Harvesting of Dunaliela Salina at Low Concentrations using Spiral Electrocoagulation (SEC)

Abstract

Harvesting of Dunaliella salina at low concentrations is more difficult to collect and requires special harvesting procedures. This is because the microalgae are more dispersed in the culture medium, making it harder to separate from the medium. When microalgae are harvested, it will produce wastewater that contains excess nutrients such as nitrate and phosphorus. Wastewater of microalgae harvesting should not contain microalgae and excess nutrients. These pollutants cause eutrophication of water bodies and ecosystem destruction when left untreated. The aims of the study were to analyze the harvesting efficiency of D salina at low concentrations and evaluation the nutrients in the wastewater produced from D salina harvesting. In this study, we used spiral electrocoagulation (SEC) with variations in voltage (16, 18, and 20 V) and electrolysis times (1, 3, and 5 min), a surface area of 88.13 cm-2, and a stirring speed of 400 rpm. The response surface method was utilized to optimize operating conditions that were CCD-randomized by five levels of two variables. Harvesting of D salina at low concentrations reached a maximum efficiency of 74.6% when voltage was set to 20 V for five minutes with surface area (Fe) 88.13 cm-2, stirring speed = 400 rpm, current intensity = 2.1 A. The power consumption required to harvest D salina at a low concentration, which is 0.426517 kWh/kg biomass, is higher compared to a higher microalgae concentration. Nutrients (nitrate and phosphate) in the wastewater were successfully reduced by 97 % using SEC within one minute under 20 volts applied.