Water is a necessity to sustain life. Yet, the unprecedented effects of climate change have triggered a hidden threat that could potentially devastate our aquatic environment — eutrophication. This hazard comes without notice, silently transforming pristine water bodies into lifeless, deoxygenated dead zones. As just one example of countless others, though certainly one closer to our homes, local citizens near Nakdong River, South Korea, are suffering from the hideous odor and death of aquatic creatures.
Fig.1. “Duration of Algal Bloom in Nakdong River has increased 2.5 times in 10 years.” Kang, Chan-soo, JoongAng Ilbo, 24 July 2023, www.joongang.co.kr/article/25179593#home. Accessed 6 Oct. 2023.
In fact, as shown in Fig. 1, the average duration of algal bloom in 4 points of the Nakdong River increased 2.5 times from 61 days in 2013 to 154 days in 2022.
Fig.2. The area affected by algal bloom each year (Source: Water Environment Information System of The Ministry of Environment of Republic of Korea. https://www.water.or.kr/?gnbIndex=5 )
The increased lasting time is not the only issue, however; the area affected by Algal Bloom is on the rise each year, with 1022 km2 affected in 2010 to 2083 km2 in 2022. The unprecedented effects of climate change further fueled this crisis, with the number of warnings increasing 2.9 times from 266 in 2013 to 788 in 2022.
Fig.3. Water Environment Information System of The Ministry of Environment of Republic of Korea, 2022년 조류(녹조)발생과 대응 연차보고서)
Eutrophication occurs when nutrients accumulate in excess, prompting the growth of algae to detrimental levels. This abnormally high concentration is noteworthy because it undermines the body of water’s value as a source of drinking water. The Nakdong River is a primary water source for Busan and Daegu, which are major cities in Korea, with Busan being the second most populous city in South Korea, and Daegu the fourth. Combined together, they are home to about 6 million people. As featured in Fig. 3 and 4, eutrophication causes an algae bloom at the reservoirs that those people rely on for drinking water. Yet, such issues are not exclusive to drinking water; the water affected by eutrophication is rich in nitrate and phosphate. This makes it difficult to secure water for all domestic, agricultural, and industrial purposes.
Fig.4. Soyang River Algal Bloom (metropolitan drinking water source)
Fig.5. Daecheong Lake Algal Bloom (Chungcheong Province drinking water source)
Upon realizing the devastating impact of eutrophication, our team, Seoul-Korea, visited the Nakdong River and Daecheong Lake, the longest river and third-largest lake in the nation, respectively. We first visited the Ham-an Dam at Nakdong River, where the manager informed us about the status quo of the eutrophication crisis in Korea. There, the manager commented on the lack of technology in both algae monitoring and nitrate removal.. Then, our team headed to Upo Wetlands near the river, where our team observed densely packed green algae covering a significant portion of the water. Our first-hand experience visiting affected areas made the scope of the issue of eutrophication tangible for our team members.
Alongside the serious public health concerns of algae-covered waters, damage to the historical, cultural, and economic significance of the river presents itself as a major issue. As a source of livelihood, trade, and tourism, the Nakdong River is important for local communities. In a certain sense, a clean and ecologically safe river can be considered a service; it generates economic growth from tourism, and the scenery (alongside clean water use) improves quality of life for both surrounding and visiting communities.
To understand the general public’s awareness of this crisis, our team decided to conduct public surveys. We set out our booth in public areas, asking a total of 12 questions to approximately 100 participants. After participants completed the verbal questionnaire, our team members reinforced the severity of eutrophication in the country and explained the importance of preventing algal blooms in daily lives. The general practices announced by the Ministry of Environment involve using just an adequate amount of detergent when doing laundry, avoiding car washing near bodies of water, and disposing of food waste only in designated areas while camping outside.
The questions asked of the participants were posed to assess the scope and depth of public awareness surrounding algal blooms, eutrophication, and their current impact.
Fig.6. Seoul-Korea conducting a public survey
Fig.7. Responses to the question ‘Have you heard of the extreme algal bloom that has happened in the rivers and lakes of South Korea?’
Fig.8. Responses to the question ‘Do you think the water in the place you live is clean?’
Fig.9. Responses to the question ‘How serious do you think the problem of algal bloom is?’
Fig.10. Responses to the question ‘Have you heard of the Algae Warning System?’
When asked whether they had heard of the eutrophication crisis in Korea, a vast majority of participants (76.4%) responded that they had. When subsequently asked whether they deemed the water in their area to be clean, however, they responded positively. These responses seem to indicate that while eutrophication is a popular issue, likely due to large coverage in mass media, their own perception of water safety was largely positive and distant from the issue of eutrophication.
Fig. 9 clearly illustrates this disparity. The graph features the participants’ damage perception of the nation’s aquatic ecosystem before and after showing images of algal blooms, categorizing their responses into four states, as shown. Initially, a low 17.1% answered “extremely serious,” with the most prevalent choice being “Serious” (48.8%). In total, 65.9% attributed a degree of seriousness to the issue of eutrophication and algal bloom. Yet, this percentage soared after introducing the participants to the actual image of the river, packed with green algae to a staggering 85.3%, demonstrating the limitation of public awareness of eutrophication and its devastating implications compared to how the issue is portrayed. This result underscores the role of media and public campaigns in raising awareness by using more realistic imagery.
Admittedly, there are several factors, including the geographical distance between the major rivers and the population, that could adversely affect public perception of the actual scope of the phenomenon. Moreover, more than half of the participants were unaware of the algae warning system in Korea. From the public survey, we found the need to raise awareness of this hazard, which often comes without notice. It is time to make a collective effort against eutrophication before it confiscates the beauty of water.
Recognizing the need for expert opinion on the existing efforts to mitigate the effects of algal bloom, we obtained an interview with Professor Yoon Kyung Cha of University of Seoul, whose research field is water quality management. She is interested in water quality and marine ecosystems. She also talked about her research, which aims to develop a system that can provide a quantitative basis required for making policy decisions related to water quality management.
During our meeting, we discussed the current water quality monitoring system, the types of significant pollutants, and how the occurrence of pollution differs with streams and lakes.
Professor Cha offered us various documents that outlined the policy and implementation of water quality measurement in Korea. Across the four main rivers of South Korea, 2,317 measurement stations conduct measurements of several indicators to create data index networks. After being collated, the measurement data is uploaded to the public domain in separate filings such as the sediment measurement or the radioactive material report. An imperfection of this system, Professor Cha noted, was the fact that the various networks mostly focused on point-sources of pollution, rather than non-point sources.
However, among them there are only 36 places that measure non-point sources of pollution. She noted that current monitoring systems were largely focused on point sources and highlighted the need for better monitoring methods on non-point sources.
Non-point sources of pollution, contrary to their point-source counterparts, encompasses all sources that are spread across a wide region and are not attributable to a single geographical source: agricultural land, mountain ranges, and even highway roads thus falling within its scope. A report filed by the National Assembly Report Service on the current efforts on water quality improvement attributed roughly 70% of all pollution onto non-point sources. Despite their significance, only 36 stations of the 2,317 stations measure non-point sources.
A difficulty in measuring such pollution arises from the fact that the nutrient run-off from these sources are a composition of several factors such as fertilizer use, exhaust from driving, household waste disposal, and more. Professor Cha highlighted the need for a more comprehensive monitoring method on non-point sources.
In addition to the current policy and implementation of water monitoring, Professor Cha offered insight into measurement methods, such as the reason behind why Chlorophyll A, a pigment found in most phytoplankton, is used as an indicator of cyanobacteria.
Also, we were able to know that although streams contain nutrients that might cause eutrophication, since the water always flows into another area, it is hard to notice if the level of nutrients involved in the body of water is getting higher.
After interviewing Professor Cha, our team pondered if there is a way to effectively monitor non-point sources of pollution. We thought that since the non-point sources of pollutants are spreaded out through a wide area, it would be hard to monitor them by using the same equipment that are used to measure the amounts of other pollutants. Then we came up with the idea of making a sensor that has an affordable price that can detect nitrate, which is one of the key factors that causes algal bloom. We assumed that if the sensor’s price was affordable, it will be possible to place many sensors in a large area, and form a monitoring system that gathers information from each sensor and keep track of the rate of pollution.
Fig.11. Examples of point and non-point sources
This is not to say that efforts are not being made to address eutrophication; immense efforts have been made in creating legislation and implementing active preventive and response measures. The current method that is used to deal with algal bloom is mostly focused on eliminating the algae that has occurred already, which is an arduous, costly task. In addition, the method is ineffective, as algal blooms can easily reoccur given adequate conditions. Therefore, the most crucial part of damage-controlling algal blooms is to prevent them fundamentally by creating an economical, accessible dissolved ion sensor.
To learn more about water-related sensors and to potentially promote our idea, our team decided to exhibit our project at Eco Fair Korea 2023. Sponsored by the Ministry of Environment, the annual exhibition opened for three days, during which 138 companies promoted their environmental initiatives and related products/services. While showcasing our own project, we actively met with other exhibitionists and managed to interview two companies specializing in sensor technology.
The first company we interviewed was Toray. Toray is a company that manufactures Total Organic Carbon (TOC) and Total Nitrate (TN) sensors. In particular, the detection of Nitrate in their sensor involves emitting light at wavelengths absorbed exclusively by the substance into the water, measuring the light that passes through the water, and calculating the absorbance. This complex and delicate process came at a pricey cost of over 40 million KRW (about $30,000) and a large size. As expected, due to the high cost, their products were only deployed in designated places such as factory wastewater treatment facilities for point source pollution control.
Another company that we interviewed was YuminST, a company that manufactures the world's first film-type chemical solution detection sensor utilizing an electronic printed circuit. Their products can detect entire categories of substances with similar chemical properties (e.g., acid). While the film-type sensor is easy to use and convenient, it costs 173,000 KRW (around $130) per meter. Again, due to its high price, YuminST’s customer base is composed of large corporations like Nexon and Samsung. Gaming companies like Nexon use the sensor for cooling water protection in server computers, while electronics companies like Samsung use it for preserving Ultra Pure Water (UPW), which is crucial for the production of semiconductors. None of these companies used the aforementioned sensors for detecting non-point source pollution.
Fig.12. Interview with Toray. Toray is a company that develops TN sensor technology. Their sensor is as large as the size of our teammate.
Fig.13. Interview with YuminST YuminST is a company that develops the world's first film-type chemical solution detection sensor.
Taking away an emphasis on cost and size, our team adopted the Arduino framework. Such as ultrasonic proximity sensors, an open-source sensor compatible with Arduino could meet our goals if it could be produced as an economical and small sensor. The open-source and educational use of Arduino would also mean that our sensor could be easily used by a variety of users, raising awareness of eutrophication-related issues.
Upon searching, however, our team could not find a pre-existing sensor compatible and comparable to Arduino sensors. Specifically, our team could not find an aqueous ion sensor meant for use in underwater environments. We consulted with the companies from above on the reasons why a sensor meant for open-source use did not exist.
A major factor limiting the development and commercial success of such a sensor was the generality associated with open-source technologies. The exhibitionist from YuminST explained that they thought Arduino was too mainstream to be used for accurate sensors. They pointed out that Arduino was primarily designed for educational purposes, and, therefore, it is specialized for versatility to enable general use. The current sensor market is quite restricted and B2B-oriented, meaning the sensors are not sold directly to the end-users. On a positive note, however, YuminST emphasized that demand existed for sensors that could be customized to specific industrial processes. Therefore, if Arduino technology can be incorporated into creating purpose-specific solutions, it may attract the attention of the current market.
Another limiting factor is the insufficient computing power available on Arduino boards. During an interview with our team, Torray, a company that manufactures Total Organic Carbon (TOC) and Total Nitrate (TN) sensors, explained that they don't use them because calculating the absorbance of TN involves very complex functions and calculations, which exceed the computational capabilities of hobbyist development boards. Torray further commented on the lack of robustness in Arduino development boards as they are primarily meant as a cheap, user-friendly instrument. Under challenging conditions, such as potentially wet environments, the use of a delicate development board could be problematic. They pointed out the high failure rate for water-related sensors due to the unavoidable corrosion and weathering of submerged electronics.
In order to overcome this major offset against the sensor industry, we decided to explore a new approach integrating synthetic biology into an Arduino framework. Entitled “Montitro,” our product will provide an accessible dissolved ion sensor addressing the weaknesses the original market possessed.
A significant boundary in global water quality monitoring systems is the costly initial setup price. Thus, we decided to incorporate synthetic biology technology with Arduino to amplify the sensor’s utility and accessibility. By using a modified E. coli bacteria that reacts sensitively against dissolved nitrates, Monitro converts 3 different color signals from indicators into data signals. Since this process does not require complex calculations, we selected the Arduino color sensor over high-end processors. The benefits of the low price boundary of Monitro will contribute to detecting non-point pollution sources, as more sensors can be installed in a denser net compared to other sensors under the same budget.
Moreover, the high failure rate for water-related sensors is oftentimes due to the electronic’s direct contact with water, causing corrosion and weathering. Hence, we aim to effectively utilize Arduino’s communicative capability to mitigate this issue. In Monitro, only the biosensor will be submerged underwater; the role of Arduino is simply to record the chromatin data from the bioindicator and send it to external applications to calculate the concentration of ions more accurately. This novel methodology will remove the possibility of water-related damage in the first place.
In addition to damage, the presence of impurities in the water diminishes the accuracy of sensors. Again, we aim to solve this problem using synthetic biology. Unlike traditional ion detection methods, a biosensor responds solely to certain ions like nitrates. Hence, Monitro will allow data collection on ion levels directly from the samples without having to test under lab conditions again. The collected data will be sent to mobile devices via wifi from the Arduino systems to be calculated, which ultimately allows both measurement and analysis to be done simultaneously with less financial and technical burdens.
In attempts to uncover the demand for our Monitro in different industries, we met Mr. Jaejun Park, the CEO of Hypergreen, a company specializing in the development and manufacturing of smart farming technology. Hypergreen envisions a world where smart farms are integrated into our daily lives in the form of furniture and interior design.
Fig.14. Interview with Mr.Park, the CEO of Hypergreen
According to Mr.Park, the nitrate sensor could be highly effective in boosting plant growth. A common issue that people who grow plants in their houses face is controlling the amount of nutrients to provide. Either an excessive amount or a limited amount will severely impact the growth. Dongmin Choi, a member of Seoul-Korea, grows various types of plants at home. As demonstrated in his blog, he says that it is difficult to measure the precise amount of fertilizer dissolved in the water, and because different plants have different sensitivities to excess nutrients, the only option available to him is to go through a trial & error process, figuring out how many drops of nutrients are needed. However, with the nitrate sensor, the steps above are unnecessary.
Fig.15. Dongmin Choi’s Blog
Mr.Park suggested Monitro could potentially serve as a remedy to this problem, alarming the owner when the nitrate is too concentrated. Mr.Park added that as long as the sensor is affordable and functioning properly, it could be popular among companies specializing in algae control and smart farming machinery production.
Our advantages are as thus:
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A novel approach to creating an Arduino-compatible biosensor. While conventional ion sensors with color indicators can only display the presence of nitrate using two colors, Monitro converts the 3 different color signals to present the degree of concentration, with each color representing a certain range.
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Outstanding sensitivity and accuracy. Monitro can detect ions or molecules at micromoles, a millionth of a mole, which demonstrates its sensitivity and accuracy compared to the competitor model, which measures at most 0.02 mg/L NO3-N.
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Responsiveness to a particular ion. Monitro is designed to be only responsive to nitrate, preventing ambiguous results from mixed compounds of various dissolved ions within the body of water.
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Small size. The practical size enables its use as a module by integrating it into other machines.
In future iterations, we see the need to improve on:
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Reusability. Monitro is designed for single-use cases, so it cannot provide continuous monitoring of concentration.
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Instant Readings. Monitro takes at least 3 hours to measure and compile the concentration fully, so this inability might be disadvantageous, especially when rapid response is necessary.
