Evaluation of the hydrolysis performance in the kitchen waste and excess sludge anaerobic co-digestion process

Abstract

Anaerobic co-digestion has been considered to be a promising energy-producing process for kitchen waste and excess sludge treatment. However, the investigation of the hydrolysis performance is still required for further improvement of this process. In this study, the results indicated that the co-digestion model can enhance the system stability during hydrolysis phase. The pH of the co-digestion group remained stable at 6.94–7.18, which had a better buffer capacity compared to the kitchen waste and excess sludge group. The maximum value of dehydrogenase activity was 949 TF μg/(L h) in the co-digestion group, 105% and 30% higher than that in the kitchen waste and excess sludge group, respectively. The protease activity in the co-digestion group reached a maximum of 2.705 U/mL at 4.5th hour, which increased by 94.3% and 46.8% than in the kitchen waste and excess sludge group, respectively. The fitting curve correlation coefficient (R²) of the kinetic model was over 0.997 in three groups, and the generation rate of methane reached 24.489 mL/h in the co-digestion group, representing the highest methane production efficiency.

Keywords:

• kitchen waste
• excess sludge
• co-digestion
• hydrolysis stage
• kinetic model

Acknowledgements

The authors would like to acknowledge Dr Lin Ye of University of Hong Kong for his linguistic help.

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

The authors are grateful for the support provided for this work by the National Natural Science Foundation of China [21276114]; the Natural Science Foundation of Jiangsu Province [BK20130126]; the Scientific and Technological Support of Jiangsu Province, China [BE2012615]; the National Scientific and Technological Support of China [2012BAC18B01–2]; and the Fundamental Research Funds for the Central Universities [JUSRP51315B, LUSRP11435].