Impact of mixing intensity and duration on biogas production in an anaerobic digester: a review

Singh, Buta; Szamosi, Zoltán; Siménfalvi, Zoltán

doi:10.1080/07388551.2020.1731413

Cited by 88 publications

(31 citation statements)

References 67 publications

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“…Generally, mixing in the anaerobic zone is essential as it promotes the distribution of substrates and microorganisms thoroughly within the digester in achieving homogeneity. Mixing can also overcome the rheological behaviour of the nature of slurry which poses complications in attaining turbulence while also forming dead zones inside the digester 13 Figure 4 depicts the capability of IAAB in treating POME that exhibits a large range of COD. It can be observed that the anaerobic COD removal efficiency somewhat increases as the strength of the wastewater increases.…”

Section: Resultsmentioning

confidence: 99%

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2020

jopeh

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Integrated anaerobic-aerobic bioreactor (IAAB) is a bioreactor technology which operates as a single treatment unit for the removal of organic matter and generation of biogas from Palm Oil Mill Effluent (POME). It is a single reactor configuration with compartmentalization in which the first, second and last compartments are designed for anaerobic, aerobic and settling processes respectively. A precommercialized IAAB (3000 m 3 ) was built at Havys Oil Mill Sdn Bhd which is located at Palong, Malaysia, with the objective of investigating its long-term performance under variable organic loads and environmental conditions with respect to effluent quality and methane yield. The pre-commercialized IAAB system was directly fed with raw POME from the palm oil mill. Based on the results, at the steady state operation of over five months, the IAAB achieved a total removal efficiency which was up to 99% for chemical oxygen demand (COD), and biochemical oxygen demand (BOD) and methane yield up to 0.26 L CH4/g COD at organic loading rate (OLR) of 2.0 -20.0 kg COD/m 3 day. The achievement of BOD <100 mg/L throughout the 150 operational days with 45% of compliance was reported. The system could significantly reduce 70% of footprint and 78% of hydraulic retention time (HRT) compared with current conventional treatment systems. Further work on optimization for the recirculation flow rate in the anaerobic zone with consideration of fluid dynamics and microbiology is required to achieve 100% compliance of BOD <100 mg/L. Keywords anaerobic, methane yield, pre-commercialized scale, chemical oxygen demand (COD), biochemical oxygen demand (BOD)

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Section: Resultsmentioning

confidence: 99%

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2020

jopeh

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“…The AD batch experiments were performed under thermophilic conditions at 55 °C ± 2. The digester content was stirred 2 min day −1 to promote bacterial growth and ensure the best performance while maintaining energy consumption as low as possible (Singh et al 2020). The biogas production was measured every day and its composition was analyzed every 2 days; the method is further described.…”

Section: Digestion Processmentioning

confidence: 99%

Efecto y evaluación agrícola de digestato anaeróbico de la FORSU como fertilizante en tritical invernal

Salcedo-Serrano

Cano-Ríos

Gutiérrez-Castillo

et al. 2022

Ecosist. Recur. Agropec.

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Anaerobic Digestion (AD) has proven to be an economically viable technology to treat the organic fraction of the municipal solid wastes (OFMSW). Research regarding the management and application of AD byproducts in Mexico, is required to encourage the private sector and local administrations to invest in this technology. In this study, fodder winter triticale (x triticosecale Wittm. ex A. Camus var. Rio Nazas) was grown to demonstrate the fertilizer effect and to evaluate the raw digestate generated from the AD under thermophilic conditions of locally sampled OFMSW, using a batch scale digester. The digestate produced was incorporated into a 6 m2 plot according to the recommender fertilization for this crop. At the same time, a crop treated with inorganic fertilizer (IF) and a control were grown, each on a plot of same dimensions, for comparison purposes. The fertilizer effect was measured in crop yield (Mg ha−1), seed efficiency (kgTriticale kgSeed−1) and bromatological value. Overall, the digestate treatment had better results in crop yield (12.54 Mg ha−1) and seed efficiency (83.61 kgTriticale kgSeed−1) than those achieved with the IF (11.16 Mg ha−1 and 74.43 kgTriticale kgSeed−1 , respectively) and the control. Whereas the bromatological value, a statistical analysis revealed that, regardless of the treatment, the mineral uptake, protein, sugar and fiber content were not significantly different (p > 0.05). Raw digestate generated from AD of the OFMSW under thermophilic conditions, is a valuable by product, rich enough to fully substitute IF for growing triticale Río Nazas.

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“…As a consequence, the scaling-up of pilot scale mixing processes is a crucial feature for maximizing current mixing and flow processes by holding all measurements within a set ratio, known as a scale-up factor [45]. Minimum periodic mixing is observed to be favorable for a successful anaerobic digestion operation [46][47][48]. Intermittent mixing with longer resting periods may result in higher biogas output and, in most situations, increased mixing time cycles have not seen much impact on biogas production, but comparable results can be produced at lower power consumption [49].…”

Section: Practical Implication Of This Studymentioning

confidence: 99%

Enhancing Efficiency of Anaerobic Digestion by Optimization of Mixing Regimes Using Helical Ribbon Impeller

et al. 2021

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The appropriate mixing system and approach to effective management can provide favorable conditions for the highly sensitive microbial community, which can ensure process stability and efficiency in an anaerobic digester. In this study, the effect of mixing intensity on biogas production in a lab-scale anaerobic digester has been investigated experimentally and via modeling. Considering high mixing efficiency and unique feature of producing axial flow, helical ribbon (HR) impeller is used for mixing the slurry in this experiment under various conditions. Three parallel digesters were analyzed under identical operating conditions for comparative study and high accuracy. Effects of different mixing speeds (10, 30, and 67 rpm for 5 min h−1) on biogas production rate were determined in 5-L lab-scale digesters. The results demonstrated 15–18% higher biogas production at higher mixing speed (67 rpm) as compared to 10 rpm and 30 rpm and the results proved statistically significant (p < 0.05). Biogas production at 10, 30, and 67 rpm were 45.6, 48.6, and 52.5 L, respectively. Higher VFA concentrations (7.67 g L−1) were recorded at lower mixing intensity but there was no significant difference in pH and ammonia at different speeds whereas the better mixing efficiency at higher speeds was also the main reason for increase in biogas production. Furthermore, model simulation calculations revealed the reduction of dead zones and better homogeneous mixing at higher mixing speeds. Reduction of dead zones from 18% at 10 rpm to 2% at 67 rpm was observed, which can be the major factor in significant difference in biogas production rates at various mixing intensities. Optimization of digester and impeller geometry should be a prime focus to scale-up digesters and to optimize mixing in full-scale digesters.

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Impact of mixing intensity and duration on biogas production in an anaerobic digester: a review

Cited by 88 publications

References 67 publications

Untitled

Untitled

Efecto y evaluación agrícola de digestato anaeróbico de la FORSU como fertilizante en tritical invernal

Enhancing Efficiency of Anaerobic Digestion by Optimization of Mixing Regimes Using Helical Ribbon Impeller

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