Hydrogen Production by Anaerobic Microbial Communities Exposed to Repeated Heat Treatments

Abstract

Biological hydrogen production by anaerobic mixed communities was studied in batch systems and in continuous-flow bioreactors using sucrose as the substrate. The systems were seeded with anaerobically digested municipal biosolids that had been heat treated at 100°C for 15 minutes. During operation, repeated heat treatments of the biomass in the reactors at 90°C for 20 minutes were performed. Results indicated that both initial heat treatment of the inoculum and repeated heat treatments of the biomass during operation promoted hydrogen production by eliminating non-spore forming hydrogen consuming microorganisms and by selecting for hydrogen producing spore forming bacteria. An operational pH of 5.5 was shown to be optimal for hydrogen production. The conversion efficiency and hydrogen yield were 0.0892 L-H 2 /g-COD and 1.5291 mole of H 2 /mole of sucrose, respectively. Terminal restriction fragment length polymorphism (T-RFLP) analysis showed that Clostridium and Bacillus species were dominant populations in the bioreactors. A positive correlation was observed between the total abundance of Clostridium species and hydrogen production during part of an operational run.

Optimizing the impact of temperature on bio-hydrogen production from food waste and its derivatives under no pH control using statistical modelling

“…Although such 6504 C. Arslan et al: Optimizing the impact of temperature on bio-hydrogen production addition can maintain a specific pH and nutrimental required for optimum bio-hydrogen production, but it also increases the cost of production (Nielsen et al, 2001;. The cost of production can be reduced by adding sewage sludge as a source of Clostridium mix culture (Fang et al, 2006). Nutritional deficiency in food waste was also balanced by adding sewage sludge that made food waste more suitable for bio-hydrogen production .…”

“…Heat treatment is mostly opted to deactivate hydrogen consumers. The traditional method of placing sewage sludge in boiling water is now no longer in practice and is replaced by microwave heating that provide more uniform heating as compared to the boiling water method (Luo et al, 2010;Wang et al, 2011;Duangmanee et al, 2007). The temperature and time for heat treatment varied from 75 to 121 • C for 15 min to 2 h, but 100 • C for 15 min was mostly reported Fang et al, 2006).…”

“…Theoretically, 553 mL hydrogen can be produced by 1 g of polysaccharides if it is totally converted into acetate. The highest practical yield of 346 mL g −1 carbohydrate was achieved by Fang et al (2006) by using rice as a source of carbohydrate (78 %), pre-treated sewage sludge as a source of Clostridium and adding a variety of nutrients. Rice waste and noodle waste has 40 % share in the total food waste produced in China (Shiwei, 2005).…”

“…So, by co-digestion, the pH of the anaerobic digestion process can be improved and it can be further adjusted to a desired initial value by adding HCl or NaOH. After adjusting the desired initial pH under co-digested conditions, the biohydrogen production can be achieved under no pH control conditions, which can reduce the cost of operation (Fang et al, 2006).…”

“…The yield of bio-hydrogen is calculated by dividing the cumulative hydrogen produced by VS, chemical oxygen demand (COD) or glucose (Chen et al, 2006;Dong et al, 2009;Fang et al, 2006). The yields are misleading if calculated in terms of added or start up values of VS, COD and glucose as it seems quite impossible that the whole of added material is converted into hydrogen.…”