a b s t r a c tEffects of different pretreatment methods on sludge inocula were evaluated with respect to hydrogen (H 2 ) production enhancement using palm oil mill effluent (POME) in a batch system. The experimental results showed that the pretreatment methods (chemical, acid, heat-shock, freezing and thawing, and base) at 35 C and initial pH 5.5 had a positive influence on H 2 production yield and chemical oxygen demand (COD) removal efficiency during the fermentative H 2 production as compared to the control experiments (without pretreatment). Heat-shock pretreatment method was shown to be a simple and useful method for enhancing both H 2 producing and COD removal processes from POME with highest H 2 yield and COD removal efficiency at 0.41 mmol H 2 /g COD and 86%, respectively.

In this study, kinetics of biological carbon, nitrogen, and phosphorous removal from a synthetic wastewater in an integrated rotating biological contactoractivated sludge system was investigated. The experimental data obtained from varying four significant independent factors viz., hydraulic retention time, chemical oxygen demand for nitrogen to phosphorus ratio, internal recirculation from aerobic to anoxic zone and disks rotating speed were used for the process kinetic modeling. In order to obtain the bioprocess kinetic coefficients, Monod, firstorder and Stover-Kincannon models were employed. As a result, Monod and Stover-Kincannon models were found to be the appropriate models to describe the bioprocess in the rotating biological contactor-activated sludge system as the determination coefficient for the first-order model obtained less than 0.79. According to the Monod model, growth yield, microbial decay rate, maximum specific biomass growth rate, and half-velocity constant coefficients were found to be 0.712 g VSS/g COD, 0.008/d, 5.54/d and 55 mg COD/L, respectively. From Stover-Kincannon model, the maximum total substrate removal rate constant and half-velocity constant were determined as 15. 2, 10.98, 12.05 g/L d and 14.78, 7.11, 6.97 mg/L for chemical oxygen demand, nitrogen and phosphorus removal, respectively. The kinetic parameters determined in this study can be used to improve the design and operation of the biological contactor-activated sludge system in full scale.

No abstract

No abstract

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.