On integration of wastewater treatment technologies and production of renewable energy sources

Abstract

The work is devoted to the study of technological processes corresponding to the require-ments of the developing closed-loop economy, which will be based on the wide use of renewable resources, maximum recycling of secondary raw materials, with the transition from fossil fuels to renewable energy sources as one of the objectives. A study of the possibility of producing fatty acid esters from renewable raw materials of plant origin-microalgae Chlorella vulgaris-with the use of municipal wastewater was carried out. Approaches to the development of technologies of fatty acid esters production and promising ways to improve the key stages of such production are con-sidered. It is shown that under certain conditions (temperature of 10-32 °S, illumination of 7-14 klx) mu-nicipal wastewater can be treated and at the same time serve as a nutrient medium in the process of cultivation of microalgae biomass with lipid content of 10-18% of dry matter. Depending on the conditions of cultivation, the cells of the Chlorella vulgaris IPPAS C-2 strain of microalgae reduce the concentration of ammonium cations, phosphate anions and total microbial number in munici-pal wastewater by 93-95% (wt.), 90-97% (wt.) and 86-95%, respectively. The influence of tech-nological conditions of the process on the biomass growth rate and fatty acid composition of accu-mulated lipids is analyzed. It is experimentally established that triglycerides, O-dialkylmonoglycer-ides and fatty acids have the greatest inhibiting effect on the microflora of wastewater. Using Han-sen solubility parameters, a system of polar and non-polar solvents consisting of ethanol and pe-troleum ether in the ratio of 1:2 (vol). was selected, which ensures the efficient conduct of the extraction process. The yield of fatty acid esters of KFAE = 45% was obtained in the course of trans-esterification reaction with the use of ethanol in the ratio with lipids 6:1 (mole) at the reaction temperature of 60 °C in the presence of an alkaline catalyst-sodium hydroxide (3% of the mass of lipids).