Effect of feeding regime on biomass productivity and biodiesel production in a high-rate pond for post-treatment of domestic wastewater

High-rate ponds (HRPs) are promising systems for producing third-generation biofuels and can be integrated into domestic wastewater treatment. Although operational parameters such as HRT, water depth, and feeding regime influence HRP performance, in this study, the HRT was kept approximately constant while only the feeding regime was varied. This study evaluated the effect of the feeding regime on biomass and lipid productivity in an HRP used for the post-treatment of domestic wastewater. The system was operated for 106 days with a water depth of 0.5 m and a 2-day HRT, divided into two phases: Phase I, with two daily feedings (HRT = 2.4±0.4 days), and Phase II with eight daily feedings (HRT = 2.2±0.2 days). Chlorophyceae and Diatomophyceae predominated throughout the experiment, while Cyanophyceae appeared following the change in feeding frequency. Effluent treatment showed no significant differences between phases, with average removal efficiencies of 60% for organic carbon, 74% for nitrogen, and 56% for phosphorus. Biomass productivity increased in Phase II, reaching 52.1 ± 18.2 g VSS·m⁻²·d⁻¹ and 0.5 ± 0.1 g chl·m⁻²·d⁻¹. Lipid productivity was also higher with more frequent feedings, reaching 13.3 g·m⁻²·d⁻¹. Palmitic acid was the predominant fatty acid in both phases, accounting for 49% of total lipids in Phase I and 52% in Phase II. These findings suggest that increasing the feeding frequency can enhance biomass and lipid production in HRPs without compromising wastewater treatment efficiency. • High-rate ponds achieved effective nutrient removal with a 2-day HRT and a 50 cm depth. • Eight daily feedings increased biomass, lipids, chlorophyll-a, and FAME production. • Palmitic acid was the dominant fatty acid, supporting biofuel suitability. • HRPs are promising for sustainable wastewater treatment and resource recovery.