Abstract:
Nowadays, the major energy source of the world is fossil fuels, such as oil coal, and natural gas. The demand of fossil fuels has increased in recent years, so the limited amount of fossil fuels results in their high price. Moreover, the combustion of fossil fuels can cause a global warming effect. Therefore, hydrogen has been increasingly focused. It is an odorless, colorless, tasteless, and non-poisonous gas. In this research, hydrogen production from ethanol wastewater via dark fermentation by using up flow anaerobic sludge blanket (UASB) reactors was investigated under mesophilic operation. A wastewater from an ethanol production plant containing chemical oxygen demand (COD) value of 60,000 mg/l was selected as a substrate. Each UASB reactor with a 24-liter liquid holding volume was operated at a temperature of 37°C and controlled pH of 5.5. The system was operated at different COD loading rates of 10, 15, 20, 25, 30, and 35 kg/m³ d. The results showed that the optimum COD loading rate was suggested at 30 kg/m³ d. Under this condition, the acceptably high hydrogen production rate of 13.3 l/d, hydrogen yield of 93.9 ml H₂/g COD removed. Specific hydrogen production rate of 41.4 ml H₂/g MLVSS d, and COD removal efficiency of 19.7% were achieved.
