Utilization of Microalgae for Urban Wastewater Treatment and Valorization of Treated Wastewater and Biomass for Biofertilizer Applications

Rapid urbanization has substantially increased freshwater consumption and consequent wastewater generation. The produced wastewater is an abundant resource of phosphorus, nitrogen, and organics. Currently, well-established activated sludge processes are utilized in conventional wastewater treatment plants to remove organics. However, removing nitrogenous and phosphorus compounds continues to be challenging and energy-intensive for urban wastewater treatment plants. Therefore, the current study aims to understand how photosynthetic microalgae can recover phosphorus and nitrogen from urban wastewater and how wastewater-grown microalgae biomass may be used as a biofertilizer and biostimulant. Utilizing microalgae biomass treated with urban wastewater as a biofertilizer promotes plant growth in a manner similar to other organic manures and conventional fertilizers while minimizing nutrient loss to the soil. Furthermore, the microalgal recovery of nutrients from urban wastewater could have potential energy reductions of 47% and 240% for nitrogen and phosphorus, respectively. In addition to producing treated wastewater suitable for a variety of irrigation systems, microalgae biomass is a potential sustainable alternative resource that could reduce conventional inorganic fertilizer usage.