Enhanced high-solids anaerobic digestion of waste activated sludge by the addition of scrap iron

Zhang, Yaobin; Feng, Yingtong; Yu, Qilin; Xu, Zhiyuan; Quan, Xie

doi:10.1016/j.biortech.2014.02.114

Cited by 141 publications

(43 citation statements)

References 31 publications

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“…All BMP tests were conducted at 35 6 1uC for 20 d. The biogas (methane) production in BMP vials was collected and monitored by using gas chromatograph (Shimadzu, GC-14C) equipped with a thermal conductivity detector. More details of the BMP tests can be found elsewhere 32,33 .…”

Section: Methodsmentioning

confidence: 99%

Zero Valent Iron Significantly Enhances Methane Production from Waste Activated Sludge by Improving Biochemical Methane Potential Rather Than Hydrolysis Rate

Liu¹,

Wang²,

Zhang³

et al. 2016

Environmental Engineering and Activated Sludge Processes

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Anaerobic digestion has been widely applied for waste activated sludge (WAS) treatment. However, methane production from anaerobic digestion of WAS is usually limited by the slow hydrolysis rate and/or poor biochemical methane potential of WAS. This work systematically studied the effects of three different types of zero valent iron (i.e., iron powder, clean scrap and rusty scrap) on methane production from WAS in anaerobic digestion, by using both experimental and mathematical approaches. The results demonstrated that both the clean and the rusty iron scrap were more effective than the iron powder for improving methane production from WAS. Model-based analysis showed that ZVI addition significantly enhanced methane production from WAS through improving the biochemical methane potential of WAS rather than its hydrolysis rate. Economic analysis indicated that the ZVI-based technology for enhancing methane production from WAS is economically attractive, particularly considering that iron scrap can be freely acquired from industrial waste. Based on these results, the ZVI-based anaerobic digestion process of this work could be easily integrated with the conventional chemical phosphorus removal process in wastewater treatment plant to form a cost-effective and environment-friendly approach, enabling maximum resource recovery/reuse while achieving enhanced methane production in wastewater treatment system. L arge amounts of organic matter from wastewater are converted into waste activated sludge (WAS) during biological treatment processes in wastewater treatment plants (WWTPs)1 . Anaerobic digestion of WAS has been widely applied to stabilize and reduce the volume of WAS as well as produce a renewable bioenergy resource in the form of methane 2-5 . The anaerobic digestion process generally consists four stages, i.e. hydrolysis, fermentation, acetogenesis and methanogenesis for methane production 6 . However, the application of anaerobic digestion is often limited by the slow hydrolysis rate and/or poor biochemical methane potential (or degradation extent) of the WAS 7-11 . In order to effectively enhance methane production from WAS in anaerobic digestion, a number of strategies have been developed, such as thermal, chemical, and mechanical methods [12][13][14][15][16][17][18][19][20][21] . However, most of these methods are cost intensive owing to high energy input or large chemical requirements 7,22,23 . Thus, alternative cost-effective approach to improve methane production from WAS in anaerobic digestion process is highly desired.Zero valent iron (ZVI), a cheap reducing agent, has been widely used in wastewater pretreatment, groundwater purification and soil remediation 24,25 . Recent studies have found that ZVI addition in anaerobic reactors for biological wastewater treatment could significantly improve chemical oxygen demand (COD) removal by ca. 25% [26][27][28][29] . Indeed ZVI can lower oxidation-reduction potential and serve as an acid buffer, thus helping maintain a stable and favourable condition for methan...

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Section: Methodsmentioning

confidence: 99%

Zero Valent Iron Significantly Enhances Methane Production from Waste Activated Sludge by Improving Biochemical Methane Potential Rather Than Hydrolysis Rate

Liu¹,

Wang²,

Zhang³

et al. 2016

Environmental Engineering and Activated Sludge Processes

Self Cite

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“…A 40 base pair GC clamp was added to the forward primer at the 5 -end to improve detection of the sequence variation in DNA fragments by subsequent denaturing gradient gel electrophoresis (DGGE) [27]. The 16S rDNA fragment was amplified using a polymerase chain reaction (PCR) thermal cycler Dice (BioRad Laboratories, Inc., Hercules, CA, USA) with a touchdown PCR method [29]. The PCR products obtained were applied in the DGGE analysis using a BioRad Dcode system (BioRad Laboratories, Inc.).…”

Section: Discussionmentioning

confidence: 99%

“…This is attributed to the reduction of the Fe(III) oxides on the RSI surface, which promoted microbial hydrolysis-acidification of complex matter, providing more organic matter for methanogenesis [1]. In addition, a previous study has suggested that RSI could enhance decomposition of propionate and created further improvements on the propionate conversion [29]. While propionate could not be utilized directly by methanogens, its biotransformation products could, ultimately enhancing methane yield.…”

Section: The Anaerobic and Microaerobic Digestion Performancementioning

confidence: 99%

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

Ruan

Cao

et al. 2017

Energies

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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 O 2 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 (H 2 S) concentration was 1933 ppmv with RSI addition. O 2 addition induced the microbial oxidation of sulphide by stimulating sulfur-oxidizing bacteria and chemical corrosion of iron, which promoted the generation of FeS and Fe 2 S 3 . 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 H 2 S 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 H 2 S concentration and improving digestion performance.

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“…Particularly, Kato et al (2012) reported that methanogenesis rates from acetate and ethanol were markedly increased by adding magnetite (crystalline conductive ferric oxide) in the enriched microbial cultures from rice paddy soil. They revealed that electroactive, iron-reducing Geobacter species were most significantly stimulated in the cultures amended with magnetite, and such increased activity of IRBs can enhance the biodegradability of complex organic compounds (Zhang et al 2014). The authors also attributed the accelerated methanogenesis to the transfer of electrons directly from electroactive bacteria to their methanogenic partner, via conductive magnetite particles, which can facilitate the reduction of carbon dioxide to methane (Cheng et al, 2009;Rotaru et al 2014).…”

Section: Introductionmentioning

confidence: 96%

Bioaugmentation of anaerobic sludge digestion with iron-reducing bacteria: process and microbial responses to variations in hydraulic retention time

Baek

Kim

Shin

et al. 2015

Appl Microbiol Biotechnol

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Although anaerobic digestion (AD) is a widely used option to manage waste activated sludge (WAS), there are some drawbacks related to its slow reaction rate and low energy productivity. This study examined an anaerobic WAS digester, augmented with an iron-reducing microbial consortium, relative to changes in microbial community structure and process performance at decreasing hydraulic retention times (HRTs) of 20 to 10 days. The enhanced methanation performance (approximately 40 % increase in methane yield) by the bioaugmentation was sustained until the HRT was decreased to 12.5 days, under Fe(3+)-rich conditions (ferric oxyhydroxide, 20 mM Fe). Enhanced iron-reducing activity was evidenced by the increased Fe(2+) to total Fe ratio maintained above 50 % during the stable operational phases. A further decrease in HRT to 10 days resulted in a significant performance deterioration, along with a drop in the Fe(2+) to total Fe ratio to <35 %, after four turnovers of operation. Prevailing existence of putative iron-reducing bacteria (IRBs) was identified by denaturing gradient gel electrophoresis (DGGE), with Spirochaetaceae- and Thauera-related organisms being dominant members, and clear dominance shifts among them with respect to decrease in HRT were observed. Lowering HRT led to evident shifts in bacterial community structure likely associated with washout of IRBs, leading to decreases in iron respiration activity and AD performance at a lower HRT. The bacterial community structure shifted dynamically over phases, and the community transitions correlated well with the changes in process performance. Overall, the combined biostimulation and bioaugmentation investigated in this study proved effective for enhanced methane recovery from anaerobic WAS digestion, which suggests an interesting potential for high-rate AD.

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Enhanced high-solids anaerobic digestion of waste activated sludge by the addition of scrap iron

Cited by 141 publications

References 31 publications

Zero Valent Iron Significantly Enhances Methane Production from Waste Activated Sludge by Improving Biochemical Methane Potential Rather Than Hydrolysis Rate

Zero Valent Iron Significantly Enhances Methane Production from Waste Activated Sludge by Improving Biochemical Methane Potential Rather Than Hydrolysis Rate

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

Bioaugmentation of anaerobic sludge digestion with iron-reducing bacteria: process and microbial responses to variations in hydraulic retention time

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