Tiếng Việt
Aquaculture is a growing and thriving industry in Vietnam. However, insufficient attention to wastewater treatment during production stages has posed risks to productivity, health, and the environment.
1. Aquaculture Wastewater Treatment for Recycling – A Challenging Task
Aquaculture, fishing, and seafood processing are key economic sectors in Vietnam, contributing significantly to export revenues and GDP growth. However, outdated production technologies in these sectors have negatively impacted sustainable development:
- Overextraction of groundwater has exacerbated coastal saltwater intrusion, causing irreversible damage.
- Coastal environmental pollution due to wastewater discharge from aquaculture farms.
The increasing severity of climate change impacts has pressured businesses to adopt high-tech aquaculture methods that minimize water usage, prioritize recycling, and reduce environmental pollution for sustainable development.
While water recycling in aquaculture has become common in developed countries, it remains underutilized in Vietnam due to high investment costs. Vietnam can only shift to a water reuse model by focusing on value and quality rather than competing solely on cost or price.
2. Importance of Water Quality in Aquaculture
Water quality is a critical factor in aquaculture, being a major cause of diseases among aquatic organisms. Native aquatic species, especially those in freshwater or brackish environments, exhibit good adaptation and resistance, making water pollution the primary driver of diseases.
Examples of waterborne diseases:
| STT | Bệnh | Nguyên nhân | Hình ảnh |
| 1 | Brown Spot Disease | Bacteria: Aeromonas hydrophila, Pseudomonas sp., Aeromonas sp. |
|
| 2 | Soft Shell Disease | Low water hardness and dietary calcium and phosphorus deficiencies |
|
| 3 | Molting Adhesion | Likely due to high NH4-N levels in rearing tanks (exact cause unknown) |
|
3. Aquaculture Wastewater Characteristics
Water used in aquaculture hatcheries or general aquaculture activities has a lower level of pollution compared to other industrial sectors. However, the pollutants present are directly toxic to aquatic species, even at very low concentrations. A prime example is ammonia, a decomposition product of organic waste. Wastewater treatment in aquaculture thus focuses primarily on ammonia removal, specifically through its transformation into nitrates via microbial nitrification processes. [1,2,3,5]
Compared to other wastewater types, aquaculture wastewater has distinct characteristics, including low ammonia concentrations, high salinity, and the presence of inhibitors (e.g., antibiotics used during farming). However, achieving high purification levels is essential for reuse purposes.
These factors significantly hinder the efficiency of autotrophic microorganisms (those converting ammonia into nitrates), which inherently grow at a slow rate. [8,10]
Another challenge in employing biological technology for aquaculture wastewater treatment is the seasonal nature of production (particularly in northern regions), small production scales, and the diversity of farmed species within a single facility.
These characteristics significantly affect the efficiency of wastewater treatment technologies, leading to:
- High construction and operational costs.
- Difficulty in maintaining system stability.
Shrimp Farm Wastewater
Shrimp farming wastewater is primarily generated from the accumulation of residual feed during feeding activities. This effluent is rich in nitrogen, phosphorus, and various other nutrients. Additionally, carbon dioxide and organic matter in the wastewater deplete oxygen levels and increase the concentrations of COD, BOD, hydrogen sulfide, ammonia, and methane. The sedimentation of sludge within wastewater and its accumulation in nearby areas further exacerbates environmental issues.
– Siphoned Wastewater
The daily discharge is approximately 2% of the pond volume, containing shrimp remains, molted shells, leftover feed, shrimp excrement, algae residues, and dead microorganisms. Pollution parameters in siphoned wastewater from intensive and super-intensive shrimp ponds exhibit extremely high contamination levels, specifically as follows:
- Parameter: Contaminant levels in siphoned wastewater from shrimp ponds at around 40 days of age.
- Regulation: Column B, QCVN 40:2011/BTNMT, National Technical Regulation on Industrial Wastewater.
| Parameter | Contaminant levels in siphoned wastewater from shrimp ponds at around 40 days of age. | Column B, QCVN 40:2011/BTNMT, National Technical Regulation on Industrial Wastewater. |
| Total N (nitơ) | 200 – 300 mg/l | 40 mg/l |
| Total P (phốt pho) | 400 – 450 mg/l | 6 mg/l |
| BOD5 | 1.200 – 1.400 mg/l | 50 mg/l |
| COD | 1.300 – 1.600 mg/l | 150 mg/l |
| Amoni (N) | 14 – 15 mg/l | 10 mg/l |
– Water Discharge from Ponds
Daily wastewater accounts for approximately 20% – 50% of the total pond volume. The pollution parameters in the discharged water typically have lower contamination levels compared to the wastewater siphoned from the pond bottom, as detailed below:
| Parameter | Contaminant levels in siphoned wastewater from shrimp ponds at around 40 days of age. | Column B, QCVN 40:2011/BTNMT, National Technical Regulation on Industrial Wastewater. |
| Total N (nitơ) | 10 – 20 mg/l | 40 mg/l |
| Total P (phốt pho) | 1 – 4 mg/l | 6 mg/l |
| BOD5 | 50 – 150 mg/l | 50 mg/l |
| COD | 100 – 300 mg/l | 150 mg/l |
| TSS | 40 – 200 mg/l | 100 mg/l |
| Amoni (N) | 3 – 7 mg/l | 10 mg/l |
– Fish Farming Wastewater
Fish farming wastewater primarily results from the high amount of uneaten feed in farming areas. Fish consume less feed compared to shrimp, typically absorbing only about 17% of the feed, while the remaining 83% dissolves in water and decomposes into organic matter. These organic compounds are difficult to degrade and contribute to the accumulation of impurities in the water.
Combined with fish excrement, these compounds form a layer of waste at the bottom of the ponds, creating favorable conditions for the growth of numerous harmful microorganisms. Additionally, the wastewater often contains residual chemicals such as antibiotics used for fish or disinfectants applied to ponds.
4. Benefits of Water Recycling and Reuse
- Reduces excessive extraction of groundwater and seawater, preserving finite water resources.
- Lowers wastewater treatment costs by reducing both the volume and concentration of pollutants.
- Enables aquaculture in areas distant from water sources and closer to markets, enhancing supply chain efficiency.
5. Key Considerations for Water Recycling in Aquaculture
- Water quality must meet specific requirements for different species and growth stages.
- Proper dilution ratios of new and recycled water prevent shock to aquatic organisms.
- Ensure removal of all pathogenic bacteria and viruses.
- Nutrient pollution levels must be controlled to avoid negative impacts on livestock development.
Contact NGO International for cost-effective aquaculture water recycling solutions.
Hotline: +84 969 867 924 & +84 969 867 925 Hotline: 0969 867 924 & 0969 867 925.
References:
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Nguồn: NGO
