Microalgae-based wastewater treatments are promising methods to remove pollutants from wastewater and produce valuable biomass byproducts. Waste streams are not only waste but also resources if suitable technologies are applied to recycle elements and bioenergy. For example, iron exchange methods can be used to recover phosphorus from wastewater and produce concentrated phosphate liquid. The anaerobic digestion processes can convert biomass wastes to biogas. This study explored the potential of microalgae-based treatment methods to remove pharmaceutical and personal care products (PPCPs) from wastewater, recover phosphorus from wastewater through an ion exchange method, and produce biogas in anaerobic digestion of prairie grass. This dissertation consists of four experiments organized by chapters modified from journal manuscripts. The first experiment evaluated the PPCPs removal from wastewater through a Revolving algae biofilm (RAB) reactor and studies the fate of PPCPs in the microalgae treatment process. The results show RAB reactors removed the PPCPs with high removal rates. The PPCPs were degraded by microalgae instead of accumulated in microalgae biomass. The second experiment studied the effect of ferrous ion addition on N-diethyl-3-methylbenzamide (DEET) removal in microalgae treatment. Ferrous ion enhanced the production of reactive oxidative species (ROS) inside microalgae cells, which can correlate with DEET degradation enhancement. The impact of acidification on the recovery of phosphorus from wastewater through iron oxyhydroxide was investigated in the third experiment. It can be noted that acidification benefited the regeneration of iron oxyhydroxide by diminishing the absorption of calcium and sodium ions on the surface of iron oxyhydroxide. The fourth experiment assessed the effects of ferrous sulfate biochar on biogas production in the anaerobic digestion of prairie grass. The small dosage of ferrous sulfate biochar increased biogas production, while large dosages retarded biogas production. The negative impacts of both iron element and sulfate ion in biochar were founded on biogas generation.