Recent Trends in Non-conventional Starches for Wastewater Treatment Applications

Coagulation and flocculation are essential processes in water and wastewater treatment. However, commonly used commercial coagulants pose environmental and health risks due to residual metal content and the large volumes of sludge they produce. As a sustainable alternative, starch-based biocoagulants have attracted increasing research interest due to their biodegradability, cost-effectiveness, and lower sludge generation, with some studies reporting up to 5-fold lower sludge volumes than with conventional chemical coagulants. Among these, non-conventional starches offer a promising solution because of their diversity, regional availability, and lack of competition with the food supply. This review explores extraction methods, modification strategies, and characterization techniques for structural and mechanistic validation. Reported studies revealed excellent pollutant removal performance under optimal conditions, including turbidity (98.91%), TSS (90.7%), COD (84.96%), color (100%), and selected metals (100%). Normalized removal efficiencies ranged from1.855% per mg/L for turbidity, 0.541% per mg/L for COD, and 1.7778% per mg/L for TSS, depending on the starch source and wastewater type. Mechanisms such as charge neutralization and interparticle bridging have also been identified. Despite challenges such as composition variability, high dosage requirements, and scalability issues, techno-economic assessments suggest potential industrial applicability. Overall, non-conventional starch-based biocoagulants hold considerable promise for sustainable wastewater treatment applications.