High-rate filamentous algal pond (HRFAP) systems offer a promising alternative to conventional municipal wastewater treatment. Research on selecting filamentous algal species for municipal wastewater bioremediation is currently limited. Chapter 2 introduces a screening protocol aimed at identifying robust cultivars suitable for HRFAP monoculture systems. Evaluating eleven cultivars under local seasonal ambient and extreme conditions played a crucial role in cultivar selection. Based on their consistent biomass productivity and bioremediation performance across ambient and extreme conditions, Klebsormidium sp. (KLEB B), Stigeoclonium sp. (STIG A) and Ulothrix sp. were identified as target cultivars for nutrient bioremediation of primary municipal wastewater. The identification of target cultivars has previously been based on laboratory conditions, which are insufficient for practical applications. Chapter 3 assessed the biomass productivity and nutrient bioremediation performance of three cultivars - Klebsormidium flaccidum, Oedogonium calcareum, and Oedogonium sp. – in outdoor HRFAP mesocosms. K. flaccidum had the highest biomass productivity and bioremediation performance, while O. calcareum had complete die-off. Competition experiments at varying stocking densities highlighted K. flaccidum dominance at lower densities (0.25 and 0.5 g FW L-1), positioning it as the preferred cultivar for nutrient bioremediation in primary municipal wastewater within HRFAP systems. Effective management of operational parameters is crucial for optimising wastewater treatment in HRFAP systems. Therefore, in Chapter 4 the effects of hydraulic retention time (HRT), stocking density, and harvest frequency on the growth and nutrient bioremediation performance of K. flaccidum in primary municipal wastewater in outdoor HRFAPs were examined during summer and winter. Seasonal conditions impacted biomass productivity, which was 48.3% higher in summer compared to winter. A HRT of 4 days was optimal for both seasons based on bioremediation of total ammoniacal-nitrogen (TAN). Lower stocking densities of 0.25 and 0.5 g FW L-1 demonstrated enhanced bioremediation efficiency, while higher densities were preferable during slower growth periods to mitigate potential toxicity risks from primary wastewater. Harvest frequencies of two, four and six days did not significantly affect nutrient removal rates across different treatments and seasons. These results highlight the importance of seasonal optimisation of HRFAP systems to maximise biomass production and nutrient bioremediation. Wastewater treatment plants (WWTPs) are major sources of per- and polyfluoroalkyl substances (PFAS) pollution entering the environment. Certain algal species have demonstrated the ability to bioaccumulate PFAS compounds, indicating their potential for removing PFAS from wastewater. Therefore, in Chapter 5 a laboratory study was conducted to assess the ability of K. flaccidum to reduce concentrations of PFAS and PFAS precursors in primary municipal wastewater under two HRTs. K. flaccidum maintained stable productivity in the wastewater. Removal rates of PFAS and PFAS precursors, however, varied considerably. Specifically, reductions were observed in three individual PFAS and in all measured PFAS precursors present in the wastewater. Despite these reductions, PFAS was not detected in the algal biomass of K. flaccidum, making it suitable for a range of biomass applications provided it remains free of other contaminants. Overall, this thesis has demonstrated that HRFAP systems are an effective alternative treatment for nutrient reduction in primary municipal wastewater. Application of the screening protocol to select target species, and seasonal optimisation of HRFAP operating parameters will enable more consistent and effective year-round nutrient bioremediation and algal biomass productivity to be achieved.