Influence of nitrogen loading rate on nutrient removal and algal biomass production using revolving algae biofilm reactor

•Biofilm reactor excels in biomass but faces challenges with real wastewater.•Nitrogen loading rate impacts removal, with 0.02 kgN/m3.d showing optimal treatment.•Nitrogen loading rate of 0.02 kgN/m3.d maximizes COD removal and biomass yield.•At 0.03 kgN/m3.d, nutrient oversaturation may impair microbial function. Microalgae-based technologies show promise due to their efficient absorption of nutrients and biomass production. The study focuses on a Revolving Algae Biofilm Reactor (RABR), a novel technology with a large sunlight-exposed surface area within a comparatively smaller footprint. This study aimed to determine the optimal nitrogen loading rate (NLR) for maximizing biomass growth and nutrient removal efficiency in a RABR system, employing both synthetic wastewater (first stage) and actual wastewater (second stage). The first stage using synthetic wastewater achieved a biomass productivity peak of 16.6 g/m2.d at the highest NLR (0.03 kg N/m3.d). Chlorophyll-a concentrations correlated positively with nitrogen loading, peaking at 12.6 mg/L at NLR of 0.02 kg N/m3.d, indicating enhanced photosynthetic activity. The second stage, utilizing real wastewater from post-anaerobic treatment, showed lower biomass productivity (2.8 g/m2.d) with notable Chemical Oxygen Demand (COD) removal efficiencies (70.2 %). NH4+-N removal dynamics varied, with an initial boost at NLR of 0.02 kg N/m3.d and followed by a decrement at NLR of 0.03 kg N/m3.d. [Display omitted]