Productivity and municipal wastewater nutrient bioremediation performance of new filamentous green macroalgal cultivars

Filamentous macroalgae show promise as an innovative treatment method to remove residual nutrients from municipal wastewater treatment plant (WWTP) effluents. Therefore, the objective of this study was to isolate and identify target cultivars of freshwater macroalgae for the bioremediation of municipal wastewater. We isolated naturally occurring cultivars of filamentous freshwater macroalgae and successfully scaled up Oedogonium calcareum, O. pringsheimii, and Klebsormidium sp. (two cultivars) into monocultures. We assessed the productivity and bioremediation performance of cultivars on-site in the effluents from two WWTP with differing levels of treatment and differing residual nutrient concentrations. Oedogonium calcareum had the highest biomass productivity (9.7 g DW m(-2) day(-1)) and lowest ash content (6.9-4.2% DW). Oedogonium pringsheimii had the best bioremediation performance, reducing the concentration of dissolved inorganic nitrogen (DIN) in the effluent over a 4-day period in batch culture from 18.6 to 2.2 mg L-1 and the concentration of dissolved reactive phosphorus (DRP) from 4.7 to 2.3 mg L-1 at the WWTP with relatively higher residual nutrient concentrations. Similarly, at the WWTP with relatively lower residual nutrient concentrations, O. pringsheimii reduced the concentration of DIN from 1.8 to 0.01 mg L-1 and the concentration of DRP from 0.03 to 0.01 mg L-1. Our results demonstrate that both O. calcareum and O. pringsheimii would be ideal species to select for the bioremediation of municipal wastewater due to their high productivities, ability to maintain unfouled monocultures in outdoor systems, and superior bioremediation performance. As a next step, continuous cultivation on-site over multiple seasons is required to confirm the suitability of these species as targets for bioremediation applications.

Automated summary

Filamentous macroalgae, specifically Oedogonium calcareum and O. pringsheimii, show potential for innovative treatment of municipal wastewater by effectively removing residual nutrients. Through on-site assessment, it was found that both species are ideal candidates for bioremediation due to their high productivity and superior performance in reducing dissolved inorganic nitrogen and dissolved reactive phosphorus concentrations in wastewater effluents. Further research is needed to confirm their suitability for long-term applications.