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MINISTRY OF EDUCATION AND TRAINING

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY

Takahiro WATARI

DEVELOPMENT OF ANAPPROPRIATE TREATMENTSYSTEM FORNATURALRUBBER INDUSTRIALWASTEWATERTREATMENT

Major: CHEMICAL ENGINEERING

Code No.: 9520301

SUMMARY OF CHEMICAL ENGINEERING DISSERTATION

Hanoi – 2022

This dissertation was finalized at Hanoi University of Science andTechnology

This dissertation could be found at:

1 TaQuang Buu Library - Hanoi University of Science andTechnology

2 National Library ofVietnam

as well as other contaminants The factories in Southeast Asian countries commonly utilize acombination of anaerobic and/or aerobic lagoon systems for treating this wastewater These existingtreatment systems have shown high chemical oxygen demand (COD) removal efficiency with easyoperational methods However, they require a large area of the lagoon, high operating costs(especially for surface aeration), and long hydraulic retention times(HRTs).In addition, the existingtreatment system also requires improvements to the effluent water quality to conform to thedischarge standards set Previous studies reported that the system achieved the Vietnamese industrialeffluent standard B However, environmental problem related to natural rubber processingwastewater has been serious in Vietnam Therefore, the effluent quality of the existing system should

be improved as soon aspossible

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 ofmethane for the treatment of different kinds of industrial wastewater Previous studies have reportedthe 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 negativeeffect on the anaerobic biological process Therefore, the development of a pre-treatment system toremove the remaining natural rubber particle is essential The effluent from the UASB reactortreating high-strength industrial wastewater still contained high concentrations of organic compoundsand nutrients Thus, an aerobic treatment system has been typically applied post-treatment to removeresidual organic matter and achieve effluentstandards

2 Research objectives and contents of thethesis

- Development of energy recovery type wastewater treatment system for natural rubber processingwastewater inVietnam

- Establishment of an optimal treatment system for natural rubber processing wastewater treatmentin Vietnam

3 New contributions to thethesis

- Current environmental issues and treatment systems for natural rubber processing wastewaterin Vietnam were characterized via not only literature review but field study andsystemized

- A novel treatment system, i.e BR-UASB-DHS, was developed to treat wastewater withhigh

organic pollution and recover biogas as energy

4 The layout of thethesis

The thesis has 99 pages in total and consisted of an introduction: 2 pages, Chapter 1: 28 pages for state of art, Chapter 2: 14 pages for Materials and Methods, Chapter 3: 40 pages for Resultsand Discussion, Chapter 4: 2 pages for Conclusions and 49 of references

Thailand Indonesia Viet Nam India China, mainland Malaysia Philippines Guatemala Côted'Ivoire Myanmar Others

Top 10 of Natural Rubber Processing Countries (2014)

2%

4%3 % 5%

1.2 Current treatment technology for natural rubber processingwastewater

The aerated lagoon and ponds have been commonly used for the treatment of thiswastewater in Southeast Asian countries On the other hand, the application of advanced treatmentprocesses such as dissolved air flotation (DAF) and upflow anaerobic sludge blanket (UASB) hasbeen limited because of installation costs and knowledge for appropriate operation The existingaerated lagoon can perform high organic removal efficiency with low operational and installationcosts Therefore, this aerated lagoon process is the most popular treatment system for natural rubberprocessing wastewater in Vietnam Currently, this process was combined with the rubber trap and/oranaerobic lagoon and achieved the effluent standard or water quality in the final effluent water inVietnamese Standard B However, the local factory consumed a large amount of electricity forwastewater treatment even higher than natural rubber production In addition, greenhouse gas (GHG)emissions from the oxidation ditch process would concern due to low dissolved oxygenconcentration and low C/N ratio in natural rubber processingwastewater

Table1.1 Characteristi

cs

of natur

al rubb

er processin

g wastewater

in Vi

1.3 Biological industrial wastewater treatmentprocess

Anaerobic digestion is a more attractive wastewater treatment process compared withaerobic wastewater treatment process The bioreactor of the anaerobic wastewater treatment process

is a very simple system and can be applied at any scale and almost any place The greatest benefit ofthe anaerobic wastewater treatment process is useful energy in the form of methane can be recovered

by anaerobic digestion In general, 40 ~ 45m3of biogas can be recovered from 100 kg-COD ofinfluent 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 energyrecovery in the form of methane The formation of well settleable sludge aggregates and theapplication of a reverse funnel-shaped internal gas-liquid-solids separation (GSS) device are keytechnologies for a successful UASB reactor Table 1.4 summarizes the process performance of theUASB reactor when treating natural rubber processing wastewater The first application of aUASB reactor for the treatment of natural rubber processing wastewater in Vietnam wasdemonstrated by Nguyen (1999) in his Ph.D research at Wageningen University The resultsshowed that the UASB reactor performance achieved around 79.8%–87.9% of total COD removalefficiency 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 isrequired for the application of UASB reactors in Vietnamese local natural rubber processingfactories Nguyen et al (2016) reported that the granulation was enhanced with the use of aluminum

removalefficiencyoftheUASBreactorincreasedto96.5±2.6%,withamethanerecoveryrateof84.9 ± 13.4%, for natural rubber processing wastewater in Vietnam Aerobic treatment is the removalprocess that oxidizes organic compounds, ammonia, smell, and iron by several aerobic bacteria underthe oxygen available conditions The bacteria or floc absorbed organic compounds and degrade towater and carbon dioxide to get energy for their breeding

Table 1.4 Application of UASB reactor for natural rubber processing wastewater treatment

Reactor type Volume Seed sludge Organic removal rate COD removal

Single Vietnam 8.55

Digested pig manure sludge 28.5 79.8-87.9% Nguyen (1999)

Single Vietnam 17

Anaerobic digester trating casava wastewater 2.65 96.5 ± 2.6 Thanh et al., (2015)

Two stage Thailand 24.8

Concentrated latex mill 1.41 82 JawjitandLiengcharernest(2010)

Two stage Thailand 997 + 597

Anaerobic pond

in the rubber factory 0.8 96.57 ± 1.3 Tanikawa et al., (2016)

1.4 Greenhouse gas emissions from the 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 heat trapped by a certainmass of the gas in question to the amount of heat trapped by a similar carbon dioxide Thewastewater treatment plant also emitted considerable GHG into the atmosphere Approximately3.4% of GHG is emitted from waste disposal and treatmentprocess

2 Material andmethods

2.1 Filedsurvey

The wastewater treatment system in a local natural rubber manufacturing factory in BinhDuong province, Vietnam was surveyed The greenhouse gases emission from an anaerobic lagoonwas collected by using a collection chamber made from polyvinyl chloride pipes and analyzed byGC-TCD and GC-ECD

2.2 Laboratory UASB-DHSsystem

Raw wastewater was collected from the coagulation process in a natural rubber factoryproducing SVR in Thanh Hoa Province, Vietnam The laboratory-scale treatment system wasoperated at the Hanoi University of Science and Technology, Vietnam

2.3 Laboratory scale ABRsystem

The anaerobic baffled reactor (ABR) made up of polyvinyl chloride pipes (diameter: 110

mm, height: 1,000 mm) had 10 compartments and a working volume of 68 L

3.1 Characterization of the current wastewater treatmentsystem

The system consisting baffled tank, aero tank, and facultative lagoon used for the treatment

of natural rubber wastewater in Binh Duong province, Vietnam was surveyed to investigate thecurrent 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 effluentquality of this factory largely exceeded the effluent standard The wastewater treatment plant isknown as one of the big GHGs emission sources However, GHGs emission from natural rubberprocessing wastewater treatment plant is not reported Thus, we measured GHG emissions from thecurrent 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 (Figure2.1)

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 nitrousoxide emission from natural rubber processing wastewater treatment systems was firstly observed

We considered that ammonia was oxidized to nitrate and nitrite at the surface of the open-typeanaerobic tank; therefore, nitrate and nitrite promptly were consumed by denitrification Finally,18.1% of the ammonia was removed from the open-type anaerobic tank, and the nitrous oxideemission factor became 0.0263 kg-NO2-N·kg-N-1 This emission factor was much higher than 0.005kg-NO2-N·kg-N-1, which is the emission factor for the direct emissions from wastewater treatmentplants applied by IPCC (2006) and similar to the emission factor for full-scale biological nutrientremoval wastewater treatment plants The emission rates (flux) from 1 m3of treated RSS wastewaterfor methane, nitrous oxide, and total GHGs were calculated as 0.054 t- CO2eq·m-3, 0.099 t- CO2eq·m-

3, and 0.153 t-CO2eq·m-3, respectively These emission rates were higher than the emission rates fromthe 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

(mg-COD·L -1 )

S-COD (mg-COD·L -1 )

SS (mg· L -1 )

VSS (mg·L -1 )

TN (mg·L -1 )

VFA

Actate (mg-COD· L -1 )

Propionate (mg-COD· L -1 )

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

part of the OAS

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 the UASB reactor for natural rubberprocessing wastewater failed due to a large amount of residual natural rubber accumulated in theUASB column Therefore, the development of efficient natural rubber removal (recovery) process isessential for the successful to apply the UASB reactor A baffled reactor can be recovered solid by itsunique design and is considered an effective pre-treatment process for natural rubber processwastewater Thus, we designed the wastewater treatment process for natural rubber processingwastewater consisting of 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.

The system showed good performance in the start-up period of phase 1 (days 1–45) andwas operated for a total of 126 days The influent of pH was 5.8 ± 0.7 and 5.3 ± 0.3, respectively,andthe proposed baffled reactor (BR)-UASB-DHS system was performed without pH adjustment Overall, high total CODremoval of 98.6 ± 1.2% and TSS removal of 98 ± 1.4% was achieved with anHRTof 42.2 h Figure 3.8 shows theCOD mass balance of the influent reactor, BR, and UASB reactor during phase 2 The BR steadilyremoved 42.3 ± 34.5% of TSS and 72.4 ± 38.2% of VSS during phase 2 Similarly, solid COD wasremoved, and the concentrations of acetate and propionate increased Therefore, the BR acted as both

a trapping tank for the residual rubber particles and anacidificationtank.TheUASBreactoralsoperformedatahightotalCODremovalefficiencyof92.7

± 2.3% with an OLR of 12.2 ± 6.2 kg-COD·m-1·day-1 The methane recovery rate, calculated fromthe removed total COD, was 93.3 ± 19.3% for phase 2 High-level COD removal efficiency andmethane recovery rates are thought to result from the efficient solid organic removal andacidification of the wastewater by the BR The BR–UASB–DHS system can decreasetheHRT;consequently, the land requirements of the system are smaller than those of currently usedtreatment systems

9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 0

Time course (days)

Time course (days)

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

3.3 Development concept of a laboratory scale ABRexperiment

120

P1 P2 P3

The COD concentrations of ABR influent and effluent were 3,420 ± 660 mg·L-1and1,500

± 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 the previous study that applied ABR to this wastewater The water quality profiles in

the ABR show theVFAconcentration also decreased longitudinally down thereactor.The UASB

reactor is the most promising system for this wastewater; some laboratory-scale UASB reactors

achieved high organic removal efficiency together with a 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%

oftotalCODremovalefficiencywithOLRof0.8kg-COD·m-3·day-1inThailand.Also,thepilotscale

UASBr e a c t o r t r e a t i n g n a t u r a l r u b b e r d i s c h a r g e d f r o m t h e R S S m a n u f a c t u r i n g p r o c

e s s p e r f o r m e d

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 to the application of the 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 deteriorated The influent and effluent COD of

ABR were 7,890 ± 680 mg-COD·L-1and 1,840 ± 1,520 mg-COD·L-1, respectively during phase3 At the

end of the experiment, the foam was observed on the water surface of the reactor In addition, the COD removal efficiency and the methane recovery ratio of ABR were

significantly decreased to50% and 20%, respectively Therefore, the optimal OLR for this wastewater should be approximately 1.5

kg-COD·m-3·day-1

(A) 20,000 18,000

14,000

80 12,000

8,000

40 6,000

4,000

20 2,000

Time course (day)

Inf Eff Removaleffeciecny

Time course (day)

Inf Eff Removaleffeciecny

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

(A)5,000 4,500 4,000

3,500 3,000 2,500