Coupled nutrient removal from the wastewater and CO2 biofixation from the flue gas of iron and steel manufacturing

CO2 mitigation through photosynthesis has attracted attention as an alternative strategy over chemical methods because it is less costly and energy-consuming. When the microalgae are fed with wastewaters containing high nitrogen and phosphorus, they remove nitrogen and phosphorus from the wastewater. Moreover, the harvested biomass from microalgal reactors constitutes a raw material for the production of different high-value chemicals and bio-fuels. This study investigated the coupled removal of CO2 from the flue gas and nutrients (nitrogen and phosphorus) in the wastewater originating from the coking unit of iron-steel industry by using microalgal photobioreactors. The results indicated that the flue gas from coking unit of a typical iron and steel factory and the wastewater from the same process supported the microalgal growth. Photobioreactors achieved CO2 fixation rates of 11.45–13.52 mg/L day. Notable nutrient (up to 77% total ammonia nitrogen (TAN) and 61% PO4) and heavy metal (72% Cr, 63% Fe, 22% Cu and over 90% Cd) removals were observed in the coking process wastewater which was used to grow microalgal cultures.