Development of an appropriate treatment system for natural rubber industrial wastewater treatment tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING
HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY

Takahiro WATARI

DEVELOPMENT OF AN APPROPRIATE TREATMENT
SYSTEM FOR NATURAL RUBBER INDUSTRIAL
WASTEWATER TREATMENT

Major: CHEMICAL ENGINEERING
Code No.: 9520301

SUMMARY OF CHEMICAL ENGINEERING DISSERTATION

Hanoi – 2019


This dissertation was finalized at
Hanoi University of Science and Technology

Supervisors:
1. Assoc. Prof. Nguyen Minh Tan
2. Prof. Takashi Yamaguchi

Reviewer 1:
Reviewer 2:
Reviewer 3:

This dissertation was accepted to be defensed by the University Doctoral
defense committee at Hanoi University of Science and Technology
Date and Time: …..../…..../…..

……h…..

This dissertation could be found at:
1. Ta Quang Buu Library - Hanoi University of Science and Technology
2. National Library of Vietnam


A. INTRODUCTION OF THESIS
1. Research Topics
Natural rubber is one of the most valuable agricultural products in Southeast Asian
countries. However, local natural rubber processing industry discharges large amounts of wastewater
from several manufacturing processes such as coagulation, centrifugation, lamination, washing, and
drying. This wastewater contains high concentrations of organic compounds, nitrogen, as well as
other contaminants. The factories in Southeast Asian countries commonly utilize a combination of
anaerobic-aerobic lagoon systems for treating this wastewater. The existing treatment systems have
shown high chemical oxygen demand (COD) removal efficiency. However, they require a large area
of lagoon, high operating costs (especially for surface aeration), and long hydraulic retention times
(HRTs). In addition, the existing treatment system also requires improvements to the effluent water
quality in order to conform to the discharge standards set. Previous studies reported that the system
achieved the Vietnamese industrial effluent standard B. However, environmental problem has been
seriously in Vietnam. Therefore, the effluent quality of existing system should be improved as soon
as possible.
An upflow anaerobic sludge blanket (UASB) reactor is one of the most promising systems,
given its high organic loading rate (OLR), low operational costs, and energy recovery in the form of
methane for the treatment of different kinds of industrial wastewater. Previous studies have reported
the application of the UASB reactor for the treatment of natural rubber processing wastewater.
However, it was determined that natural rubber particles remaining in the wastewater had a negative
effect on the anaerobic biological process. Therefore, the development of a pre-treatment system to
remove remaining natural rubber particle is essential. The effluent from the UASB reactor treating

high-strength industrial wastewater still contained high concentrations of organic compounds and
nutrients. Thus, an aerobic treatment system has been typically applied as post-treatment to remove
residual organic matter and achieve effluent standards.
2. Research objectives and contents of the thesis
- Development of energy recovery type wastewater treatment system for natural rubber processing
wastewater in Vietnam.
- Establishment of optimal treatment system for natural rubber processing wastewater treatment in
Vietnam

1


3. New contributions of the thesis
- Current environmental issues and treatment systems for natural rubber processing wastewater in
Vietnam were characterized via not only literature review but field study and systemized.
- A novel treatment system, i.e. BR-UASB-DHS, was developed in order to treat wastewater with
high organic pollution and recover biogas as energy.
4. The layout of the thesis
The thesis has 99 pages in total and consisted by introduction: 2 pages, Chapter 1: 24 pages
for state of art, Chapter 2: 13 pages for Materials and Methods, Chapter 3: 43 pages for Results and
Discussion, Chapter 4: 2 pages for Conclusions and 80 of references.

2


B. CONTENT OF THE THESIS
1. State of art
1.1 Natural rubber
Natural rubber has good wear resistance, high elasticity, high resilience and tensile strength.
It has a good dynamic performance and low level of damping. Therefore, natural rubber has been

widely used for carpet underlay, adhesives, foam, balloons and medical accessories such as rubber
gloves. The consumed total rubber amount on 2017 reached to 28,287,000 ton and it was 3%
increase compared with 2016 (IRSG report). Natural rubber production on 2017 has been increased
to 13,380,000 ton. Thailand and Indonesia produced over 60% of total natural rubber production.
The consumed total rubber amount on 2017 reached to 28,287,000 ton and it was 3% increase
compared with 2016 (IRSG report). Natural rubber production on 2017 has been increased to
13,380,000 ton. Thailand and Indonesia produced over 60% of total natural rubber production. The
production process of natural rubber products such as coagulation, centrifugation, lamination,
washing and drying used a large amount of fresh water and discharged same amount of wastewater.
These wastewaters mainly contain wash water, small amounts of uncoagulated latex and serum with
small quantities of protein, carbohydrates, lipids, carotenoids and salts.
Top 10 of Natural Rubber Processing Countries (2014)

2%

6%
Thailand

2%
4% 3%

Indonesia
Viet Nam
34%

5%

India
China, mainland

6%

Malaysia
Philippines

7%

Guatemala
Côte d'Ivoire

7%

Myanmar

24%

Others

Figure 1.1 Top natural rubber produced countries on 2014 over the world.

3


1.2 Current treatment technology for natural rubber processing wastewater
The aerated lagoon and ponds have been commonly used for treatment of this wastewater.
On the other hand, the application of advanced treatment processes such as dissolved air flotation
(DAF) and upflow anaerobic sludge blanket (UASB) have been limited. The aerated lagoon can
perform high organic removal efficiency with low operational costs and installed cost. This process
is most popular treatment system for natural rubber processing wastewater in Vietnam. Currently,
this process was combined with the rubber trap and/or anaerobic lagoon, and achieved the effluent

standard or water quality in the final effluent water in Vietnamese Standard B. However, the local
factory consumed large amount of electricity for wastewater treatment even higher than natural
rubber production. In addition, greenhouse gas (GHG) emission from oxidation ditch process would
concern due to low dissolved oxygen concentration and low C/N ratio in natural rubber processing
wastewater.

4


Table 1.1 Characteristics of natural rubber processing wastewater in Vietnam.

5


1.3 Biological industrial wastewater treatment process
Anaerobic digestion is more attractive wastewater treatment process compared with
aerobic wastewater treatment process. The bioreactor of anaerobic wastewater treatment process is
very simple system and can be applied any scale and at almost any place. Most great benefit of
anaerobic wastewater treatment process is useful energy in the form of methane can be recovered by
anaerobic digestion. In general, 40 ~ 45 m3 of biogas can recovered from 100 kg-COD of influent. A
UASB reactor is one of the most promising systems for the treatment of different types of industrial
wastewater because of its high OLR capacity, low operational costs, and energy recovery in the form
of methane. The formation of well settleable sludge aggregates and the application of a reverse
funnel-shaped internal gas-liquid-solids separation (GSS) devise are key technologies for a
successful UASB reactor. Table 1.4 summarizes the process performance of the UASB reactor when
treating natural rubber processing wastewater. The first application of a UASB reactor for the
treatment of natural rubber processing wastewater in Vietnam was demonstrated by Nguyen (1999)
as his Ph.D. research at Wageningen University. The results showed that the UASB reactor
performance achieved around 79.8%–87.9% of total COD removal efficiency at an OLR of 28.5
kg-COD·m-3·day-1. However, the remaining natural rubber particulates, such as accumulated rubber

particulates in the UASB column, affected the anaerobic biodegradation. Therefore, an effective
pre-treatment process to remove residual natural rubber particulates is required for the application of
UASB reactors in Vietnamese local natural rubber processing factories. Nguyen et al. (2016)
reported that the granulation was enhanced with the use of aluminum chloride, and the total COD
removal efficiency of the UASB reactor increased to 96.5 ± 2.6%, with a methane recovery rate of
84.9 ± 13.4%, for natural rubber processing wastewater in Vietnam. An aerobic treatment is the
removal process that oxidize organic compounds, ammonia, smell and iron by several aerobic
bacteria under the oxygen available condition. The bacteria or floc absorbed organic compounds and
degrade to water and carbon dioxide to get energy for own breeding.
Table 1.4 Application of UASB reactor for natural rubber processing wastewater treatment.
Reactor type

Volume

Seed sludge

-3

L
Single

Single
Two stage

Two stage

Vietnam

8.55

Organic removal rate COD removal
-1

(kg-COD·m ·day )

%

Reference

28.5

79.8-87.9%

Nguyen (1999)

2.65

96.5 ± 2.6

Thanh et al., (2015)

1.41

82

Jawjit and Liengcharernest (2010)

0.8

96.57 ± 1.3

Tanikawa et al., (2016)

Digested pig
manure sludge

Anaerobic
digester trating
casava
Vietnam
17
wastewater
Concentrated
Thailand
24.8
latex mill
Anaerobic pond
in the rubber
Thailand 997 + 597
factory

6


1.4 Greenhouse gas emission from wastewater treatment system
A GHG is a gas that absorbs and emits radiant energy within the thermal infrared range.
The primary GHGes in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide
and ozone. Global warming potential (GWP) is to compare the amount of hear trapped by a certain
mass of the gas in question to the amount of heat trapped by a similar of carbon dioxide. The
wastewater treatment plant also emitted considerable GHG to atmosphere. Approximately 3.4% of

GHG emitted from waste disposal and treatment process.

2. Material and methods
2.1 Filed survey
The wastewater treatment system in a local natural rubber manufacturing factory in Binh
Duong province, Vietnam was surveyed. The greenhouse gases emission from an anaerobic lagoon
was collected by using a collection chamber made from polyvinyl chloride pipes and analyzed by
GC-TCD and GC-ECD.
2.2 Laboratory UASB-DHS system
Raw wastewater was collected from the coagulation process in a natural rubber factory
producing SVR in Thanh Hoa Province, Vietnam. The laboratory-scale treatment system was
operated in Hanoi University of Science and Technology, Vietnam.
2.3 Laboratory scale ABR system
The anaerobic baffled reactor (ABR) made up of polyvinyl chloride pipes (diameter: 110
mm, height: 1,000 mm) had 10 compartments and working volume of 68 L.
2.4 Pilot UASB-DHS system
The pilot scale natural rubber processing wastewater treatment system installed at the
Rubber Research Institute of Vietnam, Binh Duong, Vietnam. The system consisted of an ABR (76.5
m3), a substrate reservoir (5 m3), a UASB reactor (3 m3), a settling tank (ST; 1 m3), and a down-flow
hanging sponge (DHS) reactor (2 m3) with an effluent recirculation.
2.5 Analysis

7


The measurement methods of pH, DO, ORP, COD, BOD, SS, TN, ammonia, nitrite, nitrate,
volatile fatty acid, biogas production and composition was described.
3. Results and discussions
3.1 Characterization of current wastewater treatment system
The system consisting baffled tank, aero tank and facultative lagoon used for treatment of

natural rubber wastewater in Binh Duong province, Vietnam was surveyed to investigate current
treatment process. The wastewater quality in several sampling points was shown in Table 3.1. The
aerobic tank was not operated well due to the electricity cost for surface aeration. The effluent
quality of this factory was largely exceeded the effluent standard. The wastewater treatment plant is
known one of big GHGs emission source. However, GHGs emission from natural rubber processing
wastewater treatment plant is not reported. Thus, we measured GHG emission from current
anaerobic tank treating natural rubber processing in Binh Duong province, Vietnam. Figure 3.2
shows the composition of the biogas collected from compartments 28, 33, and 56 using the water
substitution method during the survey in October (Figure 2.1).

Figure 2.1 Schematic diagram of open-type anaerobic system.
The emitted gas from the open-type anaerobic tank comprised 57.7%-60.8% methane,
14.5%-31.5% carbon dioxide, 10.8%-24.7% nitrogen, and 329-423 ppm of nitrous oxide. The nitrous
oxide emission from natural rubber processing wastewater treatment system was firstly observed.
We considered that ammonia was oxidized to nitrate and nitrite at the surface of the open-type
anaerobic tank; therefore, nitrate and nitrite promptly were consumed by denitrification. Finally,
18.1% of the ammonia was removed in the open-type anaerobic tank, and the nitrous oxide emission
factor became 0.0263 kg-NO2-N·kg-N-1. This emission factor was much higher than 0.005
kg-NO2-N·kg-N-1, which is the emission factor for the direct emissions from wastewater treatment
plants applied by IPCC (2006) and similar to the emission factor for full- scale biological nutrient
removal wastewater treatment plants. The emission rates (flux) from 1 m3 of treated RSS wastewater
for methane, nitrous oxide, and total GHGs were calculated as 0.054 t- CO2eq·m-3, 0.099 t8


CO2eq·m-3, and 0.153 t-CO2eq·m-3, respectively. These emission rates were higher than the emission
rates from the aerobic wastewater treatment system in cap lump processing factories.
Table 3.1 Water quality in each sampling point at a local natural rubber processing
wastewater in Vietnam

Figure 3.2 Biogas composition of compartment 28, 33 and 56.

Figure 3.6 Composition of emitted GHGs from near the influent part, the center part, and the effluent
part of the OAS.

9


Figure 2.2 Gas sampling system used in this study.
3.2 Development concept of a laboratory scale UASB-DHS system for natural rubber
processing wastewater treatment
As previous research reported the application of UASB reactor for natural rubber
processing wastewater was failed due to large amount of residual natural rubber accumulated in the
UASB column. Therefore, development of efficient natural rubber removal (recovery) process is
essential for successful to apply UASB reactor. Baffled reactor can be recovered solid by its unique
design and considered effective pre-treatment process for natural rubber process wastewater. Thus,
we designed the wastewater treatment process for natural rubber processing wastewater consisted by
BR, UASB reactor and DHS reactor (Figure 2.4).

Figure 2.4 Schematic diagram of the baffled reactor (BR), upflow anaerobic sludge blanket
(UASB), and downflow hanging sponge (DHS) combined system. (1) Substrate reservoir, (2)
pump, (3) pretreatment tank, (4) pump, (5–8) sampling ports, (9) UASB column, (10) Gas solid
separator, (11) mixer, (12) desulfurizer, (13) gas meter, and (14) distributor.

10


The system showed good performance in the start-up period of phase 1 (days 1–45), and
was operated for a total of 126 days. The influent of pH was 5.8 ± 0.7 and 5.3 ± 0.3, respectively and
the proposed baffled reactor (BR)-UASB-DHS system performed without pH adjustment. Overall,
high total COD removal of 98.6 ± 1.2% and TSS removal of 98 ± 1.4% were achieved with an HRT

of 42.2 h. Figure 3.9 shows the COD mass balance of the influent reactor, BR, and UASB reactor
during phase 2. The BR steadily removed 42.3 ± 34.5% of TSS and 72.4 ± 38.2% of VSS during
phase 2. Similarly, solid COD was removed, and the concentrations of acetate and propionate
increased. Therefore, the BR acted as both a trapping tank for the residual rubber particles and an
acidification tank. The UASB reactor also performed at a high total COD removal efficiency of 92.7
± 2.3% with an OLR of 12.2 ± 6.2 kg-COD·m-1·day-1. The methane recovery rate, calculated from
the removed total COD, was 93.3 ± 19.3% for phase 2. High-level COD removal efficiency and
methane recovery rates are thought to result from the efficient solid organic removal and
acidification of the wastewater by the BR. The BR–UASB–DHS system can decrease the HRT;
consequently, the land requirements of the system are smaller than those of currently used treatment
systems.

11


12,000

Phase 1

Phase 2

Total COD (mg-COD/L)

10,000
8,000
6,000

Influent
BR effluent

4,000

UASB effluent
2,000

DHS effluent

0
0

9,000

20

40

60
80
Time course (days)

Phase 1

100

120

140

Phase 2

Soluble COD (mg-COD/L)

8,000
7,000
6,000
5,000
4,000

Influent

3,000

BR effluent
UASB effluent

2,000

DHS effluent

1,000
0
0

20

40

60
80
Time course (days)

100

120

140

Figure 3.8 Time course of total COD and soluble COD during the operation periods.

3.3 Development concept of a laboratory scale ABR experiment

12


The COD concentrations of ABR influent and effluent were 3,420 ± 660 mg·L-1 and 1,500
± 620 mg·L-1. The highest COD removal efficiency of 92.3 ± 6.3% in this research was observed
during phase 2 when operated under OLR of 1.4 ± 0.3 kg-COD·m-3·day-1. This removal efficiency
was higher than previous study that applied ABR to this wastewater. The water quality profiles in the
ABR shows the VFA concentration also decreased longitudinally down the reactor. The UASB
reactor is most promising system for this wastewater; some laboratory scale UASB reactor achieved
high organic removal efficiency together with high methane recovery rate. However, the pilot scale
UASB reactor could be operated at low OLR condition due to influent containing high sulfate or
residual natural rubber particulars. Our research group reported that the pilot scale UASB reactor
treating natural rubber processing wastewater containing high sulfate performed 95.7 ± 1.3% of total
COD removal efficiency with OLR of 0.8 kg-COD·m-3·day-1 in Thailand. Also, the pilot scale UASB
reactor treating natural rubber discharged from RSS manufacturing process performed 55.6 ± 16.6%
for total COD removal efficiency and 77.8 ± 10.3% for BOD with OLR of 1.7 kg-COD·m-3·day-1.
There are several limitations for application of UASB reactor to this wastewater and the UASB
reactor was operated at low OLR. After increasing OLR up to 2.1 ± 0.1 kg-COD·m-3·day-1, the
process performance of ABR was deteriorated. The influent and effluent COD of ABR were 7,890 ±

680 mg-COD·L-1 and 1,840 ± 1,520 mg-COD·L-1, respectively during phase 3. At the end of
experiment, the foam was observed on the water surface of the reactor. In addition, the COD removal
efficiency and methane recovery ratio of ABR were significantly decreased to 50% and 20%,
respectively. Therefore, the optimal OLR for this wastewater should be approximately 1.5
(A)20,000

P1

P2

120

P3

18,000

Total COD (mg/L)

14,000

80

12,000
10,000

60

8,000
40

6,000
4,000

COD removal efficiency (%)

100

16,000

20

2,000
0

0
50

100

Inf.

TSS (mg/L)

(B) 600

150
Time course (day)
Eff.

250

Removal effeciecny

P2

P1

200

120

P3

500

100

400

80

300

60

200

40

100

20

0

TSS removal efficecy (%)

0

0
0

50

100

150

200

250

Time course (day)
Inf.

Eff.

Removal effeciecny

Figure 3.10 Time course of (A) Total COD and (B) TSS concentrations through phase 1 to phase 3

kg-COD·m-3·day-1.
13


COD (mg-COD/L)

(A) 5,000
4,500

Soulble COD

4,000

Acetate

3,500

Propinate

3,000
2,500
2,000
1,500
1,000
500
0
1

2

3

4

5

6

7

8

9

10

ABR compartment

COD (mg-COD/L)

(B) 5,000
4,500

Soulble COD

4,000

Acetate

3,500

Propinate

3,000
2,500
2,000
1,500
1,000
500
0
1

2

3

4

5

6

7

8

9

10

ABR compartment

Figure 3.11 Soluble COD, acetate and propionate concentrations in ABR on (A) 103 day and (B) 199
day
The soluble COD, acetate and propionate concentrations in each ABR comportments on
day 103 and day 199 were shown in Figure 3.13. The VFA concentration also decreased
longitudinally down the reactor. Almost 80% of soluble COD were acetate and propionate in the
compartments 1 to 3. The VFA values demonstrated that hydrolysis and acidogensis were the main
biochemical activities occurring in the first few compartments. On the other hands, the soluble COD
and acetate was removed in the compartment 3 to 5. In fact, most of biogas was produced from these
compartments. Therefore, methanogen could be dominant in these compartments and its produced
biogas. This result indicated that in an ABR different microorganisms develop in different
compartments resulting in phase separation.
3.4 Development concept of a pilot scale UASB-DHS system experiment
Table 3.4 lists the process performance of the treatment system during phases 1-4. Previous
studies on the process performance of existing treatment systems for natural rubber processing
wastewater are summarized in Table 3.9. The combined ABR (HRT=3.4 day) - UASB (HRT=1.8
day) - ST (HRT=0.6 day) - DHS (HRT=0.5 day) system removed 94.8 ± 2.1% of total COD, 98.0 ±
0.9% of total BOD, 71.8 ± 22.6% of TSS, and 68.3 ± 15.1% of TN during phase 3. The ABR was
installed to remove residual natural rubber particles from the influent. The ABR achieved a 31.6 ±
15.6% of total COD and 40.5 ± 16.0% of soluble COD removal efficiency during the entire
experiment. Similarly, total BOD and soluble BOD removal efficiencies of the ABR were 45.1 ±
14.5% and 50.7 ± 14.3%, respectively. In addition, TSS in the ABR influent and effluent were 200 ±
58 mg·L-1 and 166 ± 65 mg·L-1, resulting in a TSS removal efficiency of 18.7 ± 41.1%. These results
14


. Figure 2.7 Schematic and photo of the pilot scale ABR-UASB-ST-DHS system.

indicate that ABR roughly removed organic compounds in the RSS wastewater. The UASB reactor
achieved most of the organic removal and methane recovery in the system. During phase 1, the
UASB reactor had a low total COD removal efficiency of 18.6 ± 17.0% likely due to the large
amount of washed out sludge caused by the low settleability of seed sludge and high biogas
production of 370 ± 250 L·day-1. During phase 3, the UASB reactor demonstrated total COD and
BOD removal efficiencies of 55.5 ± 16.1% and 77.8 ± 10.3% with OLR of 1.7 ± 0.6
kg-COD·m-3·day-1. The efficiencies were lower than our previous laboratory scale experiments and
other anaerobic treatment systems treating natural rubber processing wastewater. On the other hand,
the UASB reactor achieved high soluble COD and BOD removal efficiencies of 70.2 ± 19.6% and
76.3 ± 7.5% during phase 3. The accumulation of natural rubber particular was frequently occurred
in the supply pipe (Figure 3.15) and required further modification for remove natural rubber
particulars. The methane recovery ratio based on removed total COD were 32.7 ± 86.4%, 41.5 ±
29.3%, and 64.3 ± 71.6% for phase 1, phase 3, and phase 4, respectively. A settling tank was installed
for trapping washed out sludge and residual rubber particles from the UASB reactor. During phases 2
and 3, the ST efficiently removed total COD (76.0 ± 7.7% and 47.2 ± 18.1%, respectively). In
addition, TSS removal efficiencies were 95.7 ± 1.8% and 60.4 ± 14.9% in phases 2 and 3,
respectively. Therefore, the ST could be protected from the unexpected sludge washed out from the
UASB reactor. The DHS reactor can serve as an effective post-treatment system for residual organic
particles and TSS removal. In this study, the DHS reactor removed 83.5 ± 10.0% of total COD, 82.6
± 11.2% of total BOD, and 73.5 ± 20.0% of TSS during the entire experiment. These organic
removal efficiencies were higher than the post-treatment DHS reactor treating the ABR effluent.

15


Figure 3.12 Accumulation of rubber particular in feed pipe and photo of wastewaters.

Figure 3.16 Time course of (A) Total COD removal efficiency and organic loading rate of UASB
reactor, (B) Total BOD removal efficiency.
Table 3.6 lists the concentrations of TN, ammonia, nitrate, and nitrite in the treatment

system. Ammonia concentrations of the ABR influent and effluent were 122 ± 49 mg-N·L-1 and 151
± 70 mg-N·L-1, indicating that ammonia could be produced from organic nitrogen by anaerobic
digestion. In addition, small amounts of nitrate detected in the ABR effluent suggested the
occurrence of nitrification in ABR. Our field survey showed ammonia was oxidized to nitrate at the
surface of ABR and nitrous oxide was emitted to the atmosphere. In fact, 213 ppm of nitrous oxide
was detected in the biogas collected from ABR on day 190 of this study. Nitrate reduction in the
16


UASB reactor indicated the possibility of denitrification of wastewater in the UASB reactor. The
concentrations of nitrous oxide in the biogas produced in UASB were 213 ppm, 72 ppm and 614
ppm on day 42, day 190 and day 264, respectively. The nitrous oxide production ratio from 1 m3 of
treated RSS wastewater was 4.737 × 10-6 m3·m-3-w.w during phase 3. The maximum nitrous oxide
concentration of 614 ppm was observed on day 264. The production rate equivalent to carbon
dioxide for 1 m3 of treated RSS wastewater for nitrous oxide in this UASB reactor was calculated as
2.77 × 10-5 t-CO2 eq·m-3-w.w during phase 3. During phase 1, the DHS reactor demonstrated low TN
and ammonia removal efficiencies of 38.8 ± 16.0% and 19.3 ± 5.8% (Figure 3.17). The nitrification
ratio (based on ammonia oxidization) of the DHS reactor also increased to 0.42 ± 0.03
kg-N·m-3·day-1 during phase 4. This nitrification rate was greater than the same sponge-type DHS
reactor treating sewage and natural rubber processing wastewater in other studies. A small amount of
nitrate production was also observed in the DHS reactor. However, TN and ammonia reduction
suggested that nitrification occurred in the reactor and nitrification products were immediately
utilized by denitrifying bacteria in the DHS reactor. According to this nitrous oxide emission ratio
(0.6% of the nitrogen load), nitrous oxide emissions from the DHS reactor were calculated as
0.00026 t-CO2 eq·m-3 - w.w. during phase 3. In total, the TN removal efficiency was 33.6 ± 17.7%,
51.3 ± 34.0%, 68.3 ± 15.1%, and 57.9 ± 7.0% in phases 1 to 4, respectively. The emission ratios for 1
m3 of RSS wastewater treatment for ABR, UASB, and DHS were calculated as 0.0129 t-CO2eq·m-3,
0.0045 t-CO2eq·m-3 and 0.00026 t-CO2eq·m-3, respectively. The UASB reactor can recover biogas as
energy, thus GHGs emission ratio from the proposed system can be reduced to 0.013 t-CO2eq·m-3,
corresponding to a 92% reduction of GHGs emissions compared with the existing open-type

anaerobic treatment systems.
Table 3.5 Nitrogen concentrations (mg-N·L-1) in the proposed system.
Phase
Parameter
Phase 1 TN
(R=0) Ammonia
Nitrate
Nitrite
Phase 2 TN
(R=1) Ammonia
Nitrate
Nitrite
Phase 3 TN
(R=4) Ammonia
Nitrate
Nitrite
Phase 4 TN
(R=4) Ammonia
Nitrate
Nitrite

Unit
-1

mg-N·L
mg-N·L -1
mg-N·L -1
mg-N·L -1
mg-N·L -1
mg-N·L -1

mg-N·L -1
mg-N·L -1
mg-N·L -1
mg-N·L -1
mg-N·L -1
mg-N·L -1
-1

mg-N·L
mg-N·L -1
mg-N·L -1
mg-N·L -1

Influent
150 ± 80
118±16
1.8 ± 2.8
N.D
143±19
64 ± 36
N.D
N.D
202±54
109±17
N.D.

ABT eff.
127±65
88 ± 30
1.6 ± 2.0

N.D
120±22
69±58
N.D.
N.D.
156±50
176±31
4.0 ± 7.5

UASB eff.
125±65
113 ± 41
1.0 ± 1.8
N.D.
126±61
99±48
N.D.
N.D.
175±54
172 ± 29
0.7 ± 0.6

152±49
88 ± 17
0.1±0.2
N.D
84 ± 38
60 ± 16
N.D.
N.D.

165±63
153 ± 21
0.9 ± 0.3

DHS eff.
123±46
77 ± 29
2.1±2.1
N.D
53 ± 39
29±33
N.D.
N.D.
58±24
49±22
4.1±4.0

N.D.
273±117
171 ± 52
1.5 ± 1.4

N.D.
224±53
232 ± 44
0.3 ± 0.4

N.D.
N.D.
252±54

197±38
224 ± 4.3 227 ± 17
0.5 ± 0.6 0.2 ± 0.5

N.D
128±36
133 ± 4.8
0.2 ± 0.5

N.D.

N.D.

R: Recirculation ratio, N.D.: Not detected

17

N.D.

ST eff.

N.D

0.1 ± 0.3


Figure 3.14 (A) Total nitrogen and (B) ammonia removal efficiency of total system and DHS reactor
during phase 1 to phase 4.

Previous studies on the process performance of existing treatment systems for natural

rubber processing wastewater are summarized in Table 3.9. The combined ABR (HRT=3.4 day) UASB (HRT=1.8 day) - ST (HRT=0.6 day) - DHS (HRT=0.5 day) system removed 94.8 ± 2.1% of
total COD, 98.0 ± 0.9% of total BOD, 71.8 ± 22.6% of TSS, and 68.3 ± 15.1% of TN during phase 3.
A combination of anaerobic and aerobic lagoons has also been widely used in Thailand, Vietnam,
and Malaysia because of its low operational cost and easy maintenance. The final effluent of our
system met the required Vietnamese national technical regulation on effluent of the natural rubber
processing industry-B except for the ammonia content (QCVN01: 2008/BTNMT, pH: 6-9, Total
BOD: < 50 mg·L-1, Total COD: < 250 mg·L-1. TSS: < 100 mg·L-1, TN: < 60 mg-N·L-1, Ammonia: <
40 mg-N·L-1). Several current treatment systems exceed the effluent regulations in Vietnam.

18


-1

Table 3.9 Process performance of the existing treatment system for treating natural rubber processing wastewater.
-1

Effluent concentration (mg·L )
Influent concenration (mg·L )
Removal effciency (%)
HRT
pH TCOD TBOD TSS TN Ammonia pH TCOD TBOD TSS TN Ammonia TCOD TBOD TSS TN Reference
days
Country Wastewater
System
Decantation - UASB - aeration
92 94 Nguyen and Luong (2012)
99
99
30.8

70 35.3
57
6.8 123
342
9.2 18,885 10,780 900 611
Vietnam CL + SVR
tank - settling and filiter
Decantation - oxidation ditch 90 79 Nguyen and Luong (2012)
99
98
137
160
74
50
8.4 567
361
9.1 26,914 8,750 740 766
Vietnam CL
settling and filiter
Decantation -oxidation ditch 86 95 Nguyen and Luong (2012)
99
98
34.5
300 40.6
70
8.2 466
302
8.55 19,029 7,830 2,220 813
Vietnam CL
settling and filiter

Decantation -oxidation ditch 93 86 Nguyen and Luong (2012)
99
99
47
65
60
92
7.4 107
350
8.23 14,466 9,200 850 450
Vietnam CL + SVR
settling and filiter
Decantation - flotation 96 88 Nguyen and Luong (2012)
99.5 99
33
60 74.9
85
8.1 120
285
9.42 26,436 13,820 1,690 651
oxidiation ditich - settling and Vietnam CL + SVR
filiter
Decantation - flotation - UASB
92 87 Nguyen and Luong (2012)
99
99
30.3
129
39
61

7.9 127
686
8.09 13,981 7,590 468 972
Vietnam CL
- aeration tank - settling and
filiter
Decantation -oxidation ditch 92 95 Nguyen and Luong (2012)
99
99
50
67
94
60
8.59 11,935 8,780 1,164 1,306 1,043 6.6 130
Vietnam CL + SVR
settling and filiter
Dissolved air flotation 89 91 Syutsubo et al. (2015)
98
13
33
98
7.8 136
341
867 372
5.37 5,610
Vietnam CL + SVR
anaerobic lagoon - anoxic
lagoon - aerated tank
Dissolved air flotation - lagoon
80 90 Syutsubo et al. (2015)

98
27
41
70
7.8 128
154
357 394
6.34 5,350
Vietnam CL + SVR
- aeration tank - aerated tank
87 74 Watari et al. (2016b)
99
97
20
57
27
35
8.1 102
108
5.5 3,700 3,450 200 220
42
Vietnam RSS
ABR - DHS
37 56 Watari et al. (2016b)
97
94
77
97
126
92

8.1 222
108
5.5 3,700 3,450 200 220
14.2
Vietnam RSS
ABR - Algal Tank
98 48 Watari et al. (2016a)
99
100
220
36
7.6 120
200
1,470 420
5.3 8,430
2.0
Vietnam RSS
ABR - UASB -DHS
- Thanh et al. (2016)
74
96
72
7.4 102
279
7.1 1,450
0.8
Vietnam RSS
UASB
- Boonsawang et al., (2008)
60

271
1.95 3,350 1,855 340 661
4
Thailand CL
UASB
- Tanikawa et al. (2016)
96
5.5 9,710 8,670 1,780 1,370
11.5
Thailand CL
UASB - UASB - DHS
64 84 Ibrahim et al. (1980)
99
98
0
22 1,313 36
56
7.1
17
7.16 2,675 1,871 3,645 231
Malaysia CL
Oxidation Ditch Process
- Madhu et al. (2007)
90
93
Malysia CL
Stablilisation pond
72 67 This study (during phase 3)
98
95

53
53
46
36
7.7 140
110
5.5 3,940 3,320 170 200
6.3
Vietnam RSS
ABR-UASB-ST-DHS
Note: ABR: anaerobic baffled reactor, CL: Concentrated latex, DHS: down flow hanging sponge, RSS: Ribbed smoked sheet, ST: settling tank, SVR: standard Vietnamese rubber, UASB: upflow anaerobic sludge

19


CONCLUSIONS
1. The water quality and greenhouse gas emission from the existing treatment system treating natural
rubber processing wastewater in Vietnam was surveyed. The effluent from existing treatment was
exceed the discharge standard. In addition, open-type anaerobic system emitted not only methane,
but also nitrous oxide had high GWP.
- The final effluent of existing process was Total COD of 730 mg·L-1, TSS of 200 mg·L-1 and TN of
60 mg-N·L-1, respectively.
- The emission rates (flux) from 1 m3 of treated RSS wastewater for methane, nitrous oxide, and total
GHGs by open-type anaerobic system were calculated as 0.054 t- CO2eq·m-3, 0.099 t- CO2eq·m-3,
and 0.153 t-CO2eq·m-3, respectively.
2. Laboratory scale UASB-DHS system and ABR system was demonstrated treatment of natural
rubber processing wastewater. Both systems performed good process performance and were capable
for treating natural rubber processing wastewater.
- The laboratory scale UASB reactor performed high-level total COD removal at 92.7 ± 2.3% with
an OLR of 12.2 ± 6.2 kg-COD m−3 day−1 and 93.3 ± 19.3% methane recovery.

- The laboratory scale ABR performed good process performance of 92.3 ± 0.3% COD removal
efficiency with OLR of 1.4 ± 0.3 kg-COD·m-3·day-1 without pretreatment.
3. Pilot scale UASB-DHS system was operated in an actual natural rubber processing factory.
- The system generated same effluent quality compared with current treatment system.
- Approximately 80% of hydraulic retention times can be reduced.
- The system could be significantly reduced GHGes emission.
4. The proposed system could be an appropriate treatment system for treating natural rubber
processing wastewater in Vietnam.
- The system achieved high organic removal efficiency together with energy recovery form as
methane.
- The existing treatment system and proposed system need more effective nitrogen process for
achieve the discharge standard.

20


PUBLICATION LIST

1. D. Tanikawa, K. Syutsubo, T. Watari, Y. Miyaoka, M. Hatamoto, S. Iijima, M. Fukuda,
N. B. Nguyen, T. Yamaguchi (2016), “Greenhouse gas emissions from open-type
anaerobic wastewater treatment system in natural rubber processing factory”, Journal of
Cleaner Production, Vol. 119, pp. 32–37
2. P. T. Tran, T. Watari, Y. Hirakata, T. T. Nguyen, M. Hatamoto, D. Tanikawa, K.
Syutsubo, M. T. Nguyen, M. Fukuda, L. H. Nguyen, T. Yamaguchi (2017), “Anaerobic
Baffled Reactor in Treatment of Natural Rubber Processing Wastewater: Reactor
Performance and Analysis of Microbial Community”, Journal of Water and Environment
Technology, Vol. 15, no. 6, pp. 241–251.
3.

T. Watari, T. C. Mai, D. Tanikawa, Y. Hirakata, M. Hatamoto, K. Syutsubo, M. Fukuda,

N. B. Nguyen, T. Yamaguchi (2017), “Performance evaluation of the pilot scale upflow
anaerobic sludge blanket – Downflow hanging sponge system for natural rubber
processing wastewater treatment in South Vietnam”, Bioresource Technology, Vol. 237,
pp. 204–212.
4. D. Tanikawa, T. Watari, T. C. Mai, M. Fukuda, K. Syutsubo, N. B. Nguyen, T.
Yamaguchi (2018) “Characteristics of greenhouse gas emissions from an anaerobic
wastewater treatment system in a natural rubber processing factory,” Environmental
Technology, Vol.11, pp. 1–8.

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