2.1.1 Team Crouton interviewed Professor Shan

Figure 1

Huimei from Guilin University of Technology has been deeply engaged in academic fields such as water source cleaning and heavy metal treatment, via an online meeting. To further improve our products, we asked Professor Shan, "How can our project goals be linked to Sustainable Development Goals 4, 6, 9, and 14?"

In the interview, Professor Shan pointed out that during product development, it is necessary to pay attention to the transformation process of substances and the products formed during this process and consider how to remove these potentially harmful substances.

No matter which purification method is used, such as the microbial agent our team is currently using, after reducing hexavalent chromium to trivalent chromium, even if our result meets the national water quality standards, further sedimentation is still necessary because trivalent chromium is easily oxidized back to hexavalent chromium. The trivalent chromium in the water must be removed to eliminate the hidden danger. Only in this way, are we able to eliminate possible negative impact on the nearby ecosystem and the daily water supply of local residents, and form a sustainable development industry.

Professor Shan also mentioned that hexavalent chromium is a very common heavy metal in industrial production, and both the leather and printing industries may generate such pollutants. Meanwhile, the toxicity and mobility of hexavalent chromium are far stronger than those of other heavy metal pollutants. The purification of industrial wastewater containing high concentrations of hexavalent chromium has always been highly concerning and challenging in the academic field. Crouton's project is of therefore meaningful with its focus on chromium pollution issues.

Water safety is closely related to our daily life and production. Compared with other heavy metals that pollute water sources, hexavalent chromium and its different forms are not well-known to people. The public awareness of water quality safety related to chromium pollution is relatively insufficient, but the consequences of hexavalent chromium pollution are more serious than those of other heavy metals. Having learned of this information, Crouton will conduct lectures about chromium pollution in the community during the Education session and post related content on our social media accounts.

2.1.2 Team Crouton interviewed Dr. Bao

Figure 2

The interview with biosafety expert Dr. Bao provides practical guidance for achieving SDG6 clean water and sanitation and SDG12 responsible consumption and production. Dr. Bao's detailed explanation of previous treatment methods allows our team to realize the advantages of a cost-effective and fast-responding system of purification among bioremediation methods to address issues such as bioaccumulation and biomagnification in water bodies. This directly addresses SDG6 on providing an efficient way of purification and addresses SDG12 by implying the cost-effectiveness of our product if this advantageous method is built. Additionally, regarding SDG12, his insights about the movement of heavy metals through soil, plants, and food chains lead us to consider practical monitoring of Cr(VI) levels in treated water and surrounding materials, making water treatment safer, more efficient, and outweighing the costs of monitoring.

Figure 3

In our interview with Director Xu from Weipu company, we aquire the presence of hexavalent chromium (Cr6+) in industrial wastewater. Our group learned that Cr6+ is not consistently monitored across all industrial facilities, and its detection frequency can be low. Xu expressed Cr6+ does not appears in wastewater streams frequently, and it depends heavily on the type of industrial process. While it is recognized as highly toxic, many companies focus on broader wastewater parameters rather than specifically testing for Cr6+.

Infrequent monitoring of Cr6+ may hinder efforts to ensure water safety and environmental protection, as potential contamination events could go unnoticed. Director Xu highlighted that in some sectors—like electroplating or chemical manufacturing—the likelihood of Cr6+ presence is higher.

Additionally, Director Xu mentioned that lead is an important item among all heavy metal tests, and national regulations require that almost all foods undergo lead content testing. For food additives, such as shrimp or beef seasoning agents, a lead content exceeding 5 mg/kg is considered higher than normal value.

Figure 4

Our group interviewed Mr. Zhang, an investor, to gain a perspective of common questions, problems, and considerations of investors that may be interested in our product. Mr. Zhang shared his perspective as an investor, listing the key considerations of an investor; explained how the market works, informing us about market drivers, existing technologies, and areas worthy of development; and advising us on what to do, giving advice for methods to attract investors.

Mr. Zhang remarked that one of the most common problems faced by smaller enterprises is the cost of waste treatment, commonly costing them 10-20% or even more of their annual revenue. Furthermore, initial setup costs are also extremely high, averaging at around 1.8 million RMB. Furthermore, existing technologies are either inefficient, expensive, or produce toxic byproducts. This suggests that any method of waste treatment that would cost less or is safer than the current value would have a huge market potential.

Mr. Zhang also stated some market drivers and problems we might face, including strict environmental laws that are turning even stricter day by day, forcing companies to comply to these laws. Large corporations are also pressured by ESG frameworks, namely environmental, social, and governance.

Mr. Zhang gave further advice for us, suggesting some target industries and features that would be especially appealing to consumers. Target industries include electroplating, leather, manufacturing of semiconductors, electronics, automotives, and chromium plating in the aerospace industry. Mr. Zhang advised that an investor would prioritize core technology competitiveness, market size, and a strong team. For the project to succeed, it must focus on lowering reagent and energy consumption, reducing sludge, and turning waste into value. A successful model should include long-term, full-services solutions and consulting, which can become an effective and essential partner for clients.

Figure 5

In this interview, we talked with Mr. Huang, a factory owner. We learned that wastewater treatment plants in Shanghai primarily handle domestic sewage, not industrial ones. They perform monthly tests and did not detect any exceedances. Specifically about Cr(VI), the levels are below the detection limit, and it is simply reported as compliant. Many enterprises have their own specialized treatment methods and follow pre-treatment standards(specific regulations about heavy metals,organic pollutants, and other substances), before they release wastewater out.

Mr.Huang states that workers in relevant industries(e.g., electroplating), children, and pregnant women are often most visibly impacted.

When Mr.Huang talked about how his factory purified sewage water, he introduced the activated sludge process. This method uses concentrated microbes to break down pollutants in the water. However, there are challenges as fluctuations in incoming water quality. Sometimes a severe change in concentration of some pollutants could disrupt the microbial ecosystem, which could cause increasing costs, process upsets, or even could lead to a lengthy restart.

The treated wastewaters are usually reused in the plant: landscape ponds with fish and plants, cool equipment, heat them using heat pumps for many processes, and also for other purposes, such as water for street washing.

For our bio-remediation project, he commented that we could test on real industrial wastewater, not just lab-made samples. Real effluent contains very complex mixtures of different pollutants that could affect microorganisms' performance, rate, or survival. He also suggested we be patient and allow a longer experimental period to see if the bacteria can adapt and become effective after multiplying many generations. He added that using any new technology in an existing plant would need strict environmental impact assessments and approvals from authorities like the Ecology and Environment Bureau.

Mr. Sun and Mr. Xu, the chief engineer and the director of the environmental monitoring station of the Yangpu district of Shanghai, China, made a visit to our team's laboratory and accepted our interview. We intend to ask questions about current hexavalent chromium detection methods and how hexavalent chromium damages the environment. They both responded with a very passionate attitude. Their answers and suggestions enhance our understanding of our project and SDG goals 6, 2, 14, and 15.

Figure 6

Mr. Sun noted that if heavy metals such as hexavalent chromium are dispatched into bodies of water， they will eventually end up in confined underground waters and affect the entire area， thus the cleansing of bodies of water is extremely crucial in environmental protection. This case may also apply to bacteria such as E. coli; thus, ethical issues and biological safety issues are in desperate need of being addressed. Moreover, biological accumulation is a relatively more crucial compared to other environmental problems, and thus heavy-metal pollution needs to be minimized for this problem to be solved. Since heavy metals will not degrade naturally, chromium needs to be secured using cleaning methods.

Mr. Xu claims that most hexavalent chromium pollution in Shanghai China comes from certain traditional firms, especially electropating firms, and the rubble of demolished gas stations. Their industrial sewage contains alot of hexavalent chromium and most need to be degraded before sended to the sewage treating plant. If heavy metals bind with organic chemicals, their toxicity will rise exponentially due to their affinity with organisms.

Quote: Harms of the environment ultimatley becomes consequences harming humans ourselves.

Figure 7

We conducted an online interview with Dr. Wang who has met several patients suffering from exposure to heavy metals, including Cr(VI). Dr. Wang Dongfeng's feedback about Cr(VI) contamination and our work is especially important to guide us to the path of reaching SDG3, good health and well-being. The interviewee provided valuable insight about the specific harms done by Cr(VI) and other heavy metals, including epidermic, circulatory, gastrointestinal, developmental, hepatic and renal diseases associated with exposure to Cr (VI). He also provided several pathways of exposure as well as ways to avoid them. The workers in factories involving leather work, metal frames, printing, and other similar subcategories as well as the residents near these sites are in close contact with Cr(VI) and other hard metals. Daily items such as leather clothing, makeup, and dyes often contain heavy metals that can negatively impact our health. Therefore, avoiding these products, though difficult, is an effective choice; the doctor himself has maintained this habit. He remains sanguine that greater public awareness of heavy metals in everyday materials and emissions, as well as improved safety practices among workers, could reduce the number of Cr(VI) exposure cases in hospitals. He believes it is desirable to shift from “healing” to “preventing.” Dr. Wang’s information underscores that addressing Cr(VI) contamination is essential to protecting the well-being of every person in the industrialized society. By detailing the specific symptoms and consequences of exposure in a direct and uncompromising way, he reminds us that these hazards are dangerous, potentially fatal, and impose unbearable financial and emotional burdens. Also, by connecting medical realities with everyday practices, our conversation with Dr Wang educates us that achieving good health globally requires the public to be aware of and care for this issue.

Figure 8

In the interview with Dr. Bao, Dr. Bao mentions that it is hard for the public to be aware of the dangers wrought by heavy metal pollution during times with no significant emergent crises. Therefore, we strived to achieve our best at educating children to be aware of the pollution that happens worldwide even though their lives are not, fortunately, heavily impacted by these elements. We believe by teaching children about the dangers of Cr(VI) pollution and how bacteria can help neutralize it, our activity directly advanced SDG4 on quality education about sustainable development and the environment. At the same time, introducing them to the harmful effects of pollutants and the need for cleaner solutions promoted SDG12 of responsible consumption and production, as the children's lives are relevant with the industrialized society they live in. By becoming aware of how human activities create harmful waste and how sustainable approaches, including bioremediation, can reduce environmental harm, young students were given early exposure to environmental science in an interactive way. In fact, one of the children informed us that he would like to "do science" in the future during the coloring session of our education activity. Therefore, the session also supported SDG8 of decent work and economic growth. We are able to encourage children to value workplace and environmental safety and even allow them to consider working in the field of environmental protection.

Hexavalent chromium (Cr(VI)) pollution poses detrimental effects to public health, the enviornment, and industry. Chromium's extreme toxicity is highlighted by Dr. Wang, a doctor working in Shanghai, when he mentioned the various diseases and conditions associated with Cr(VI) exposure. Despite the large-scale health risks that chromium pollution poses, Proffesor Shan of Guilin Univeristy of Technology notes, "the public awareness of water quality safety is relatively ineffficient". In response to the increasing enviornmental burden that Cr(VI) pollution plays on the enviornment, Mr. Zhang, an investor in similar markets, highlights that strict environmental laws are being developed that enforce ESG frameworks. Experts have highlighted long-term and comprehensive solutions in industries such as electroplating, leather, semiconductor manufacturing, electronics, automotives, and the aerospace industry. Mr. Zhang, in particular, noted the cost of waste treatment, with 10-20% of annual revene for mid-sized companies, with initial setup costs averaging around 1.8 million RMB. Our interview with biosafety expert Dr. Bao reaffirmed our product's fulfillment of SDG6 & SDG12 by showing the advantages of a cost-effective and immediate purification system. Through discussions with various experts and stakeholders, we've come to understand both the real-world application of SDG goals and criteria of a valuable product.

SDG 6: Clean Water and Sanitation

SDG 6.1 Access to safe and affordable drinking water

Current generic treatment methods for hexavalent chromium often struggle with efficiency and cost, which Professor Shan has emphasized as "a widespread and serious problem due to the high cost of current treatment methods". Mr. Zhang added to quantify that treatments now can consume,"more than 10-20% of a small enterprise's revenue", which makes an effective safe water treatment unaffordable to many. Efficiently turning Cr(VI) into Cr(III), facilitating the subsequent precipitation, and completely removing the contaminant, our method of treatment for pollutants costs 40% lower than conventional treatment prices; thus, we can make safe water treatment affordable and accessible. We especially appeal to smaller polluting enterprises, encouraging them to protect drinking water resources.

SDG 6.3 Improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally

To target pollution at its origin, Professor Xu and Professor Sun said,"The application of the genetic strand is most suitable in the electroplating industry, where most chromium pollution occurs." We targeted a biological treatment system designed for point-source industrial applications, which directly reduces pollution; helps halve the proportion of untreated wastewater, particularly benefiting smaller enterprises; and eliminates dumping at where it is produced.

The sewage plant manager states their treated water has "better quality indicators than normal water" and is reused "for ornamental areas, for raising fish." Our system could enhance this circular economy by ensuring that industrial wastewater enters treatment plants at higher quality, ultimately supporting safer water reuse and contributing to substantially increasing recycling globally.

SDG 14: Life Below Water

SDG 14.1 Prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities

Dr. Bao warned that chromium pollution “actually affects the water bodies by polluting water systems when chromium flows downstream until reaching the ocean” These effects emphasize the importance to cut pollution at its origin to prevent long-term harm to both marine ecosystems and organisms depending on it. The extreme mobility of chromium compounds allows them to migrate from industrial wastewater through groundwater systems or rivers into marine ecosystems, which represents a severe form of land-based marine pollution. Similarly, Mr. Zhang An Dong said that “once Cr(VI)s seep into groundwater, it can significantly affect the entire environment of soil and human habitat.” By offering a treatment method that reduces chromium concentration in water priorly to its release, we can efficiently precipitate Chromium out of wastewater and prevent it from entering rivers, groundwater, and oceans, cutting off a major source of heavy metal pollution before it reaches aquatic ecosystems.

SDG 14.2 Sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience, and take action for their restoration in order to achieve healthy and productive oceans

Heavy metal contamination can threaten the resilience of marine and coastal ecosystems as Dr. Bao noted: “many heavy metals have a noticeable effect on people, including their nervous system, development, and the development of cells.” Dr. Bao also emphasized that "heavy metal contamination could affect many water-depending organisms and ecosystems: aquatic plants, aquatic microorganisms, and aquatic animals are all subtle to bioaccumulation since they come in direct contact with the contaminated water resources." Chromium could accumulate through aquatic food webs which harms biodiversity and weakens ocean health as a whole. Purifying hexavalent chromium-containing water at its industrial source, our treatment helps prevent pollutants from entering rivers and coastal waters, reducing long-term stress on marine life. From an industry perspective, Mr. Zhang observed that “environmental protection policies are driving enterprises to upgrade their wastewater treatment systems,” This reflects a broader shift toward technologies that protect vulnerable environments. By supporting the sustainable management of marine and coastal ecosystems using more eco-friendly and less-impacting treatments, we could strengthen their resilience, and reduce adverse impacts before they occur.

SDG 15: Life On Land

SDG 15.1 Ensure the conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains and drylands, in line with obligations under international agreements

Professor Xu noted, "Groundwater... a highly protected resource," and gave a strong warning against the release of genetically engineered bacteria into the natural environment, especially groundwater. This key is in protecting local ecosystems and the environment as a whole. Professor Shan remarked, "If polluted water is used for irrigation, the soil becomes contaminated as well," noting the direct relationship between water pollution and land health. Thus, controlling water pollutant levels is crucial to conserving terrestrial ecosystems. Dr. Bao accentuated that "the effects of heavy metal contamination also apply to soil, organisms that depend on soil, aquatic habitats, and aquatic organisms" Our product is designed to detect and remove Cr(VI), a major harmful pollutant, from water sources, which would purify the water sources and make it more suitable for use. This would also reduce the amount of Cr(VI) entering the soil through irrigation or other use of water. However, since putting our bacteria directly into our water sources is unacceptable by law in many places and may have adverse effects on the natural ecosystem of many areas, our team's product is designed to hold bacteria in a facility, preventing any leakage of bacteria into the environment.

SDG 15.5 Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity and protect and prevent the extinction of threatened species

Heavy metal contamination threatens the resilience of marine and coastal ecosystems, as Dr. Bao noted: “many heavy metals have a noticeable effect on people, including their nervous system, development, and the development of cells.” These same toxins can accumulate through aquatic food webs, harming biodiversity and weakening ocean health over time. By intercepting hexavalent chromium at its industrial source, our approach helps prevent pollutants from entering rivers and coastal waters, reducing long-term stress on marine life. From an industry perspective, Zhang observed that “environmental protection policies are driving enterprises to upgrade their wastewater treatment systems,” reflecting a broader shift toward technologies that protect vulnerable environments. Our solution aligns with SDG 14.2 by supporting the sustainable management of marine and coastal ecosystems, strengthening their resilience, and reducing adverse impacts before they occur.

SDG 2: Zero hunger

SDG 2.1 End hunger and ensure access by all people, in particular the poor and people in vulnerable situations, including infants, to safe, nutritious and sufficient food all year round.

Chromium pollution exists across the world, the most adverse version of it being Hexavalent Chromium (Cr(VI)). The existence of chromium in food, common in less developed regions, continues to harm and impact millions of people, causing them to lack safe food. As Professor Shan pointed out, a commonly overlooked source of chromium in food is soil contamination, remarking that "if polluted water is used for irrigation, the soil becomes contaminated as well". Our product is designed to remove Cr(VI) from water sources, thus preventing further contamination of soil and food sources, ensuring a safe food supply for people, especially those living in vulnerable and polluted areas.

SDG 2.3 Double the agricultural productivity and incomes of small-scale food producers, in particular women, indigenous peoples, family farmers, pastoralists and fishers, including through secure and equal access to land, other productive resources and inputs, knowledge, financial services, markets and opportunities for value addition and non-farm employment.

Our project contributes to SDG 2.3 by reducing the financial burden on small-scale food producers when treating heavy metal contamination in water, which directly affects soil quality, crop safety, and workers' livelihoods. According to Dr. Zhang, companies's operating costs associated with treating wastewater containing hexavalent chromium largely depends on the company's size. As middle or smaller enterprises conduct fewer investments, and their economies of scale are far lower, their treatment systems tend to be slightly behind, with the percentage around 10~20% or higher, of their total revenue; In comparison, for large enterprises, the percentage is around 3~8%. By offering a lower-cost synthetic biology solution for detecting and reducing hexavalent chromium, our project ensures smaller producers' access to safe water, protects crops from pollution-related losses, and sustains safer access to markets. In this way, we not only improve agricultural productivity but also expand the social reach of environmentally responsible practices.

SDG 3: Good health and well-being

SDG 3.9 Substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination.

Dr. Bao stressed during our discussion that "[the most significant health risks hexavalent chromium poses] also includes carcinogenicity, and the toxicity to the liver and kidneys is very strong." He emphasizes how chromium contamination, in addition to being an environmental issue, is also a severe risk to human health -- especially for workers and other locals living close to chromium-using and chromium-emitting industries. Our project addresses this risk by identifying and reducing hexavalent chromium in water systems, transforming it into the less harmful trivalent form. Our project also prevents polluted water sources from further affecting nearby soils, ultimately lowering human exposure to a chemical strongly linked with cancer and organ damage. 

SDG 8: Decent work and economic growth

SDG 8.8 Protect labour rights and promote safe and secure working environments for all workers, including migrant workers, in particular women migrants, and those in precarious employment

By dealing with the chromium pollution from industries, our project ensures that people live and work in safe, nontoxic environments. As Professor Sun has noted in the interview, "the pollution mainly affects humans, as heavy metals tend to deposit in the bodies of animals and will eventually end up in the human body". Anyone, including local residents, factory workers, and even us who come into close contact with chromium-polluted water sources, is at risk of developing cancer a few years later. It is difficult for them to prevent this risk their working environment has already been polluted by chromium. According to Professor Shan, "complete removal of all chromium species is essential to ensure safe water quality and prevent health risks". The goal of our product is to provide a safe and secure working environment for all workers and consumers by eliminating chromium pollution in local water sources, aligning with SDG 8.8.

SDG 9: Industry, innovation and infrastructure

SDG 9.2 Promote inclusive and sustainable industrialization and, by 2030, significantly raise industry’s share of employment and gross domestic product, in line with national circumstances, and double its share in least developed countries

For the health of workers' employment and the sustainable development of industries, we need to build a safer working environment and reduce chromium pollution within it. As Dr. Bao has indicated, "[Chemicals in water sources] is a very significant impact, and many heavy metals have a noticeable effect on people, including their nervous system, development, and the development of cells in many aspects". A working environment filled with chromium pollution poses a very high risk of cancer to workers. The disease not only deprives workers of their ability to work but also causes them great pain, which brings economic losses and great life pressure to families. Our product design, to the greatest extent, considers the needs of both the workers and the companies economically.

SDG 9.4 By 2030, upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes, with all countries taking action in accordance with their respective capabilities

According to Professor Zhang, “For a small or medium-sized wastewater treatment plant, its initial investment is roughly around 1.8 million yuan on average.” Every year, the government and enterprises spend hundreds of millions of yuan on sewage treatment, hoping to attain a sustainable reusage of resources and environmental friendly industrial development. In the interview, Professor Zhang has stressed, “Based on my past data, the global market [of water treatment] is at about ten billion dollars. The future growth trend is still quite promising, making it an excellent sector". This not only provides our product and company with a prosperous future market, but also reminds us of the extremely high profit of this business area, suggesting possible alternatives. With our product, we can significantly reduce the cost for sewage treatment paid by both the government and the enterprises, leading a trend of clean technology adoption.

The revolutionary approaches of synthetic biology for environmental remediation need to be analyzed for potential risks which should be minimized. The members of our group recognize the environmental problems that occur when engineered microorganisms enter natural ecosystems because of ecological disruption and gene transfer and unintended byproduct accumulation. Our framework includes containment and monitoring and risk assessment protocols which operate throughout development to maintain safety and sustainability.

The system functions inside regulated bioreactors and wastewater treatment facilities instead of direct release to natural water sources for preventing engineered strains from entering the environment. The method enables hexavalent chromium removal at industrial sites while minimizing exposure to the environment.

The process of Cr(III) immobilization and precipitation transforms the hazardous hexavalent form into stable insoluble compounds that can be safely removed. The process eliminates recontamination and protects both local drinking water sources and nearby ecosystems from unknown threats.

The workflow design includes biosecurity features through auxotrophic modifications which decrease environmental release risks because they restrict microbial survival outside controlled settings.

The prevention of adverse effects requires public awareness programs as a final measure. The combination of educational outreach with technology deployment helps prevent misinformation and misuse because public knowledge about chromium pollution remains low. Our solution benefits both communities and industries through educational outreach which teaches them about its advantages and limitations.

Currently in China, over 20 million hectares of farmland are affected by heavy metal pollutants such as Cr(VI), with direct losses of more than 2 billion RMB. By reducing Cr(VI) pollution, our team's project has the potential to restore fertile, arable land in China and decrease the possibility of long-term food supply losses, an issue that affects every resident in the country. Moreover, our project could also restore safe drinking water in both rural and urban settings, mitigating the healthcare, public, or migratory pressures brought by Cr(VI) contamination. As such, this improvement would enable a more stable, healthy population, thereby reducing the long-term financial burden of healthcare and extermination on local governments as well as households.

Additionally, our product also benefits the industries troubled by the expense and energy intensity of existing treatments, such as adsorption, membrane separation, and ion exchange, by offering a low-cost, eco-friendly alternative of bioremediation with engineered bacteria, reducing treatment plant operating expenses. This can reduce treatment operation expenses of these stakeholders and lower industrial compliance costs. In the long term, our project might have the effect of stimulating growth in innovative green biotechnology markets and enhancing China’s overall economic resilience toward heavy metal pollution by protecting public health, agriculture, and industry multilaterally.

Potential long-term benefits: Sustainable and Complete Ecosystem Restoration

• Unlike "pump-and-treat" methods that contain a plume, engineered bacteria can work in-situ for extended periods, continuously reducing toxic, mobile Cr(VI) to less toxic, immobile Cr(III). This offers a path to truly eliminate the contamination source rather than just manage it, leading to a fundamental restoration of the aquifer's health over decades.
• By de-toxifying the groundwater, the technology can enable the long-term recovery of microbial, plant, and invertebrate communities that form the base of the local food web, ultimately benefiting entire ecosystems dependent on this water source.

Potential Long-term risks:

Over many generations, the engineered genetic circuits could mutate or fail. Bacteria might lose their remediation function, or worse, their built-in safety "kill switches" could become inactive, allowing for uncontrolled persistence or proliferation.

Alteration of Subsurface Biogeochemistry: Introducing a massive, sustained population of engineered bacteria will consume nutrients and oxygen and produce metabolites. This could shift the local redox conditions, potentially mobilizing other trapped contaminants like arsenic or vanadium, creating a new pollution problem.

Although our product could eliminate heavy metal contamination from water, we also face challenges in fulfilling environmental regulations toward genetically modified organisms (GMOs) in China if we aim for mass implementation. For instance, the Ministry of Agriculture and Rural Affairs (MARA) of the People's Republic of China provided a biosafety evaluation framework, with requirements for genetically modified microorganisms such as genetic stability, non-pathogenicity, and monitoring systems for environmental release, which could slow down the process of widely implementing our project.

Throughout our approach to the SDGs, we might face many challenges. Regarding SDG 4, raising public awareness about pollution and heavy metals can face misinformation and distrust. It is complicated to ensure that the elderly or underage individuals before high school gain a full, longstanding understanding of Cr(VI) contamination and the ways to eliminate it. Schools and communities may lack resources to promote effective biotechnology education, and people still see little reason to attend public awareness campaigns only to learn.

In SDG 6.3, to improve water quality by reducing pollution, eliminating dumping, and minimizing the release of hazardous chemicals, and in 6.5, to implement integrated water resources management, we face challenges because large-scale implementations must pass the national biosafety evaluations for GMOs. Moreover, coordination between local water authorities, biotech companies, and regulators is a complex process, as we need to ensure that the elimination of Cr(VI) is proven effective and expedient to various stakeholders. We also face challenges in achieving goals 14.1, preventing and significantly reducing marine pollution of all kinds, including from land-based activities, and 14.2, sustainably managing and protecting marine and coastal ecosystems. We are concerned that allowing genetically modified microorganisms to come into contact with aquatic systems risks leading to unexpected ecological imbalances, which is also a source of public opposition. Additionally, using Cr(VI) and modified microorganisms in our experiment also faces the risks of leakage into the environment. Ensuring that our treatment does not negatively impact aquatic biodiversity requires long-term monitoring of the environments where this method is implemented, which is costly and time-intensive.

It is essential to resolve the obstacles we might face on our path to eliminate Cr(VI) contamination. To address the transience of knowledge among the educated population, we believe it is wiser to form long-term cooperations with schools, school clubs, and local communities where pollution is severe rather than one-off short presentations. For SDG 6 and SDG 14, monitoring is, though costly, necessary to ensure that our product does not cause ecological harm unintendedly. Microorganisms would be confined in our hardware, allowing safe testing without release into natural waters. After experiments, all bacterial cultures and chromium-containing wastes are disposal using ways aligned with laboratory safety regulations.