Harnessing Microalgae for the Treatment of Effluent from Anaerobic Digestion of Cassava Starch Wastewater

The cassava starch industry is a significant contributor to Thailand’s economy but generates substantial wastewater, which is typically treated via anaerobic digestion (AD) coupled with biogas production. However, these digestates still contain elevated levels of nitrogen, phosphorus, and residual organic matter, necessitating further treatment to meet public discharge standards. This research investigated the efficacy of two locally sourced algal strains, Chlorella and Scenedesmus, for nutrient removal from effluent at a 50% concentration. The results demonstrated that the microalgae exhibited rapid growth within the first 2-3 days of cultivation. After 7 days, Scenedesmus exhibited a superior nutrient removal efficiency, achieving 56% nitrate and 67% phosphorus reduction, compared to 33% nitrate and phosphorus removal by Chlorella. The use of a mixed algal culture further enhanced nutrient removal efficiency, achieving up to 97% for nitrate removal and 82% for phosphorus removal. These findings suggest that combining different algal species leads to significantly higher removal efficiency than individual strains. Moreover, the resulting algal biomass can be used as biofertilizer, for energy production, or to extract valuable compounds. The use of algae also provides a sustainable and eco-friendly solution. Despite these advantages, the low cell concentration inherent in suspended algae systems limits their overall treatment efficiency. Future studies should focus on optimizing algal cell density to further enhance system performance.