CHAPTER 4. RECOMMENDATIONS TO INCREASE LOW ADAPTIVE
4.3 Technological recommendation for increasing AC of aquaculture households
These households have the highest AC among the three systems. Some indicators of these households below the total score need to be improved. The proposed technology can help these households strengthen low indicators and parameters such as low awareness of aquaculture farmers and environmental efficiency. Because this model is evaluated to have high economic efficiency, the study proposes the application of recirculating aquaculture system (RAS) to treat waste, wastewater and reuse water to optimize the efficiency between the economy and environment. This technology will be introduced in detail in part 4.3.
4.3 Technological recommendation for increasing AC of aquaculture households
From the results of assessing the AC of aquaculture systems in Cho Moi district, the study highly appreciated the cement/rubber tank system because of the outstanding and comprehensive advantages in all 04 adaptive components as regards climate change and sustainable development. Therefore, the RAS model is introduced based on the inheritance of the advantages of cement/rubber tank system and overcome its limitations. Technology solutions are judged to ensure the system operates continuously and achieve high environmental efficiency.
According to the survey of aquaculture households, there are 22 out of 60 households, accounting for 36.7% of total aquaculture households who want to switch to the model of applying RAS technology or advanced techniques to increase economic and environmental efficiency, of which was 40% of raising fish in earthen ponds and 70% of raising in cement/rubber tanks interest in. No one living in floating houses agreed to change the system because they persistently keep their daily life on the river. Those planning to switch their systems to RAS want to be
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supported by the government in terms of loans, technology transfer and training to operate the system smoothly and effectively (see Figure 4.1).
Figure 4.1 The survey result of household‟s anticipation for implementing RAS to improve their current farming practices
4.3.1 RAS introduction
Before fish stocking, input water is treated to create a suitable habitat for young fish. During the culture process, the fish feces is pushed by the strong water flow out from the oxygen aeration system (venturi) to the end of the tank. The pump system is responsible for pumping out sludge waste into a mechanical and biological filtration system. After the filtration system, the waste from the fish tank is removed and is used as a rich nutrient resource to grow the plants, then the filtered water is led back to the main tank. After 5-7 days, the amount of water is pumped into the fish tank to compensate for the loss of water due to evaporation and leak (see figure 4.2).
20 20 20
8
14
4
7
2
5
2 2
0 5 10 15 20 25
Floating house Earthen Pond Cement/rubber tank
Number of households Positive attitude toward RAS loan technology transfer training
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Figure 4.2 Diagram describes RAS operation
Filtration system was constituted by two levels: physical and bio-filtration.
The physical filtration system is a plastic barrel functioned as a clarifier tank that contains 03 compositions: a filter net, an overflow pipe and an effluent sludge pipe (see figure 4.3) to prevent large particles such as fish feces, organic matters, dust, etc. from entering into bio-filter system. The treated water after this system still exists harmful microorganisms and particles needed to be removed in bio-filter system.
Filtration system
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Figure 4.3 The composition of a mechanical filtration system
The biological filtration system is low-cost, convenient, and highly anti bacteriostatic materials. This system includes 2 parts: layers of bio-filter materials (see figure 4.4) and a vegetable planting system (see figure 4.2) installed behind the main tank. The first layer containing low cost materials such as mat filters is functioned to remove big and medium particles surviving after the mechanical filtration system. The second layer containing materials to eliminate small organic matters and retain good bacteria for dissolving poisonous compounds in the third layer which contains ceramic, lava stones.
Figure 4.4 Three layers of a bio filter are introduced to purify water quality Filter net
Layer 1
Filter big particles after mechanical filtration
Layer 2
Filter tiny particles and retain good bacterias
Layer 3
Remove poisonous compounds
Overflow pipe
Effluent sludge pipe
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4.3.2 RAS strengths
- Cultivated fish have a filtration system, so the water quality and culture environment are guaranteed, saving energy and labor costs for replacing water.
Moreover, the total amount of wastewater is recycled, so the surrounding environment is guaranteed.
- Fish grow fast, be healthy, and have fewer diseases due to the designed pond with a pump system and aeration through venturi tube; create a flowing water environment for growing fish.
- High economic efficiency due to not need large areas, suitable for places with poor water quality or inclement weather.
- The cost for adding RAS system is much cheaper than other advanced technology. The extra investment for under 100 m2 of cement/rubber tank is calculated about 20 million VND. That is affordable for low income farmers.
- The project helps farmers better understand hi-tech agriculture, technology approach, and understand the importance of improving production techniques to create safe and quality products for the community, thereby bringing high efficiency to producers.
- Changing production habits and practices of farmers toward cleanness, contributing to improving incomes for poor households, and less land.
In this study, fish raising households in cement/rubber tanks were proposed to install RAS systems because they took advantage of the available infrastructure and proven strengths to reduce costs and manpower for increasing AC to CC.
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