The BioWheel


By Jaeho Kim, THINK 2013 Winner

Abstract

Eutrophication is nature's response to occasional spikes in nutrient runoff levels in bodies of water; however, the intensity and frequency of eutrophication has dramatically increased in the last 50 years due to the implementation of synthetic fertilizers to meet the demands of the 7 billion people living on Earth. Eutrophication caused by fertilizer runoff is a problem that continues to build and spring up in various places around the world: from the Gulf of Mexico to the Mediterranean, eutrophication has impacted the shrimp and other fishery industries worldwide. Currently, no clear and proactive solution has been proposed to address this looming issue. I have devised an improved and scalable version of Algal Turf Scrubbers (ATS), which is currently used on algae farms in order to harvest the algae as fuel. The BioWheel is a space-efficient and cost-effective algal scrubber that rotates on a water wheel, simultaneously harvesting algae while generating electricity. My BioWheel prototype was an overall success, reducing pollution by decreasing the nitrate and phosphate levels in seawater significantly concentrated into the growth of the algae. During 3 weeks of testing, these pollution levels dropped from 4 ppm of nitrate to 0 ppm and from 2 ppm of phosphate to nearly 0 ppm.


Problem

There has been an increasing amount of awareness of the dangers regarding the degradation of our water quality and marine ecosystems. Recent efforts have been made to cap carbon emissions and limit chlorofluorocarbons in order to reduce carbon dioxide in our atmosphere. These responses were made to the immediate danger posed to our everyday lives: the hole in the ozone layer and eventual global warming were more pressing than any other environmental problem. However, many have overlooked the damage and risks associated with the environmental disasters of ocean bleaching, pollution, and more recently, eutrophication. Eutrophication refers to the process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. It is a result of human activity when fertilizer runoff from agricultural farms and industrial waste from factories contaminate the oceans, rivers, and lakes. As a consequence, all bodies of water next to developing civilizations are at risk. Eutrophication has spread in many parts of the globe and now affects major bodies of water such as the Mediterranean and the Gulf of Mexico.

When eutrophication threatens the aquatic ecosystem, the excess nitrogen and other pollutants become nutrients for algae, which grow to create an algal bloom. The algae in the water die off from overcompetition, and the decay of the dead algal matter (microbial consumption of dead algae) leads to hypoxic zones (defined by the lack of oxygen in the water) and eventually dead zones. Dead zones—exactly what they sound like, patches of water devoid of life—lead to economic failure of neighboring economies that depend on the sea for their food. Louisiana and neighboring states are harmed by this phenomenon. However, this is more of a problem in developing countries such as India, China, or many South American and African countries. Countries such as India and Niger have a high population growth rate, increasing demand for intensive agricultural production. This leads to excessive use of chemical fertilizers that runoff into the rivers and oceans. The most effective way to stop eutrophication would be to stop using fertilizers altogether. But this is impractical, so developing countries put few restrictions on fertilizer use. Eutrophication from human activities is a growing problem that needs to be addressed: it is not in governments' best interests to limit the growth and prosperity of peoples in developing countries, but at the same time, it is harmful in the long term to allow eutrophication destroy our oceans and water supply as well.


Solution

A practical solution to eutrophication would be an invention that both reduces eutrophication and also allows continued development. My solution is an invention that will implement nature's way of removing waterborne pollutants: algae. Algae have existed almost as long as the oceans have and use sunlight and chemical nutrients such as nitrogen, potassium and phosphorus in order to grow. These chemicals are found in excess supply as a result of fertilizer pollution. Microalgae, especially diatoms, cyanobacteria, and dinoflagellates, are very effective at removing pollutants from the water as part of their metabolism and growth.

My solution is an improvement upon the Algal Turf Scrubbers that are currently used to harvest algae as a source of biofuel, but are not currently used to purify water. This new invention can harness the power of algae to filter the water and generate both biofuel and hydroelectric power at the same time.

I call it the BioWheel, a water wheel which hosts microalgae farms on its modular paddles. The use of natural microalgae has already been implemented in the aquarium hobby industry in the form of algae scrubbers, and as massive Algal Turf Scrubbers near industrial plants. My BioWheel improves on these designs to create three benefits: convenience, environmental impact, and energy production.

Convenience: The conventional algae turf scrubbers (ATS) on the market today have several problems of practicality. First, conventional ATS's are designed for huge bodies of water which make them expensive and too large in scale to implement for different uses. My BioWheel requires a fraction of the cost, and because of its simplicity of design, allows customizable scale by adapting to bodies of water of various size. Second, conventional ATS's make it difficult to remove algae; for example, one commercially available ATS requires an algae vacuum harvester, a marine motor vehicle the size of a van. However, my BioWheel allows easy removal of algae with easy sliding pads which does not require the use of a one-ton waterborne vehicle. The removable sliding algae pads can be taken right out of the water by hand for convenient harvest back at a plant or office. The BioWheel's convenience will make it the most practical and inexpensive algal scrubber in the market today.

Environmental Impact: The BioWheel reduces the human impact on the environment in many ways. First, the BioWheel's algae farms reduce pollution through algal absorption of excess nitrogen and phosphorous from the water, which cleans the water supply. As an incidental benefit, mass growth of algae also reduces ocean acidification caused by taking up excess carbon dioxide which entered the water from excess levels in the atmosphere. Second, the BioWheel can prevent algal blooms. The algae are held in place by a system of adhesive algae pads, microfibers of 1 mm thickness interlocking with each other similar to a Velcro design. These adhesive pads collect free-floating algae. Eventually this pad develops into a thick coat of periphytons—assortment of algae and cyanobacteria that attach onto surfaces—which will allow the BioWheel to further collect almost all algae. Once the pads fill up with algae, simply remove the pads and harvest the algae to prevent a large buildup that leads to a destructive algal bloom. Third, the rotation of the BioWheel insures that aquatic organisms such as fish will not be trapped and killed like they are in the static filter design of conventional ATS systems.

Energy Creation: The rotation of the BioWheel produces benefits that non-rotating conventional Algal Turf Scrubbers do not. First, the rotation of the water wheel aerates the algae evenly, providing for maximum growth and nutrient intake because microalgae demands even distribution of sunlight and oxygen among different cells. These large masses of algae, especially the lipid-rich species of Botryococcus braunii, Dunaliella, and Chlorella, will be harvested to make biofuel, a usable form of energy. Second, the rotation of the BioWheel provides an incidental benefit: hydroelectric power. The BioWheel, while aerating the algae farms, will be able to generate electricity through connection to a generator. This makes it very beneficial for the private or governmental installer as it can be utilized to either power a nearby factory or to feed energy into the local grid.


Materials and Methods

The actual design of the BioWheel was somewhat altered from the original design. The original design consisted of six paddles, but it was modified for the experiment as the water flow was too inefficient to move a wheel with just six paddles. Moreover, the original design demanded a constant outflow of electricity into a battery to generate electricity, but given the unexpected weight of the wheel and the limit of the powerheads, the generator was installed for just a day. However, this will not be a problem in real-life applications as the real wave currents of the ocean are more than sufficient to power the wheel. The experiment also had to be slightly altered due to the unavailability of microalgae. The initial plan was to raise the microalgae myself, but the lack of variety and slowness of growth led me to purchase macroalgae very similar to microalgae in growth and nutrient uptake, called Chaetomorpha. Otherwise, the experiment was conducted in a fashion very similar to the one planned, although at a slightly faster speed because of the reduction of the initial nitrate and phosphate concentrations (to match the natural seawater levels more accurately).

Estimated budget:

ItemAmountCost
Water wheel (will be made of acrylic panes)1$200
Algae$0
Microfiber mesh (adhesive for algae population)$50
Acrylic sliding plates (removable algae storage)8$50
100 gallon aquarium (to simulate an ocean or river) 1$1100
Powerheads (simulate currents)2$160
Water heater (maintain conditions for algae survival)1$100
Potassium nitrate (simulated pollutant)3 lbs$25
Trisodium phosphate (simulated pollutant)1.5 lbs$25
Water test kits (pollution levels)4$140
Crank generator (hydroelectric power)1$80
Metal rod (connecting generator to wheel)1$50
Total:$1980

Actual budget:

VendorItemCost
SoCal Tropical Fish OutletViaAqua titanium heater$59.40
Industrial Plastic Supplyacrylic$190.19
Bulk Reef Supplyphosphate colorimeter, pH and NO3 test kits, refractometer$157.86
Amazing Aquariums and Reefs40 × 30 × 20 aquarium and powerhead$1139.99
PetSmartMaxi-Jet Powerhead 1200$46.43
Reef CleanersChaetomorpha$48.51
Lowe's4 × 32 gallon trash cans$72.25
Joannmesh$4.30
Amazon.compotassium nitrate$11.00
Amazon.commotor (generator)$39.90
Amazon.comacrylic glue$46.52
Bearings Directbearings13.58
Total:$1829.93

The budget was closely followed to prevent overspending. The water wheel and the sliding plates were all to be made with acrylic under $250, and I managed to buy custom cut acrylic at the industrial plastic supply for $190. The aquarium itself happened to be under the $1100 I estimated for the budget. The water testing kits were slightly pricier than the budget entailed, but the differences in cost were covered by the extra leftover. I ended up not requiring a metal rod and a crank generator, instead opting for an acrylic rod (included in the purchase of acrylic from the Industrial Plastic Supply warehouse) and a motor from Amazon to replace the generator. Overall, I was under my estimated budget, even though I added in algae and bearings to the cost.


Results

The results yielded a satisfactory trend for the BioWheel. There were three crucial factors in the experiment that had to happen: growth in algae, reduction of nutrients, and the generation of power. All three were accomplished to a great extent, although the power generation was only done for a day because the powerheads were too weak to produce a continuous output of power. The microalgae had to be switched out for a more convenient solution, macroalgae. Despite the fact that the constantly aerated environment of the BioWheel is not suitable for macroalgae (unlike microalgae, they do not grow in dense colonies to minimize water loss), the algae grew well. There was an average of 239.1% in growth. The first trial had significantly higher growth because before the second trial, I built a translucent canopy on top of the tank to prevent leaves and bugs from falling in. This is promising for real applications with microalgae and real ocean water. The BioWheel also excelled at removing excess nutrients. It was able to decrease the nitrate level from 4 ppm (0.2 ppm is the normal parameter in natural seawater) to 0 ppm in 2 weeks, while the phosphate level decreased from 2.5 ppm (< 0.03 ppm is the normal parameter in natural seawater) to almost 0 ppm in 2 weeks. The BioWheel was also able to generate electricity for the day (continuous output of 1.1 V) and power an LED bulb at times. This would be more practical in real-life applications with the stronger currents. Through this experiment I learned the practicality and the power of this device. In a larger scale, I hope to implement the BioWheel as a viable, eco-friendly solution that prevents algae blooms and eutrophication.


Acknowledgments

I thank the THINK team for all of the effort they put into planning and mentorship. I also thank the generous sponsors, Thomson Reuters and Chevron. Their funding made the project possible. Without them, I would not have been able to make the trip to MIT, which completely changed my outlook on this project.