Investigating the efficiency of biogas production using modelling anaerobic digestion of baker's yeast wastewater on two-stage mixed-UASB reactor

Abstract

Baker’s yeast wastewater containing about 20,000 mg COD l−1 organic compounds was used to produce biogas in a two-stage mixed-UASB rector. The main goal is to model this system and compare the results with the laboratory model. Therefore, based on the existing laboratory model, including a mixed-UASB reactor, a mathematical modeling simulation was developed using the Monod equation to justify the behavior of the reactors. The experiments were performed over 40-day periods. According to modeling, by increasing the concentration of inlet wastewater, the removal of organic compounds was increased, while the methane production efficiency was decreased. In the concentration range from 1.55 to 4.1 mg COD cm−3, the lowest and the highest amount of chemical oxygen demand efficiency was 9.05% and 35.98%, respectively. The volume of obtained biogas from wastewater at the end of 40 days was 113.4 L. Experiments show that for a period above 40 days, the biogas production time in the methanogenic reactor is negligible and baker's yeast wastewater is completely decomposed into acidic compounds. Because of the high sensitivity of methanogenic bacteria to pH, it is important to keep the pH value between 6.8 and 7.8, so it is better to maintain the alkalinity about 1500 to 7500 mg CaCO3 l−1 to create a good reactor capacity.