SRBioQuencher, aims to solve the problem of sewer pipe corrosion and hydrogen sulfide gas production caused by sulfate-reducing bacteria by introducing engineered E. coli. Hydrogen sulfide, carbon monoxide and methane are the most common toxic flammable and explosive gases found in drainage wells. Among them, hydrogen sulfide has many dangers:
How to solve the problem these gases caused in sewers? We focused on sulfate-reducing bacteria (SRB) and methanogenic bacteria (MA). They are the culprits of sewer gas production. Through further searching, the team learned that these two types of bacteria can form a difficult-to-remove biofilm on the walls of drainpipes, of which SRB are the key species in the microecological community. Therefore, by removing the SRB biofilm, the problem of gases in sewers can be solved. Among them, using engineered microorganisms is an ideal ecological control method that is non-toxic and environmental-friendly.
PEST is a commonly used macro-environmental analysis tool, which is based on the four aspects of Political, Economic, Social, and Technological. It can also provide us with ideas to analyze iGEM projects on a macro level. Through extensive review of the literature and discussions in the team, the following are the issues that we focused on in solving the hydrogen sulfide problem in sewers.
| Political | Economic | Social | Technological |
|---|---|---|---|
|
1.Active policy support: New technology and ecological civilization 2.Safety policies and laws |
1.High cost of original cleaning method 2.Reduce financial burden of the government 3.Open new markets |
1.Large-scale city sewer system 2.Potential danger of sewer diseases 3.Resource crowding 4.Gain public trust |
1.Irreplaceable of the new technology 2.Ample theoretical evidence 3.Effect verification |
1. Policy support: The Chinese government encourages the construction of ecological civilization in cities, of which urban infrastructure construction is an important part; the development of high technology, especially biotechnology, is a wind vane for the high-quality development of society. Solving environmental problems with biological methods has become a popular research field.
2. Government regulations on standards and safety issues of drainage pipe operation and maintenance: Technical Regulations on Detection and Evaluation of Urban Drainage Pipes, Technical Regulations on Safety of Urban Drainage Pipe Maintenance; and safety issues on the use of GMOs: Law of the People's Republic of China on Biosafety. The team will be required to comply with the basic safety policies during the design process, and to demonstrate the effectiveness of the treatment with sufficient experimental evidence.
1. The operation and maintenance cost of municipal drainage pipes in Chengdu is about 45 RMB/year/meter, the annual operation and maintenance cost of urban drainage pipes is 330 million. The cost of disease repair is about 50 million RMB. Corrosion caused by hydrogen sulfide and SRB biofilm is common, which suggests that the biofilm-related O&M costs will be a burden to the drainage operating companies.
2. Our technology, as a supplement to existing drainpipe wall cleaning technology, can open a whole new market without crowding out existing technology.
3. Considering the economic burden on government of the need to maintain drains using SRBioQuencher, we should minimize the expected costs and be more cost-effective and sustainable than existing methods.
1. There are currently 7,400km of municipal drainage networks in Chengdu city, of which about 3,000km are sewage networks. This is a large and complex system and careful consideration is needed when adjusting.
2. The drainage system in Chengdu is seriously damaged, with potential public and occupational safety risks, and remedial action is urgent. In the latest pipeline census, more than 100,000 major defects above the third level (repairs required) were found. In addition to this, there are more than 10,000km of head-end drainage pipe networks under the autonomous jurisdiction of community, with a disease rate greater than 70%.
3. At present, 95% of the detected drainage pipe defects can be solved by non-excavation repair. The remaining 5% require road excavation and pipe replacement. These pipe maintenance operations cause inconvenience to residents as they take up road space and sometimes result in community-wide water supply suspension.
4. Social concerns about the current urban drainage system, including public safety and occupational safety issues caused by pipe corrosion, require urgent attention.
5. Social concerns about the safety of introducing bacteria created by genetic engineering technology into urban public water facilities.We need to ensure that the program is safe enough to gain trust from the public.
1. Irreplaceability of the new technology: Currently, the main methods for removing sludge and biofilm from the walls of drainage pipes are pipe cleaning robots, high-pressure water gun flushing, and manual work in wells. None of them can completely and continuously remove biofilm from pipe walls.
2. The application of GMOs in the environment is an important research direction in synthetic biology. the team searched through the literature to obtain sufficient theoretical basis to prove the feasibility of the technology.
3. Rigorous validation is required to ensure that the SRBioQuencher achieves the desired removal of SRB biofilm and hydrogen sulfide gas in the drainage system, and that biosafety module operates properly.
From the results of the discussion, compliance with safety normative policies, reduction of economic burden, technical soundness and validation are some of the main issues to be focused on in the project. These issues were fed into the design and results of the Integrated Human practices, experimentation and modeling section.
In particular, the Sustainable Development Goals (SDGs) provided a fresh perspective in analyzing the potential impacts of the topic and the broader value to achieve. Please visit the Sustainable Development Goals (SDGs) page for more information.
Fig.1 The stakeholders related to SRBioQuencher
The next step is stakeholder analysis. As the figure shows, from the management, supply, using and maintenance of the drainage system, there are many stakeholders who are related to the urban drainage system. This mode of operation gives a flexible feedback mechanism. Through feedback from end-users, workers, and smart devices, the drainage company, scientists, and the water authority maintain or adjust the system to ensure that it operates efficiently. In a broader sense, the drainage system itself and natural bodies of water are also stakeholders that should not be ignored in the design process.
Through data review and expert visits, we believe that the solution of directly placing the encapsulated engineered bacteria into the drainage pipe through the inspection well is more ideal. The location and amount of placement have been modeled and experimentally verified, which can better cover the area in the pipeline where the SRB biofilm grows more and achieve the ideal effect of bacteria removal. The placement devices will be installed by drainage workers in each drainage inspection well, and all the devices in the city will be networked, and the amount of placement can be adjusted according to the actual situation.
For more information on the calculation of placement strategies and costs, please see the page of application layer modeling.