Development of an appropriate treatment system for natural rubber industrial wastewater treatment
MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY
DEVELOPMENT OF AN APPROPRIATE TREATMENT SYSTEM FOR NATURAL RUBBER INDUSTRIAL WASTEWATER TREATMENT
CHEMICAL ENGINEERING DISSERTATION
Hanoi – 2019
MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY
DEVELOPMENT OF AN APPROPRIATE TREATMENT SYSTEM FOR NATURAL RUBBER INDUSTRIAL
Major: CHEMICAL ENGINEERING Code No.: 9520301
CHEMICAL ENGINEERING DISSERTATION
SUPERVISORS: 1. Assoc. Prof. Nguyen Minh Tan 2. Prof. Takashi Yamaguchi
Hanoi - 2019
ACKNOWLEDGMENT Firstly I would like to thank the teachers in the PhD program, the officers in the Department of Education, Hanoi University of Science and Technology. Thank you for all the guidance and support you have made for me while I have fulfilled the dissertation. Working with colleagues in the Department of Chemical Engineering has been a privilage. I would like to thank you from the bottom of my heart for your constant encouragement. Finally I am so glad to have a supervisor like Assoc. Prof. Nguyen Minh Tan. Ever since I have started to work under your supervision, I have learned a lot which really helps me to become a better person. Thank you! You are the best supervisor ever. I hope to receive some words of encourgement and full support from the readers in order to make my PhD disertation better. Hanoi, 2.12.2019 Author of the dissertation
I hereby certify that the dissertation "Development of an appropriate treatment for industrial rubber industrial wastewater treatment" is my own research project. The data and results stated in the doctoral dissertation are honest. I hereby declare that the information cited in the doctoral dissertation has been fully originated./.
Hanoi, 2.12.2019 ON BEHALF OF SUPERVISORS
Assoc. Prof. Nguyen Minh Tan
TABLE OF CONTENTS Introduction Objective Task Current Problems and its solution 1. State of the art 1.1 Natural rubber 1.1.1 Natural rubber processing process 1.1.2 Natural rubber processing wastewater 1.2 Current treatment technology for natural rubber processing wastewater 1.2.1 Biological aerobic and anaerobic pond 1.2.2 Upflow anaerobic sludge blanket 1.2.3 Anaerobic baffled reactor 1.2.4 Activated sludge process 1.2.5 Swim bed tank 1.2.6 Down flow hanging sponge reactor 1.2.7 Dissolved air floatation 1.2.8 Membrane bioreactor 1.2.9 Combination of treatment system for natural rubber processing wastewater 1.3 Industrial wastewater treatment process 1.3.1 Characteristics of anaerobic wastewater treatment and the degradation pathway of anaerobic digestion 1.3.2 Anaerobic industrial wastewater treatment technology 1.3.3 Characteristics of aerobic wastewater treatment and the degradation 1.4 Greenhouse gas emission from wastewater treatment system 2 Material and methods 2.1 Filed survey 2.1.1 Greenhouse gases collection and analysis 2.2 Laboratory UASB-DHS system 2.2.1 Raw wastewater 2.2.2 System description and operational conditions 2.3 Laboratory scale ABR system 2.3.1 Raw natural rubber processing wastewater 2.3.2 System description and operational conditions 2.4 Pilot UASB-DHS system 2.5 Analysis 2.5.1 Potential of hydrogen 2.5.2 Dissolved oxygen 2.5.3 Chemical oxygen demand
2.5.4 Biochemical oxygen demand 2.5.5 Suspended solid 2.5.6 Total nitrogen 2.5.7 Ammonia, nitrite and nitrate 2.5.8 Volatile fatty acid (VFA) 2.5.9 Biogas production and composition 3 Results and Discussions
45 45 46 46 47 48 49
3.1 Characterization of current wastewater treatment system 3.1.1 Characterization of greenhouse gas emission process from current anaerobic tank 3.2 Development concept of a laboratory scale UASB-DHS system for natural rubber processing wastewater treatment 3.2.1 Process performance of laboratory scale UASB-DHS system 3.3 Development concept of a laboratory scale ABR experiment 3.3.1 Process performance of ABR 3.3.2 Determinates profiles inside the ABR 3.4 Development concept of a pilot scale UASB-DHS system experiment for treatment of natural rubber processing wastewater 3.4.1 Process performance 3.4.2 Nitrogen removal and greenhouse gas emissions 3.4.3 Performance comparison of ABR-UASB-DHS system and existing treatment system 3.5 Design guideline for full scale UASB-DHS system for natural rubber processing wastewater in Vietnam 3.5.1 Reactor design for natural rubber processing wastewater 22.214.171.124 Pre-treatment process for UASB reactor 126.96.36.199 UASB reactor 188.8.131.52 DHS reactor 3.5.2 Calculation of Energy consumption and generation for operation of UASB-DHS system 184.108.40.206 Energy consumption of UASB-DHS system 220.127.116.11 Energy production of UASB-DHS system 4 Conclusions
Figure list Top natural rubber produced countries over the world on 2014 Natural rubber harvested area and production in Vietnam Natural rubber production area in Vietnam Natural rubber manufacturing process Schematic diagram of coagulation process Full scale biological pond in Vietnam Schematic diagram of UASB reactor Various reactor configuration of ABR Basic water flow in conventional activated sludge Principle of downflow hanging sponge reactor and full-scale DHS in India Development history from DHS G1 to DHS G6 Anaerobic digestion scheme of organic compounds. Aerobic biological degradation pathway
Schematic diagram of open-type anaerobic system. Gas sampling system used in this study. (A) Location of Thanh Hoa province, Vietnam, (B) Thanh Hoa Rubber Factory, (C) Coagulation process in natural rubber sheet producing process. 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, (5–9) sampling ports, (10) UASB column, (11) Gas solid separator, (12) mixer, (13) heated water column, (14) water bath, (15) desulfurizer, (16) gas meter, (17) distributor. Protocol for preparation of natural rubber processing wastewater following actual factory methods. Schematic diagram of anaerobic baffled reactor. Schematic and photo of the pilot scale ABR-UASB-STDHS system.
33 35 36
Present treatment system of a local natural rubber processing factory. Biogas composition of compartment 28, 33 and 56. Methane gas emission rate and COD concentration of each compartment.
Figure 3.4 Figure 3.5
COD mass balance in the OAS Nitrous oxide rate and ammonia concentration in each compartment.
Composition of emitted GHGs from near the influent part,
the center part, and the effluent part of the OAS. Time course of pH and temperature during the operation periods. Time course of (a) total COD, (b) soluble COD, (c) TSS, (d) VSS and (e) TN during the operation periods. COD mass balance of the influent, BR effluent, and UASB effluent. Time course of (A) Total COD and (B) TSS concentrations through phase 1 to phase 3 Soluble COD, acetate and propionate concentrations in ABR on (A) 103 day and (B) 199 day Accumulation of rubber particular in feed pipe and photo of wastewaters Time course of (A) Total COD removal efficiency and organic loading rate of UASB reactor, (B) Total BOD removal efficiency. (A) Total nitrogen and (B) ammonia removal efficiency of total system and DHS reactor during phase 1 to phase 4.
Table list Characteristics of natural rubber processing wastewater in Vietnam. National technical regulation on the effluent of natural rubber processing industry in Vietnam. (QCVN 01-MT: 2015/BTNMT) Type of treatment process applied in Vietnam. Application of UASB reactor for natural rubber processing wastewater treatment. Comparison of technologies used for natural rubber processing wastewater treatment. Benefits of anaerobic treatment process. Application of anaerobic technology to industrial wastewater Global warming potential of greenhouse gases. Water quality of natural rubber processing wastewater obtained from a natural rubber sheet producing factory in Thanh Hoa Province. Summary of the initial operational conditions for the two operating phases. Operational conditions for anaerobic baffled reactor. Initial operational conditions through phases 1 to 4. Water quality in each sampling point at a local natural rubber processing wastewater in Vietnam Summary of process performance of the treatment system. Summary of the process parameters of the system during entire experimental period. Biogas production and compositions of the UASB reactor. -1
Nitrogen concentrations (mg-N·L ) in the proposed system. Characteristics of natural rubber processing wastewater in Thailand, Malaysia and Vietnam Process performance of the existing treatment system for treating natural rubber processing wastewater.
13 17 26 27 30 32 37
38 40 43 51 63 74 75 78 81 83
Abbreviation words list ABR AnMBR BOD BR CL COD DAF DHS DO GHG GRABAA GSS GWP HRT MBR OAS OLR ORP PVC RSS SRB ST SVR TN TSR TSS UASB VFA VSS pH
anaerobic baffled reactor anaerobic membrane bioreactor biochemical oxygen demand baffled reactor concentrated latex chemical oxygen demand dissolved air flotation downflow hanging sponge dissolved oxygen greenhouse gas granular-bed anaerobic baffled reactor gas-liquid-solids separation global warming potential hydraulic retention time membrane bioreactor open-type anaerobic system organic loading rate oxidation reduction potential polyvinyl chloride ribbed smoked sheet sulfate-reducing bacteria settling tank standard Vietnamese Rubber total nitrogen technically specified rubber total suspended solids upflow anaerobic sludge blanket volatile fatty acid volatile suspended solids potential of hydrogen
Introduction Natural rubber is one of the most valuable agricultural products in Southeast Asian countries. Vietnam is the 3
largest natural rubber-producing country, and
natural rubber production in Vietnam is increasing each year. However, the natural rubber industry discharges large amounts of wastewater containing high concentrations of organic compounds, nitrogen, and other contaminants from several manufacturing processes such as coagulation, centrifugation, lamination, washing, and drying. The natural rubber processing factories in Southeast Asian countries commonly use a combined anaerobic-aerobic lagoon system for treating natural rubber processing wastewater because of the low installation costs. The existing treatment systems have been demonstrated to achieve a high chemical oxygen demand (COD) removal efficiency of 65 to 90% with easy operational methods. However, they require a large area for the lagoon, high operating costs (especially for surface aeration), and long hydraulic retention times (HRTs). However, the effluent water quality of these existing treatment systems needs to be improved in order to conform to the established discharge standards.
An upflow anaerobic sludge blanket (UASB) reactor is one of the most promising systems for the treatment of different types of industrial wastewater because of its high organic loading rate (OLR), low operational costs, and energy recovery in the form of methane. 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 particles is essential. Moreover, when a UASB reactor is used to treat high-strength industrial wastewater, the effluent still contains high concentrations of organic compounds and nutrients. Thus, an aerobic treatment system is typically applied as a post-treatment to remove residual organic matter and meet effluent standards. A downflow hanging sponge (DHS) reactor is one of the most effective aerobic treatment systems applied as a 1
post-treatment with the UASB reactor to treat different types of industrial wastewaters.
Objective Current wastewater treatment systems used to treat natural rubber processing wastewater in Vietnam consume a large amount of electrical energy and have a large negative impact on the environment. In this study, we characterized the process performance (e.g., water quality and biogas emission) of the current wastewater treatment system and developed an energy-recovery type advanced wastewater treatment system to reduce greenhouse gases (GHGes) emission and improve the effluent quality resulting from the treatment of natural rubber processing wastewater.
Tasks (Scientific and practical meanings) 1) Characterization of the current wastewater treatment system used to treat natural rubber processing wastewater in Vietnam To investigate the current situation of natural rubber processing wastewater treatment in Vietnam, field and journal paper surveys were conducted. Moreover, greenhouse gas emissions from an existing anaerobic lagoon were measured to determine the environmental impact on global warming. This research will make clear problems in current situation of natural rubber processing wastewater treatment in an actual site. Moreover, GHGes emission from current wastewater treatment system firstly investigated. 2) Development of an energy-recovery type wastewater treatment system The UASB-DHS system has been applied to treat domestic sewage and several types of wastewater. In addition, the UASB-DHS system was successfully applied in Thailand to treat natural rubber processing wastewater, which contained a high concentration of sulfuric acid. In this study, we examined the application of the UASBDHS system for treating natural rubber processing wastewater in Vietnam and 2
evaluated its process performance at the laboratory scale and in a pilot-scale experiment. This result expected that establishment of next generation wastewater treatment process that can achieve not only wastewater treatment but also energy recovery.
3) Establishment of an optimal treatment system for natural rubber processing wastewater treatment in Vietnam Following these results, we established an optimal treatment system for natural rubber processing wastewater treatment in Vietnam.
Current Problem and its solution · The discharge amount of industrial wastewater in Vietnam is expected to increase each year. · A conventional activated sludge process is usually applied to treat industrial wastewater in developed countries, but the installation, operation, and maintenance of this type of system is very expensive. · The UASB-DHS system we developed is known to be an energy-recovery and energy-saving wastewater treatment system and has been applied to several types of wastewater. · If the application of the UASB-DHS system to natural rubber processing wastewater in Vietnam is successful, it could reduce the operational costs and greenhouse gas emissions and improve the effluent quality. Moreover, this advanced wastewater treatment technology can be applied to not only natural rubber processing waste water, but also other industrial wastewaters emitted in Vietnam.
1. State of the art 1.1. Natural rubber Rubber is widely used in industry and can be categorized as natural rubber and synthetic rubber. Natural rubber consists of polymers of the organic compound isoprene, with minor impurities consisting of other organic compounds and water. Natural rubber has good wear resistance and high elasticity, 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 . On the other hand, synthetic rubber is produced from coal oil. Synthetic rubbers are more resistant to oil, certain chemicals, and oxygen and have better aging and weathering characteristics and good resilience over a wider temperature range. Both natural rubber and synthetic rubber can be used properly according to the application, but they are combined like an automobile tire. The total amount of rubber consumed in 2017 reached 28,287,000 tons, and this was a 3% increase compared with the amount consumed in 2016 over the world (IRSG report). In 2017, the amount of natural rubber produced increased to 13,380,000 tons. Thailand and Indonesia produce over 60% of the total amount of natural rubber (Figure 1.1).
Vietnam is the 3
largest natural rubber producer in the world and
produced 1,094,500 tons in 2017 . The quality of the natural rubber produced and the harvested area in Vietnam have increased each year (Figure 1.2). The rubber tree is grown mostly in the Binh Phuoc, Binh Duong, Tay Ninh, and Dong Nai provinces in the Southeast region in Vietnam because of their favorable climate and suitable land for the optimal growth of rubber trees (Figure 1.3). The optimal growth conditions for rubber trees are as follows:
· Rainfall of around 250 cm that is evenly distributed without any marked dry season and with at least 100 rainy days per year · Temperature range of about 20 to 34°C, with a monthly mean of 25 to 28°C 4
· Atmospheric humidity of around 80% · About 2,000 hours of sunshine per year at a rate of 6 hours per day throughout the year · Absence of strong winds
Top 10 of Natural Rubber Processing Countries (2014)
Thailand Indonesia Viet Nam
2% 4% 3%
India China, mainland Malaysia Philippines
Guatemala Côte d'Ivoire
Figure 1.1 Top natural rubber produced countries over the world on 2014 .
Figure 1.2 Natural rubber harvested area and production in Vietnam 
Central Northern region region
Figure 1.3 Natural rubber production area in Vietnam .
1.1.1 Natural rubber processing process Natural rubber is harvested mainly in form of the latex from the rubber tree (Hevea brasiliensis) or other trees. Figure 1.4 show the production process for rubber products in a natural rubber processing factory . The latex is a sticky, milky colloid that is obtained by making an incision in the bark and collecting the fluid in vessels in a process called “tapping.” Raw natural rubber latex is collected from a rubber tree, and ammonia is immediately added to keep it at a high pH to prevent coagulation. Anti-coagulation measures are especially necessary under wet weather conditions and with lattices that have a strong tendency for pre-coagulation. Therefore, the amount of anti-coagulant used during the wet season is higher than that used in the dry season. Nguyen (1999) noted that the amount of ammonia that should be added to latex to prevent natural coagulation depends on the season . -1
· Dry season: 0.5-1.5 kg·tons dry rubber (0.05 – 0.15% wet weight) The amount of ammonia also depends on the distance from the collection site to the processing factory.
After it is transferred to the factory, natural rubber latex is first filtered through a mesh screen to removed collated rubber, particles, leaves, and other material. Then it is diluted with tap water. Acids such as acetate or formic acid are added to coagulate it into a natural rubber block (Figure 1.5). The coagulated natural rubber is pressed to make a rubber sheet and smoked in a furnace. Finally, the rubber sheet is washed with tap water and dried in the sun. The products of natural rubber latex are manufactured in a local factory into three types of raw rubber sheets: technically specified rubber (TSR), concentrated latex (CL), and ribbed smoked sheet (RSS). TSR is graded in a quality inspection after it is formed. TSR is also called “blocked rubber” or “crumb rubber” because of its
morphology. TSR is the most widely used type in the US and European countries. RSS is a smoked rubber sheet and largely used in industry
Figure 1.4 Natural rubber manufacturing process .
Figure 1.5 Schematic diagram of coagulation process 
1.1.2 Natural rubber processing wastewater The main products from local natural rubber processing factories are CL and RSS. The production processes for these products such as coagulation, centrifugation, lamination, washing, and drying use a large amount of fresh water and discharge the same amount of wastewater. In Vietnam, surface water and ground water are mostly 3
used. Previous study reported that in Vietnam 25 m wastewater is discharged from the 3
production of 1 ton of RSS from fresh latex, whereas approximately 18 m wastewater is discharged to produce 1 ton of CL . This wastewater heavily polluted, and it is causes environmental problems because of insufficient wastewater treatment . The characteristics of natural rubber processing wastewater are very different between the RSS and latex production processes. Table 1.1 summarizes the effluent quality of natural rubber processing wastewater in Vietnam. Nguyen (2003) surveyed 27 rubber processing factories in five provinces and summarized the quality of their effluents . These wastewaters mainly contained wash water and small amounts of uncoagulated latex and serum with small quantities of proteins, carbohydrates, lipids, carotenoids, and salts. The wastewater discharged from the CL producing process is the most polluted wastewater compared to other wastewaters because this wastewater contains high concentrations of uncoagulated rubber particles and organic matter .
The COD and total suspended solids (TSS) in latex wastewater are approximately 9
and 500 mg·L , respectively. The wastewater discharged from
factories producing standard Vietnamese Rubber (SVR) rubber sheets is acidic (e.g., pH 4.8~5.5). The main organic compounds in this natural rubber processing wastewater are volatile fatty acids (VFAs). Acetate and formic acid have been widely used for field latex coagulation in Vietnam. Specifically, the natural rubber processing wastewater collected from the coagulation process at a rubber processing factory in Thanh Hoa province, Vietnam, was reported to contain 4,000 mg-COD·L 1
acetate and 4,500 mg-COD·L propionate . Both CL wastewater and SVR wastewater contain a high concentration of -1
ammonia (e.g., 100 mg-N·L to 1,000 mg-N·L ). Ammonia is added to the latex in the tapping cups and collecting buckets to increase the pH of the latex to prevent premature coagulation. The amount of ammonia added to latex to prevent natural coagulation depends on the season and the distance from the collection site to the processing factory . The wastewater from CL factories contains a high concentration of nitrogen.
The industrial effluent discharge standards for environmental protection are usually provided by the government. Natural rubber processing wastewater is one of the largest sources of industrial wastewater pollution in Southeast Asian countries, and usually, specific and strict effluent standards are established for natural rubber processing factories. In Vietnam, the Ministry of Natural Resources and the Environment provides national technical regulations for the effluent of the natural rubber processing industry (QCVN 01-MT: 2015/BTNMT). The Vietnamese effluent standards for water quality are shown in Table 1.2. Standard A is applied for effluent discharged into the domestic water supply (used for daily activities, except directly for drinking and cooking). Standard B is applied for other water supplies other than the domestic water supply). The national technical regulations published 2015 contain two categories: new factories (started operation after 31/March/2015) and existing factories (started operation before 31/March/2015). 10
Table 1.1 Characteristics of natural rubber processing wastewater in Vietnam.
Table 1.2 National technical regulation on the effluent of natural rubber processing
industry in Vietnam. (QCVN 01-MT: 2015/BTNMT)
1.2. Current treatment technology for natural rubber processing wastewater As mentioned above, natural rubber processing wastewater contains large amounts of organic compounds and nitrogen. In addition, unbiodegradable natural rubber particulates remain in the wastewater, and thus, the wastewater treatment system needs to remove these rubber particulates. Currently, several types of wastewater treatment systems have been applied for natural rubber processing wastewater treatment (Table 1.3). In natural rubber producing countries such as Southeast Asian countries, low-cost wastewater treatment systems for treating this type of wastewater are desirable. The effluent treatment processes in use in Vietnam were surveyed by Nguyen (2003) . Aerated lagoons and ponds are commonly used for the treatment of this wastewater. On the other hand, the application of advanced treatment processes such as dissolved air flotation (DAF) and an UASB reactor has been limited. Therefore, simple, natural processes such as the biological pond method have been widely applied.
Table 1.3 Type of treatment process applied in Vietnam . Type of treatment process Aerated lagoon Pond