High-solid Anaerobic Co-digestion of Sewage Sludge and Cattle Manure: The Effects of Volatile Solid Ratio and pH.

Xiaohu Dai,Jing Yi,Yang Chen,Dong Zhang

doi:10.1038/srep35194

Abstract

High-solid anaerobic digestion is an attractive solution to the problem of sewage sludge disposal. One method that can be used to enhance the production of volatile fatty acids (VFAs) and the generation of methane from anaerobic digestion involves combining an alkaline pretreatment step with the synergistic effects of sewage sludge and cattle manure co-digestion, which improves the activity of key enzymes and microorganisms in the anaerobic co-digestion system to promote the digestion of organic waste. In this study, we describe an efficient strategy that involves adjusting the volatile solid (VS) ratio (sewage sludge/cattle manure: 3/7) and initial pH (9.0) to improve VFA production and methane generation from the co-digestion of sludge and manure. The experimental results indicate that the maximum VFA production was 98.33 g/kg-TS (total solid) at the optimal conditions. Furthermore, methane generation in a long-term semi-continuously operated reactor (at a VS ratio of 3/7 and pH of 9.0) was greater than 120.0 L/kg-TS.

Highlights

Anaerobic co-digestion has several benefits for the digestion of different materials, including increased cost-efficiency, the synergistic degradation of treated materials, optimal moisture and nutrient concentrations, the dilution of inhibitory compounds such as ammonia, the degradation of products such as lipids, and the production of biogas[6,7]
One method that can be used to enhance the production of volatile fatty acids (VFAs) and the generation of methane from an anaerobic digestion system is to combine the alkaline pretreatment step with the synergistic effects of sewage sludge and cattle manure co-digestion, which improves the activity of key enzymes and microorganisms in the anaerobic co-digestion system to promote the digestion of organic waste
The results show that the total VFA production at the volatile solid (VS) ratio of 3/7 was higher during the 6th to 16th day of fermentation than that at the other VS ratios and the sewage sludge- or cattle manure-only reactors

Summary

Introduction

Anaerobic co-digestion has several benefits for the digestion of different materials, including increased cost-efficiency, the synergistic degradation of treated materials, optimal moisture and nutrient concentrations, the dilution of inhibitory compounds such as ammonia, the degradation of products such as lipids, and the production of biogas[6,7]. There is little information regarding the use of high-solid anaerobic co-digestion of sewage sludge and cattle manure to improve volatile fatty acid (VFA) production and methane generation. One method that can be used to enhance the production of VFAs and the generation of methane from an anaerobic digestion system is to combine the alkaline pretreatment step with the synergistic effects of sewage sludge and cattle manure co-digestion, which improves the activity of key enzymes and microorganisms in the anaerobic co-digestion system to promote the digestion of organic waste. The objectives of this study were[1] to study the feasibility of using high-solid anaerobic co-digestion of sewage sludge and cattle manure under mesophilic conditions[2]; to investigate the combined effects of the sewage sludge to cattle manure ratio and the initial pH on the production of VFAs and the generation of methane and to determine the optimal conditions and related mechanisms for maximum VFA production and methane generation; and[3] to analyze the microbial community under the optimal conditions for VFA production and methane generation using 454 high-throughput sequencing in a semi-continuous fermentation experiment

Objectives

Methods

Results

Conclusion