Understanding Ultrasound
Ultrasound consists of sound waves with frequencies above the human hearing range, approximately 20 kHz. Over the past several decades, industries have adopted ultrasound technology widely because of its unique properties. For instance, ultrasound waves reflect off surfaces, enabling applications like sonar, medical imaging (such as echography), cleaning microscopic contaminants, and innovative water treatment solutions that improve water quality and control algae growth in reservoirs and other water bodies.
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Applications in Modern Industry – Industries today rely on ultrasound for various applications. In sonochemistry, it accelerates chemical reactions, aids emulsification, and facilitates compound extraction. Ultrasound also disrupts biological cells, removes trapped gases, and breaks down contaminants in liquids, ensuring cleaner, safer outcomes. In healthcare, ultrasound produces detailed non-invasive images, such as those of unborn babies or certain conditions like cancer, making it indispensable for diagnostics.
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Effects of ultrasound on water – When applied in water treatment, ultrasound’s effects depend on factors like wave power, frequency, and shape. One key phenomenon it triggers is cavitation, where bubbles form, grow, and collapse violently in a liquid. This process generates localized high heat (up to 5000 Kelvin) and extreme pressure (~1000 atm), commonly used to sterilize laboratory and hospital equipment.
Not all applications of ultrasound rely on cavitation. The LG Sonic system, for example, employs specific ultrasonic sound waves to control algae and certain bacteria without causing cavitation. Instead, it uses mechanical forces, such as resonant waves and sound pressure, to suppress algae growth and prevent biofilm formation.
How it works ?
The system uses specialized transducers to emit ultrasonic frequencies precisely calibrated to target algae at a cellular level. This eco-friendly, cost-effective method disrupts algal growth cycles, causing the algae to weaken, sink, and eventually die. As a result, water clarity and overall health significantly improve, all without relying on harmful chemicals
Effects of ultrasound on aquatic life
The safety and environmental compatibility of the system make it an excellent solution for water treatment, with minimal or even beneficial impacts on aquatic organisms.
- Amphibians and Their Larvae– Research shows that ultrasonic algae control fosters a healthier environment for amphibians. Reduced algae levels decrease competition for nutrients, promoting the growth of larvae and ova populations.
- Zooplankton and Water Insects– A study in Slovenia found no harmful effects of ultrasound on zooplankton and aquatic insects at tested frequencies. These organisms thrive when algae are controlled, as oxygen depletion is reduced, and the food supply improves.
- Fish and Fish Larvae– Fish are generally unaffected by ultrasound technology. While species like American shad can detect high-frequency sounds up to 180 kHz, the frequencies used by LG Sonic are outside this range. Studies on fish, including rainbow trout, show no mortality or tissue damage from ultrasonic exposure. Although hearing abilities vary among fish—such as sardines and anchovies detecting sounds up to 4 kHz—LG Sonic’s frequencies have proven safe for fish while enhancing water quality.
It is important to note that hearing abilities vary among fish species. For example, species like sardines and anchovies detect sounds only up to 4 kHz, which is far below the ultrasonic frequencies. Overall, the technology has been proven to be harmless to fish populations while improving water quality.
- Prawns and Gas Bubbles – In prawn farms, ultrasound prevents the formation of harmful gas bubbles that can cause decompression sickness (DCS). By collapsing gas micronuclei, ultrasound improves the overall health of prawns without affecting dissolved oxygen levels.
The effect of ultrasound on algae
Algae are a diverse group of plant-like organisms found in various habitats. They are photoautotrophic, containing chlorophyll, and have simple reproductive structures without true roots, stems, or leaves. Algae range from unicellular organisms to complex multicellular forms, sometimes resembling vascular plants.
These organisms, considered contaminants, are present in vegetation, air, soil, and water. Their microscopic spores are continuously introduced into water bodies by wind, rain, and dust storms. Algae grow rapidly in stagnant water exposed to sunlight and temperatures above 4°C. They can produce slime and odors, interfere with filtration systems, and significantly increase chlorine demand. Their growth is further encouraged by phosphates and nitrates in the water.
Planktonic, Filamentous and Macrophytic
Algal growth occurs in three basic forms: planktonic, filamentous, and macrophytic.
- Planktonic algae are single-celled, microscopic organisms that float freely in the water. When these algae are extremely abundant or “bloom”, they can turn the water green. Less often, they can turn the water to other colours, including yellow, grey, brown, or red.
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Filamentous algae, also known as “string algae” or “pond scum,” form fine green threads that create floating mats, often attached to rocks, plants, or docks. These mats can be removed manually before using ultrasound treatment to ensure effective sound penetration. Left untreated, dense mats may absorb the ultrasound, reducing its reach. Treated algae float to the surface and should be regularly removed, allowing the technology to distribute sound evenly through the water column.
- Macrophytic algae resemble true plants in that they appear to have stems and leaves. A commonly-occurring macrophytic algae is called Chara or musk grass (due to its strong musky odour.) Chara feels coarse to the touch because of lime deposits on its surface, earning it another common name – stonewort. Most Macrophytic algae cannot be controlled with the existing forms of ultrasound.
Both filamentous algae and planktonic algae respond to ultrasound more or less in the same manner. However, in both types of algae, another distinction can also be made namely the green algae and the blue-green algae.
Figure 1 and 2 – From Left to Right, Bacteria cell-structure of filamentous algae and All other plant-like cell structures
Problems faced
Blue-green algae, or cyanobacteria, cause odour, taste issues, and can harm humans and animals. During warm seasons, they dominate lakes and reservoirs due to their ability to absorb nutrients and sunlight effectively. Cyanobacteria have gas-vesicle systems that allow them to move vertically in water, sinking to absorb nutrients from decomposing material and rising to the surface for sunlight.
Ultrasonic waves rupture these gas vesicles, causing the algae to sink, where they die from lack of light. The cell membrane also detaches from the cell wall.
Green algae share characteristics with plant cells but are not classified as plants. They have vacuoles, chloroplasts, and rigid cell walls, which enable photosynthesis and nutrient storage. Ultrasound disrupts their structure, causing chlorophyll loss, ruptured vacuoles, and cell death. Low-frequency ultrasound creates shear stress, rupturing cell walls and membranes, and sometimes causing cell lysis.
Conclusion
The LG Sonic system offers an innovative and eco-friendly solution for water treatment and biofilm growth in water bodies. By emitting specific ultrasonic frequencies, it safely targets algae without disrupting aquatic ecosystems. Research has consistently shown that our devices pose no harm to fish, amphibians, or zooplankton while improving the health and clarity of water.
This technology is particularly valuable in reservoirs, lakes, cooling towers, and similar applications where water quality is critical. Unlike traditional chemical treatments, ultrasound provides a sustainable, long-term solution for maintaining clean water.
For those seeking an effective and environmentally conscious water treatment method, this technology stands out as a proven solution backed by science and real-world applications.
