Syamimi Afiqah Abdul GhaniChng Lee MueiSwee Pin YeapDerek Juinn Chieh ChanJing GengLeong Sim Siong0000-0002-1476-4074Pey Yi, TohTohPey YiH. NisarS. SethupathiY.L. PangK.T. TanN. binti Abdul AzizK.M.C. Wong2025-10-232025-10-23202510.1051/e3sconf/202560301003https://dspace-cris.utar.edu.my/handle/123456789/11549Food processing wastewater poses significant environmental challenges due to high pollutant levels, necessitating effective treatment methods. While Chlorella vulgaris has shown promise in wastewater treatment, the optimal light/dark photoperiod regimes for maximizing biomass growth, nutrient removal efficiency, and COD reduction remain underexplored. This study evaluates the effects of 12H:12H light/dark and 24H light photoperiods on the performance of C.vulgaris in treating food processing wastewater. The 12H:12H photoperiod achieved 73% COD removal with a biomass yield of 0.44 g/L, while the 24H light achieved 75% COD removal with a biomass yield of 1.02 g/L. Both photoperiods fully removed ammonia by day 12. Although the 24H light period increased biomass production, it is energy-intensive, whereas the 12H:12H photoperiod is more energy-efficient but requires further evaluation. These findings highlight the importance of optimizing photoperiod regimes to enhance the efficacy of microalgae-based wastewater treatment. This research supports sustainable wastewater management in the food industry and aims to meet regulatory standards through tailored photoperiod strategies. © The Authors, published by EDP Sciences.entext::conference output::conference proceedings::conference paper