Rohit Dey

• Rapidly expanding anthropogenic activities are generating increasing volumes of wastewater globally each year, the majority of which remains inadequately treated before being released into aquatic ecosystems. Microalgal technologies offer a promising alternative for nutrient recovery in wastewater treatment, demonstrating significant advantages over conventional methods that are often energy-intensive and costly. Inadequate treatment not only leads to environmental pollution but also results in the irreversible loss of valuable nutrients, thereby disrupting the nutrient cycle. In recent years, the extraction of bioactive compounds from microalgae has attracted substantial attention. However, much of the research has remained confined to laboratory-scale studies with a focus on either energy efficiency or bioproduct synthesis, limiting their practical applicability. A major bottleneck in the scalability of algal-based systems is the energy- and cost-intensive nature of biomass harvesting, which can contribute up to 20–30% of total downstream processing costs. Additionally, the dependence on sunlight and large land areas further restricts the feasibility of microalgae-based wastewater treatment technologies in diverse environments. This study addresses three critical challenges associated with algae-based wastewater treatment. First, an innovative cultivation approach was developed to enable continuous wastewater treatment across two contrasting seasonal conditions—summer and winter. Second, the characteristics of wastewater post-treatment were analysed to identify fouling factors affecting the harvesting process. Third, a novel strategy was implemented to induce “hyper compensation” and “luxury uptake” of inorganic phosphorus by microalgae, achieving an exceptional phosphorus recovery rate of nearly 96%. To fully capitalize on the treated biomass, a novel bioplastic/bio-composite was developed by combining polylactic acid with phosphorus-enriched microalgae.