Study on hydrogen production with hysteresis in UASB

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Polyethylene terephthalate (PET) manufacturing generates esterification wastewater.
• Wastewater treatment often involves biological processes for resource recovery.
• Hydrogen (H2) production is a potential valuable outcome of anaerobic wastewater treatment.

Purpose of the Study:

• To investigate the impact of temperature fluctuations on hydrogen production.
• To evaluate the effect of different organic loading rates on H2 yield and associated parameters.
• To identify hysteresis phenomena in H2 production and related chemical species during temperature cycling.

Main Methods:

• Utilized a 10-L upflow anaerobic sludge blanket (UASB) reactor.
• Treated esterification wastewater from a PET plant.
• Applied two organic loading rates: 4.5 kg COD m(-3)d(-1) and 2.2 kg COD m(-3)d(-1).
• Gradually stepped temperature up and down between 11-25°C, monitoring H2 production and chemical oxygen demand (COD), acetate, propionate, and butyrate concentrations.

Main Results:

• Hydrogen production showed a positive correlation with temperature, especially at the higher organic loading rate.
• Hysteresis curves were observed for H2 production and concentrations of COD, acetate, propionate, and butyrate at 4.5 kg COD m(-3)d(-1).
• At the lower organic loading rate (2.2 kg COD m(-3)d(-1)), H2 production hysteresis was minimal, though other parameters exhibited counterclockwise hysteresis.

Conclusions:

• Temperature is a critical factor influencing H2 production efficiency in UASB reactors treating PET esterification wastewater.
• Hysteresis in H2 production and related parameters suggests complex microbial community responses to temperature changes, particularly under higher organic loads.
• Understanding these temperature-dependent dynamics and hysteresis is crucial for optimizing anaerobic digestion processes for enhanced biohydrogen generation.