Water quality restoration by harvesting mixed culture microalgae using Moringa oleifera.

Abstract

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 15ml/L of MO extract, pH 8, mixing time 5min, mixing rate 30rpm, 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±1.5mg/m3 , total nitrogen (TN) from 20.37±4.64 to 12.10±1.19mg/L, and total phosphorus (TP) from 2.05±0.10 to 1.61±0.24mg/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.