Effect of biogas recirculation strategy on biogas upgrading and process stability of anaerobic digestion of sewage sludge under slightly alkaline condition

A modified version of an in-situ CO2 removal process was applied during anaerobic digestion of food waste with two types of walnut shell biochar at bench scale under batch operating mode. Compared with the coarse walnut shell biochar, the fine walnut shell biochar has a higher ash content (43 vs. 36 wt%) and higher concentrations of calcium (31 vs. 19 wt% of ash), magnesium (8.4 vs. 5.6 wt% of ash) and sodium (23.4 vs. 0.3 wt% of ash), but a lower potassium concentration (0.2 vs. 40% wt% of ash). The 0.96–3.83 g biochar (g VSadded)-1 fine walnut shell biochar amended digesters produced biogas with 77.5%–98.1% CH4 content by removing 40%–96% of the CO2 compared with the control digesters at mesophilic and thermophilic temperature conditions. In a direct comparison at 1.83 g biochar (g VSadded)-1, the fine walnut shell biochar amended digesters (85.7% CH4 content and 61% CO2 removal) outperformed the coarse walnut shell biochar amended digesters (78.9% CH4 content and 51% CO2 removal). Biochar addition also increased alkalinity as CaCO3 from 2800 mg L-1 in the control digesters to 4800–6800 mg L-1, providing process stability for food waste anaerobic digestion.

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High-solid anaerobic digestion of sewage sludge: achievements and perspectives

Frontiers of Environmental Science & Engineering ◽

10.1007/s11783-020-1364-4 ◽

2020 ◽

Vol 15 (4) ◽

Author(s):

Ying Xu ◽

Hui Gong ◽

Xiaohu Dai

Keyword(s):

Anaerobic Digestion ◽

Sewage Sludge ◽

Value Added ◽

Organic Wastes ◽

Process Stability ◽

Municipal Solid Wastes ◽

High Solid ◽

Treatment Research ◽

Pre Treatment ◽

And Performance

AbstractHigh-solid anaerobic digestion (HS-AD) has been applied extensively during the last few decades for treating various organic wastes, such as agricultural wastes, organic fractions of municipal solid wastes, and kitchen wastes. However, the application of HS-AD to the processing of sewage sludge (SS) remains limited, which is largely attributable to its poor process stability and performance. Extensive research has been conducted to attempt to surmount these limitations. In this review, the main factors affecting process stability and performance in the HS-AD of SS are comprehensively reviewed, and the improved methods in current use, such as HS sludge pre-treatment and anaerobic co-digestion with other organic wastes, are summarised. Besides, this paper also discusses the characteristics of substance transformation in the HS-AD of SS with and without thermal pre-treatment. Research has shown that the HS effect is due to the presence of high concentrations of substances that may inhibit the function of anaerobic microorganisms, and that it also results in poor mass transfer, a low diffusion coefficient, and high viscosity. Finally, knowledge gaps in the current research on HS-AD of SS are identified. Based on these, it proposes that future efforts should be devoted to standardising the definition of HS sludge, revealing the law of migration and transformation of pollutants, describing the metabolic pathways by which specific substances are degraded, and establishing accurate mathematical models. Moreover, developing green sludge dewatering agents, obtaining high value-added products, and revealing effects of the above two on HS-AD of SS can also be considered in future.

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Sludge minimization by disintegration at different wastewater treatment plants

Water Practice & Technology ◽

10.2166/wpt.2008.010 ◽

2008 ◽

Vol 3 (1) ◽

Author(s):

Luchien Luning ◽

Paul Roeleveld ◽

Victor W.M. Claessen

Keyword(s):

Organic Matter ◽

Wastewater Treatment ◽

Anaerobic Digestion ◽

Sewage Sludge ◽

New Technologies ◽

Wastewater Treatment Plants ◽

Treatment Plant ◽

Biological Degradation ◽

Ongoing Research ◽

Sludge Minimization

In recent years new technologies have been developed to improve the biological degradation of sewage sludge by anaerobic digestion. The paper describes the results of a demonstration of ultrasonic disintegration on the Dutch Wastewater Treatment Plant (WWTP) Land van Cuijk. The effect on the degradation of organic matter is presented, together with the effect on the dewatering characteristics. Recommendations are presented for establishing research conditions in which the effect of sludge disintegration can be determined in a more direct way that is less sensitive to changing conditions in the operation of the WWTP. These recommendations have been implemented in the ongoing research in the Netherlands supported by the National Institute for wastewater research (STOWA).

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Gasification as an optimum alternative for the sludge management

Water Practice & Technology ◽

10.2166/wpt.2011.0080 ◽

2011 ◽

Vol 6 (4) ◽

Cited By ~ 2

Author(s):

C. Peregrina ◽

J. M. Audic ◽

P. Dauthuille

Keyword(s):

Power Generation ◽

Anaerobic Digestion ◽

Sewage Sludge ◽

Combined Heat And Power ◽

Gas Production ◽

Waste Reduction ◽

Fluidised Bed ◽

Sludge Management ◽

Gas Cleaning ◽

Cleaning System

Assimilate sludge to a fuel is not new. Sludge incineration and Combined Heat and Power (CHP) engines powered with sludge-derived anaerobic digestion gas (ADG) are operations widely used. However, they have a room of improvement to reach simultaneously a positive net power generation and a significant level of waste reduction and stabilization. Gasification has been used in other realms for the conversion of any negative-value carbon-based materials, that would otherwise be disposed as waste, to a gaseous product with a usable heating value for power generation . In fact, the produced gas, the so-called synthetic gas (or syngas), could be suitable for combined heat and power motors. Within this framework gasification could be seen as an optimum alternative for the sludge management that would allow the highest waste reduction yield (similar to incineration) with a high power generation. Although gasification remains a promising route for sewage sludge valorisation, campaigns of measurements show that is not a simple operation and there are still several technical issues to resolve before that gasification was considered to be fully applied in the sludge management. Fluidised bed was chosen by certain technology developers because it is an easy and well known process for solid combustion, and very suitable for non-conventional fuels. However, our tests showed a poor reliable process for gasification of sludge giving a low quality gas production with a significant amount of tars to be treated. The cleaning system that was proposed shows a very limited removal performance and difficulties to be operated. Within the sizes of more common WWTP, an alternative solution to the fluidised bed reactor would be the downdraft bed gasifier that was also audited. Most relevant data of this audit suggest that the technology is more adapted to the idea of sludge gasification presented in the beginning of this paper where a maximum waste reduction is achieved with a great electricity generation thanks to the use of a “good” quality syngas in a CHP engine. Audit show also that there is still some work to do in order to push sludge gasification to a more industrial stage. Regardless what solution would be preferred, the resulting gasification system would involve a more complex scenario compared to Anaerobic Digestion and Incineration, characterised by a thermal dryer and gasifier with a complete gas cleaning system. At the end, economics, reliability and mass and energy yields should be carefully analysed in order to set the place that gasification would play in the forthcoming processing of sewage sludge.

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HIGH-SOLIDS ANAEROBIC DIGESTION OF SEWAGE SLUDGE —EFFECTS OF PRETREATMENT OF WASTE ACTIVATED SLUDGE

Journal of Japan Society of Civil Engineers Ser G (Environmental Research) ◽

10.2208/jscejer.74.iii_187 ◽

2018 ◽

Vol 74 (7) ◽

pp. III_187-III_194 ◽

Cited By ~ 1

Author(s):

Masanobu TAKASHIMA ◽

Nobuichi NAKAO

Keyword(s):

Anaerobic Digestion ◽

Sewage Sludge ◽

Activated Sludge ◽

Waste Activated Sludge ◽

High Solids

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Mass and energy integration study of hydrothermal carbonization with anaerobic digestion of sewage sludge

Renewable Energy ◽

10.1016/j.renene.2020.11.103 ◽

2020 ◽

Author(s):

C.I. Aragón-Briceño ◽

A.B. Ross ◽

M.A. Camargo-Valero

Keyword(s):

Anaerobic Digestion ◽

Sewage Sludge ◽

Hydrothermal Carbonization ◽

Energy Integration

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Co-Management of Sewage Sludge and Other Organic Wastes: A Scandinavian Case Study

Energies ◽

10.3390/en14123411 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3411

Author(s):

Clara Fernando-Foncillas ◽

Maria M. Estevez ◽

Hinrich Uellendahl ◽

Cristiano Varrone

Keyword(s):

Anaerobic Digestion ◽

Sewage Sludge ◽

Resource Recovery ◽

Organic Wastes ◽

Industrial Wastes ◽

Wastewater Management ◽

Sewage Sludge Management ◽

The Common ◽

Green Chemicals

Wastewater and sewage sludge contain organic matter that can be valorized through conversion into energy and/or green chemicals. Moreover, resource recovery from these wastes has become the new focus of wastewater management, to develop more sustainable processes in a circular economy approach. The aim of this review was to analyze current sewage sludge management systems in Scandinavia with respect to resource recovery, in combination with other organic wastes. As anaerobic digestion (AD) was found to be the common sludge treatment approach in Scandinavia, different available organic municipal and industrial wastes were identified and compared, to evaluate the potential for expanding the resource recovery by anaerobic co-digestion. Additionally, a full-scale case study of co-digestion, as strategy for optimization of the anaerobic digestion treatment, was presented for each country, together with advanced biorefinery approaches to wastewater treatment and resource recovery.

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