Septic tank effluent contains high organic and nutrient contents. This study aimed to evaluate treatment performance of an AB-PBR treating the septic tank effluent. The experimental unit employed a transparent plastic media made from recycled drinking water bottles for attached-growth biofilm. Red LED lamp (light intensity ∼100 μmole/m²/s) was applied as an energy source for the growth of algal-bacterial biofilm in the AB-PBR. The experimental results showed that AB-PBR operated at the hydraulic retention time (HRT) of 3 days gave the highest chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal efficiencies of 64, 45 and 35%, respectively, by which the effluent COD concentrations could meet the effluent standards of Thailand (Pollution Control Department (PCD), Thailand, 2010), but the effluent TN and TP concentrations needed to be further removed. The Stover-Kincannon model was applied to determine the kinetic values of COD and TN removals with R² values greater than 0.8. Microbiological examinations indicated Chlorella sp. is the predominant algal species growing in the AB-PBR, while the amplicon sequencing information analytical results revealed the bacterial phylum of Proteobacteria to be the predominant bacterial group.