Exploring the\nSynergistic Effects of Mixing, Initial\npH Variability, and Light Wavelength on Diatom-Mediated Wastewater\nRemediation

Though diatoms as agents to remove silica pollutants\nhave already\nbeen tested, the factors governing the photobiological process remain\nunexplored. The current process was developed to optimize various\ncombinations of abiotic factors like pH (5, 6, 7, 8, and 9), mixing\nconditions (aeration, magnetic stirrer, and shaking-induced mixing),\nand light wavelength (red: 665–630 nm, blue: 465–430\nnm, and white: 665–420 nm) for silica removal using diatom <i>Navicula</i> sp. from WC media. A combination of pH 7 and magnetic\nstirrer mixing (80–100 rpm) gave the best silica removal at\n11.93 ± 0.15 mg L<sup>–1</sup>d<sup>–1</sup>. This\noptimized process with blue wavelength light increased the silica\nremoval rate to 14.43 ± 0.37 mg L<sup>–1</sup>d<sup>–1</sup> and biomass productivity to 95.15 ± 1.34 mg L<sup>–1</sup>d<sup>–1</sup>. Further, bioremediation of cooling tower blowdown\nwater was tested under optimized and unoptimized conditions. A silica\nremoval rate of 13.90 ± 0.26 mg L<sup>–1</sup>d<sup>–1</sup> was achieved under optimized conditions, 3.69-fold greater than\nthe unoptimized conditions (3.77 ± 0.42 mg L<sup>–1</sup>d<sup>–1</sup>). Additionally, this process removed >99%\nof\ntotal dissolved phosphate (3.05 ± 0.10 mg L<sup>–1</sup>d<sup>–1</sup>), nitrate nitrogen (12.27 ± 0.49 mg L<sup>–1</sup>d<sup>–1</sup>), and 54.27% chemical oxygen\ndemand. Such optimization of abiotic factors using diatoms helps in\nachieving green silica-rich wastewater bioremediation.