Team:UMaryland/Implementation
Implementation
Phosphorus Sequestration Units & Bioreactor
Phosphorus run-off is an ubiquitous problem affecting many bodies of water across the world. It also varies in size and scale; for example, one family may overuse fertilizer which runs off into a small pond in their backyard, or a massive industrial-scale farm may be producing phosphorus pollutants which run off into the Atlantic Ocean.
What is unique about our project is that the beads and bioreactor we have created are scalable to fit any need. Additionally, through our human practices work, we spoke to Alicia Mulkey, who serves as Secretary of the Maryland State Soil Conservation Committee. She mentioned that small farmers did not want large form-factor bioreactors which took up their valuable land that they could instead be using for crops. As such, our proposed implementation includes having the reactor inflows and outflows underground, to minimize the area that is taken up by the system.
In terms of implementation, we would manufacture bioreactors of various sizes to fit different recycling needs. Then, the bioreactor and beads could be ordered and installed in the body of water which the customer wishes to filter water in. Then, over time the customer can replace the beads, but the bioreactor should last for a very long time. Large projects would be implemented with the help of a state, federal, or local government and identifying sites which could use the most uptake of phosphorus as well as where phosphorus should be released. Then, larger or custom-order bioreactors would be made to house the beads, and the devices would be installed at the preselected locations.
Due to the modular nature of the beads, we can implement this project in a variety of ways. Even excluding the bioreactor, the beads themselves could be manufactured at scale and sold to other companies and interested parties which have their own ideas of how to use them.
Phosphorus Detection Methods
The initial plan when conceiving this project was to develop a biosensor which would be partnered with the phosphorus cleaning bioreactor to provide readings of phosphorus in the water and ensure the device was removing phosphorus from the water effectively. However, after meeting with experts in agricultural development at the Maryland Department of Agriculture as well as farmers who are the primary stakeholders in product deployment, we found that a biosensor would not be a cost-effective solution compared to readily available phosphorus monitoring solutions. This report will cover the existing phosphorus sensing methods available on the market and explore their advantages and disadvantages as well as explain how our biosensor design would function if it were to be deployed.
Modern farmers have a great variety of methods available to them to check the levels of phosphorus their farms release into the environment. Of the phosphorus sensing devices that exist there are two primary soil sensors and runoff sensors. Soil sensors function by being placed directly into the soil of farmland and monitoring phosphorus levels in their immediate surroundings. Due to their nature many individual sensors must be used to build a complete picture of phosphorus levels across a tract of farmland. There are a number of benefits to soil-based phosphorus sensors including their ability to detect phosphorus presence as it is in the soil which allows for both surface level runoff into streams and groundwater runoff into subterranean aquifers to be accounted for. In addition, soil-based phosphorus sensors are often paired with other sensors in a single deployable device which offers additional incentive for farmers as the information provided to them can be used to optimize fertilizer use and improve crop yield. An example of a multifunction sensor on the market today is the Teralytic company which produces wireless sensors which connect to a central application to help farmers optimize crop yields and minimize runoff pollution.
Despite these advantages, there are some significant drawbacks to the usage of soil-based phosphorus sensors. Due to the fact that they must be placed throughout fields in large numbers the sensors can be difficult to maintain and expensive to install. This is especially true for certain crops which require a significantly higher density of sensors to benefit from their use. A further drawback to soil-based sensors is that they cannot be used to detect runoff from livestock.
As an alternative to soil-based phosphorus sensors farmers also have the option of using aquatic sensors which detect phosphorus in the runoff water that comes off the farms. Unlike soil sensors which must be placed around the entire farmland, water sensors can be placed in one or two strategic areas and detect the phosphorus that is leaving the farm through surface water runoff into waterways. The most common way water sensors are deployed is through the creation of a monitoring station into which runoff from the farm is pumped and analyzed for phosphorus content among other contaminants. This method is effective for determining the amount of phosphorus in the surface runoff from the farm overall and is much more simple and less expensive to maintain than soil-based sensor systems. These monitoring stations can either be constructed out of a combination of commercially available sensors or purchased as an independent system which is made for the express purpose of monitoring runoff.
Due to the fact that these sensors test the runoff water and not the presence of pollutants in the soil they can be used to monitor runoff from livestock fields which is something soil based phosphorus sensors struggle with. The lower cost and increased flexibility comes at the price of being unable to determine specific details such as which locations of the farm are causing the highest levels of phosphorus pollution with the same resolution as soil-based sensors. In addition these sensors cannot be practically used to measure the amount of phosphorus escaping into the earth through underground runoff into the groundwater.
As can be seen methods of testing phosphorus in farm runoff already exist and are often linked with other essential measurement devices which precludes the need for a standalone biosensor. Despite this, if cost effective, in the future it may be feasible to include a built in phosphorus biosensor in the design of our bioreactor. Such a biosensor would function through the use of a phosphorus sensitive genetic on-switch which allows the expression of green fluorescent protein (GFP) in the presence of high levels of phosphates. This would be achieved through the use of a phosphate sensitive protein system involving the genes PhosA and PhosB in which PhosA acts as a repressor to the paired gene when it interacts with complexes formed by PhosB and phosphate. In the inverter design this phosphate sensitive system would be paired with a repressor based transcription factor such as LacI/Plac or TetR/Ptet such that the presence of phosphates inhibits the LacI which allows GFP to be produced and a fluorescent signal to be seen. This system as previously stated would be most effective if actively paired with the bioreactor that removes phosphates from the water as it could be used as a measure of the function of the bioreactor and alert users to when the bioreactor may be failing.
The proposed mechanism for a phosphate sensing biosensor which could be paired with the phosphate sequestering bioreactor. Based on the work by Hong Kong University of Science Technology, our team mentor, Yan, collaborated with us to develop a potential mechanism for this phosphate biosensor.