Inspiration
Eutrophication is a major problem in lakes and ponds worldwide, especially those in close proximity to farmland. They occur when a variety of factors, such as warm temperatures and nutrient loading from excess nitrogen and phosphorus, combine to create an environment that allows the excess growth of harmful red and green algae. In addition to creating dangerous toxins, this algae tends to collect at the surface of standing bodies of water, blocking sunlight from reaching the bottom where essential aquatic plants reside. Since they can't photosynthesize, this harshly lowers the oxygen content in the water, killing fish and other aquatic species. Not only does eutrophication tip the ecosystem out of balance, but it also makes water unsafe for human consumption.
Successful methods for controlling algal blooms have been developed, such as mechanical and chemical means. However, they are often time-consuming, expensive, or harmful to the environment. Ultrasound is a more recent method that is being explored for its possible applications in environmental engineering. Using a process called acoustic cavitation, ultrasonic waves generate bubbles in water that, when burst, rupture the vacuoles of algal cells and cause them to lose buoyancy and die, sinking to the bottom of the water. Not only is this environmentally friendly and has minimal-to-no impact on surrounding wildlife, but it effectively clears the algae off the surface of the water and can more quickly restore balance to the system. These ideas generated the basis for our project. We strive to create a cost-effective and minimal design that can kill algal cells with ultrasound sensors with the resources we have on hand.
What it does
It uses the principles of acoustic cavitation to rupture the vacuoles inside algae cells, which causes them to sink and die and clears up the water surface. This has proven to be the safest method at algal bloom removal, since the ultrasonic waves barely affect the surrounding aquatic life unlike chemical methods previously tested.
How we built it
We used an Arduino Uno to power two HC-SR04 ultrasonic sensors and a 9g Servo motor. The sensors are used to emit 40kHz sound waves, which is the most effective frequency at killing algae according to multiple studies. They are attached to a 3D-printed arm that is spun by the Servo motor. The Servo is attached to the lid of an espresso container, which is also used to store the components. Despite us not being able to 3D print a container, ironically using the espresso container makes the electronics system waterproof.
Challenges we ran into
During the initial design process, we had to keep changing the design due to time constraints. Initially we wanted our design to be able to move through the water based on patterns in the light, which are indicative of algae concentrations. However, our hardware isn't waterproof, so we couldn't create a hovercraft that could navigate beneath the surface. Another idea we had was to let the design move on its own based on patterns in turbidity using a water turbidity sensor, because areas of higher relative turbidity are also indicative of algal concentration. However, there are multiple factors that affect turbidity besides algal blooms, such as sediment, so readings of algal bloom concentration would be inaccurate. We also didn't have much materials to create an aesthetically-pleasing design, such as seamless waterproofing.
Accomplishments that we're proud of
We successfully tested our prototype's ability to make small ripples in dirt-covered water that simulates algal blooms in a still body of water. This shows how effective our design is at making excitations in water, which would in result kill off the algae. We also filmed ourselves with the prototype under the rain, highlighting that it's waterproof in rainy conditions.
What we learned
We learned how to successfully work under time and material constraints, as well as improvise with the materials we had at hand (such as using Scotch tape for waterproofing and using a metal coffee container). We learned more things about Arduino and circuitry as well. In addition, an important skill we gathered was adapting based off of changing conditions as working as a team.
What's next for U-HALK: Ultrasonic Harmful Algae Killer
We were thinking of using a rack and pinion system to move the arms out to larger radii, as well as implementing a camera and machine learning to identify which algal bloom spots are alive and dead to tell the microcontroller if it should extend its arms out or not to kill more algae.
Log in or sign up for Devpost to join the conversation.