Figure 1. A map of arsenic contamination levels in Arizona in parts per billion (ppb) (7)

About half of the United States’ population relies on ground sources for their water consumption (3). In the Colorado Plateau aquifers, arsenic is the most abundant trace element, found at concentrations as high as 14%. Roughly 43% of all Colorado Plateau aquifers have high or moderate concentrations of inorganic contaminants that pose a threat to human health (4). The current maximum contaminant level for arsenic set by the EPA is 10 µg/L, but concentrations as high as 3,000 µg/L have been found in American water sources (6). High arsenic groundwater contamination is due to a combination of the FeS-rich mineralogy, agricultural history, and historically active mining industry of the Southwestern United States, particularly in Arizona (5). Arsenic contamination is of special concern to rural and native communities in Arizona because they rely on water sourced from private, unregulated wells (7). Our filter design team decided to also develop a cheaper solution to the original filter design because we wanted to account for implementation feasibility in rural areas.

Initial arsenic exposure results in nausea, abdominal pain, and diarrhea. Chronic arsenic exposure causes arsenic to accumulate in the major organs - the lungs, kidneys, heart, and liver. The gastrointestinal tract, spleen, nervous systems, and the muscles also receive smaller deposits. Arsenic is a well-established carcinogen and can thus result in cancers in the major organ systems to which it is deposited (10).

Arizona’s arsenic levels pose significant health risks - About 17% of the 1,346 Arizonan water source sites tested in a 2008 study had arsenic levels above 10µg/L (9). Furthermore, a study in Clinical Toxicology found that a community in Arizona exposed to arsenic levels higher than the EPA limit of 10µg/L in their tap water had elevated arsenic levels in their urine samples (8).

With the information about the significant arsenic contamination in Arizonan water sources as well as the serious impact of chronic arsenic exposure on human bodies, our team decided that improving our bioremediative algae iGEM design from last year would be a responsible way to improve our community. Last year, our project did not receive community input on the level we’d have preferred due to IRB constraints. This year, we wanted to involve stakeholders to a higher degree. We also wanted to develop a filter design that took into account implementation feasibility for rural communities. Finally, our wet lab team wanted to alter the biomechanics of arsenic uptake using a arsenate reductase gene from the yeast Saccharomyces cerevisiae, which has stronger metabolic similarities with algae. Our wet lab approach this year also took advantage of pre-existing heavy metal sequestration pathways in C. reinhardtii in order to increase the likelihood of our genes of interest being expressed by the algae.

Read about our design process on our Engineering Success page here.

Our team decided that the stakeholders of our project fit into two categories: industrial and civil. Industrial stakeholders are those that can provide input to our design process by means of confirming existing mechanical or engineering assumptions. Civic stakeholders are those who could provide information about the larger, human context of arsenic contamination and remediation. After our Human Practices subteam got social-behavioral IRB training and had our IRB paperwork approved, we started reaching out to civic and industrial stakeholders in our community and beyond. We were able to interview 3 of the 9 stakeholder organizations we contacted.

We interviewed two industrial stakeholders - MicroBio Engineering, an algae engineering firm, and the Arizona Department of Environmental Quality, a state organization based in Arizona.

In their interview, ADEQ emphasized that current heavy metal chemical remediation methods are insufficient because they generate a significant amount of byproducts such as waste rock and tailings. This waste must be buried on-site, as much of it does not meet landfill requirements. Thus, the development of bioremediation methods that generate repurposable waste could improve the quality of remediated environments. In our project, the presence of concentrated toxic waste as a byproduct of the water filtration system lends itself to further exploration of how this waste can be detoxified or reused for a different purpose. Clearly defining waste management methods for arsenic-saturated algae could be an important next step for our project.

ADEQ also emphasized the importance of understanding the culture of the community, such as significant artifacts, people, and places before initiating remediation. Additionally, they mentioned their agency conducted biological and ecological surveys of the surrounding area to generate a comprehensive analysis of their site. ADEQ’s response enhanced the significance of our team’s project - developing a biological system capable of combating heavy metal contamination has the ability to decrease the burden that inorganic contaminants place on the natural environment.

The interview with the CTO of MicroBioengineering informed the details of algal growth chambers for the filter team. More specifically, we learned that algae farms have “2-8 day hydraulic residence times in their growth reactors”, a range that we used to estimate how often our growth chamber design would need to be replenished. This was important for the filter design input requirements.

View our filter design on our Proposed Implementation page.

From the civic stakeholders side, we interviewed an environmental health scientist from a federal government organization that chose to stay unnamed under the IRB consent process. As an environmental health scientist, their job is to guide communities as they deal with heavy metal exposure by introducing health education and targeted risk-reduction recommendations. The scientist mentioned that their recommendations were often implemented in the affected communities, with the biggest barriers being financial or risk-aversive - communities often seemed hesitant to adopt new practices. What our team took away from this interview was that a well-researched and open relationship between the affected community and the scientists would go a long way in developing trust. If our project were to be implemented in the future, the effort would benefit from doing social and cultural surveys of the community, holding a town hall for questions and feedback about the technology, developing educational materials about genetically modified organisms, and even allowing residents the option to refuse implementation of Chlamydomon[As] in their community if they so choose.

Our team also engaged with mentors from ASU who have worked in industrial communities.

From Dr. Taylor Weiss, an ASU associate professor and member of the Arizona Center for Algae Technology and Innovation (AzCATI), our team learned that engineered high-technological design is often not implementable in the real world due to its expense. For example, a disk stack centrifuge, one of the components of our high-tech filter, costs over 10,000 USD. Communities looking to remediate their contaminated water would not find such a cost a feasible alternative to buying bottled water. Dr. Weiss suggested we also look at alternative remediation processes such as algae ponds and analyze an additional population - livestock. In response to Dr. Weiss's advice, we created a design for a simple sedimentation pond structure with an additional clarifier. This low-tech solution, which could be adopted to remove arsenic from water for consumption by cattle and other livestock, allows for the flow of the water stream to help filter out the contaminants naturally instead of requiring high energy inputs.

We also interviewed another mentor, Dr. Bruce Rittmann, the director of the Biodesign Swette Center for Environmental Biotechnology at ASU. Dr. Rittmann recommended we implement a kill switch into our algae so we could ensure control over the organism. Though our lab started with a strain that was dependent on arginine, slow growth made it necessary to switch to a more practical cell wall-deficient strain, CC-400. This was a compromise we needed to make due to the time constraints posed by the competition timeline – however, the same arsenic uptake pathway could be implemented into an arginine auxotrophic strain in long-term projects.

Figure 2. Members of the ASU iGEM team meeting with Dr. Bruce Rittmann. (Left to Right: Dr. Bruce Rittmann, Priyati Sharma, Gabriella Cerna, Carol Lu.)

Through our conversations with academic, civic, and industry stakeholders, our approach towards our project changed significantly, both in the way that we engineered C. reinhardtii and especially in the way we designed our water filtration system. Though our stakeholder interviews were helpful, we were limited by the novelty of our field. Bioremediation is not widely practiced by industry professionals, and relevant academic knowledge is often constrained to the mechanisms of uptake. In the future, it would be prudent to start the IRB process at an earlier stage and heavily research scientists and engineers who have niche knowledge of arsenic or heavy metal bioremediation. The development of our filter would greatly benefit from a deeper, more comprehensive search for such experts. Furthermore, out of the 9 stakeholders we contacted, 3 consented to an interview. Starting IRB earlier and allocating more time to research possible interviewees would benefit human practices greatly.

Working with laboratory organisms in a real-world environment is difficult. Real-world implementations of Chlamydomon[As] would likely necessitate the use of a more robust algal strain to bypass the challenges associated with maintaining the growth of laboratory organisms. Despite the design constraints that exist, going through the process of breaking down each of our decisions and understanding their impact on our user group and other stakeholders was immensely valuable in forming a well-rounded understanding of both the problem we are tackling and the opportunities that exist to devise solutions for it.

Next Steps

1. Start the IRB process, including researching stakeholders, in January.
2. Connect with professionals who have worked with indigenous and rural communities to gain better insight into the scope of a potential filter design.
3. Connect with professionals who have worked with indigenous and rural communities to understand any preconceived notions or hesitations these groups may have towards the use of GMOs.