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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 – 2022 This dissertation was finalized at Hanoi University of Science and Technology Supervisors: Assoc Prof Nguyen Minh Tan 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: Ta Quang Buu Library - Hanoi University of Science and Technology National Library of Vietnam A INTRODUCTION OF THESIS Research Topics Natural rubber is one of the most valuable agricultural products in Southeast Asian countries However, the 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 and/or aerobic lagoon systems for treating this wastewater These existing treatment systems have shown high chemical oxygen demand (COD) removal efficiency with easy operational 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 existing treatment system also requires improvements to the effluent water quality to conform to the discharge standards set Previous studies reported that the system achieved the Vietnamese industrial effluent standard B However, environmental problem related to natural rubber processing wastewater has been serious in Vietnam Therefore, the effluent quality of the 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 the 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 post-treatment to remove residual organic matter and achieve effluent standards Research objectives and contents of the thesis - Development of energy recovery type wastewater treatment system for natural rubber processing wastewater in Vietnam - Establishment of an optimal treatment system for natural rubber processing wastewater treatment in Vietnam New contributions to 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 to treat wastewater with high organic pollution and recover biogas as energy The layout of the thesis The thesis has 99 pages in total and consisted of an introduction: pages, Chapter 1: 28 pages for state of art, Chapter 2: 14 pages for Materials and Methods, Chapter 3: 40 pages for Results and Discussion, Chapter 4: pages for Conclusions and 49 of references B CONTENT OF THE THESIS 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 a 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 in 2017 reached 28,287,000 tons and it was a 3% increase compared with 2016 (IRSG report) Natural rubber production in 2017 has increased to 13,380,000 tons Thailand and Indonesia produced over 60% of total natural rubber production The consumed total rubber amount in 2017 reached 28,287,000 tons and it was a 3% increase compared with 2016 (IRSG report) Natural rubber production in 2017 has increased to 13,380,000 tons 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 the 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% 34% Indonesia Viet Nam India 5% China, mainland 6% Malaysia Philippines 7% Guatemala Côte d'Ivoire Myanmar 7% Others 24% Figure 1.1 Top natural rubber produced countries in 2014 over the world 1.2 Current treatment technology for natural rubber processing wastewater The aerated lagoon and ponds have been commonly used for the treatment of this wastewater in Southeast Asian countries On the other hand, the application of advanced treatment processes such as dissolved air flotation (DAF) and upflow anaerobic sludge blanket (UASB) has been limited because of installation costs and knowledge for appropriate operation The existing aerated lagoon can perform high organic removal efficiency with low operational and installation costs Therefore, this aerated lagoon process is the 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 a large amount of electricity for wastewater treatment even higher than natural rubber production In addition, greenhouse gas (GHG) emissions from the oxidation ditch process would concern due to low dissolved oxygen concentration and low C/N ratio in natural rubber processing wastewater Ta bl e 1 Ch ar act eri sti cs of na tur al ru bb er pr oc es sin g wa ste wa ter in 1.3 Biological industrial wastewater treatment process Anaerobic digestion is a more attractive wastewater treatment process compared with aerobic 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 of the 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 be 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) device 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) in 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 kgCOD·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 pretreatment 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 Aerobic treatment is the removal process that oxidizes organic compounds, ammonia, smell, and iron by several aerobic bacteria under the oxygen available conditions The bacteria or floc absorbed organic compounds and degrade to water 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 L Seed sludge Single Vietnam 8.55 Single Vietnam 17 Digested pig manure sludge Anaerobic digester trating casava wastewater 24.8 Concentrated latex mill Anaerobic pond in the rubber factory Two stage Two stage Thailand Thailand 997 + 597 Organic removal rate COD removal (kg-COD·m-3·day-1) % 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) 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 certain mass of the gas in question to the amount of heat trapped by a similar carbon dioxide The wastewater treatment plant also emitted considerable GHG into the atmosphere Approximately 3.4% of GHG is emitted from waste disposal and treatment process 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 at the 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 a working volume of 68 L 2.4 Pilot UASB-DHS system The pilot scale natural rubber processing wastewater treatment system was 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; m3), and a down-flow hanging sponge (DHS) reactor (2 m3) with an effluent recirculation 2.5 Analysis The measurement methods of pH, DO, ORP, COD, BOD, SS, TN, ammonia, nitrite, nitrate, volatile fatty acid, biogas production, and composition were described Results and discussions 3.1 Characterization of the current wastewater treatment system 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 the 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 largely exceeded the effluent standard The wastewater treatment plant is known as one of the big GHGs emission sources However, GHGs emission from natural rubber processing wastewater treatment plant is not reported Thus, we measured GHG emissions from the 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 systems 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 from 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 m of treated RSS wastewater for methane, nitrous oxide, and total GHGs were calculated as 0.054 t- CO 2eq·m-3, 0.099 t- CO2eq·m3 , 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 Sample pH Wastewater from coagulation process Wastewater from washing process BT eff AT eff Facultative lagoon eff T-COD S-COD -1 SS -1 VSS -1 (mg· L ) VFA TN -1 (mg·L ) -1 (mg-COD·L ) (mg-COD·L ) (mg·L ) 5.6 6,430 6,020 650 250 420 6.4 2,830 1,250 77 24 5.9 5.9 7.0 3,970 3,390 730 3,040 3,360 480 510 420 100 42 91 Actate Propionate (mg-COD· L-1) (mg-COD· L-1) 810 760 - 27 220 300 60 800 830 125 284 220 34 Figure 3.2 Biogas composition of compartments 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 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 rubber processing wastewater failed due to a large amount of residual natural rubber accumulated in the UASB column Therefore, the development of efficient natural rubber removal (recovery) process is essential for the successful to apply the UASB reactor A baffled reactor can be recovered solid by its unique design and is considered an effective pre-treatment process for natural rubber process wastewater Thus, we designed the wastewater treatment process for natural rubber processing wastewater 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 (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 was performed without pH adjustment Overall, high total COD removal of 98.6 ± 1.2% and TSS removal of 98 ± 1.4% was achieved with an HRT of 42.2 h Figure 3.8 shows the COD mass balance of the influent reactor, BR, and UASB reactor during phase The BR steadily removed 42.3 ± 34.5% of TSS and 72.4 ± 38.2% of VSS during phase 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 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 Total COD (mg-COD/L) 12,000 Phase Phase 10,000 8,000 6,000 Influent BR effluent UASB effluent DHS effluent 4,000 2,000 0 20 40 Phase 60 80 Time course (days) 100 120 140 Phase Soluble COD (mg-COD/L) Influent BR effluent UASB effluent DHS effluent 9,000 20 40 60 80 Time course (days) 100 120 140 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 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 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 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 the VFA concentration also decreased longitudinally down the reactor 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% 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 the 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 kgCOD·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-1 and 1,840 ± 1,520 mg-COD·L-1, respectively during phase 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 to 50% and 20%, respectively Therefore, the optimal OLR for this wastewater should be approximately 1.5 kg-COD·m-3·day-1 (A)20,000 120 P1 P2 P3 18,000 100 Total COD (mg/L) 14,000 80 12,000 10,000 60 8,000 40 6,000 4,000 COD removal efciency (%) 16,000 20 2,000 0 50 100 Time course (day) Eff Inf TSS (mg/L) (B) 600 150 250 Removal effeciecny P2 P1 200 120 P3 500 100 400 80 300 60 200 40 100 20 0 50 100 150 200 250 TSS removal efcecy (%) 0 Time course (day) Inf Eff Removal effeciecny COD (mg-COD/L) Figure 3.10 Time course of (A) Total COD and (B) TSS concentrations through phase to phase (A) 5,000 4,000 4,500 3,500 3,000 Soulble COD 2,500 Acetate 2,000 Propinate 1,500 1,000 500 10 ABR compartment COD (mg-COD/L) (B) 5,000 Soulble COD 4,500 Acetate 4,000 Propinate 3,500 3,000 2,500 2,000 1,500 1,000 500 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 comportment on day 103 and day 199 were shown in Figure 3.11 The VFA concentration also decreased longitudinally down the reactor Almost 80% of soluble COD were acetate and propionate in compartments to The VFA values demonstrated that hydrolysis and acidogensis were the main biochemical activities occurring in the first few compartments On the other hand, the soluble COD and acetate were removed in compartments to Most 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 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 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 a 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 The accumulation of natural rubber particular was frequently occurred in the supply pipe (Figure 3.12) and required further modification to remove natural rubber particulars The methane recovery ratio based on removed total COD was 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 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 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 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 3.5 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 into 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 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 m of treated RSS wastewater was 4.737 × 10-6 m3·m-3-w.w during phase The maximum nitrous oxide concentration of 614 ppm was observed on day 264 The production rate equivalent to carbon dioxide for 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 During phase 1, the DHS reactor demonstrated low TN and ammonia removal efficiencies of 38.8 ± 16.0% and 19.3 ± 5.8% (Figure 3.14) The nitrification ratio (based on ammonia oxidization) of the DHS reactor also increased to 0.42 ± 0.03 kg-N·m -3·day1 during phase 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·m3 - w.w during phase 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 to 4, respectively The emission ratios for m3 of RSS wastewater treatment for ABR, UASB, and DHS were calculated as 0.0129 t-CO 2eq·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-CO 2eq·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 TN (R=0) Ammonia Nitrate Nitrite Phase TN (R=1) Ammonia Unit -1 Influent 150 ± 80 118±16 mg-N· L mg-N· L-1 mg-N· L-1 1.8 ± 2.8 N.D mg-N· L-1 ABT eff 127±65 88 ± 30 UASB eff ST eff 125±65 152±49 113 ± 41 88 ± 17 DHS eff 123±46 77 ± 29 1.6 ± 2.0 N.D 1.0 ± 1.8 N.D 0.1±0.2 N.D 2.1±2.1 N.D mg-N· L-1 143±19 120±22 126±61 84 ± 38 53 ± 39 -1 64 ± 36 N.D N.D 69±58 N.D N.D 99±48 N.D N.D 60 ± 16 N.D N.D 29±33 N.D N.D 202±54 156±50 175±54 165±63 58±24 Nitrate mg-N· L mg-N· L-1 109±17 N.D 176±31 4.0 ± 7.5 172 ± 29 0.7 ± 0.6 153 ± 21 0.9 ± 0.3 49±22 4.1±4.0 Nitrite mg-N· L-1 N.D N.D N.D N.D N.D Nitrate Nitrite Phase TN (R=4) Ammonia Phase TN (R=4) Ammonia Nitrate Nitrite mg-N· L mg-N· L-1 mg-N· L-1 mg-N· L-1 -1 mg-N· L 273±117 mg-N· L-1 171 ± 52 mg-N· L-1 1.5 ± 1.4 -1 mg-N· L -1 N.D 224±53 232 ± 44 252±54 197±38 224 ± 4.3 227 ± 17 128±36 133 ± 4.8 0.3 ± 0.4 0.5 ± 0.6 0.2 ± 0.5 0.2 ± 0.5 N.D N.D N.D 0.1 ± 0.3 R: Recirculation ratio, N.D.: Not detected Figure 3.14 (A) Total nitrogen and (B) ammonia removal efficiency of the total system and DHS reactor during phase to phase 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 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·L1 ) Several current treatment systems exceed the effluent regulations in Vietnam Table 3.9 Process performance of the existing treatment system for treating natural rubber processing wastewater Wastewater HRT days Decantation - UASB - aeration Vietnam tank - settling and filiter Decantation - oxidation ditch Vietnam settling and filiter Decantation -oxidation ditch Vietnam settling and filiter CL + SVR - 9.2 18,885 10,780 900 611 342 6.8 123 57 70 35.3 30.8 99 99 92 94 Nguyen and Luong (2012) CL - 9.1 26,914 8,750 740 766 361 8.4 567 50 74 160 137 98 99 90 79 Nguyen and Luong (2012) CL - 8.55 19,029 7,830 2,220 813 302 8.2 466 70 300 40.6 34.5 98 99 86 95 Nguyen and Luong (2012) Decantation -oxidation ditch Vietnam settling and filiter Decantation - flotation oxidiation ditich - settling and Vietnam filiter Decantation - flotation - UASB - aeration tank - settling and Vietnam filiter CL + SVR - 8.23 14,466 9,200 450 350 7.4 107 92 60 65 47 99 99 93 86 Nguyen and Luong (2012) CL + SVR - 9.42 26,436 13,820 1,690 651 285 8.1 120 85 60 74.9 33 99.5 99 96 88 Nguyen and Luong (2012) CL - 8.09 13,981 7,590 972 686 7.9 127 61 39 129 30.3 99 99 92 87 Nguyen and Luong (2012) Decantation -oxidation ditch Vietnam settling and filiter Dissolved air flotation anaerobic lagoon - anoxic Vietnam lagoon - aerated tank CL + SVR - 8.59 11,935 1,043 6.6 130 60 94 67 50 99 99 92 95 Nguyen and Luong (2012) CL + SVR - 5.37 5,610 341 7.8 136 - 98 33 13 98 - 89 91 Syutsubo et al (2015) 850 468 8,780 1,164 1,306 - 867 372 Dissolved air flotation - lagoon 6.34 5,350 357 394 154 7.8 128 70 41 27 98 80 90 Syutsubo et al (2015) Vietnam CL + SVR - aeration tank - aerated tank ABR - DHS Vietnam RSS 42 5.5 3,700 3,450 200 220 108 8.1 102 35 27 57 20 97 99 87 74 Watari et al (2016b) ABR - Algal Tank Vietnam RSS 14.2 5.5 3,700 3,450 200 220 108 8.1 222 92 126 97 77 94 97 37 56 Watari et al (2016b) ABR - UASB -DHS Vietnam RSS 2.0 5.3 8,430 1,470 420 200 7.6 120 36 220 100 99 98 48 Watari et al (2016a) UASB Vietnam RSS 0.8 7.1 1,450 279 7.4 102 72 96 74 - Thanh et al (2016) UASB Thailand CL 1.95 3,350 1,855 340 661 271 60 - Boonsawang et al., (2008) UASB - UASB - DHS Thailand CL 11.5 5.5 9,710 8,670 1,780 1,370 96 - Tanikawa et al (2016) Oxidation Ditch Process Malaysia CL 7.16 2,675 1,871 3,645 231 17 7.1 56 22 1,313 36 98 99 64 84 Ibrahim et al (1980) Stablilisation pond Malysia CL 93 90 - Madhu et al (2007) ABR-UASB-ST-DHS Vietnam RSS 6.3 5.5 3,940 3,320 170 200 110 7.7 140 36 46 53 53 95 98 72 67 This study (during phase 3) 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 Influent concenration (mg· L-1) Effluent concentration (mg·L-1) Removal effciency (%) pH TCOD TBOD TSS TN Ammonia pH TCOD TBOD TSS TN Ammonia TCOD TBOD TSS TN Reference Country System CONCLUSIONS The water quality and greenhouse gas emission from the existing treatment system treating natural rubber processing wastewater in Vietnam was surveyed The effluent from the existing treatment exceeded the discharge standard In addition, an open-type anaerobic system emitted not only methane but also nitrous oxide and had high GWP - The final effluent of the 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 m3 of treated RSS wastewater for methane, nitrous oxide, and total GHGs by the 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 Laboratory scale UASB-DHS system and ABR system demonstrated treatment of natural rubber processing wastewater Both systems performed good process performance and were capable of 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 Pilot scale UASB-DHS system was operated in an actual natural rubber processing factory - The system generated the same effluent quality compared with the current treatment system - Approximately 80% of hydraulic retention times can be reduced - The system could be significantly reduced GHG emissions 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 from methane - The existing treatment system and proposed system need a more effective nitrogen process to achieve the discharge standard 20 PUBLICATION LIST 21 ... 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... internal gas-liquid-solids separation (GSS) device are key technologies for a successful UASB reactor Table 1.4 summarizes the process performance of the UASB reactor when treating natural rubber... process 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