Free Nitrous Acid (FNA)-Based Pretreatment Enhances Methane Production from Waste Activated Sludge

Wang, Qilin; Ye, Liu; Jiang, Guangming; Jensen, Paul D.; Batstone, Damien J.; Yuan, Zhiguo

doi:10.1021/es402933b

Cited by 252 publications

(196 citation statements)

References 27 publications

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“…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][8][9][10][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] .…”

mentioning

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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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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“…This represents an ample supply of renewable FNA that could be applied onsite for sludge treatment [33,34] or transported upstream for sewer applications [14].…”

Section: Economic Assessment For Fna Productionmentioning

confidence: 99%

Producing free nitrous acid – A green and renewable biocidal agent – From anaerobic digester liquor

Law

Wang

et al. 2015

Chemical Engineering Journal

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101

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Recent studies have shown that free nitrous acid (FNA) at parts per million is strongly biocidal to a broad range of microorganisms involved in wastewater management. Applications have been developed, where FNA is used to deactivate anaerobic sewer biofilms thus suppressing sulfide and methane production in sewers, or to lyse secondary sludge resulting in reduced sludge production and enhanced biogas production. This study examines the feasibility of producing FNA from a waste stream namely the anaerobic sludge digestion liquor, thus providing a source of FNA for the above applications within wastewater systems. Complete nitritation was achieved in a lab scale sequencing batch reactor (SBR) treating reject wastewater. Under stable operation, the system sustained more than 90% conversion of the 1.0 and 0.8 g NH 4 + -N/L contained in the synthetic and real digester liquor, respectively, to nitrite. Each liter of this nitrite rich effluent 2 could be acidified to pH 2 with only 66 mmole of H + , due to the low level of alkalinity in the effluent. This converts almost all of the nitrite to FNA providing an ample source of FNA for sewer and sludge pretreatment applications. Despite the high nitrite concentration in the reactor, minimal N 2 O was produced with an emission factor of 0.08% of the ammonium nitrogen converted. Finally, an economical assessment of a theoretical full-scale installation for FNA production was conducted and compared with the costs of producing this FNA from a commercial nitrite supply.

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“…This methane-rich gas is used to supply heat and electricity for the wastewater treatment process and buildings. Although the biodegradability of WAS by anaerobic digestion varies with certain characteristics such as COD:TOC ratio, carbohydrate, protein and lipid concentrations, the biogas yield is generally relatively low with 50-200 L CH4 kg volatile solids(VS) -1 compared to 600-800 L CH4 kg VS -1 for municipal organic waste [2][3][4]. Pre-treatment of this substrate, however, shows great advantages and may allow an immediate and distinct increase in methane yields [3].…”

Section: Introductionmentioning

confidence: 99%

A case study for a cost-benefit-based, stepwise optimization of thermo-chemical WAS pre-treatment for anaerobic digestion

Nagler

Aichinger

Kuprian

et al. 2016

J Mater Cycles Waste Manag

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Waste-activated sludge (WAS) may be considered a resource generated by wastewater treatment plants and used for biogas-generation but it requires pre-treatment (PT) for enhanced biogas-yields and reduced WAS disposal costs. To date, a number of studies on the optimization of such PT focused on improved biogas yields but neglected inferred energy and resource consumption. Here, we aimed to identify the most promising thermo-chemical PT-strategy in terms of net energy output and cost-efficiency by optimizing PT temperature and the amount and sort of the alkaline reagent used. We compared methanepotentials and disposal costs of untreated and treated WAS and conducted an annual cost-benefit calculation. We defined 70°C and 0.04 M NaOH as ideal PT-conditions being both, low-energy demanding and efficient. Applying these conditions, enhanced biogas-yields and improved dewaterability led to reduced electricity and disposal costs of 22 and 27%, respectively, resulting in savings of approx. 28% of the yearly WAS-related expenditures of a wastewater treatment plant. Despite multiple benefits in running costs, the implementation of WAS-PT was not recommendable in the presented case study due to high investment costs.

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Free Nitrous Acid (FNA)-Based Pretreatment Enhances Methane Production from Waste Activated Sludge

Cited by 252 publications

References 27 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

Producing free nitrous acid – A green and renewable biocidal agent – From anaerobic digester liquor

A case study for a cost-benefit-based, stepwise optimization of thermo-chemical WAS pre-treatment for anaerobic digestion

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