Sustainable sorbents for phosphorus recovery and pathogen removal in wastewater treatment

The growing need for sustainable technologies in environmental management has driven research into effective resource recovery methods. One significant challenge is addressing the contamination of water bodies by pathogens (Escherichia coli, Salmonella, and cyanobacteria) and excessive nutrient loads, particularly phosphorus, which contribute to eutrophication and environmental degradation. The aim of this work is to evaluate the effectiveness of calcium and iron oxide composites (CaFeOxide) in removing pathogens and recovering phosphorus from wastewater, with the goal of reducing environmental pollution and enabling the reuse of spent sorbents. The study employed coagulation tests, zeta potential measurements, and microbiological analysis to investigate the sorbent’s performance. The experimental results demonstrated that CaFeOxide composites significantly reduced phosphorus levels in wastewater. Using 2 g/L of the composite, phosphorus concentrations were reduced from 27.4 mg/L to 3.74 mg/L, achieving an 84% reduction. At a higher dosage of 10 g/L, phosphorus removal reached 96%, although the 2 g/L dosage was deemed more economical for practical applications. Additionally, CaFeOxide reduced Bacillus subtilis spores in wastewater by 36.88%, further validating its pathogen reduction capability. The experiments also included soil treatment using the recovered sorbent, which demonstrated its ability to modify soil pH and sustain microbial populations. For instance, at 25 mg of CaFeOxide per kilogram of soil, the pH increased from 8.86 to 9.33, while at 250 mg, the pH rose significantly to 12.08. Despite these pH changes, the microbial population in the soil remained stable, with no statistically significant difference (p > 0.05) observed between the control and treated samples. This indicates that CaFeOxide does not negatively impact soil microbial activity. The findings suggest that CaFeOxide is a viable material for both phosphorus recovery and pathogen reduction in wastewater, with the added benefit of soil amendment potential. Future research should explore the long-term effects of CaFeOxide on soil ecosystems and its performance in removing other pollutants, such as heavy metals and organic contaminants. Additionally, DNA-based microbial analysis could provide further insights into the sorbent’s influence on microbial communities. This research is funded by Fundamental and applied research projects of the Latvian Council of Science “Unused Latvia’s natural mineral resources for the development of innovative composite materials for phosphorus recovery from small municipal and industrial wastewater treatment plants to implement the principles of circular economy (CircleP, No. lzp-2021/1-0090)”.