By Assoc. Prof. Ir. Dr. Poo Balan Ganesan
Imagine a bubble. Now divide it by over one-hundredth of a millimetre in diameter and you get microbubbles. Slightly larger than one micrometre, microbubbles and their generation are of utmost importance in many scientific fields. It has a wide array of practical applications from wastewater treatment, disinfection, medical uses, engineering and aquaculture.
A group of researchers led by University of Malaya’s Assoc. Prof. Ir. Dr Poo Balan Ganesan, have sought to prove this idea by investigating the effects of microbubble aeration on biofloc formation, water quality and the growth of whiteleg shrimps.
Their study confirms that microbubble aeration have profound positive effects on the growth of biofloc cultures and farmed shrimp.
Consistent with previous studies, with the right type of generator, this method can be applied to other forms of aquaculture.
Microbubble aeration is a process of producing air bubbles at a micro-scale (less than 200 micrometer). These bubbles tend to stay suspended in water for a longer period, thus resulting in an increase in mass transfer and dissolved oxygen level in the water.
However, this is not the case for macro-scale bubbles (mm), which rises fast vertically in water due to the buoyancy force. Consequently, it results in poor mass transfer between air and water.
Biofloc, specifically cultured microorganisms, are introduced into the water to form microbial protein from fish waste and other organic matter in the water, which recycles waste nutrients as fish food.
Through the application of microbubble generators that increase dissolved oxygen in tanks, there is a potential to greatly increase the production of aquafarms and improve the metabolism of aquatic life.
Biofloc Technology is the new “blue revolution” in aquaculture for sustainable aquaculture by using minimum resources like feed, water and land. However, Biofloc requires extensive and efficient oxygenation in order to maintain the nitrogen cycle and generate sufficient mixing intensity to keep bioflocs in active suspension for good water quality control.
In particular, biofloc technology systems can benefit significantly from microbubble generators. These systems utilise the nitrogen cycle to encourage the growth of beneficial bacteria colonies, which feed on organic waste (faeces, excess feeds and dead matter) and produce nutritional aggregates that can be fed to fish or crustaceans.
As one of the most popular commercial crustacean species in the world, whiteleg shrimp (litopenaues vannamei) thrives on biofloc systems. Due to the intensive rearing of whiteleg shrimps, bioflocs can address environmental and ecological sustainability concerns such as water quality control and cost-effective, disease-free production.
Based on the research, shrimps cultured in tanks utilising microbubble aeration grew larger and faster than shrimps without microbubble aeration. This is due to the growth of bioflocs and heterotrophic bacteria which are significantly enhanced by microbubble aeration.
The design of the microbubble generator also determines the effectiveness, efficiency and size of the bubbles produced. One of the simplest and most practical designs utilises air injection combined with a venturi-type geometry system (a system that speeds up the flow of water by constricting it in a cone-shaped tube) to produce large amounts of microbubbles at a rapid rate.
Dr Poo Balan believes that the data from his studies can help encourage aquafarmers to adopt an intensive/super-intensive nursery culture integrated with a microbubble aeration system and biofloc technology for better productivity.
“Doing something related to living stock makes me feel excited,” says Dr Ganesan. “On top of that, this is a societal, impact-orientated work for food security and sustainability.”
Edited by Kevin Bathman
* This is the personal opinion of the writer or publication and does not necessarily represent the views of Science Media Centre Malaysia
Assoc. Prof. Ir. Dr. Poo Balan Ganesan is an academician and researcher at Universiti Malaya since 2011 focusing on teaching & studies related to fluid mechanics and heat transfer. A notable research output is a patent and copyright of micro-bubble aeration nozzle for aquaculture farming in collaboration with the University of Teeside, UK. As for a research outcome to our community, PooBalan is providing technical trainings on an urban aquaculture farming based on recent technologies.