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Abstract A hybrid anaerobic activated sludge and rotating biological contactor (AnAS-RBC) reactor with sludge return was investigated for biological hydrogen production from molasses by a mixed culture of hydrogen-producing bacteria via a dark fermentation process. The pH was not controlled during the experiments. The effects of organic loading rate (OLR) and disk rotational speed (DRS) on process performance were studied using response surface methodology. Both OLR and DRS showed significant effects on all process responses. High levels of DRS were found favorable for efficient process. Optimal mixing of the bacterial culture contributed towards higher acetate production resulting in higher hydrogen production. The highest hydrogen production (168 mL/g COD) was achieved by applying OLR and DRS of 23 g/L.d and 30 rpm, respectively. In this study, the highest percentage of hydrogen in biogas produced was 87% in hydraulic retention time of 12 h. Highlights • Using a hybrid AnAS-RBC reactor for biohydrogen production from molasses. • Focusing on the effects of OLR and DRS, and delineating the mixing behavior. • The DRS exerted stronger effect than OLR on all process responses. [ABSTRACT FROM AUTHOR]

The major problem associated with UASB reactors for biotransformation of organic matter to hydrogen is the long start-up period (2-4 months) required for the growth of the microbial granules. In this study, an integration of granular sludge system and a fixed film reactor in a single reactor was applied to overcome this problem. An up-flow anaerobic sludge blanket-fixed film (UASB-FF) reactor was initially inoculated with heat pretreated seed sludge as inoculum and operated as closed-loop fed-batch for five days (HRT = 24 h; 38 °C; pH 5.5). The reactor was continuously fed with fresh pre-settled POME in order to shorten the start-up period. The organic loading was gradually increased from 4.7 to 51.8 g/L d. Granular sludge rapidly developed within 22 days. Specific hydrogen production rate was 0.514 L H2/gVSS d at the end of the start-up period. Speedy development of bio-granules was attributed to biomass recirculation and the establishment of a fixed film at the upper section of the UASB-FF reactor that resulted in improved interactions among the bacterial consortium. [ABSTRACT FROM AUTHOR]

Abstract: Effects of three selected variables viz. biomass concentration, initial chemical oxygen demand (COD) concentration and initial bicarbonate alkalinity (BA) on biological hydrogen production from palm oil mill effluent (POME) using the granulated sludge in batch culture were investigated. The experimental results were analyzed and modeled using a central composite design (CCD) of response surface methodology (RSM). In order to carry out a comprehensive analysis of the biohydrogen production process, indicative parameters namely hydrogen yield (YH), specific hydrogen production rate (SHPR), and COD removal efficiency were studied as the process responses. Maximum hydrogen yield (124.5 mmol H2/g CODremoved) and specific hydrogen production rate (55.42 mmol H2/g VSS.d) were achieved at CODin 3000 and 6500 mg/l, MLVSS 4000 and 2000 mg/l, and initial BA 1100 mg CaCO3/l, respectively. [Copyright &y& Elsevier]

Hydrogen (H2) is one of renewable energy sources known for its non-polluting and environmentally friendly nature, as its end combustion product is water (H2O). The biological production of H2 is a less energy intensive alternative where processes can be operated at ambient temperature and pressure. Dark fermentation by bacterial biomass is one of multitude of approaches to produce hydrogen which is known as the cleanest renewable energy and is thus receiving increasing attention worldwide. The present study briefly reviews the biohydrogen production process with special attention on the effects of several environmental and operational factors towards the process. Factors such as organic loading rate, hydraulic retention time, temperature, and pH studied in published reports were compared and their influences are discussed in this work. This review highlights the variations in examined operating ranges for the factors as well as their reported optimum values. Divergent values observed for the environmental/operational factors merit further exploration in this field. [ABSTRACT FROM AUTHOR]