Efficient nutrient recycling from wastewater to deserts: A comparative study on biocrust cyanobacteria performance

Wastewater is rich in nutrients, while desert regions often suffer from severe nutrient shortages, potentially leading to eutrophication and desertification in respective landscapes. Cyanobacterial cultivation emerges as a promising solution by extracting nutrients from wastewater and transferring them to deserts using cyanobacteria-induced biocrust technology. In this study, two biocrust inducing cyanobacteria, Microcoleus vaginatus and Scytonema javanicum were cultivated in synthetic and municipal wastewater, respectively, to assess their capabilities of nutrient removal and biocrust induction. Both cyanobacteria demonstrated effective removal of nitrogen and phosphorus from either synthetic or municipal wastewater, achieving removal rates exceeding 90 %. Sterilization experiments on the municipal wastewater confirmed that indigenous microorganisms did not influence cyanobacterial performance, though the two cyanobacteira exhibited contrasting growth and metabolic behaviors. Specifically, S. javanicum achieved higher biomass accumulation, reaching up to 6.05 ± 0.87 mg Chl-a L−1, whereas M. vaginatus produced more exopolysaccharides, up to 40.98 ± 2.96 mg L−1 in the municipal wastewater. The cyanobacteria harvested from the municipal wastewater effectively promoted biocrust formation, validating the feasibility of transferring nutrients from wastewater to deserts through cyanobacteria-induced biocrusts. Considering their varied growth behaviors, our findings advocate for the use of a combination of diverse cyanobacteria strains to optimize cultivation and inoculation technologies.