Effect of mild-temperature H ₂O ₂ oxidation on solubilization and anaerobic digestion of waste activated sludge

Abstract

Efficient sludge management is among the most challenging issues in wastewater treatment today, and anaerobic digestion is regarded as a viable solution. Mild-temperature H ₂O ₂ oxidation was examined for enhanced solubilization and biogas production of waste activated sludge (WAS). The effects of pretreatment factors (i.e. temperature and H ₂O ₂ concentration) on the degree of WAS disintegration (DD) and biogas yield (BY) were assessed by response surface analysis within the design space of 60–90°C and 0–200 mM H ₂O ₂. Significant sludge disintegration (up to 23.0% DD) and visibly enhanced BY (up to 26.9%) were shown in the pretreatment trials. Two response surface models to describe how DD and BY respond to changes in the pretreatment conditions were successfully constructed (R²>0.95, p<0.05). The models showed totally different response surface shapes, indicating the DD and BY were influenced by pretreatment conditions in very different ways. DD was dominantly affected by temperature and showed higher model responses at the high-temperature region, while the BY response peaked in the low-temperature and mid-level H ₂O ₂ region. This observation implies that the enhanced solubilization of WAS was not directly translated into an increase in biogas production. Our results showed that WAS can be efficiently disintegrated by H ₂O ₂ oxidation under mild-temperature conditions for enhanced anaerobic digestibility. Within the explored region of pretreatment conditions, the maximum BY was estimated to be 82.1 mL/gCOD_added (32.8% greater than the untreated control) at (60.0°C, 74.2 mM H ₂O ₂).

Keywords:

• anaerobic digestion
• hydrogen peroxide (H ₂O ₂)
• pretreatment
• response surface analysis
• waste activated sludge

Acknowledgements

This research work was carried out with the financial assistance of Ulsan Green Environment Center (UGEC), Korea and of the 2013 Research Fund of Ulsan National Institute of Science and Technology (UNIST).