Investigation of the Role of Selected Fungal Strains in the Removal of Phosphate and Nitrate in Synthetic Wastewater

Abstract

Aims: This study investigate the role of four fungi species in the removal of phosphate and nitrate in a low nutrient synthetic wastewater. Also investigated was the effect of initial inoculum size on the nutrient removal ability of the strains. Materials and Methods: The fungal strains used for the study were Aspergillus niger, Aspergillus flavus, Absidia spp and Fusarium spp Four different initial inoculum sizes of each of the respective isolates were used for the nutrient removal studies. After inoculation with the test strains, aliquot samples were taken from the media at time zero and every 24h, for the estimation of total phosphate, nitrate and pH in the medium, using standard methods. Results: All the strains showed nitrate removal ability, irrespective of the initial inoculum size used for inoculation. After 96 h, the percent nitrate removed ranged from 25.25% to 77.52%, 26.12% to 39.80%, 8.88% to 44.23% and 29.50% to 87.34%, in the presence of Aspergillus niger, Aspergillus flavus, Absidia spp and Fusarium spp, respectively. None of the fungi exhibited phosphate removal ability, except Aspergillus niger which showed very slight potential for phosphate removal. Despite the observed differences in nitrate concentration removed by the different strains, these differences were not observed to differ significantly between the initial inoculum sizes used for investigation (p≤ 0.05). Similarly, the phosphate concentrations in the presence of the test strains did not differ significantly between the different initial inoculum sizes (p≤ 0.05). The pH values of the wastewater inoculated with the fungal strains increased with time of incubation. This trend was also observed irrespective of the initial inoculum size used. Conclusion: The study was able to provide an insight into the phosphate and nitrate removal efficiency of the test strains under the experimental conditions. Keywords: Phosphate; nitrate; fungi; nutrient removal; wastewater.