A Recirculating Aquaculture System (RAS) is an efficient and environmentally sustainable aquaculture technology that recycles water through advanced treatment processes, minimizing water consumption and environmental impact.
RAS Workflow:
Water circulates between the culture tank and treatment units:
Culture Tank → Solid Waste Removal → Biofiltration → Oxygenation/Disinfection → Return to Culture Tank.
Culture Tank: Core unit for rearing aquatic species (e.g., fish, shrimp).
Physical Filtration: Removes solid waste (e.g., feces, uneaten feed) via drum filters or protein skimmers.
Biofiltration: Converts toxic ammonia (NH₃) into nitrite (NO₂⁻) and nitrate (NO₃⁻) using nitrifying bacteria.
Oxygenation System: Maintains dissolved oxygen (DO) levels (e.g., pure oxygen injection, aerators).
Disinfection: UV sterilizers or ozone treatment to eliminate pathogens.
Temperature Control: Heating/cooling systems (e.g., heat pumps, heat exchangers) for optimal water temperature.
Water Quality Monitoring: Real-time tracking of pH, DO, ammonia, etc.
Water Efficiency & Eco-Friendliness
Recycles >90% of water, reducing daily exchange to 5-10% (vs. traditional systems). Ideal for water-scarce regions or strict regulatory environments.
Precision Control & Stable Production
Stable water quality (DO >5mg/L, ammonia <0.5mg/L) enables year-round, season-independent farming with adjustable pH/temperature.
High-Density Farming & Space Savings
Stocking densities 10-50x higher than ponds (e.g., salmon at 50-80kg/m³), suitable for urban/land-based facilities.
Reduced Disease Risk & Sustainability
Closed systems minimize pathogen exposure; UV/ozone lowers antibiotic use, aligning with green aquaculture trends.
Environmental Sustainability
Centralized waste treatment reduces pollution. Integrates with aquaponics (nutrient recycling) and renewable energy (e.g., solar).
Technology-Intensive Operation
Requires skilled management for biofilters/automated systems. Energy costs account for 30-50% of OPEX.
High ROI for Premium Species
Initial CAPEX: ~$50-100/m³, but ideal for high-value species (e.g., salmon, sturgeon) with shorter cycles and premium market access.
| Feature | RAS | Traditional (Pond) |
|---|---|---|
| Water Use | 90%+ recycling | High dependency on natural sources |
| Stocking Density | Very high (industrial scale) | Limited by environment |
| Environmental Control | Full automation (year-round) | Weather-dependent (seasonal) |
| Disease Risk | Low (closed system) | High (open water exposure) |
| Eco-Impact | Minimal discharge | Wastewater runoff |
| CAPEX | High | Low |
