A need for phosphorus removal is becoming increasingly evident as some wastewater treatment plants struggle to meet wastewater effluent nutrient requirements. High nutrient levels in wastewater effluents have also caused ongoing tension between the state of Oklahoma and Arkansas regarding the pollution of the Illinois River. This research seeks to establish the relationship between nitrogen to phosphorus ratio in wastewater and the level of nutrient reduction using Chlorella vulgaris. Seed cultures of Chlorella vulgaris were added into solutions with various ratios of nitrate to phosphate representative of treated domestic wastewater and the removal of nitrogen and phosphorus were measured in this study. Results showed phosphate is the limiting factor for Chlorella vulgaris. The removal of nitrate from phosphate-limited wastewater effluent increased significantly by the growth of Chlorella vulgaris when supplemented with phosphate. This suggests that algal nutrient removal might not be suitable as a tertiary treatment for all wastewater effluent. This study will enhance wastewater treatment plants’ knowledgebase about further nutrient reduction techniques, and in turn, make more informed decisions
