Loại bỏ chất thải nhựa trôi nổi trên sông tại Việt Nam: Kết quả sơ bộ cho trường hợp nghiên cứu tại thành phố Cần Thơ

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LOẠI BỎ CHẤT THẢI NHỰA TRÔI NỔI TRÊN SÔNG TẠI VIỆT NAM: 
KẾT QUẢ SƠ BỘ CHO TRƯỜNG HỢP NGHIÊN CỨU 
TẠI THÀNH PHỐ CẦN THƠ
REMOVING FLOATING MACRO PLASTIC WASTE FROM 
THE WATERWAYS OF VIETNAM: PRELIMINARY RESULTS FOR A 
CASE STUDY IN CAN THO CITY
Cor Lange¹, Tran Van Ty², Liliane Geerling1 and Tran Van Tuan2
Tóm tắt:
Nghiên cứu này tập trung vào việc loại bỏ chất thải nhựa trên hệ thống sông nước Đồng bằng sông 
Cửu Long. Rất nhiều chất thải nhựa trôi nổi bao gồm có thể tái chế PET và LDPE, và rất nhiều PS đã 
được tìm thấy trên hệ thống sông/kênh, dẫn đến việc khó tái chế và gây độc cho môi trường. Nghiên cứu 
này đã đánh giá và phân tích các dữ liệu khác nhau về chất thải nhựa trong hệ thống sông nước của thành 
phố Cần Thơ, dựa trên câu hỏi nghiên cứu: Làm thế nào và ở đâu có thể thu gom được chất thải nhựa ở 
thành phố Cần Thơ? Và giải pháp thu gom nào là hiệu quả và hữu dụng nhất? Dữ liệu chủ yếu được thu 
thập từ các cuộc trao đổi với các bên liên quan, khảo sát thực địa và nghiên cứu tài liệu. Ngoài ra, để xác 
định vị trí đặt hệ thống thu gom (giải pháp kỹ thuật), số liệu thủy văn đã được đo đạc và so sánh với dữ 
liệu trước đó.
Từ khóa: Chất thải nhựa, chất thải nhựa vĩ mô nổi, lưu vực nhựa, thành phố Cần Thơ
Abstract:
This study focuses on removing plastic waste from the water system of the Mekong delta. Many 
kinds of the floating macro plastic waste in the canals including the recyclable PET and LDPE, also a 
lot of PS were found that may lead to be hard to recycle and toxic to the environment. This research 
evaluated and analyzed different data about the plastic waste in the water system of Can Tho city, based 
on the research question of: How and where can floating macro plastic waste be caught in Can Tho city? 
And what is the most efficient and effective way to achieve this? Mainly the data was collected from 
meetings with stakeholders involved, field observations and extensive desk research. Furthermore, to 
determine the placement of the catchers (technical measure), hydrological measurements was conducted 
and compared with previous data.
Keywords: Plastic waste, floating macro plastic waste, plastic catchment, Can Tho city
1. Introduction
Macro plastic is most common in coastal areas and shorelines, river banks and sea and fresh water 
bodies. This type of plastic waste is bigger than 5 mm in size. The problem of macro plastics was 
already recognised since the 1990’s. A lot of countries now have regulations or clean up campaigns to 
solve the problem of macro plastic litter. Just like micro plastics, macro plastics are also digested a lot 
by local wildlife, especially marine species (Li et al., 2016). Plastic pollution increases each year with 
8% worldwide. Most of the plastic produced is single use plastic, which is thrown away instantly. Some 
countries already try to combat this by banning or making customers pay for plastic bags. Plastic bags 
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are visible. Vietnam is one of the major contributors to the worldwide plastic problem. Solving the 
problem in Vietnam’s Mekong Delta will have a positive impact on the global plastic problem (Plastic 
Soup Foundation, 2018).
Plastic waste in the Mekong river basin is a major problem for Vietnam, and the rest of the world. 
Most of the plastic waste ends up in our environment, rivers and oceans. Vietnam is in the top five of most 
polluting countries when it comes to plastic due to their plastic use lifestyles (Christian et al., 2017). This 
is thus one of the major sources of marine plastic debris. To tackle this challenge, this research looked 
into ways of removing the plastic from the water system in Can Tho city, but more importantly where 
the plastic waste can best be collected. There are several places suitable for the removal of plastic waste. 
Several options to remove the plastic are also likely, like a floating plastic catcher, informal collection 
and collection by boat, although there will of course be some issues such as the invasive water hyacinth 
which traps the plastic waste.
The main research question is how and where can floating macro plastic waste be caught in 
Can Tho city and what is the most efficient and effective way to achieve this? Partial sub-questions 
are used to answer the main research question stated above. These partial questions are: (1) Where 
does floating macro plastic accumulate in the water system of Can Tho city? Different areas in 
Can Tho city were mapped to get a clear overview of the plastic waste problem, and areas suitable 
for plastic catchment were identified by field observations and measurements; (2) What are the 
different types of floating macro plastics found in the waterways of Can Tho city? Different kinds 
of plastics were classified and mapped in the Can Tho waters and then compared with other r ...  
data from different organisations; and (3) What options are there for the city of Can Tho to get the 
plastic out of the water with technical measures in the waterways of Can Tho city? Opportunities 
to improve the waste collection with a multi criteria analysis and meetings with experts were 
identified. Secondary data will first be collected in order to gain in-depth understanding of issues 
at hand, after which primary data will be collected from expert views. This will give the research 
a solid and verified data.
2. Research Area
Vietnam is a country that discharges a lot of plastic waste into its rivers and thus ends up in the 
oceans which are in the end negatively effects the health of the global environment (Patpicha and 
Juarawee, 2018). Can Tho city is one of the bigger cities in south Vietnam, located in the middle of 
the Mekong delta area and considered the capital of the delta (Figure 1) (Moglia et al., 2011). Previous 
research from Can Tho University (CTU) has indicated that plastic waste in the water system of Can 
Tho city is a major problem. The research focused on the four areas indicated in Figure 1. These 
areas where chosen on the result of an exploratory field trip. Some of these areas contain structures 
like brides, barriers, piers and walking bridges. The sites are chosen because of plastic accumulation 
which was visible from the exploratory visit. Also area three has already been researched by other 
researchers (Smit and Weert, 2018) which can offer a chance of comparing research results. All the 
areas are selected to be possible places for catching floating macro plastics in a certain way. All 
selected areas have a proper accessibility to the water, making a pilot plastic catcher possible. During 
the first field observation it was low tide, this was done by purpose to see the plastic accumulation on 
the canal banks.
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3. Methodology
This research partly relied on the view of experts and other stakeholders involved gaining a 
detailed understanding in the problematic use of plastics in Vietnam and the plastic catchment 
designs made by local Vietnamese people involved. Qualitative expert meetings were meant to 
enlighten many challenges about plastic waste in the waters of Can Tho city. The expert meetings 
consist of a single round of discussion in which experts are independently questioned and asked 
for their opinion regarding the subject and the design of the technical measure. The expert and 
stakeholder meetings were primarily focussed on determine which kind of plastic catcher is 
suitable. The stakeholders and experts consisted of Vietnamese people who designed a plastic 
catchment method and external experts from Recycled Island Foundation Rotterdam. Framework 
of methodology is shown in Figure 2.
3.1. Secondary data
Combing the qualitative expert meetings with secondary data gathering through online resources 
leading to a detailed understanding of Can Tho approach deal with the plastic waste issue and determine 
which technical measure is best suited. Data was collected through external desk research.
3.2. Primary data
Area analysis: An area analysis was conducted to identify the research areas. The area analysis 
described general information about the characteristics of the area including a layer analysis by looking 
into the substrate, network and occupation layers.
Field observations: The secondary data was added in form of photos and own educated assumptions 
regarding the field trips (Ninh Kieu walking bridge and Cai Khe market). These two places are major 
gathering spots for local and tourists. The other two research areas are the major canals of Can Tho 
with a bridge structure and a water retention area in the city. These places in the city can also be a good 
example for the people to learn about plastic pollution. The field observations contain information 
about the volume of the plastic by observing and counting the visible floating macro plastics in 10×10 
meter squares, different types of plastic and the overall situation. The situation may differ from for 
example the presence of water hyacinth, plastic types a composition, opportunities for plastic catchers. 
The field observations can also be used to make a map of Can Tho city where much of the plastic 
accumulates, and also indicate which kind of plastic types are most common there. The research area 
was also selected on basis of present structures and opportunities for floating macro plastic removal. 
To determine the plastic composition and map out the plastic waste problem in Can Tho city by an 
assessment of 10×10 meter squares. In these squares, different plastics were classified and counted 
(plastic bags, bottles, styrofoam etc).
Velocity and cross-section measurements: After one particular area was chosen based on the area 
analysis, further research was to determine where the specific technical measure would be implemented. 
This was done by conducting velocity and depth measurements at the chosen research area (Figure 3).
3.3. Multi Criteria Analysis (MCA) analysis
A Multi Criteria Analysis (MCA) was used to determine the best technical measure suited for this 
area. The results of the expert meetings and literature analysis were also taken into account in the MCA. 
Furthermore, a MCA was also made to examine the suitable area for the placement of a plastic catcher. 
Some criteria were used including passive system, use of local material, accessibility, function in tidal 
system, flexibility, feasibility and easy to empty for extraction.
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Figure 1. Map of the Mekong delta and Overview of the four chosen areas, source (Ngo, Pathirana, 
Zevenbergen, & Ranasinghe, 2018) and Google Maps
Figure 2. Framework of methodology
Figure 3. Field measurement of cross-sections and velocity
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4. Results and Discussion
The four research areas have been observed multiple times and all areas are found to be heavily 
polluted with plastic debris as can be seen in the Figure 4. Area 1 already has a barrier to hold back waste 
and is not suitable for plastic catchment. Area 2 could be used for plastic catchment, but it would be 
better to remove plastic in area 3 or 4. Since Area 3 has already been researched to implement a plastic 
catcher, it is logical that Area 4 would be the place to implement a plastic catcher due to the end of the 
canals, and it would be also best of course to place multiple catchers.
Figure 4 shows the result of the field observations about the floating macro plastic waste in the canals 
of Can Tho city. As can be seen, the majority of the plastic waste is PS and LDPE. PS or Polystyrene is 
not positive because this type of plastic is hard to recycle and easily breaks down into small particles. On 
the other hand, LDPE is recyclable and found in abundance. Furthermore, in many of the observations, 
PET was also present, ranging from 3 – 19%. PET is usually found in the form of plastic bottles and can 
be collected. Other types found in the canals are HDPE and PC. PC is polycarbonate and polylactide and 
hard to recycle. To conclude, in the canals of Can Tho there are many different types of floating macro 
plastic waste found, especially the recyclable PET, LDPE and the non-recyclable PS or polystyrene more 
commonly known as packaging foam. 
Different types of plastics (Ryedale, 2019):
• Polyethylene Terephthalate, PET(E) plastic, sometimes absorbs smell and flavour of food and 
drinks, commonly recycled (mostly bottles, jars, rope and carpet fibre).
• High-Density Polyethylene, HDPE, is commonly recycled, hard bottles like containers for milk 
etc. not recyclable for food and drink plastic.
• Polyvinyl Chloride, PVC, is sometimes recycled, used for pipes, harmful when ingested.
• Polypropylene, PP, is occasionally recycled, strong and withstands high temperatures and 
conditions (bottle caps, lunchboxes and other hard material).
• Polystyrene, PS, is commonly recycled but difficult to recyclecoffee cups, plastic food boxes, 
packaging foam. 
• Type 7 is Miscellaneous and are not defined by the previous six types of plastics such as 
polycarbonate and polylactide often difficult to recycle.
The measurements were conducted at seven cross sections at Ninh Kieu bridge to Cai Khe market 
and into the Cai Khe canal. The measurements were performed during low and high tide to compare 
and determine the best locations to place the plastic catcher. The deepest point at low tide is 5.1 meters 
and at high tide 6.9, the average tide difference is around 1.8 meters at its highest point. The velocity 
ranges from 0.06 to around 0.30 m/s. The requirement for a floating plastic catcher is at least one meter 
deep. It would be unsafe to place the catcher in the middle of the river due to boat traffic. At Cai Khe 
market there is a suitable place for placement in depth and velocity. But Cai Khe market is not the best 
place to implement a catcher because it will miss a lot of floating plastic waste which is produced in 
Cai Khe market and near Ninh Kieu indicated by the field observations. To conclude, near Ninh Kieu 
bridge, Rach Cai Khe Canal or at Cai Khe market would be the best option, it is suitable in hydraulics 
and accessibility during high and low tide. Furthermore there are opportunities there to make the plastic 
catcher attractive or educative to the people (Figure 5 and 6).
During the literature analysis and expert meetings, there were several designs analysed. In the end, 
the research concluded with the best technical measure which can be used to remove plastic from the 
waters of Can Tho city. The expert meetings resulted in the elaboration of three catcher designs (by 
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CTU and Recycled island foundation Rotterdam as shown in Figure 7 and 8). In the end, the design of 
CTU and Recycled island foundation would appear to be the best possible solutions due to their passive 
systems, feasibility and capacity by MCA. The design of CTU is very promising but is still in the 
concept phase. It is also very similar to the design of Recycled island foundation. This would open up an 
opportunity for collaboration of the design of CTU and the experience of Recycled island Foundation. 
The MCA indicated that the designs of Recycled Island Foundation Rotterdam from CTU are the most 
suitable. Due to the local design of CTU and his connection with CTU, it would be the better option in 
combination with the experience from recycled island foundation. It is both flexible, adjustable and a 
passive plastic catcher. However a pilot test is needed for further research.
Figure 4. Composition of floating macro plastic waste
PET = Polyethylene terephthalate; HDPE = High-density polyethylene; 
LDPE = Low-density polyethylene; PS = Polystyrene; PC = Polycarbonate; 
PVC = Polyvinyl chloride; PP = Polypropylene
Figure 5. Overview of situation in canal system and possible placement for plastic waste catcher
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Figure 6. Spatial overview of the design
Figure 7. Design from Recycled island foundation Rotterdam (on the left) and from CTU (on the right)
Figure 8. Top-view of catcher designed from CTU
5. Conclusions
To conclude, this research investigated the possibility of the implementation of a plastic waste 
catcher in the canals of Can Tho city. Furthermore, this case mapped the plastic waste accumulation and 
the composition of floating macro plastic waste. A passive catcher similar to CTU and Recycled island 
foundation Rotterdam turned out to be the best suited for different criteria. A collaboration between 
different stakeholders would be the most benefitting approach. 
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6. Recommendations
Further study in the social aspects of plastic waste in Can Tho: This research focuses on the technical 
measures used to solve the plastic waste problem in Can Tho city. But this is treating the symptoms of 
a bigger problem. Extended research is needed in the social aspect about the plastic waste problem in 
general and how people deal with their household waste and awareness. The plastic catcher can function 
as a tool for awareness, especially if it is made from recycled plastic waste material. This will enable the 
local people to learn about the global plastic waste problem.
Implementation of the plastic catcher: Creation of a pilot test in the canals of Can Tho in collaboration 
with VHL, CTU, HZ and 100 resilient cities. The creation of a living lab is promising and recycled 
island foundation involved would be most favourable. This will enable another research topic about the 
composition of plastic waste caught by the catcher and will enable more research about the by catch of 
for example water hyacinth. Further research is needed in an operational catcher and the composition of 
the caught waste and by catch, especially processing of the caught waste.
References
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occurrence and effects. Department of Science and Environmental Studies, The Hong Kong Institute of 
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University. Thesis report.
Date of receipt: 20/2/2020
Review date: 04/3/2020
Date acceptedfor posting: 04/4/2020
1 Hz university of applied sciences, the Netherlands.
2 Can Tho University, Vietnam.