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Energies 2017, 10(2), 258; doi:10.3390/en10020258

The Influence of Micro-Oxygen Addition on Desulfurization Performance and Microbial Communities during Waste-Activated Sludge Digestion in a Rusty Scrap Iron-Loaded Anaerobic Digester

1,2
,
1,2,* , 1,2
,
1,2
and
1,2
1
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China
2
College of Environment, Hohai University, Nanjing 210098, China
*
Author to whom correspondence should be addressed.
Academic Editor: Ihsan Hamawand
Received: 23 November 2016 / Revised: 14 February 2017 / Accepted: 16 February 2017 / Published: 21 February 2017
View Full-Text   |   Download PDF [2715 KB, uploaded 21 February 2017]   |  

Abstract

In this study, micro-oxygen was integrated into a rusty scrap iron (RSI)-loaded anaerobic digester. Under an optimal RSI dosage of 20 g/L, increasing O2 levels were added stepwise in seven stages in a semi-continuous experiment. Results showed the average methane yield was 306 mL/g COD (chemical oxygen demand), and the hydrogen sulphide (H2S) concentration was 1933 ppmv with RSI addition. O2 addition induced the microbial oxidation of sulphide by stimulating sulfur-oxidizing bacteria and chemical corrosion of iron, which promoted the generation of FeS and Fe2S3. In the 6th phase of the semi-continuous test, deep desulfurization was achieved without negatively impacting system performance. Average methane yield was 301.1 mL/g COD, and H2S concentration was 75 ppmv. Sulfur mass balance was described, with 84.0%, 11.90% and 0.21% of sulfur present in solid, liquid and gaseous phases, respectively. The Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis revealed that RSI addition could enrich the diversity of hydrogenotrophic methanogens and iron-reducing bacteria to benefit methanogenesis and organic mineralization, and impoverish the methanotroph (Methylocella silvestris) to reduce the consumption of methane. Micro-oxygen supplementation could enhance the diversity of iron-oxidizing bacteria arising from the improvement of Fe(II) release rate and enrich the sulphur-oxidising bacteria to achieved desulfurization. These results demonstrated that RSI addition in combination with micro-oxygenation represents a promising method for simultaneously controlling biogas H2S concentration and improving digestion performance. View Full-Text
Keywords: micro-oxygen; anaerobic digestion; chemical corrosion; average methane yield; sulfur-oxidizing bacteria; desulfurization efficiency; sulfur balance micro-oxygen; anaerobic digestion; chemical corrosion; average methane yield; sulfur-oxidizing bacteria; desulfurization efficiency; sulfur balance
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Ruan, R.; Cao, J.; Li, C.; Zheng, D.; Luo, J. The Influence of Micro-Oxygen Addition on Desulfurization Performance and Microbial Communities during Waste-Activated Sludge Digestion in a Rusty Scrap Iron-Loaded Anaerobic Digester. Energies 2017, 10, 258.

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