This application scenario was developed by the iGEM team Purdue 2016 in collaboration with Synenergene. In this scenario we aim to show how the results of our project could be applied in both domestic and industrial contexts in the developed and developing world. Additionally, we seek to thoroughly outline the potential consequences of these applications in current political, ethical, and technological contexts.
In concert with an assortment of other nutrients, water phosphates in excess of 25 micrograms per liter are known to drive the growth of harmful algal blooms (HABs) during periods of warmer temperatures ( ≥25°C). These blooms compromise water quality by choking oxygen from aquatic ecosystems and leaching neurotoxins and hepatotoxins such as microcystin and nodularin into sources of potable water. In so doing HABs cost global industry more than ten billion USD in damage and threaten both chronic and acute harms to human health every year.
This propensity for consequence was no more evident than in the Summer of 2014 when over 500,000 residents along the southern coast of Lake Erie were left without water for over 48 hours. Though this incident may seem isolated, with continued global agricultural development and a predicted 1.5-4°C increase in temperature over the next century, the likelihood and intensity of HABs will only increase in the coming decades.
As such, there is a serious need for not only efforts to address the issues surroundings HABs but with those concerning phosphorus misuse. Currently there are no federal restrictions in the US on water phosphate pollution and similar laissez-faire approaches prevail in many African and Asian-Pacific nations. Though estimates vary, like oil, phosphorus is a nonrenewable resource and, like oil, phosphorus production and supply will at some time in the near future fail to meet global demands. Therefore, as a means of bridging the gap between supply and demand better recycling or reclaiming methods must be established.
How does it work?
Our project focuses on providing the biological and mechanical designs necessary to remove excess phosphorous from water sources. Our solution uses a three part system to achieve this design goal. Capture, Store, Extract. The bacteria, embedded in xerogel beads to prevent their release, are engineered for an increased ability to take up phosphates. This “luxury” uptake is a system adapted from phosphorus accumulating organisms (PAOs) which are currently used in waste treatment plants. Once inside the cells, increased expression of ATP dependent and independent polyphosphate kinases binds the phosphate into polyphosphate polymers. The endogenous system for storage in E. coli. The genes that would normally free phosphates from this chain are downregulated until expressed by a user defined trigger. The cells then release much of their phosphate and “dump” it into the surrounding media. The media can be transported elsewhere while the cells stay embedded in the exogel beads. This phosphate enriched media can be further refined to further valorize our product.
Patent & Business Plan
The patents we would issue on our system would be two fold. The first would be patents concerning the genetic pathways to induce luxury phosphorus uptake, store that phosphorus and release it on command. This would allow us to benefit from the retail value of our organism. We would couch this within the unique ability to capture, store, and release compounds from the environment in a more concentrated form allowing the patent to potentially cover more than just phosphorus. The second level of our patents would concern the way these engineered bacteria are housed within the xerogel beads, and the larger phosphorus reclamation module that allows them to uptake luxury amounts of not just phosphorus but other compounds that have increased value when concentrated from the environment.
Our business plan would have three levels to allow flexibility on our part and on the part of those wanting to implement this system. The first level of this model would involve our company directly owning and operating the system. This would allow us to collect the phosphorus to sell without competing interest from a stakeholder. This could be implemented in high phosphorus areas (where phosphorus could be easily collected and resold) or as a pilot program for cities or environmental groups to demonstrate how our system would work. The second level would allow us to rent out the reclamation module along with the organisms to cities, farmers, or homeowners. This would allow these stakeholders to benefit from the collected phosphorus by selling it to us or on the open market. We would be selling replacement parts and packaged bacteria to allow refills once the filters become less efficient. This second level would benefit from those who might not want to directly manage their system but view it as an investment where they can profit from the waste phosphors they may generate or have access to. The third level of our business plan would involve the leasing of the whole system, with propagation and encapsulation methods. This would allow groups to have complete control over the process to fit their specific needs. The phosphorus they accumulate could be sold back to our business for wholesale or could be sold on the open market.
Our system collects and concentrates phosphorus out of the environment. Since there are a wide range of possible applications, the flexibility of our system can truly be tested. Below are some possible applications our team and stakeholders have identified, however we expect many more will be identified as our technology proliferates.
Wastewater Treatment Plants: Current wastewater treatment plants are being pressured by the Environmental Protection Agency to reduce the levels of phosphorus in post-treatment wastewater. A common biological method of phosphorus removal is incubation with phosphorus-accumulating organisms (PAOs). Their ability to store luxury amounts of phosphorus is what our system attempts to imitate, our system however benefits from a common and well understood chassis and the ability to engineer the organism effectively.
Home Bioreactors: Our system could be implemented on the scale of the home instead of the community. Allowing citizens to take ownership of their resources and environmental impact. A easy to use home based bioreactor would open to doors to modular design, which would allow widespread remediation, taking strain off the wastewater treatment plant.
Tile Drains: The largest use of phosphorus is in fertilizers spread on agricultural fields. When this farmland experiences heavy rainfall, sections of the field can flood and phosphorus can be washed into nearly waterways. A common solution to flooding is an underground tile drain system, that allows water in over-saturated soils to drain into a ditch or waterway. Placing our phosphorus reclamation module (PRM) at the outlet of these pipes or at chokepoints in the ditches and waterways would allow collection of the runoff phosphorus before it was able to spread further into the environment.
Floating Phosphorus Reclamation Module (PRM): While it may be useful to concentrate efforts of phosphorus collection as close to the source as possible, that is sometimes impossible. To counter this our team designed a floating PRM which could be placed on buoys in lakes and rivers to steadily decrease the phosphorus load in the surrounding water and help decrease the chance of algal blooms.
Methane Digester: A novel use for our system would be in combination with methane digesters. These digesters use bacteria to break down organic matter and produce methane which can be used for energy. The resulting effluent (broken down nutrient mash) can be placed on the field to act as fertilizer. While some nutrients in the effluent are effectively used and considered limiting (nitrogen), others can build up in the soil over time (phosphorus). Eventually the built up phosphorus will leach from the soil to nearby bodies of water. This problem may be avoided by extracting phosphorus out of the effluent before being applied to the field, using a system similar to our PRM.
Production & Costs
Our current working prototype costs around $40 to produce from easily obtainable parts (Two 5-gallon buckets, 3 canisters, 3 filters, tubing, pump motor). The final design will require either a power source or solar panels, which will drive up the initial cost. The biggest cost however will come from bead construction and filter replacement over the lifetime of the device. The filtration is done in two parts, a physical filter for larger particulates, and a packed bed of beads with our genetically modified E. coli inside, both of which are housed in a plastic cannister attached to the holding tanks. This filtration system will need to have both parts replaced once a month, which will cost approximately $2 per filter. Bead replacement will cost approximately $2-$3 per cannister including costs for E.coli propagation and silica bead production. If the final design contains 4 cannisters, monthly maintenance will be $16-$20. Ultimately, these monthly costs will decrease as economies of scale begin to work in our favor.
Biocontainment: As with most iGEM projects, biocontainment is a serious risk. Our even more so since the primary use of our technology is directly in the environment we are attempting to protect. Our first line of defense would the build of the phosphorus reclamation module (PRM), the beads used to hold and suspend the bacteria need to be engineered and refined to reduce the risk of leaching (bacteria escaping). Filters would be installed on the input and output flows of the PRM. Both to prevent sediment build up in the filter housing and to prevent bacteria from being released through the output.
Our team has considered the practical and theoretical constraints of a kill switch capable of causing self-destruction if the integrity of the PRM becomes compromised. This killswitch would lower the likelihood that a viable cell could escape the PRM and propagate in the wild. While be believe in reducing the risk of release, cell or colonies do not appear to pose as huge a risk as the engineered system might.
Dual-Use Technology: In the most simple terms, our project takes a resource (Phosphorus in the form of orthophosphate) that is dispersed in the environment and collects it into a highly concentrated form. This allows it to be more useful, removes it from the environment, and increases the value of the concentrated product. However this can pose several obvious risks of abuse.
Calcium phosphate (commonly found in rock deposits), can be mixed with carbon and heated to produce White Phosphorus (also called yellow phosphorus or tetraphosphorus) which was used in smoke, tracer, illumination, and incendiary munitions. There has been debate on whether munitions of this type qualify as incendiary weapons, which are prohibited by Protocol III of the Convention on Certain Conventional Weapons (part of the well known Geneva Convention). While smoke munitions, the most common use of phosphorus, are given an exception for use, the danger still remains that the collected phosphate may be a target for those seeking to do harm.
Munitions aren’t the only dangerous use of this collected phosphorus. The collected phosphorus could be used for the result it was built to avoid. Accidental (or intentional) release of concentrated phosphorus could spur algae blooms in the region our system is in place to protect, as phosphorus is generally the limiting resource, this creates a vulnerability in our system as any puncture of the storage container could result in contamination of the body of water.
Our system was designed to collect phosphorus, however we acknowledge that this system can be applied to collect other chemicals or nutrients of interest. Our model could be used to collect herbicides, harmful chemicals, and could be used in consort with other iGEM projects such as the 2013 project of Nanjing or Dundee. As we expand this model to collect other resources the risks will have to be evaluated on a case-by-case basis and modifications to our system should be undertaken to mitigate as many risks as possible.
“Playing God”: As with most iGEM projects, we will surely be accused of “playing God” in our desire to implement a system and assuming we have foreseen and planned for all the outcomes. Obviously this isn’t true, there are serious concerns with a project of this scale, and therefore we propose several questions to further critical examination of our system. There is the concern that our system will work too well. That it could possibly strip the ecosystem of phosphorus. We apply phosphorus in the form of fertilizer because it can be the limiting nutrient for crop growth. However, if our system overperforms, we may strip enough from the aqueous environment that it may cause detrimental effects to the plants that rely on that environment.
Why our product?
Due to the wide variety of applications and our flexible three leveled business model our system is able to be implemented across a wide range of environments and levels of need. By capturing and concentrating a valuable compound out of the environment we at once provide an environmental service and monetary incentive for its widespread implementation. Our system will allow anyone to capture and monetize the resource around them, taking control of their own waste and environmental impact.
Future use and application
The core of our system was designed and engineered to capture, store, and extract a valuable compound from the environment. Besides an expansion in the number of locations and scale of implementation of our phosphorus system; the true benefit is the ability to easily change out the xerogel beads and embedded bacteria in order to capture other resources. We could easily see this being implemented with other projects such as Nanjing’s 2013 project which attempted to capture and breakdown pharmaceuticals in water. Or Dundee’s 2013 project which captured the toxins produced by algae to remediate the surrounding water. As humanity's needs expand, our system is ready to adapt, collecting and concentrating useful, harmful, or valuable compounds out of water systems. This will hopefully encourage and promote an economy surrounding reclaiming resources from waste streams.
Our phosphorus reclamation module (PRM) has the flexibility required to operate in the myriad of environments identified as major contributors of phosphorus contamination in water. Our business plan facilitates use of our product over the widest range of clients from single citizen users to whole cities, municipalities, and states. We engineered a way to reclaim a resource from what was otherwise considered a waste stream and concentrated it to increase its value and drive the economics of demand and supply. As the price of phosphorus increases it will become more and more feasible to deploy our PRMs in more places. We will be able to improve the environment and profit from the remediated phosphorus. The flexibility of our system even extends to other compounds allowing groups to cater the reclamation to their individual problem. The flexibility of our business plan and implementation will allow our product to be used by as many as possible, and in doing so, increases the good it can do.