Seasonal nitrogen removal in an outdoor polyculture at Nordic conditions

Microalgae is one of the next generation extraction techniques for nutrient removal from wastewater. The nutrients are recovered into microalgal biomass, rich in proteins, lipids and carbohydrates giving an added value that can be used for societal products such as biofuel, bioplastics, feed and fertilizer. We investigated N removal, biomass quality and safety of treating industrial leachate water by a polyculture of local microalgae and bacteria in open raceway ponds, supplied with industrial CO2 effluent, during winter, spring and autumn in SE Sweden. During spring when most TN was removed, the Chlorophyta genera Dangeardinia and Monoraphidium dominated. The bacterial community remained stable throughout the seasons with a large proportion of cyanobacteria. We showed efficient nutrient recovery of multiple waste streams by cultivating microalgae in outdoor raceway ponds in Nordic conditions during winter, spring and autumn.