Application of nanotechnology in anaerobic digestion for biohydrogen production improvement from natural coagulation/flocculation sludge using metallic oxide nanoparticles

The production of second-generation biohydrogen from organic waste by the dark fermentation process is a solution to reduce the immense volume of waste generated by the food industry. In this study, a coagulation sludge was recovered from the settling tank after treating cheese whey wastewater by natural coagulation/flocculation process. The sludge was used as a substrate for dark fermentation. In the biodigestion study, mixed culture from a biological treatment plant was used as inoculum. The whole process was set under defined conditions to favor hydrogen production. A series of Inoculum/Substrate (I/S) ratios (1/2, 1/3, 1/4, 1/5 and 1/6, g VS inoculum/g VS substrate) were studied in order to determine the optimum ratio for better biohydrogen production. The optimum (I/S) ratio was found to be 1/2 resulting in the highest biohydrogen volume of 237 mL/gVS. The production of biohydrogen as a function of the concentration of different nanoparticles has been studied. Several nanoparticles have been synthetized and tested: CuO, Fe2O3, TiO2. The production of biohydrogen has varied widely depending on the concentration and type of nanoparticles used. All the studied nanoparticles showed an evolution of biogas production. The maximum biohydrogen volume increase was obtained by TiO2 NPs at 0.5 mg/L of concentration noting more than 337% of a biohydrogen volume improvement (total produced volume 800 mL/gVS).