 volts, which
higher than that used in the circulating catholyte scheme. This value is within
the manufacturer's instruction range (6 ÷ 8 V), but a little higher compared
with non-circulating catholyte scheme. This leads to an increase in the cost of
electricity compared with the Russian version.
3.1.2.4. Effects of sodium chloride quantity used on the supowa parameters

Figure 3.13. Dependence of the supowa parameters on the amount of NaCl
supplied
The amount of NaCl supplied was chosen from 18 to 24 g/h, equivalent
to
the
amount
of
NaCl
supplied
in
the
diagram
of supowa producing with revolving catholyte.
3.1.2.5.
pH adjustment of the
supowa solution
To obtain neutral supowa solution,
the wet-gas oxidants mixture should
be mixed with a portion of catholyte
of pH 10 to 11. The optimal mixing
ratio of the catholyte with the
oxidants mixture should be selected Fig 3.14. The change of pH of
to obtain a neutral supowa solution supowa follow depending on the
(pH 6.5 to 7.5). The value is choosen oxidants/catholyte ratio
in a range of 3 ÷ 4%.
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3.1.2.1. Operation of SUPOWA equipment system in an optimal mode:

The results in Table 3.3 shows that this device uses a higher voltage
than the circulating catholyte method, because the resistance of the noncirculatingcatholyte is higher than the revolving catholyte. However, the
operating temperature of the electrolysis chamber is lower, the operating
mode is more stable, the frequency of electrode washing is lower because of
the low deposition and precipitation of carbonate salts and metal hydroxide on
the membrane. The parameters of the supowa prepared by non- circulating
catholyte scheme are similar to the supowa using circulating catholyte
scheme, as well as to the product prepared by the Russian device.
Table 3.3. Optimal operating mode of non-circulating catholyte diagram
Parameters
Unit
Value
The concentration of oxidants in the mg/L
500
anolyte product
Oxidants capacity
g/h
>7,5
pH
6,5 ÷ 7,5
Voltage UDC
V
7,5 ÷ 8,0
Catholyte flow rate
L/h
2,0 ÷ 2,5
Amount of NaC salt supplied
g/h
18÷24
Electricity power consumed to produce W.h/g

9,0 ÷ 9,6
one unit of oxidants
Amount of salt consumed to produce one
g/g
2,3 ÷ 2,91
unit of oxidants in the product
o
The temperature of the cathode chamber
C
38 ÷ 39
Oxidants/catholyte mixing ratio
%
3÷4
3.1.2. Study the storage capability and product quality’s changes during
storage
In this study, the supowa parameters used are as follows: pH 6.59; ORP
900 mV; TDS 1100 mg/L; Oxidants concentration 528 mg/L, stored for 96 hours
(4 days) in two plastic bags B1 and B2 with lids, at room temperature of 25°C. B1
has a surface area of 1256 cm2, B2 has a surface area of 50 cm2. The parameters
of the supowa solution change with storage time as shown in Table 3.5:
Table 3.5. Supowa parameters depend on storage time
Store Parameters TN 1 TN 2 TN 3 TN 4 TN 5 TN 6 TN 7 TN 8
mode Time (h)
0
2
4
8
24
48
72

96

B1

pH
ORP(mV)
TDS
(mg/L)
[Oxidants]
(mg/L)

6,59
900

6,66
899

6,58
898

6,55
887

6,55
884

6,53
885

1100 1100 1090 1075 1060

1047

1028

1000

528

469

455

440

528

6,55
902

523
14

6,69
898

496

493

B2

pH
ORP(mV)
TDS(mg/L)
[Oxidants]
(mg/ L)

6,59 6,62 6,64 6,58 6,51
900 901 898 898 896
1100 1100 1100 1095 1086

6,36
897
1080

6,34
893
1065

6,33
891
1045

528

486

482

469

528

520

510

499

The experiment data showed that for both modes of solution storage in B1
and B2 with lids, the supowa parameters (pH, TDS, ORP, oxidants
concentration,...) have decreased slowly over time. This is because the
metastable components in the solution undergo dissipative degradation
according to the law of increasing entropy to return to the thermodynamic
equilibrium. However, degradation in B2 is slower than that in B1 thanks to
its small surface area, which significantly limits evaporation of oxidants.
It can be seen that, in order to storage longtime the SOS while
maintaining high disinfection effect, it is necessary to store the solution in a
closed space.
3.1.4. Comments
It is possible to summarize and compare on some advantages and
disadvantages of the two methods producing SOS in table 3.6.
Table 3.6. Comparison of advantages and disadvantages of 2 methods
Method
producing
SOS
by Method producing SOS by noncirculating catholyte diagram
circulating catholyte diagram

Consume lower voltage, which means Consume higer voltage, which means
more electric power are saved (about more electric power are consumed
9 W/g chlorine)
(about 10 W/g chlorine)
Have to clean the electrode more The working time without electrode
frequently because of the deposition cleaning is long (cleaning 1 time per 2
in cathode chamber (daily, maximum months, up to 3 months) beacause the
7 days), which means more time and deposition in cathode chamber is less,
chemicals are consumed (at least 160 which means more time and chemicals
minutes and 8 liters of chemicals for are saved (about 20 minutes and 1 liter
cleaning the electrodes in 2 months)
of chemicals for electrode cleaning in 2
months)
The operating mode will be less stable if The operating mode is more stable
the electrode cleaning is not frequently
The complexity of the details when Cost of production are saved by
manufacturing
equipment
will simplifying the details
increase the cost of production
It can be seen that each method of preparing the SOS has its own
advantages and disadvantages. It is difficult to confirm which diagram is
better. The choice a suitable diagram should be made base on the operating
conditions and the specific benefits.
15


3.2. Research on the improvement of equipment for the preparation of
SOS
3.2.1. Technological design

3.2.1.1. Production diagram: shown in Figure 3.8
3.2.1.2. Capacity of equipment
The device is designed to use the MB-11 electrolytic chamber, which
has oxidants capacity of 30 g/h (equivalent to 60 liters of solution).
3.2.1.3. Flow diagram of the electrolytic chambers: Figure 3.19
Ra catolit
Ra anolit
siêu oxy hóa

Figure 3.19. Flow
diagram of four
electrolytic chambers

Dung dich nước và NaCl
Nước vào

3.2.1.4. Scheme of power supply for 4 electrolytic cells: shown in Figure 3.20

Figure 3.20. Power
supply diagram for
4 electrolytic cells

3.2.1.5. Technology Diagram of equipment producing supowa: Figure 3.21

Figure 3.21. Technological Diagram for preparing the SOS using 4 MB-11
modules
(1) Electrolytic Cell MB-11
(2) DC power
(3) Control cabinet
(4) Filter 5 µm

(5) System for washing electrode with acid HCl
(6) Ion exchange (column soften the water)
16

(7) Salt solution tank
(8) Salt solution pump
(9) Softened water tank
(10) Supowa tank
(11) Flow meter
(12) Softened water pump


3.2.2. Manufacturing equipment

Figure 3.22. Supowa equipment

Figure 3.23. ECA system with 4
MB - 11 modules

3.2.3. Equipment testing
Experimental data showed that the supowa equipment operate quite
stable during the 30-hour trial period. Oxidants capacity can be achieved:
0.5233 g/L × 59.1 L/h × 16 h/d = 494.8 g/d.
Compared with similar equipment manufactured by Delphin company
(Russia), the SOS of the two equipments have similar characteristics. The
Supowa equipment consumes more power than Russian device due to its
higher voltage (8 V vs. 6.6 V), but the Supowa operates more stable due to
less deposit on the electrode. Furthermore, the temperature of electrochemical
chamber is more stable so the product quality is not so much affected.
3.2.4. General comment

Successful improvement of the hydraulic diagram of the superoxidizerd
solution production system using non-circulatingcatholyte scheme instead of
revolving mode has reduced the cathode temperature during operation. The
equipment is more stable in the tropical climate of Vietnam.
- It is possible to make localization of equipment for the production of SOS
except for the import of electrochemical chamber.
- The equipment Supowa producing SOS has achieved all the requirements
set out: the quality of the supowa, the construction fitness of equipment, the
level of simplicity and flexibility when installing, using, maintenance and
replacement;
- The Supowa equipment system which produces SOS operates stably, met
the requirements of continuous operation for wastewater treatment stations in
small hospitals (or medical centers) with a capacity of 150 beds.
3.3. Studies on the application of SOS to disinfect hospital wastewater
3.3.1. The disinfection effect of the SOS on some pathogenic
microorganisms commonly encountered in hospital wastewater
3.3.1.1. The dependence of the disinfection effect of the SOS on oxidants
concentration and time of exposure.
17


The object studied was coliforms 104 CFU/ml. Coliform exposed to the
SOS at concentrations of 0; 0,1; 0.25; 0.5; 1.0 mg/L for 5 minutes. The result
showed that the minimum concentration of SOS used to kill coliforms 104
CFU / mL is 0.5 mg/L in 5 minute of exposure time.

Figure 3.24. The dependence of the
Figure 3.25. The dependence of
disinfection effect of supowa solution the disinfection effect of the SOS
on the oxidants concentration

and sodium hypochlorite (with the
same concentration) on the time of
exposure
Similar experiments were performed with sodium hypochlorit. The
results shown in Figure 3.44. Results showed that the SOS had significantly
higher disinfection efficacy than sodium hypochlorit. This demonstrates that
in the SOS there is not only a disinfecting agent ClO- (the main ingredient in
sodium hypochlorite) may also be the presence of other highly active oxidants
such as H2O2, O3, 1O2, HO, HO2 …[67, 70]. This is the main reason for the
difference in disinfection efficiency of SOS compared to sodium hypochlorit
in particular and other chlorinated chemicals in general.
3.3.1.2 The dependence of the disinfection effect of the supowa solution on the
pH of the solution:
Coliform 106 CFU/100 mL exposed to SOS with oxidant concentration
of 0.5 mg/L for 30 seconds. The pH of the mixture was adjusted from 6.0 to
8.0.

Figure 3.26. The dependence of the
disinfection effect of the supowa
solution on the solution pH

18

Some studies have also
shown that the antimicrobial
activity of electrochemical
oxidized solutions at low pH is
higher than when it is at high
pH,
but with high pH,

corrosion is reduced [83] and
the stability is enhanced [40], it
also provides appropriate ability
to kill germ [84].


3.3.1.3 . The dependence of the antiseptic effect of SOS on the amount of
ammonia contained in the mixture which needs to be sterilized
The object studied was coliform 106 CFU/100 mL in mixtures of
ammonium at concentrations of 1, 3, 10, 20, 30 mg / L; exposed to SOS for
30 seconds, 5 minutes, 30 minutes.
disinfectant activity than hypochlorous acid.
The higher the ammonium
concentration, the lower the
disinfection effectiveness of
supowa. Thus, the presence of
ammonium in the mixture which
needs to be sterilized influences
significantly on the disinfection
effect of supowa solution. This
Figure 3.27. The dependence of the
may be due to the fact that
disinfection effect of the oxidation
ammonium ions reacted with
solution on the NH4+ concentration is
HOCl in the SOS forming
in the solution
chloramine with
a lower
3.3.1.4. The dependence of the disinfection effect of supowa solution on

BOD5 in the mixture which needs to be sterilized, compared with sodium
hypochlorite
The object studied was coliform 106 MPN/100 mL in solutions with the
following composition: BOD5 = 9 mg/L, COD = 29 mg/L; BOD5 = 28,6
mg/L, COD = 61mg/L; BOD5 = 43,2
mg/L, COD = 89 mg/L; BOD5 = 89,6
mg/L, COD =168 mg/L;BOD5 = 173
mg/L; COD =327 mg/L; These
solutions were exposed to supowa
and sodium hypochlorite (for
comparison) at 1 mg/L for 5 minutes,
15 minutes, 30 minutes.
The results are shown in Figure
3.28. They showed that the
disinfection effect of the supowa
solution decreased with increasing of
BOD value. This is due to the
oxidants in supowa solution exposed
to a solution containing bacteria and Figure 3.28. The dependence of the
disinfection effect of supowa solution
organic substances that oxidized
on BOD5 content in solution, compared
with sodium hypochlorite

19


BOD to other compounds which are not antiseptic or weakly
disinfectants [96]. In addition, the activation elements in SOS such as O3, O,
1

O2, H2O2, HO2, HO,etc., can also be easily reduced to a stable state or lower
activation because of the organic ingredients. Therefore, the disinfection
effect of the SOS is also weakened. Compared to sodium hypochlorite, it can
be seen that even in cases when the organic content of the disinfected solution
is high, supowa solution still exhibits higher disinfection efficacy than sodium
hypochlorite. However, at larger exposure times, the difference of
disinfection efficiencies is reduced.
Thus, with the BOD5 value in wastewater is about 50 mg/l, the
disinfection efficiency of the SOS can be achieved to 100% when the
concentration of the disinfectant is 1 mg / L and the disinfection time is 15
minutes. In case of BOD5 value in wastewater increase, it is necessary to
increase the concentration of disinfectant or increase the time of exposure.
The above results suggest that it is possible to use SOS to reduce BOD5 value
in wastewater and to disinfect wastewater, but it requires the use of higher
doses of oxidants.
3.3.1.5 Testing on mixed samples
The study assumed that hospital wastewater contains: coliform 106
MPN/100ml, NH4+ = 10,6 mg/L, BOD5= 52,3 mg/L, COD = 101,4 mg/L; pH
=7,1. The exposition to supowa is at 1; 1,5; 2; 2,5; 3 mg/L in 15 minutes. The
results showed that with 15 minutes exposure in the organic environment, all
coliforms were killed only by supowa with a concentration of 1mg/L (Table
3.9).
The same experiment was conducted with a mixture of four specific
bacteria in hospial wastewater. The study assumed hospial wastewater
contains: coliform 106 MPN/100mL, Salmonella 106 bacterias/100mL,
Shigella 106 bacterias /100mL and Vibrio cholera 106 bacterias /100mL; NH4+
= 10,6 mg/L, BOD5/COD = 52,3/101,4 mg/L; pH =7,05. Supowa
concentrations used are 1 and 1.5 mg/L; exposure time: 15 minutes. Results
are shown in Table 3.10.
Table 3.10. Results of the determination of alive bacterias after disinfecting

wastewater by supowa at different concentrations
Exp Supowa
Alive
erim concentrati Coliform
ent ons (mg/L)
01
0
2.4 x 107
(control)
02
1,0
9,3 x 101
03

1,5

Not
Detected

Alive
Salmonella

Alive
Shigella

7.0 x 106

2.5 x 106

1,2 x 101

8

Not
Detected

Not
Detected

20

Alive Vibrio
Alive
cholera
Vibrioparahaemol
ity-cus
Not
2.8 x 106
Detected
Not
1,4 x 101
Detected
Not
Not Detected
Detected


Results showed that oxidation concentration at 1.0 mg/L of supowa
with 15 minutes of exposure was not enough to completely kill four coliforms
106 MPN/100mL, Salmonella 106 bacteria/100mL, Shigella of 106

bacterias/100mL and Vibrio cholera 106 bacterias/100mL at the same time,
but it could decrease by more than 5 log10 in all four categories. Disinfection
efficiency of 99.99% demonstrates strong bactericidal activity of supowa
solution.
This is more evident with the supowa content of the oxidants at a
concentration of 1.5 mg/L: all four types of bacteria in the hospital
wastewater with a density of 106 bacteria/100mL were completely killed.
Bacterial density was decreased > 6 log10 after the disinfection. Thus, this
concentration of supowa is suitable for the disinfection of hospital wastewater
with the simultaneous presence of four bacteria species characteristic of the
hospital at a density of 106 bacteria/100mL, NH4 + concentrations of about
10mg/L and BOD5 concentrations of about 50mg/L (this is the standard limit
of hospital wastewater treatment must be reached physico-chemicaly before
the disinfection).
Compared with the active chlorine dose regulation for wastewater
disinfection after completing the biological treatment of 3 g/m3 for a
minimum 30 minutes exposure [10], using supowa has saved up to 50% of the
disinfection cost and exposure time.
3.3.2. Applying supowa solution to disinfect hospital wastewater
3.3.2.1. Study of the possibility of trihalomethane formation during water
disinfection process by supowa solution
Experimental water samples were sterilized with different disifectants:
chlorine gas, NaOCl and supowa at the dose of 5 mg/L and ozone
concentration of 1 mg/L. Results of THMs analysis of water samples are
shown in Figure 3.29.

Figure 3.30. Possibility of forming Figure 3.31. The amount of THMs
THMs of different disinfectants
increases with the amount of
disinfectant

The results showed that the increase in total THMs content was almost
proportional to the amount of disinfectants in the water (Figure 3.30). In the
21


four types of disinfectants used, supowa solution produced considerably
lower byproduct (only after ozone). These results are similar to the results of
Fenner and Reynolds [11] from University of West of England when studying
the formation of THMs in water which contained natural organic matter. They
found that the chloroform concentration formed decreases by up to 50% when
using electrochemical activation water (ECAW) as a disinfectant instead of
using hypochlorite for water which contained algae and humic compounds.
This can be explained that ClO- is very active agent for THMs formation [12].
In addition, studying the effect of pH and temperature of the water which
need to be sterilized by supowa, the obtained data showed that the
dependence of THMs concentration on pH was not follow linear proportions,
it tended to increase slowly at high pH. When pH was increased from 5.3 to
9.2, total THMs concentration increased to nearly 60%. Some studies have
shown similar phenomena when using chlorine gas as a disinfectant [12,132].
The researchers suggested that in high pH environment, activated chlorine
converts to ClO- which interact very easily with organic acids (such as humic
acid) to form THMs. Total THMs formed when sterilizing at 38°C were more
than twice as effective at 15°C. This has been found in some THMs
concentration surveys in water treatment plants in summer and winter. This
may be explained that the THMs forming reactions are heat-absorbing
reactions, which will be more favorable at high temperatures.
Therefore, in cases where there is a strict regulation on the content of
THMs in water after treatment, the factors affecting the formation of THMs
such as active ingredient, temperature, pH, etc. of the disinfection process still
need to be considered. Under normal circumstances, the use of supowa can

reduce the formation of THMs by 40% to 50% compared to chlorine gas or
NaOCl.
3.3.2.2. Testing on the hospital wastewater sample
Testing object: wastewater of Huu Nghi Hospital.
Analytical results of wastewater before and after disinfection with
supowa solution (of concentration was 1.5 mg/L) for 15 minutes (indicators
following the QCVN 28:2010/BTNMT) showed that: In fact, the wastewater
after physiological treatment of the Huu Nghi Hospital was not reached the
standard (ammonium concentration was 4 times higher than the prescribed).
However, only the coliform appeared and the remaining three other bacterias
were not detected in the water. In this case, the concentration of 1.5mg / L of
the supowa disinfectant still ensures complete the disinfection. Inaditon, it
also reduced significantly the levels of ammonia and BOD5 by supporting the
oxidation of these pollutants.
Another experiment was also conducted on wastewater from the Huu
Nghi Hospital, but coliform count was 106 MPN/100mL, Salmonella count
22


was 106 bacterias/100mL, Shigella count was 106 bacterias/100mL và Vibrio
cholera count was 106 bacterias/100mL. All of these bacteria were added in.
The mixture was disinfected with supowa 1.5 mg/L and 2 mg/L for 15
minutes. The amount of bacteria that survived after the disinfection was
determined. Results showed that the supowa concentration of 1.5 mg/L can
reduce 4÷5 log10 bacteria count in wastewater. A supowa concentration of 2
mg/L (2 g/m3) can sterilized completely the hospital wastewater with bacteria
count of about 106 MPN (bacteria)/100mL (under other physicochemical
norms is eligible under QCVN 28: 2010/BTNMT).
3.3.2.3. Testing at the hospital wastewater treatment plant
The object studied was the wastewater treatment system of the Huu

Nghi Hospital and 354 Military Hospital. The disinfectant used at that time
was chloramine B with concentration of 2g/m3. Alternative disinfectant is
supowa with concentration of 2g/m3. The tested samples was taken at the
after-treatment tap of the system. These experiments were conducted
simultaneously by the Institute of Environmental Technology and the
Biochemistry Departments of both hospitals.
The results demonstrate the remarkable disinfection performance of
supowa, in particular compared with chloramine B. With the same
concentration of disinfectant, supowa completely killed coliform count of 106
- 108 MPN / 10mL, while chloramine B reduced only 3 ÷ 4 log10.
3.3.2.1.
Xây dựng quy trình công nghệ khử trùng nước thải bệnh viện sử
dụng nước siêu oxy hóa
3.3.2.4. Developing the disinfection process the hospital wastewater by SOS
The disinfection method using the new disinfectant will be devoloped
based on the existing process and just the disinfection method (concentration
of disinfectant, disinfection time, method of mixing the disifectant) will be
changed to be suitable.
SOS was stored in a container and pumped into the wastewater
treatment system by dosing pump. This dosing pump is electrically connected
and operated simultaneously with the before-treatment wastewater pump
(Figure 3.35).
Beforetreatment
wastewater
pump

Standard wastewater
treatment system before the
sterilization (depends on
each specific object)

Dosing pump

Wastewater after
treatment

Superoxidized
solution
(supowa, anolit)

Figure 3.35. Location of addition the disinfection solution
23


CONCLUSION
1 The scientific basis of the application of non-circulating catholyte operation
mode to manufacture equipment producing supowa solution in Vietnam was
established, allowing to reduce the operating temperature of the module to
below 39oC. This has contributed to increase the longevity and stable
operation of the equipment, satisfied the requirements of 150-bed small
hospital waste water treatment plant (or medical centers).
2. The superoxidizing solution obtained from the supowa equipment has the
following characteristics: ORP ~ 900 mV, neutral pH, TDS ~ 950 mg/L,
oxidants concentration of approximately 510 mg/L. The solution can be used
to disinfect hospital wastewater up to environmental standards in accordance
with QCVN 28: 2010/BTNMT (column A) for microbiological criteria. The
disinfection power of supowa solution was much stronger than other
chlorinated disinfectants (such as sodium hypochlorite, chloramine B
3.The use of supowa solutions to disinfect water sources can reduce the
formation of THMs from 40% to 50% compared to chlorine gas or NaOCl.
4. The amount of supowa solution for disinfection the hospital wastewater

after treatment (with NH4+ ~ 10 mg/L, BOD ~ 50 mg/L, COD ~ 100 mg/L,
coliform concentration 106 MPN/100mL, Salmonella 106 bacteria/100mL,
Shigella 106 bacteria/100mL and Vibrio cholera 106 bacteria/100mL), with
exposure time 15 minutes, range from 1.5 ÷ 2 g/m3 (3 ÷ 4 L/m3).
5. Results of the thesis have opened a new direction in application of high
technology to disinfect drinking water and wastewater safely for human,
friendly for environment and significantly reduce the risk of poisoning
chlorine gas for workers who operate the devices directly. With new research
results in the world, more specific tasks have been given to put superoxidizing
solution to use with low cost, high performance, safe and good for disinfect
hospital wastewater, contribute to limiting the spread of pathogens from
health facilities.

24


LIST OF PUBLIC WORKS
1. Nguyen Thi Thanh Hai, Nguyen Hoai Chau, Nguyen dinh Cuong, Hoang Thi
Thanh Binh. Study on the method of preparation of superoxidized disinfection
solution. Vietnam Journal of Science and Technology. 2011, 49 (4), 111-116.
2. Nguyen Thi Thanh Hai, Nguyen Hoai Chau, Nguyen Van Ha, Hoang Thi
Thanh Binh, Hoang Van Tu, Pham Minh Thinh. Study the effect of
disinfection of the SOS on pathogenic bacteria commonly found in water.
Vietnam Journal of Science and Technology, 2012, 50 (2B), 303-309.
3. Nguyen Thi Thanh Hai, Nguyen Hoai Chau. Method of water disinfection
with anolyte solution in-place prepared. Patent Utility Solution No. 1285,
2015. National Office of Intellectual Property, Ministry of Science and
Technology.
4. Nguyen Thi Thanh Hai, Nguyen Van Ha, Nguyen Hoai Chau, Hoang Van tu,
Nguyen Anh Vu. Study on the possibility of using electrochemical activation

solution to minimize the formation of trihalomethane in the process of
disinfecting drinking water. Vietnam Journal of Science and Technology,
2014. 52 (2D), 55-61.
5. Le Thanh Son, Ngo Quoc Buu, Nguyen Hoai Chau, Nguyen Thi Thanh Hai.
Electrochemical synthesis of disinfecting peroxocarbonate solutions and
assessment of their antimicrobial effects. Journal of Research in Environmental
Science and Toxicology (ISSN: 2315-5698), 2014, 2(8), 161-166.
6. Nguyen Thi Thanh Hai, Hoang Thi Que, Nguyen Thi Nguyet. Study the effect
of BOD on disinfection effect of supowa, compared with javen. Workshop
proceedings for starting up cooperation between IET/VAST and CTWW/UTS
on environmental training and research, 2016, 62-66.
7. Hoang Thi Que, Nguyen Thi Thanh Hai. Study the effect of raw material and
water quality on the basic parameters of the SOS. Proceedings of the
workshop "Youth of Institute of Environmental Technology with scientific
research and technological development", 2015, 71-75.
8. Nguyen Thi Nguyet, Nguyen Thi Thanh Hai. The effect of pH on the
effectiveness of water disinfection of the SOS for pathogenic bacteria
commonly found in water sources. Proceedings of the workshop "Youth of
Institute of Environmental Technology with scientific research and
technological development", 2015, 50-54.
9. Nguyen Hoai Chau, Nguyen Trong Boi, Ho Thi Thanh Tam, Huynh Thi Ha,
Nguyen Thi Thanh Hai. Auto Washing and Disinfection Device of non-metal
instruments in microbiological and biochemical laboratories.. Patent Utility
Solution No. 1602, 2017. National Office of Intellectual Property, Ministry of
Science and Technology.

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