Microalgae-based treatment of shrimp aquaculture wastewater: mecha-nistic trade-offs, process integration, and...

Shrimp aquaculture wastewater has emerged as a critical environmental challenge because it combines high nutrient loads, salinity stress, fluctuating organic inputs, and outdoor operational variability. These features make treatment more difficult than for many conventional wastewaters. Microalgae-based technologies are increasingly viewed as promising solutions because they couple nutrient removal with biomass generation and resource recovery. However, the field remains constrained by unresolved trade-offs involving biomass retention, harvesting burden, fouling, and process stability, which continue to limit translation from laboratory studies to pilot- and farm-scale applications. This review integrates bibliometric mapping and critical thematic synthesis of 424 publications to examine how the field has evolved and where it is heading. The analysis shows clear convergence toward high-rate algal ponds (HRAPs), attached-growth systems, membrane-enabled intensification, nutrient recovery, and circular bioeconomy integration. Across these trajectories, no single reactor architecture resolves the full treatment challenge. Instead, technological evolution is increasingly driven by hybrid and integrated systems that redistribute functions across suspended, attached, and membrane-retained biomass. This review proposes a mechanistic trade-off framework for shrimp wastewater treatment and argues that future progress depends on standardization, pilot-scale and multi-season validation, safe biomass valorization, and the development of salinity-resilient, load-resilient, and farm-deployable integrated systems.