Phycoremediation of wastewater by diatoms and microalgae

Abstract

Native microalgae and diatoms were isolated from wastewater collected from Jayanti Ki Rao (JKR) Channel, Kharar. Morphological characterisation showed dominant diatom species Navicula sp. and Nitzschia sp. These diatoms along with previously isolated microalgae Chlorella sp. (DGNH-3) and Scenedesmus sp. (DGNH-4), were employed to evaluate their phycoremediation potential by treatment of effluent from Sewage Treatment Plant (STP) of Thapar Technology Campus, Patiala. The performance of individual cultures and mixed consortia was assessed based on dissolved oxygen enhancement, biomass productivity, nutrient removal, and improvement of wastewater quality. Wastewater treatment significantly improved water quality parameters. Dissolved oxygen (DO) increased from 2.34 ± 0.01 mg/L to 10.4 ± 0.01 mg/L in the control (77.5% increase), 10.09 ± 0.01 mg/L in the diatom treatment (76.81% increase), and 11.5 ± 0.01 mg/L in the algal–diatom consortium (79.65% increase). Biological oxygen demand (BOD) decreased from 190 ± 0.02 mg/L to 41 ± 0.02 mg/L in the control (78.42% reduction efficiency), 23 ± 0.02 mg/L in the diatom treatment (87.89% reduction efficiency), and 20 ± 0.02 mg/L in the consortium (89.47% reduction efficiency). Total dissolved solids (TDS) were reduced from 1.30 ± 0.03 ppm to 0.757± 0.03 ppm (41.77% reduction), 0.786 ± 0.01 ppm (39.54% reduction), and 0.615 ± 0.03 (39.54% reduction) ppm in the control, diatom, and consortium treatments, respectively. Similarly, conductivity declined from 1658 ± 0.02 μS/cm to 1193 ± 0.04 μS/cm (control) (28.04% reduction), 1173± 0.02 μS/cm (diatoms) (29.25% reduction), and 1163 ± 0.02 μS/cm (consortium) (29.86% reduction), demonstrating that the algal–diatom consortium achieved the highest overall remediation efficiency. Biomass productivity demonstrated effectiveness of microalgae in simultaneous treatment of wastewater and biomass generation. These findings overall confirm that microalgal–diatom consortia are an efficient environmentally sustainable solution for wastewater cleanup.