2026-03-01 REGIONAL STUDIES IN MARINE SCIENCE 2026 95(卷), null(期), (null页)
Freshwater scarcity is intensifying worldwide. Tertiary-treated municipal wastewater offers a low-cost nutrient source for aquaculture yet carries risks of heavy-metal accumulation. We integrated the floating fern Azolla filiculoides with Nile Tilapia to polish five wastewater ratios (0, 25, 50, 75, and 100 %) and supply supplementary feed. Over 90 days, Azolla reduced NH4-N by 50-70 %, NO3-N by 60 % and phosphate by 55 %, while raising dissolved oxygen. Azolla biomass accumulated Cd, Pb, Zn, Cu, Mn and Fe up to 96 % more than the control, keeping fish muscle below FAO/WHO thresholds. Growth of Tilapia (2.3 g to 52-61 g) was maintained or improved at 25-50 % effluent with Azolla, whereas 100 % effluent without Azolla depressed yield by 36 %. Fillet protein (15.4 %) and lipid (6.3-6.8 %) were unaffected. Azolla therefore offers a dual-purpose, naturebased solution for safe wastewater reuse in arid-zone aquaculture, aligning with SDG 6 (clean water) and SDG 2 (food security).