Introduction
Intensive mariculture produces significant wastewater rich in nitrogen, phosphorus, suspended solids, and residual organic compounds. Traditional treatment methods may struggle to maintain high nutrient removal efficiency while minimizing operational costs. In this context, microalgae-based technologies have gained attention as a sustainable solution, simultaneously removing nutrients and generating valuable biomass for use as feed, fertilizer, or bioenergy. Recent research has focused on understanding single-species and multi-species microalgae systems, as well as their integration with hybrid treatment technologies.
Single-Species Microalgae Systems
Single-species microalgae systems utilize well-characterized strains, such as Chlorella vulgaris and Scenedesmus sp., to assimilate nitrogen and phosphorus from wastewater. Laboratory studies demonstrate that under controlled light and nutrient conditions, these strains can achieve up to 80–90% nutrient removal, converting wastewater nitrogen and phosphorus into algal biomass. The simplicity of single-species cultivation allows for predictable growth and ease of monitoring but may be sensitive to environmental fluctuations such as temperature, pH, and influent variability.
Combined Microalgae Consortia
To improve resilience and treatment efficiency, researchers have explored multi-species microalgae consortia. By combining green algae with cyanobacteria or diatoms, these systems leverage complementary metabolic pathways that enhance nutrient uptake, especially for ammonium and phosphate. Multi-species consortia exhibit improved stability under varying wastewater compositions and can tolerate seasonal environmental changes better than monocultures. These consortia also promote microbial diversity, which further stabilizes biochemical transformations and enhances effluent quality
Integration with Hybrid Treatment Systems
Hybrid approaches combining microalgae cultivation with dynamic membranes or recirculating aquaculture systems (RAS) have shown significant promise. Dynamic membranes retain algal biomass, allowing the treated water to be recirculated, thus improving nutrient removal efficiency and reducing water consumption. Such integration supports high-density algal growth and continuous operation, bridging laboratory-scale studies with commercial applications. Moreover, hybrid systems can reduce energy input and facilitate the recovery of algal biomass for economic utilization.
Challenges and Limitations
Despite their potential, microalgae technologies face operational challenges. Light penetration in dense cultures can limit photosynthetic efficiency, while fluctuating temperatures and nutrient imbalances may affect growth rates. Biomass harvesting is energy-intensive, and cost-effective scalable methods are still under development. Additionally, refractory organic compounds in mariculture effluent can resist algal uptake, necessitating supplementary treatment approaches such as advanced oxidation or co-treatment with bacteria.
Future Prospects and Sustainability
Microalgae systems also offer carbon sequestration benefits by converting dissolved inorganic carbon into biomass, contributing to greenhouse gas mitigation. Endogenous consortia tailored to local wastewater conditions provide a route toward net-zero carbon operations in aquaculture facilities. Integration with AI-assisted monitoring can optimize growth conditions, nutrient assimilation, and biomass harvesting in real time, further improving operational efficiency. The combination of molecular-level monitoring, hybrid system design, and intelligent process control represents a comprehensive strategy for sustainable wastewater treatment.
Conclusion
Microalgae-based wastewater treatment presents a viable and sustainable option for mariculture operations. Both single-species and multi-species systems, particularly when integrated with dynamic membranes or RAS, achieve high nutrient removal and generate usable biomass. Ongoing research into operational optimization, energy-efficient harvesting, and AI-driven monitoring will enhance the practicality and scalability of these technologies. Overall, microalgae offer a path toward environmentally responsible and economically beneficial wastewater management in modern aquaculture.