Microalgae-based Wastewater Treatment and Production of Value Added Products

Using microalgae in wastewater treatment is a cost-effective and environmentally friendly alternative to energy-consuming conventional methods. Microalgae include cyanobacteria and eukaryotic algae, which can bio-fix CO₂ and utilize nutrients such as nitrogen and phosphorus in the wastewater, reducing their concentrations and aiding in biomass production. These microorganisms help to remove nutrients by photosynthesis of carbon dioxide into oxygen so that heterotrophic bacteria can utilize the oxygen to degrade the soluble organic pollutants and augment wastewater treatment operations. Phosphorus recovery with algae granules has been particularly effective and essential for resource recycling in the circular green economy. Emerging contaminants, including pharmaceutical and personal care products (PPCPs), agrochemicals, single-use plastics, and heavy metals, are detected in wastewater and rivers and are causing a threat to humans and aquatic organisms. In contrast, single-use plastic contributes to pollution by microplastics. Water sources are affected by the effluence of heavy metals, which are by-products of different industries. Microalgae can remove contaminants and produce biofuels, among other benefits. This chapter explores the ability of microalgae to recover nutrients from wastewater, reduce greenhouse gases, and remove pollutants to improve the sustainability of wastewater treatment systems.