In this article, we explore how sensor technologies can be used to monitor freshwater pollution. Continue reading to learn more.
Image Credit: Maksim Safaniuk/Shutterstock.com
Water covers more than 70% of the Earth and is essential to sustain life on Earth. Industrialization over the last century has resulted in a significant increase in the quantity of pollutants and negatively affects the water quality of freshwater reservoirs.
Reducing the concentration of pollutants in freshwater bodies is a priority of governments worldwide. Now, novel sensors are being developed to support accurate, real-time freshwater pollution monitoring.
How Does Freshwater Become Polluted?
While freshwater constitutes less than 3% of Earth's total water, our daily lives are predominantly connected to freshwater rather than saltwater. However, the diversity and increase in the size of the industrial sector, a growing population, and extensive agricultural industry have raised the pollutant concentration.
Studies conducted on freshwater sites have revealed the existence of over 100,000 different pollutants. Most of these pollutants are either released during industrial operations or used frequently in domestic households. Consequently, these chemicals can enter freshwater sources. Additionally, more than half of the total chemical production is harmful to the environment.
Freshwater Pollution Situation in Major Countries
The Environmental Protection Agency (EPA) conducted a study on the rivers and lakes present in the United States. The results revealed that almost 30% of the freshwater streams contain different pollutants.
The findings indicated that 55% of these water bodies were classified as impaired. The primary contributors to stream pollution were identified as bacteria, sediment, and nutrients.
On a global scale, several countries like China are also facing severe freshwater pollution. Estimates indicate that freshwater resources for 82% of the global population face significant threats, with developing countries experiencing a more critical situation compared to developed nations.
In 2020, an estimation revealed that a substantial 80% of municipal wastewater discharged into freshwater reservoirs remained untreated. Consequently, millions of tons of heavy metals and various pollutants were annually released into water bodies.
Pesticides and Heavy Metal Detection in Freshwater Bodies
Pesticides and heavy metals are highly dangerous for humans and aquatic organisms. The presence of these chemicals is a major cause of freshwater pollution. To determine the water quality by measuring different pollutants, researchers have been working on developing different types of sensors, such as chemical and biosensors.
In a recent study published in the Journal of Sensors, a review of the use of sensors for detecting pesticides and heavy metals has been presented.
The average Limit of Detection (LOD) for pesticide sensors assessed in the review was 72.53 ± 12.69 ng/ml. The review of the sensors revealed that around 32.8% of the sensors had LODS, having a value higher than 10 ng/ml. However, less than 50% of the sensors were able to detect pesticides whose concentrations were around 3 ng/ml.
For heavy metals detection, the study reported an average Limit of Detection (LOD) for the sensors at approximately 65.36 ± 47.51 ng/ml. Sensors focused on Ag exhibited the highest sensitivity, while those designed for detecting Fe and Cr demonstrated the lowest sensitivity.
These findings reveal that there is a dire need for the development of sensors with increased sensitivity to safeguard both human health and aquatic organisms.
Portable Optical Sensor for Detection of Micro-plastics
The presence of microplastics in freshwater bodies is a concern for environmentalists worldwide. Detecting these smaller plastics in real-world conditions and freshwater bodies proves challenging due to their varied shapes, size distribution, and additional properties like transparency, translucency, and surface roughness.
In an article published in Chemosphere, an exploration into the use of two distinct optical phenomena for detecting transparent and translucent microplastics of various shapes and sizes in freshwater is conducted. The analysis specifically involves transparent polyethylene terephthalate (PET) and translucent low-density polyethylene (LDPE).
A portable prototype optical sensor has been introduced, showcasing the ability to simultaneously measure both specular laser light reflection and transmission from micro-plastic particles. Integrating these dual detection modes makes it feasible to assess the type, size, and non-planarity of two distinct micro-plastic types.
The transparent PET exhibited a more distinct signal than the translucent LDPE across different sizes. In contrast, the translucent LDPE notably distorted the interference pattern, resulting in a speckle pattern.
In scenarios involving the two micro-plastics in water, the size of the floating translucent LDPE played a significant role in the magnitude of the specular reflection signal and the formation of the speckle pattern, similar to the case of a single micro-plastic. While the data obtained from the training set shows promise, further refinement of the prototype and analysis methods is necessary.
Case Study: Freshwater Monitoring by IISD
In 2020, the International Institute for Sustainable Development deployed sensors and AquaHive low latency telemetry platform for real-time freshwater monitoring. Hourly data from the sensor on Lake 227 was transmitted to the cloud and analyzed by experts, which helped them record the trends. The sensor was also sent an alert when any changes occurred in the water. As the setup was used to detect chlorophyll in water, it demonstrates how sensors can be used to monitor algal blooms in freshwater, and could be expanded to monitoring other major pollutants.
Future Trends
The domain of water quality and water pollution sensor technology is in constant progression, boosted by the growing demand for smart sensors that are more accurate, reliable, and versatile. Recent progress in microfabrication and nanotechnology holds the potential for smaller, more portable sensors, facilitating their deployment in remote or challenging locations.
The evolution of sensors capable of simultaneously measuring various parameters (such as pH, dissolved oxygen, turbidity, and nutrients) will aid in streamlining the data collection by eliminating the need for multiple sensors at a single monitoring site.
Furthermore, integrating machine learning and artificial intelligence algorithms into these sensors will empower them to analyze intricate datasets, identify patterns, and predict forthcoming water quality conditions. This advancement marks a crucial step toward enhanced efficiency of freshwater quality monitoring. As such, the future is focused on increased efficiency and sensitivity of these sensors.
References and Further Reading
Disen Sensor, (2023). Potential Future Advancements In Water Quality Sensor Technology. [Online] Available at: https://disen-sensor.com/potential-future-advancements-in-water-quality-sensor-technology/ [Accessed 2 December 2023].
Stanley, M., (2021). Watching the Water: The case for real-time freshwater monitoring. [Online] Available at: https://www.iisd.org/articles/insight/watching-water-case-real-time-freshwater-monitoring [Accessed 29 November 2023].
Asamoah, O. et. al. (2019). A prototype of a portable optical sensor for the detection of transparent and translucent microplastics in freshwater. Chemosphere, 231, pp. 161-167. Available at: https://doi.org/10.1016/j.chemosphere.2019.05.114
Xiang, H. et. al. (2020). Sensors applied for the detection of pesticides and heavy metals in freshwaters. Journal of sensors. 8503491, pp. 1-22. Available at: https://doi.org/10.1155/2020/8503491
U.S. Environment Program, (2023). Freshwater-Form of Pollution. [Online] Available at: https://www.unep.org/beatpollution/forms-pollution/freshwater [Accessed 28 November 2023].
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.