The aquaculture industry is booming, but the increasing demand comes with a growing responsibility for eco-friendly disinfection practices. Peracetic acid (PAA) emerges as a turning point in this field, offering a potent, safe, and sustainable solution for water disinfection.
A scientific review published by researchers from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, the US Department of Agriculture, the Technical University of Denmark, the Freshwater Institute, and Nofima, summarizes scientific knowledge on safe PAA concentrations for fish and its effectiveness against various undesirable microorganisms and their excreted substances. Additionally, the document provides insights and recommendations on PAA application for the aquaculture industry.
A Long History, a Promising Future
First synthesized in 1902, PAA has a long history as a reliable disinfectant in various industries. Now, its potential in aquaculture is gaining deserved attention. Unlike traditional methods like formalin (carcinogenic) or chlorine (harmful byproducts), PAA offers a safer and more sustainable alternative.
Understanding PAA
- Chemical Name: Peracetic acid (IUPAC), commonly known as PAA or peroxyacetic acid.
- Composition: Commercial PAA products are mixtures containing acetic acid, hydrogen peroxide, PAA itself, and water. Stabilizers ensure product stability.
- Safety: Unlike formaldehyde, PAA poses no known carcinogenic risks. Its strong odor discourages prolonged exposure, unlike ozone.
Safety First: Why PAA Makes Waves
- Safer for humans: Unlike formalin, a known carcinogen, PAA poses no carcinogenic risk to humans.
- Fish-friendly: PAA rapidly decomposes, minimizing harm to fish. Studies show strong recovery and physiological adaptation in fish exposed to appropriate PAA concentrations (generally below 2 mg/L).
- Pathogen elimination: PAA effectively attacks and eliminates pathogens throughout the aquaculture water, unlike methods like UV radiation or ozone, which only disinfect running water.
- Environmentally responsible: PAA quickly breaks down into harmless byproducts, posing minimal risk to the environment.
The Power of Low: Effective and Eco-friendly
The key to successful PAA application lies in finding the “optimal point” between fish safety and disinfection effectiveness. In freshwater, 1-2 mg/L (active PAA, not product) is generally safe for fish and effective against microbes. Higher concentrations can be tolerated in brackish/marine water due to faster degradation.
While fish can adapt to repeated PAA use at safe levels, chronic exposure can cause mild reversible changes. To minimize this, consider periodic or semi-continuous application modes, allowing fish to recover between treatments.
Precautions and Considerations
- Fish larvae and alkalinity: Special care is needed with young fish and low alkalinity water. Reduce PAA concentration or supplement with sodium bicarbonate to enhance fish resilience.
- Acclimation: Start with lower PAA doses during the initial application to allow fish adjustment and assess disinfection spread within your system.
- Monitoring: Use DPD-based chlorine meters (properly disposed of test waste) to estimate PAA concentration and monitor other water parameters like pH and nitrogen compounds (especially in RAS) for fish health and biofilter function.
Redox potential approach: A universal control method
Since PAA toxicity is influenced by water chemistry, finding a universal ideal concentration is challenging. This is where the redox potential comes into play:
- Maintaining a redox potential of around 300 mV appears to be safe for fish and effective against bacteria, according to limited studies. Further research is needed to confirm this, especially in real-world settings.
Applications and Regulations
PAA has gained ground in the aquaculture industry:
- Surface disinfection: PAA is commonly used to disinfect equipment, facilities, and fish eggs.
- Water disinfection: The EU and the US recently approved PAA for use in aquaculture water, even with fish present (certain restrictions apply).
Challenges and Solutions
While PAA shines in terms of safety and efficacy, some hurdles remain:
- Maintaining PAA levels: PAA degrades rapidly, so maintaining effective concentrations in large aquaculture systems can be challenging.
- Delivery optimization: Ensuring uniform PAA distribution within complex aquaculture setups requires careful design and application strategies.
Conclusion
PAA offers a valuable tool for disinfection in aquaculture facilities when used strategically. By understanding the factors influencing its efficacy and safety, fish farmers can create a healthy environment for their fish while promoting sustainable aquaculture practices.
As research continues to refine application methods, PAA has the potential to revolutionize water disinfection, ensuring a healthy future for both fish and our planet.
Contact
Dibo Liu
Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries
Müggelseedamm 301, 12587 Berlin, Germany.
Email: dibo.liu@outlook.com
Reference (open access)
Liu, D., Straus, D. L., Pedersen, F., Good, C., Lazado, C. C., & Meinelt, T. Towards sustainable water disinfection with peracetic acid in aquaculture: A review. Reviews in Aquaculture. https://doi.org/10.1111/raq.12915
