Gulab Singh

Excessive growth of microalgae results in the eutrophication and degradation of water quality in lakes and ponds. Microalgae have proved to be very beneficial for sustainable development. Its applications, starting from growth to death, make them a valuable resource for food and energy production. However, presence of microalgae in surface water sources affects water quality and its beneficial uses. The excess nutrient-rich agriculture runoff also adds problems to the downstream systems. Nutrient removal and microalgae harvesting are considered the most problematic task for improving water quality of surface waters. The main objective of the present study was to improve the water quality of nutrient rich waters using attached growth systems. The use of batch and continuous flow baffled attached growth systems has successfully improved the water quality and produced algal biomass that can be utilized or transformed into other valuable products. The performance of continuous flow baffled attached growth system was better and it improved the quality of oligotrophic, mesotrophic, eutrophic and hypereutrophic waters by removing>95% of TN and TP in 35, 63, 63 and 4 days, with biomass productivity of 2.69 ± 0.21, 3.17 ± 0.06, 3.61 ± 0.16 and 4.64 ± 0.3 g_DWm⁻² day⁻¹, respectively.

Excessive growth of microalgae due to use of fertilizers, detergents, and discharge of domestic waste results in the eutrophication and degradation of the water quality of lakes and ponds. The present study aimed to improve the quality of pond water by harvesting mixed cultures of microalgae grown in a pond using Moringa oleifera (MO) extract as a coagulant. The study comprises evaluating the effects of coagulant dose, pH, mixing time, mixing rate, settling time, temperature, and algal biomass concentration on nutrient and microalgae cell removal. The pond water quality restoration was assessed by characterization of raw and MO‐treated water. The MO was found to be very effective for mixed culture microalgae harvesting with flocculation efficiency of 92.97% at dose of 15 ml/L of MO extract, pH 8, mixing time 5 min, mixing rate 30 rpm, and 20‐min settling time. The results have shown significant improvement in pond water quality with reduction in turbidity from 388.16 ± 48.23 to 8.39 ± 1.0 NTU, chlorophyll‐a from 635.01 ± 86.20 to 15.03 ± 1.5 mg/m³, total nitrogen (TN) from 20.37 ± 4.64 to 12.10 ± 1.19 mg/L, and total phosphorus (TP) from 2.05 ± 0.10 to 1.61 ± 0.24 mg/L.Practitioner points: Production of biomass and water quality improvement of the pond at the same time MO extract shows better removal efficiency at a lower dose with fast kinetics Cost‐effective flocculant saves time and energy during flocculation Common bioflocculant to remove both microalgae and nutrients.