Investigation of the Characteristics and Growth of Chlorella variabilis via Biosorption of a Steel Industry Wastewater

Abstract

Industrialization is rapidly increasing by releasing a wide range of pollutants such as persistent organic pollutants, heavy metals, dyes to the environment. These pollutants to elimination require strongly effective treatment methods. Biosorption is a promising technology compared to the most wastewater treatment method which uses biomaterials to remediate the pollutants. This study aimed at investigating the removal of pollution parameters of a steel industry wastewater by using Chlorella variabilis microalgae. Additionally, after the treatment, investigation of efficient utilization of used microalgae into the biodiesel fuel is the other main objective. Microalgae strains were inoculated to the diluted and undiluted wastewater samples and cultured at 200 rpm, 27 degrees C and 2 Klux light in a shaking incubator. Wastewater was diluted with tap water in different proportions by volume. During the culture/treatment period, pH, temperature, and optical density were measured. After the treatment, lipid content, fatty acid compositions of the biomass, and metal ions amount of the treated wastewater were determined. The growth of biomass was observed barely for all samples. The highest lipid content (26%) and lipid productivity 0.74 mg/L day were observed in the undiluted sample. The fatty acids composition was determined to be rich in Pentadecanoic acid (63.3%) and the Cetane Number (CN) value of the methyl ester mixture of algal oil was calculated as 65.26 for the same culture media. Also, the removal of 85% iron and 60% zinc was achieved in the undiluted sample. The maximum biosorption capacities of Chlorella variabilis for Fe, Cu, and Zn ions were 867, 118, and 52 mg/g dry biomass, respectively. As a result, the study suggests that using microalgae in wastewater treatment is hopeful for the development of environmentally friendly, more efficient, and economical technologies. Besides, due to the high amount of cetane number in this oil, it is suitable to be used as a source of raw material in biodiesel production.