Review of the Factors Affecting Modeling Oxygen Transfer by Fine-Pore Diffusers in Activated Sludge

Baquero-Rodríguez, Gustavo Andrés; Lara-Borrero, Jaime Andrés; Nolasco, Daniel; Rosso, Diego

doi:10.1002/wer.1082

Cited by 6 publications

(8 citation statements)

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“…MLSS must be between 10 and 15 g/L to have a basic efficiency in the transfer of oxygen into the biomass [ 33 ]. The range of α-factor on air diffusers is 0.3–0.85 [ 6 ].…”

Section: Resultsmentioning

confidence: 99%

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study)

Asgari,

Seid-Mohammadi,

Shokoohi

et al. 2023

Microb Cell Fact

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Background In this study, the effect of static magnetic fields (SMFs) on improving the performance of activated sludge process to enhance the higher rate of microbial growth biomass and improve sludge settling characteristics in real operation conditions of wastewater treatment plants has been investigated. The effect of SMFs (15 mT), hydraulic retention time, SRT, aeration time on mixed liquor suspended solids (MLSS) concentrations, mixed liquor volatile suspended solids (MLVSS) concentrations, α-factor, and pH in the complete-mix activated sludge (CMAS) process during 30 days of the operation, were evaluated. Results There were not any differences between the concentration of MLSS in the case (2148.8 ± 235.6 mg/L) and control (2260.1 ± 296.0 mg/L) samples, however, the mean concentration of MLVSS in the case (1463.4 ± 419.2 mg/L) was more than the control samples (1244.1 ± 295.5 mg/L). Changes of the concentration of MLVSS over time, follow the first and second-order reaction with and without exposure of SMFs respectively. Moreover, the slope of the line and, the mean of α-factor in the case samples were 6.255 and, − 0.001 higher than the control samples, respectively. Changes in pH in both groups of the reactors were not observed. The size of the sluge flocs (1.28 µm) and, the spectra of amid I' (1440 cm−1) and II' (1650 cm−1) areas related to hydrogenase bond in the case samples were higher than the control samples. Conclusions SMFs have a potential to being considered as an alternative method to stimulate the microbial growth rate in the aeration reactors and produce bioflocs with the higher density in the second clarifiers.

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“…MLSS must be between 10 and 15 g/L to have a basic efficiency in the transfer of oxygen into the biomass [ 33 ]. The range of α-factor on air diffusers is 0.3–0.85 [ 6 ].…”

Section: Resultsmentioning

confidence: 99%

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study)

Asgari,

Seid-Mohammadi,

Shokoohi

et al. 2023

Microb Cell Fact

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“…Furthermore, the higher depth of the AGS reactors contributed to a higher energy usage since the specific energy usage per volume of air increases sharply with the counterpressure for rotary lobe type of blowers (AtlasCopco, 2015; van Leuven et al, 2010) as further detailed below. A higher depth increases the oxygen transfer efficiency, which can be offset by the increased pressure that leads to higher energy usage per volume of air (Baquero‐Rodríguez et al, 2018). In a theoretical comparison of AGS and CAS with EBPR where the same water depth was considered (5 m), the aeration energy usage was estimated to be similar in the two systems (Bengtsson et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…Compared to the relatively new AGS technology, CAS processes have been widely studied regarding energy usage, biogas production, and environmental impacts (Foladori et al, 2015; Hao et al, 2018; Llácer‐Iglesias et al, 2021; Silva & Rosa, 2022; Yang et al, 2010). For example, aeration efficiency has been extensively studied for CAS systems (Baquero‐Rodríguez et al, 2018) but scarcely for AGS processes (Strubbe et al, 2023). Similarly, the biogas production process from activated sludge has been broadly studied regarding methods and improvements (Uthirakrishnan et al, 2022), but the studies of waste AGS biogas potential are few (Bernat et al, 2017; Cydzik‐Kwiatkowska et al, 2022; Guo et al, 2020; Jahn et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Case study of aerobic granular sludge and activated sludge—Energy usage, footprint, and nutrient removal

Ekholm

Blois²,

Persson

et al. 2023

Water Environment Research

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This study demonstrates a comparison of energy usage, land footprint and volumetric requirements of municipal wastewater treatment with aerobic granular sludge (AGS) and conventional activated sludge (CAS) at a full‐scale wastewater treatment plant characterized by large fluctuations in nutrient loadings and temperature. The concentration of organic matter in the influent to the AGS was increased by means of hydrolysis and bypassing the pre‐settler. Both treatment lines produced effluent concentrations below 5 mg BOD7 L‐1, 10 mg TN L‐1, and 1 mg TP L‐1, by enhanced biological nitrogen‐ and phosphorus removal. In this case study, the averages of volumetric energy usage over one year were 0.22 ± 0.08 and 0.26 ± 0.07 kWh m‐3 for the AGS and CAS, respectively. A larger difference was observed for the energy usage per reduced P.E., which was on average 0.19 ± 0.08 kWh P.E.‐1 for the AGS and 0.30 ± 0.08 kWh P.E.‐1 for the CAS. However, both processes had the potential for decreased energy usage. Over one year, both processes showed similar fluctuations in energy usage, related to variations in loading, temperature, and DO. The AGS had a lower specific area, 0.3 m2 m‐3 d‐1, compared to 0.6 m2 m‐3 d‐1 of the CAS, and also a lower specific volume, 1.3 m3 m‐3 d‐1 compared to 2.0 m3 m‐3 d‐1. This study confirms that AGS at full‐scale can be compact and still have comparable energy usage as CAS.

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“…This inseparable link explains why fine bubbles in thick sludge must necessarily coalesce into coarser bubbles to experience reduced shear during their faster rise. Thus, any fine bubble, regardless of its origin, will have to coalesce to follow the path of least resistance (Baquero Rodriguez et al, 2017). This supports the hypothesis that at some point, the concentration of sludge would be sufficiently high to promote bubble coalescence and de facto nullify the difference between fine bubbles and coarse bubbles.…”

Section: Introductionmentioning

confidence: 99%

Oxygen transfer comparison of jets and coarse bubble aeration in concentrated sludge

Steele

Warner

Rosso

2023

Water Environment Research

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The South Truckee Meadows Water Reclamation Facility (STMWRF) in Washoe County, Nevada, commissioned a biosolids facility with jet aerated aerobic digestion. The jet aerators were not performing as designed, so they were tested on‐site in the new tanks in both clean and process water according to ASCE standards. The aerators failed by substantial margins. To make up for the aeration shortfall, Washoe County elected to replace the jet aerators with coarse bubble aerators and to add the additional blower capacity necessary to meet the oxygen requirements in this configuration. After partial replacement, with one basin containing coarse bubble diffusers and the other still containing jets, the efficiency of both systems was tested in process water. The jets and coarse bubble diffusers had similar results for OTE and αSOTE, whereas the coarse bubble diffusers had substantially higher aeration efficiency after accounting for the jet pump power draw. Overall, the project demonstrated the deleterious effects of highly concentrated non‐Newtonian sludge on the coalescence of fine bubbles and ultimately jet aeration efficiency, confirming the incompatibility of fine bubbles and thick sludge. Our results can be extended to other bioreactors operating at MLSS concentration above 1%. Practitioner Points Fine bubble systems perform worse than coarse bubbles in thick sludge due to bubble coalescence. The alpha factor is a function of sludge thickness; hence, claims of constant alpha are unrealistic. Polymers and additives for sludge thickening should be carefully evaluated because they can affect adversely oxygen transfer. Independent verification of aeration system manufacturer claims prevents design issues and subsequent disputes.

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Review of the Factors Affecting Modeling Oxygen Transfer by Fine-Pore Diffusers in Activated Sludge

Cited by 6 publications

References 0 publications

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study)

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study)

Case study of aerobic granular sludge and activated sludge—Energy usage, footprint, and nutrient removal

Oxygen transfer comparison of jets and coarse bubble aeration in concentrated sludge

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