Evaluation of pretreatment methods and initial pH on mixed inoculum for fermentative hydrogen production from cassava wastewater

Abstract

The main factors that affect the biohydrogen production from renewable resources are continually studied because their limitations are variable and depend largely on the substrate type, especially when using real wastewater. Inoculum pretreatment and pH are critical factors that govern the metabolic pathways driving the fermentative hydrogen production. In this work, the influence of inoculum pretreatment and initial pH on the fermentative production of hydrogen was investigated using cassava wastewater in anaerobic batch reactors at room temperature (29.0–34.5 °C). A mixed factorial design was performed to evaluate the effect of initial pH and inoculum pretreatment on hydrogen yield. Two pretreatment methods were evaluated (chemical and heat), and the initial pH was examined at three levels (5.7, 5.4, and 5.0). The pretreatments efficiently inhibited the activity of hydrogen-consuming bacteria for short periods. The highest biogas production, 91 ± 14 mL, was achieved with chemical pretreatment at pH 5.4, and 86 ± 12 mL of biogas was obtained with heat pretreatment at pH 5.0. Moreover, the results showed that the optimum pH interval for fermentative hydrogen production from cassava wastewater was between 5.0 and 5.4, and the highest yield of H2 was 1.25 ± 0.01 mol H2 mol−1 carbohydrates with heat pretreatment.