Team:ASTWS-China/Human Practices

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General Background and Motivation

As a new type of material, plastic products have the advantages of light weight, waterproof, durable, mature production technology and low cost, which are widely used in the world and are increasing year by year. The plastics that remain in the environment will accumulate for a long time, which has been know by ordinary people. But what more people don't know is the potential hazards of plastics, such as the impact of microplastics on water resources and the whole food chain, not to mention nano-/microplastics lurking in kinds of food.
We vaguely feel that, in this iGEM season, we ASTWS-China not only need to complete the real genetic engineering challenge, but also need to do something to make public we come into contact with pay more attention to plastic degradation. On the other hand, getting more information to make our products more practical and make it have the potential for further application is also our goal. As a result, we collected information and inspiration through publicl survey, field trip and expert interviews.

Public Survey

We collected a total of 236 questionnaires online and offline for collecting the public's real view and vision toward plastic pollution. The respondents come from all ages with differnt educational backgrounds.

Plastics have been widely used in modern life, appearing in all aspects of human activities. From the survey results, more than 90% of peopple use plastic products frequently. There are the infrastructure to dispose properly of the vast majority of their plastic or recycle it. However, waste classification does not cooperate with the plastic treatment process: nearly 40% of people still do not properly dispose of plastic through waste sorting according to the graph below.

It seems that public hold a negative view on current siituation of plastic pollurion, and there are more than 84% of respondents hold a view that the pollution of plastic products to water is a serious problem. But actually, when we analyze their understanding of microplastic particles, we find that the public's understanding of plastic pollution is one-sided: there are 47.88% of people have no idea about microplastic particles, and more than two-thirds of the respondents knew nothing about the formation of microplastics of respondents.

As for the treatment methods and plastic polution control, reducing the use of plastic products and improving the mechanism of plastic degradation received the most support. Moreover, there is no doubt that government intervention is necessary. Most people (48.73%) think that the government should solve the problem of plastic pollution by strengthening the governance of micro plastics, while others think that it can be managed by means of science popularization, law and punishment.

After understanding our solution of genetic engineering, the public gave us a lot of support, about 60% of people think that the idea of using genetic engineering to solve plastic pollution is very promising.

All in all, we have gained a lot of useful information through this survey, and also found opportunities for in-depth communication with the public. More efforts have been done in our further work.

Field Trip

1. Garbage Plant in Hangzhou
2. Department of ecological environment of Zhejiang Province
In order to understand the details of the current plastic waste treatment and arouse critical thinking and more inspiration, our team took a field trip to a garbage plant, which took in all sorts of plastics from streets. Garbage plant is a waste transfer station between the garbage concentration point and the treatment plant in order to reduce the garbage freight. This is where the garbage collected from each collection point is collected and then transferred to larger vehicles or other vehicles with lower freight rates for further transport to the disposal site. The transfer capacity of the transfer station is about 1000-4000 tons per day. However, according to the official data, only 1/4 of annual plastic production could be recycled, and the rest were either burnt or disposed into the ocean, which would go through further breakdown and eventually become microplastics. Other source of microplastics could be from sewage of households, since many products contain microplastic particles inside. However, for the treatment of nano-/microplastics, the staff here know little about it.

We therefore futrher interviewed Mr. Chen, director of Hangzhou department of ecological environment, on the rules of urban plastic waste disposal. We are surprised to learn that there is no special instrument for measuring nano-/microplastics in the environment, the equipment that has been put into use at present is dedicated to the detection of microorganisms, like E. coli, which also have special indicators for for reference. This reminds us that our plastic collection and degradation equipment should also have a separation device.

Professional Interviews

Expert list：

  1. Dr. Ji Rong, Nanjing University
  2. Dr. Yuan Zhihua, Institute of Urban Environment,Chinese Academy of Sciences
  3. Dr. Lai chunyu,The University of Queensland
  4. Dr.Wu Jiyong, Shanghai Mokai Environmental Technology Co., Ltd

  • New understanding of plastic pollution

    We are informed that the pollution of microplastics in the environment is currently widely recognized. Microplastics have been detected everywhere in the world, as in various environmental media, foods, and organisms. From the expert's reply, we have a new understanding of plastic pollution. Dr.Ji from Nanjing University pointed out that we should pay attention to distinguish micro plastic pollution from plastic pollution. At present, the plastic pollution and its harm are reported by many media. In addition to microplastics (generally < 5 mm in size, but also considered to be < 1 mm in size), there are many very small nanoplastics in the environment that deserve attention. Because of their small size, nanoplastics are easier to accumulate in the food chain, but also because they are very small, it is a challenge to detect them. According to Prof. Yuan from Institute of Urban Environment,Chinese Academy of Sciences, there is no specific international standard to limit these pollutants in wastewater. Therefore, there is no clear way for wastewater treatment plants to treat such pollutants. In China, there are still some shortcomings in rural sewage treatment, and the discharge standards of urban sewage treatment plants need to be improved. Many water bodies in China have not completely got rid of pollution. Therefore, chinese government will continue to pay attention to the effective treatment of sewage and increase investment in the future, which also includes the treatment of nano-/microplastic pollution.

  • Technology of dealing with plastic pollution

    “Nano-/microplastic pollution is a common environmental problem in the world”, Prof. Yuan said, “Because of the wide range and difficult degradation of the pollution, it is impossible to eliminate the nano-/microplastic particles existing in the environment in a short time. In other words, currently there is no effective way to deal with the dilemma”.
    According to Dr.Ji, theoretically, the processing technology can be divided to recollection and decomposition. In the environment, microplastics can be collected when the concentration is very high,and it can’t be done completely. It is difficult to separate the plastic particles from the environmental media efficiently. There are physical, chemical and biological methods to decompose microplastics:Physical decomposition can only change plastic from large particles to small, so it can not decompose plastics completely; Strong oxidants used in chemical degradation will also kill other organic matter and organisms in the environment. So it seems to be no choice left but to apply the biological method.
    However, plastics have emerged in the past 100 years. Microorganisms in the environment have not yet evolved corresponding enzymes to efficiently degrade the chemical bonds in plastics. At present, scientists have found an enzyme that can degrade PETs, but this enzyme can not efficiently degrade PET in natural environment. It still has a long way to go before it can be widely and efficiently used.
    Dr. Ji also pointed out that, like any pollution control, the best technology to control plastic pollution is to prevent plastic from entering into the environment and reduce the use of plastics (such as disposable plastics), use of plastic substitutes, or use biodegradable plastics. Some of the plastics on the market are not real degradable plastics, but are degraded from large particles to small ones, which leads to more microplastics. The real degradable plastics are polylactic acid plastics polymerized by biomolecules, such as lactic acid, which can be completely degraded by microorganisms and finally turned into CO2. The team of academician Zhang Quanxing of Nanjing University has developed the production process of sudden lactic acid plastics and is ready for mass production.

  • How does the sewage treatment system work?

    Through our interviews with experts from diverse fields, we gradually learned the overall process of purification and the methods to make improvements. After interviewing an anonymous director of a local sewage treatment plant, our group learned how the treatment plants process wastes. A typical sewage treatment plants use a series of tanks to treat the wastewater, the process usually contains 6 steps and generally involves three stages, called primary, secondary and tertiary treatment, besides pretreatments. After grate and grit screening, wastewater will usually be treated by micro-organism (in anaerobic and aerobic tanks) between twice sedimentation. Most of large particles will be cleaned out from the water, however, the microparticles including microplastics may remain. This makes us think that biological devices can be installed in the existing sewage treatment process.
    As far as we know, MBR (Membrane Bio-Reactor) is a membrane bioreactor that widely used in the field of wastewater treatment and water resources reus. So we consulted Dr.Wu who experts in membrane bio-reactor about the possibility of using this technology in our project. Dr. Wu replied that MBR is mainly composed of organic materials such as PVDF (polyvinylidene fluoride), so it is very difficult to integrate biofilms with it. Thus if we intend to integrate our idea with the sewage treatment plant, the most plausible way is to place it inside the sludge.
    Dr. Lai from The University of Queensland introduced the related knowledge of biomembrane system to us. The biomembrane system he introduced was mainly a kind of hollow fiber membrane. The membrane is hollow with very small nano scale pores outside. Introduce some gas into the membrane, and the gas will slowly spread to the outside of the membrane. The biofilm produced by E.coli can be attached to the outside of the membrane. He also emphasized that plastics are difficult to be degraded, and most organisms are unable to degrade plastics or degrade them very slowly. However, E.coli grows fast and has rapid metabolism. How to match the growth&metabolism of bacteria with degradation process is a problem to be solved. It is possible to achieve this goal by gene editing or gene recombination, but, he said, it certainly will encounter many difficulties.
    During the interviews, we also managed to solve some dilemmas. One of the greatest problems we had to encounter was that we don't know how to achieve biofilm adhesion to the support materials. Dr. Lai pointed out that biofilm has different effects on different supporting materials. It is necessary to test the adhesion of different materials and biofilms. The adhesion of biofilm can be natural adhesion without human intervention. We can set up a process to get rid of bacteria that don't stick.

Conclusion

We were surprised at what these human practice works have brought us.

  • The public's awareness of environmental protection is very high, but most people only have a vague and general understanding of plastic pollution and solutions, with many biases.

  • The best way to control the pollution of plastics is to start from the production of plastics, including the production of real desgradable plastics. The effective waste classification combining with degradation technology also contribute to solve the plastic dilemmas.

  • The key to eliminate microplastic and all kinds of pollutants is government control. Water pollution prevention and control is an important part of our country's construction, and it has always been highly valued by the government. In recent years, China has made great progress in the field of sewage treatment, and the sewage of major cities and towns in the country has basically been effectively treated. In the future, the Chinese government will continue to attach importance to the effective treatment of sewage and water pollution.

  • At present, there is no good biofilm supporting device in water treatment plant. It is a work that we must overcome to realize the biofilm adhering to the support without external force; Different from physical and chemical methods, the life cycle of E.coli is very short, we should keep the activity of E.coli biofilm; when using biofilm as filter in sewage treatment system, the most feasible way is to put it into sludge. As for PETase, the degradation rate of wild-type can not degrade of plastic in a short time. We need to improve the performance of our PETase through genetic engieering.

We have gained a lot of achievement and inspiration in the work of human practice，including better understanding of plastic pollution, how to further communicate with the public and obtain ideas of application design.

In depth background learning & Science communication

From the interview with Dr. Ji, we knew the difference between nano-/microplastic pollution and plastic pollution. It turns out that like most of the public, we only know the harm of microplastic pollution, but we don't know the degree of its harm and the causes of its formation. This is the place we need to learn further, and moreover, we should also share the knowledge with more people.
Also, there is a large part of the population lack of daily waste sorting awareness and general knowledge of plastic pollution, which lead us to do more promotion and popular science in the science communication. We hope that through our efforts, people of all ages, whether old or young, can participate in the comprehensive control of plastic pollution. Only in this way will there be more calls for plastic degradation technology.

More inspiration in applied design

Since recollection and physical/chemical degradation of microplastic have been proved ineffective in some terms, it seems to be no choice left but to rely on the biological method.
Interviewing an anonymous director of a local sewage treatment plant, our group learned how the treatment plants process wastes. We decided to implant a separate tank after the secondary sedimentary pool to process the sludge from two sedimentary tanks and aerobic/anaerobic tanks, then our genetically modified E.coli will be put into use. Although modern technology allows us to use bio-membrane as filter, which is commonly placed in treatment plants, we cannot combine them with our modified E.coli, the most plausible way is to place it inside the sludge.

Opportunity of partnership

Dr. Ji had pointed a important thing of low degrade efficiency of wild type PETase, which was also pointed out by TJUSLS_China 2020 iGEM team at the beginning of our cooperation. TJUSLS_China told us that they are trying to raise the working temperature of PETase to a temperature that can destroy the structure of PET, leading to our further thinking and project improvement. Then we propose to combine the PETase produced by biofilm strengthening system with the high temperature resistance factor of TJUSLS_China, and try to increase its degradation efficiency under high temperature environment.