Newton:Micro bubble aeration system for nursery pond of shrimp aquaculture in Malaysia under energy, water quality and biofloc circulation constraints

Lead Research Organisation: University of Teesside
Department Name: Sch of Science, Engineering & Design

Abstract

This project proposes the adoption of micro-bubble aeration technologies as a potential new direction for shrimp aquaculture, for the benefit of shrimp farmers in Malaysia and the government agencies which oversee their industry. The project seeks to harness efficient new technologies, and help to reduce the cost and environmental impact of shrimp farming to place the industry on a more sustainable footing both economically and environmentally.

Previous studies have indicated that shrimp aquaculture in Malaysia is intensive, but less productive than neighbouring countries including Indonesia, Thailand and Vietnam (Thean et al, 2016), which has led to a focus on potential measures to boost productivity, including by improving farm management practices and the deployment of resources (Gazi et al, 2014). Due to the importance of agriculture to the Malaysian economy (approximately 7.2% of Malaysian GDP in 2010 and contributing 10.9% of total employment), and with the identification of low productivity and quality as a key challenge (MARDI, 2015), this project has the potential to make a significant contribution as a route to improving shrimp farming processes.

The project will address the following research questions:

- What are the detailed characteristics of a micro-bubble aeration system in terms of its operational capabilities? (Off-field test based study)
- What is the suitable micro-bubble aeration system and configuration for a nursery pond of shrimp Aquaculture? (Off-field test based study)
- What is the energy/power requirement of a micro-bubble aeration system? (Off-field test based study)
- What is the effect a micro-bubble aeration system on bio-floc and its circulation? (Off-field test based study)
- What is the effect of a micro-bubble aeration system on water quality and shrimp growth? (On-field test)
- What is the effect of a micro-bubble aeration system on water effluent? (On-field test)

The outcome of the project will be disseminated to the Malaysian Ministry of Agriculture and Agro-based Industry, and then to the shrimp industry more broadly. This dissemination activity will be based on sharing the evidence gathered in the field test in Malaysia, and will include measures of shrimp farming productivity, energy and water use, and effluent reduction, in order to promote the potential of the project outcomes.

Planned Impact

The primary beneficiaries of this project are shrimp farmers in Malaysia, and the government bodies which oversee the agriculture and aquaculture industry.

The project seeks to harness and optimise new technologies, and to reduce the cost and environmental impact of shrimp farming in order to place the industry on a more sustainable footing both economically and environmentally. The aim is to develop a micro-bubble aeration system to improve water cleanliness, quality and shrimp growth, and to support the circulation of bio-floc, whilst operating at the same or reduced energy requirements.

Previous studies have indicated that shrimp aquaculture in Malaysia is intensive, but less productive than neighbouring countries including Indonesia, Thailand and Vietnam, which has led to a focus on potential measures to boost productivity, including by improving farm management practices and the deployment of resources. The project has the potential to contribute to the improvement of shrimp farming processes, which is especially significant given the importance of agriculture to the Malaysian economy.

The outcome of the project will be disseminated to the Malaysian Ministry of Agriculture and Agro-based Industry, and subsequently to the shrimp industry more broadly. This dissemination activity will be based on sharing the evidence gathered in the field test in Malaysia, and will include measures of shrimp farming productivity, energy and water use, and effluent reduction, in order to promote the potential of the project outcomes.
 
Description The project started in May 2017. The following was achieved at Teesside 1. we have produced one paper on developing the design of the micro bubble generator entitled: Effects of the geometrical configuration of air-water mixer on the size and distribution of micro-bubbles in aeration systems. The abstract of the paper: The objective of this work is to present a novel geometrical configuration for micro-bubble generators (MBGs) to improve dissolved-oxygen levels in water. Among various methodologies from literature, orifice and Venturi MBGs have been considered as baseline cases. Experimental data from the literature have been used to verify a CFD case developed to model the dynamics of microbubble generators. As a result, the validated CFD setup has been implemented on a modified Venturi-type generator, where air is injected coaxially with respect to the tube axis, while a helicoid wall at variable pitch angle is used. Results show a reduction in the mean bubble diameter distribution from the baseline Venturi tubes, particularly, at low-speed inlet velocities. This is of interest, especially to decrease the energy requirement for most common water aeration system. The paper was submitted for Asian-Pacific chemical Engineering Journal, under review. 2. The experimental rig was designed based on literature review and CFD study. We start receiving the component required to build the experimental rig. we expect the experimental rig will be ready by end of March and initial test will be started in March/April. Experimental setup for the microbubble generator
Introduction
The aim of this report is to provide an update on the current work on the microbubble generator project for shrimp aquaculture farms. The main objective of this work is to optimise the efficiency of the present technology, in order to increment the growth rate of shrimps, while reducing the amount of clean water and input energy to run the nursery farm facility.
From the available literature (Argawal, Jern, & Liu, 2011; Marui, 2010) it has been demonstrated that nanobubbles and microbubbles have the capability of releasing free OH- radicals in water. As a result, nanobubbles have the potential to disinfect water through detoxification and degradation of organic pollutants. This circumstance is beneficial, as a reduced amount of clean water is desired, compared to current farms - this would also reduce the environmental impact of shrimp aquaculture facilities.
On the other hand, in order to increase the shrimp rate of growth it is necessary to maximise the amounts of dissolved oxygen in water. In fact, higher levels of dissolved oxygen can accelerate the shrimp's metabolism together with their overall weight (Ohnari, 2001; Chowdhuri, Talib, & Yahya, 2013).
Nanobubbles are of particular interest for the reasons mentioned above. However, due to their nature, nanobubbles can only release dissolved oxygen within weeks or months, due to their strong molecular bonds, similar to ice. Therefore, a promising development - which is under attention of the present investigation in vertical water columns - is the production of microbubbles with diameter in the range of 20 - 50 µm. In this way, uniform clouds of microbubbles can efficiently release oxygen in short time and within a small volume, e.g. the chamber for experimental testing, which is also presented in this report.
Due to energy requirement considerations, an initial design has considered orifice (Sadatomi, Kawahara, Matsuura, & Shikatani, 2012) and Venturi microbubble generators (Kawamura, et al., 2004; Kawashima, Fujiwara, Saitoh, Hishida, & Kodama, 2005), since they can induce bubble breakup without using any moving parts - e.g. internal porous rotating plates (Sadatomi, Kawahara, Kano, & Ohtomo, 2005) - which would need an additional energy input. A CFD model has been setup to compare with experimental data for both orifice and Venturi configurations. The main output parameter taken into account is the size distribution of microbubbles at the tube outlet - at different inlet velocities and volumetric qualities for the air-water mixture. Results, which are gathered in a manuscript submitted for peer review to the Canadian Journal of Chemical Engineering , show reasonable agreement with experiments for the Venturi microbubble generator (Kawashima, Fujiwara, Saitoh, Hishida, & Kodama, 2005), especially in the distribution of microbubbles. For this reason, we have shaped our research into modifying the current Venturi microbubble generator, by producing a novel design which could reduce the size of current microbubble distributions from mean diameters of the order of 100 µm to the range of 20 - 50 µm mentioned above. This concept has been implemented by extruding a helicoid volume of material in the chamber ahead of the Venturi throat section. In this way, the gas-liquid mixture of air and water is forced into strong swirling motions which, combined with the pressure recovery effect (due to the throat section), can recreate the appropriate conditions for bubble breakup, i.e. pressure fluctuations in near-phase with the bubbles natural frequency. In this way, there is constructive interaction between trains of fluid eddies and the bubble film, so that turbulent oscillations can be amplified until bubble breakup. This process is of importance to reduce the size of large microbubbles and to achieve finer and more uniform distributions at the outlet section of the microbubble generator.
This report focuses on the experimental test rig facility, which is currently being built at Teesside University. This includes: a) a prototype of the microbubble generator used to produce fine microbubble distributions; b) the experimental setup to record microbubbles in a finite volume of water; c) an image processing method to extract histograms of bubble diameter from visualisation of a cloud of microbubbles.
1. Experimental setup
1.1. Test rig
The test rig facility to conduct investigation on the modified Venturi microbubble generator is illustrated in Figure 1. Tests are being conducted on a rectangular chamber containing water. The chamber is directly connected to the microbubble generator in a closed loop cycle. Water in the test chamber is initially deprived of dissolved oxygen by adding nitrogen gas (N2) directly in the test chamber for 20 - 40 min. This is done to ensure that dissolved-oxygen measurements are not biased by pre-existent dissolved oxygen (DO) concentration in the continuous phase of water. DO levels are simultaneously measured through a DO meter probe and flow visualisation of microbubbles - which is fully-detailed in Section 2.3. Microbubbles are injected from a pressurised-air line (6.0 bar) which feeds directly into the microbubble generator. Simultaneously, water is pressured to the microbubble generator by using a centrifugal pump (max. flow rate: 18 l/min) which has been selected to reproduce the volumetric quality implemented from test cases in the literature (Kawashima, Fujiwara, Saitoh, Hishida, & Kodama, 2005). Finally, a personal computer is connected with a high-speed camera to record and extract the mean distribution of microbubbles produced in the Venturi generator. In this visual measurement, the use of a lamp and a microscopic lens is fundamental to extract contours of microbubbles, hence, their diameter and distribution. Due to the fact that water is pumped at low flow rates (max. 18 l/min), an additional settling chamber ahead of the microbubble generator might be considered to remove the air bubbles previously produced in the test chamber. In this way, the water inlet conditions would not be modified. Additionally, injection of nitrogen gas ahead of the microbubble generator might also be considered for the same reasons mentioned above.
The most relevant items purchased for the experimental setup are listed below:
• Water pump, Xylem LVM Centrifugal Pump - 18L/min, 12 V;
• Water tank acrylic clear sheets, size: (2x) 220mm x 1000mm x 10mm; (2x) 200mm x 1000mm x 10mm; (1x) 220mm x 220mm x 15mm;
• Water/Air flow meter, Cole-Parmer Acrylic Flowmeter Kit, SS, 16 LPM Air / 450 GPH;
• DO meter + probe + cable + thermometer, Fisher Scientific™ Traceable™ Portable Dissolved Oxygen Meter;
• Halogen lamp, LEDVANCE LED Floodlight, 1 LED - 50 W, IP65 230 V.
High-speed camera sensor and coupled microscope objective lens are selected based on specifications from previous literature (Gordiychuk, Svanera, Benini, & Poesio, 2016; Sadatomi, Kawahara, Matsuura, & Shikatani, 2012; Yin, Li, Li, Liu, & Wang, Experimental study on the bubble generation characteristics for a venturi type bubble generator, 2015) to correctly extract contours of microbubble clouds and to determine the mean diameter of the distribution:
1. Maximum shutter speed or exposure time equal to 1/30000 s = 33.3 µs - to avoid image blurring;
2. Maximum acquisition rate equal to 25 FPS - to avoid that same bubbles are acquired more than once (this value is also based on the bubble convection speed, estimated to be of the order of 25 - 30 cm/s);
3. Minimum sensor resolution equal to 1.0 Mpx - to clearly visualise bubble contours;
4. Estimated sensor pixel size: 10 - 30 px - to clearly visualise microbubble contours;
5. System of microscopic lenses with magnification factor of at least 30X for a desired field of view equal to 2.32 mm x 7.73 mm - to observe microbubbles of minimum diameter equal to 10µm.

1.2. Microbubble generator
A modified version of the Venturi microbubble generator has been designed by removing a helicoid volume of material from the tube chamber ahead of the throat section . This is done to force the air-water mixture into a swirling motion which can potentially disrupt microbubbles and produce finer and more uniform distributions. A prototype has been manufactured at the University workshop. Since the difference between the inner and outer diameter is designed to maximise swirling and due to manufacturing challenges to face the design of the device, the helicoid section has been manufactured by: a) extruding a portion of material with height of approximately 2mm and with prescribed specifications for the helicoid profile; b) introducing a series holed rings (plastic washers) in sequence, into the helicoid guide. Washers are preliminarily warmed before being pushed into the helicoid vane, to ensure that they are connected one to each other and no discontinuities are present. Finally, the Venturi throat section has been manufactured through standard material grooving from the inner side of the tube.


1.3. Image processing for microbubble distributions
Image processing is implemented together with the DO levels measurement, in order to establish how the mean diameter of the bubble distribution can affect the oxygenation of the water volume in consideration in the test rig facility. A movie of bubble frames is recorded to extract contours and determine their mean diameter and distribution. The procedure detailed in this section for a single image for simplicity can easily be applied to a sequence of movie frame.
References
Argawal, A., Jern, W., & Liu, Y. (2011). Principle and applications of microbubble and nanobubble technology for water treatment. Chemosphere, 84, 1175-1180.
Chowdhuri, A., Talib, A., & Yahya, K. (2013). A review on marine shrimp aquaculture production trend in Malaysia and the world perspective. researchgate.net.
Gordiychuk, A., Svanera, M., Benini, S., & Poesio, P. (2016). Size distribution and Sauter mean diameter of micro bubbles for a Venturi type bubble generator. Experimental Thermal and Fluid Science, 70, 51-60.
Kawamura, T., Fujiwara, A., Takahashi, T., Kato, H., Matsumoto, Y., & Kodama, Y. (2004). The effects of the bubble size on the bubble dispersion and skin friction reduction. Proceedings of the fifth symposium on smart control of turbulence. Tokyo.
Kawashima, H., Fujiwara, A., Saitoh, Y., Hishida, K., & Kodama, Y. (2005). Experimental study of frictional drag reduction by microbubbles: laser measurement and bubble generator. Proceedings of the fifth symposium on smart control of turbulence. Tokyo.
Levich, V. G. (1962). Physiochemical hydrodynamics. Englewood Cliffs, NJ.
Marui, T. (2010). An introduction to micro/nano bubbles and their applications. The 14th World Multi-Conference on Systemics, Cybernetics and Informatics, 1, -.
Ohnari, H. (2001). Fisheries experiments of cultivated shells using micro-bubbles technique. Journal of the Heat Transfer Society of Japan - 40, 2-7.
Sadatomi, M., Kawahara, A., Kano, K., & Ohtomo, A. (2005). Performance of a new micro-bubble generator with a spherical body in a flowing water tube. Experimental Thermal and Fluid Science, 29, 615-623.
Sadatomi, M., Kawahara, A., Matsuura, H., & Shikatani, S. (2012). Micro-bubble generation rate and bubble dissolution rate into water by a simple multi-fluid mixer with orifice and porous tube. Experimental Thermal and Fluid Science, 41, 23-30.
Yin, J., Li, J., Li, H., Liu, W., & Wang, D. (2015). Experimental study on the bubble generation characteristics for a venturi type bubble generator. International journal of heat and mass transfer, 218-224.
Yin, J., Li, J., Li, H., Liu, W., & Wang, D. (2015). Experimental study on the bubble generation characteristics for a venturi type bubble generator. International Journal of Heat and Mass Transfer, 91, 218-224.
Ziou, D., & Tabbone, S. (1998). Edge detection techniques: An overview. Internationa Journal of Pattern Recognition and Image Analysis, 537-559.
3. Interview with Research professional. The article title was: My winning proposal: Strong rapport brings in first Newton win 4. 4. Outcomes or what have been achieved at Malaya University:

1. Visited few farms to understand further the actual shrimp farming and to fine tune my lab-scale experiment.
2. Hired research assists ( one PhD student and temporary project assistant) .
3. Attended a comprehensive training course on - shrimp culturing and water quality and biofloc.
4. Designed and developed a lab-scale experiments at University Malaya research lab for number of sensitivity studies. This includes sourcing a suitable materials, pumps, pipings, fittings. Having a small lab size was quite a challenge during water tank sourcing.
5. Fine tune the flow condition in each and every tank to suit the required experiments.
6. Water preparation for biofloc and biofloc development. Observed various kind of relevant microorganisms in the water.

The main finding sine March 2017 are:
1. One conference paper is published in conference, April 2019 Rome, Italy
2. Two papers under preparation and will be published soon,
3. Patent proposal was submitted to Teesside university in December 2018 for initial assessment to approve the funding for patent application.
4. Two PhD students will completed their study by end of 2019.
Exploitation Route We need to make a direct contact with shrimp farmer in Malaysia by organizing some workshop, in local news paper or TV station. we also need to communicate ministry of agriculture and local authorities in Malaysia. it could useful to attend conferences in both courtiers to show the advantage of using microbubble.

if the patent application processed and accepted, we will try to commercialize it.
Sectors Agriculture, Food and Drink,Energy,Environment