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The present study aimed to determine the effect of a 17.6 mT static magnetic field (SMF) on the efficiency of anaerobic digestion (AD) of municipal sewage sludge (MSS). The SMF had a significant impact on methane (CH4) production efficiency, the levels of fermentation rate (ηFMSS) vs. removal rate (ηVS), and the structure of the anaerobic bacteria...
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... authors' own research showed that MFAs had a significant impact on CH 4 production efficiency (Figure 4), as well as on η F MSS and ηVS, and the structure of the anaerobic bacteria consortia (Table 3). CH 4 levels in V1 averaged 62.3% ± 3.1% ( Figure 5), with Y VS in CH 4 at 387 ± 23 dm 3 CH4 /kgVS ( Figure 6). The η F MSS reached 68.6% ± 2.1%, with ηVS at 33.8% ± 1.4% (Figure 7). ...
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... authors' own research showed that MFAs had a significant impact on CH4 production efficiency (Figure 4), as well as on ηFMSS and ηVS, and the structure of the anaerobic bacteria consortia (Table 3). CH4 levels in V1 averaged 62.3% ± 3.1% ( Figure 5), with í µí± at 387 ± 23 dm 3 CH4/kgVS ( Figure 6). The ηFMSS reached 68.6% ± 2.1%, with ηVS at 33.8% ± 1.4% (Figure 7). ...
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... authors' own research showed that MFAs had a significant impact production efficiency (Figure 4), as well as on ηFMSS and ηVS, and the structur anaerobic bacteria consortia (Table 3). CH4 levels in V1 averaged 62.3% ± 3.1% (F with í µí± at 387 ± 23 dm 3 CH4/kgVS ( Figure 6). The ηFMSS reached 68.6% ± 2.1%, w at 33.8% ± 1.4% (Figure 7). ...
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... í µí± was noted in V2 and V3, reaching 417 ± 19 dm 3 CH4/kgVS and dm 3 CH4/kgVS, respectively ( Figure 6). The CH4 content in the biogas was at 65.2% ± and 66.1% ± 1.9% (V3) ( Figure 5). ...
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... proportion of Bacteria (EUB338) was found to have no effect on the effici methanogenesis, with a slight negative correlation between this group of microor and ηFMSS (R 2 = 0.612) (Figure 9). was noted in V2 and V3, reaching 417 ± 19 dm 3 CH4 /kgVS and 431 ± 22 dm 3 CH4 /kgVS, respectively ( Figure 6). The CH 4 content in the biogas was at 65.2% ± 2.7 (V2) and 66.1% ± 1.9% (V3) ( Figure 5). ...
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... SMF exposure times significantly (p = 0.05) decreased CH4 yields in V5. The CH4 content in the biogas was 61.5% ± 1.7% (V4) and 59.7% ± 2.2% (V5) (F whereas í µí± decreased to 396 ± 18 dm 3 CH4/kgVS (V4) and 389 ± 18 dm 3 CH4/kg ( Figure 6). Bacteria (EUB338) prevailed in the anaerobic bacteria consortium, acc for over 70%. ...
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... CH4 content in the biogas fell within the narrow range of 54.8% (V7) to 55.2% ± 1.2% (V6) ( Figure 5). The í µí± values were also similar, approx 360 dm 3 CH4/kgVS in both variants ( Figure 6). The proportions of Archaea (ARC91 anaerobic microbial communities decreased to the lowest of the recorded values, ± 11%, whereas that of Methanosaeta (MX825) fell to 6% ± 2% (V7) ( Table 3). ...
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... SMF exposure times significantly (p = 0.05) decreased CH 4 yields in V4 and V5. The CH 4 content in the biogas was 61.5% ± 1.7% (V4) and 59.7% ± 2.2% (V5) (Figure 5), whereas Y VS in CH 4 decreased to 396 ± 18 dm 3 CH4 /kgVS (V4) and 389 ± 18 dm 3 CH4 /kgVS (V5) ( Figure 6). Bacteria (EUB338) prevailed in the anaerobic bacteria consortium, accounting for over 70%. ...
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... CH 4 content in the biogas fell within the narrow range of 54.8% ± 1.9% (V7) to 55.2% ± 1.2% (V6) ( Figure 5). The Y VS in CH 4 values were also similar, approximating 360 dm 3 CH4 /kgVS in both variants ( Figure 6). The proportions of Archaea (ARC915) in the anaerobic microbial communities decreased to the lowest of the recorded values, i.e., 20% ± 11%, whereas that of Methanosaeta (MX825) fell to 6% ± 2% (V7) ( Table 3). ...
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Proper disposal and utilization of dead pig carcasses are problems of public concern. The combination of hydrothermal pretreatment (HTP) and anaerobic digestion is a promising method to treat these wastes, provided that digestion inhibition is reduced. For this reason, the aim of this work was to investigate the optimal HTP temperature (140–180°C)...
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... Another frequently mentioned major obstacle to the competitiveness of AGS is the limited knowledge about the management and final neutralisation of excess sludge. One of the most popular, well-known and widely used methods for processing the sewage sludge produced in wastewater treatment plants is anaerobic digestion [9]. It is a very well-known technology that is commonly used as one of the processing steps of typical suspended activated sludge to stabilise it, reduce its volume, improve dewaterability, remove organic matter, improve sanitary and fertilising properties, reduce odour nuisance, and produce biogas or biomethane [10]. ...
The use of aerobic granular sludge is a promising and future-proof solution for wastewater treatment. The implementation of this technology requires the development of efficient and cost-effective methods for the management of excess sludge. The aim of the research was to evaluate the effects of hydrodynamic cavitation on the efficiency of aerobic granular sludge digestion. Respirometric measurements were performed at a temperature of 38 °C and an initial organic load of 5.0 gVS/L. The changes in the properties of the pretreated biomass, the kinetics of methane fermentation, the amount and composition of the biogas produced, and an energetic evaluation of the process were carried out. A significant influence of hydrodynamic cavitation on the transfer of organic compounds into the dissolved phase was demonstrated. The degree of solubilisation was 37% for COD and 42% and for TOC. The efficiency of CH4 production from the pretreated sludge reached a value of 496 ± 12 mL/gVS, which corresponds to an increase of 19.6% compared to the raw biomass. The influence of cavitation on the CH4 content of the biogas was not observed. Strong correlations were found between the efficiency of anaerobic digestion and the concentration of dissolved organic compounds and the hydrodynamic cavitation time used. The gross energy yield was closely correlated with the amount of CH4. The highest comparable values of 3.12 Wh/gTS to 3.18 Wh/gTS were found in the variants in which the hydrodynamic cavitation (HC) time was between 15 min and 50 min. The highest net energy production of 2890 kWh/MgTS was achieved after 15 min of pretreatment.
... Another frequently mentioned major obstacle to the competitiveness of AGS is the limited knowledge about the management and final neutralisation of excess sludge. One of the most popular, well-known and widely used methods for processing the sewage sludge produced in wastewater treatment plants is anaerobic digestion [7]. It is a very well-known technology that is commonly used as one of the processing steps of typical suspended activated sludge to stabilise it, reduce its volume, improve dewaterability, remove organic matter, improve sanitary and fertilising properties, reduce odour nuisance and produce biogas or biomethane [8]. ...
... The net energy output (ENout) in Wh/gTS was calculated as (5): 7 ENout= EGout − ES (5) The net energy gain (Enet) in Wh/gTS was calculated by subtracting the energy output in the nvariant and the energy output in variant 0 (without cavitation) as follows (6): ...
The use of aerobic granular sludge is a promising and future-proof solution for wastewater treatment. The implementation of this technology requires the development of efficient and cost-effective methods for the management of excess sludge. The aim of the research was to evaluate the effects of hydrodynamic cavitation on the efficiency of aerobic granular sludge digestion. Respirometric measurements were performed at a temperature of 38°C and an initial organic load of 5.0 gVS/L. The changes in the properties of the pre-treated biomass, the kinetics of methane fermentation, the amount and composition of the biogas produced and an energetic evaluation of the process were carried out. A significant influence of hydrodynamic cavitation on the transfer of organic compounds into the dissolved phase was demonstrated. The degree of solubilisation was 37% for COD and 42% and for TOC. The efficiency of CH4 production from the pre-treated sludge reached a value of 496±12 mL/gVS, which corresponds to an increase of 19.6% compared to the raw biomass. The influence of cavitation on the CH4 content of the biogas was not observed. Strong correlations were found between the efficiency of anaerobic digestion and the concentration of dissolved organic compounds and the hydrodynamic cavitation time used. The highest net energy production of 2.89 Wh/gTS was achieved after 15 minutes of pre-treatment.
... Zieliński et al. [59] reported increased the microbial diversity and degradation efficiency of organic matter in anaerobic digestion bacteria exposed to a magnetic field. Zaidi During the first 48 h of fermentation, the 5 and 42 mT treatments showed the highest Ys growth rates (7 CFU/g), with significant differences (p < 0.05) compared to the control and other treatments (Figure 8c). ...
... Zieliński et al. [59] reported increased the microbial diversity and degradation efficiency of organic matter in anaerobic digestion bacteria exposed to a magnetic field. Zaidi et al. [60] found that applying a magnetic field to wastewater treatment systems led to the removal of pollutants, while Ma et al. [61] reported that an external static magnetic field at 14 mT enhances the reduction of antibiotic-resistance genes during pig manure composting. ...
... The observed differences in microbial population dynamics suggest that magnetic fields can potentially be used as a tool to manipulate the fermentation process and improve the quality of cocoa products. Moreover, it is noteworthy that the optimal intensity, duration, and other parameters of the magnetic field may vary depending on the specific fermentation process and the microbe being used [58][59][60]67]. ...
A Helmholtz-type electromagnetic emission device, which uses an oscillating magnetic field (OMF), with potential applications in biotechnological research, was built and validated. The coils were connected to an alternating current (AC) generator to generate a 0.5 to 110 mT field at their center. OMF measurements were performed with a Hall effect sensor with a digital signal connection (Arduino nano) and data output to a PC using LabVIEW v2017SP1 software. The fermentation process of the cocoa bean variety CCN 51, exposed to four levels of OMF density for 60 min (0, 5, 40, and 80 mT/60 min), was analyzed. Different variables of the grain fermentation process were evaluated over six days. The ANOVA test probed the device’s linearity, accuracy, precision, repeatability, reliability, and robustness. Moreover, CCN 51 cocoa beans’ EMF-exposure effect was evaluated under different OMF densities for 60 min. The results show the validity of the equipment under working conditions and the impact of EMF (electromagnetic fields) on the yield, deformation, and pH of cocoa beans. Thus, we concluded that the operation of the prototype is valid for use in biotechnological studies.
... For example, during anaerobic fermentation of municipal drain sludge, the extended time (432 min/day) significantly reduced the output of CH4, as well as the population of methanogenic bacteria. At the same time, the highest content of methane in biogas (66.1% ± 1.9%) was found in the variant with the influence of the magnetic field of 144 min/day [33]. ...
The purpose of research is determining the conditions of stimulating effect of the combined influence of constant and variable electromagnetic fields on the substrate and microorganisms in the bioreactor. This goal is achieved by solving the following tasks: development of mathematical model, conducting numerical simulation to determine the distribution of magnetic field in active zones of the stator-bioreactor system; conducting experimental researches during the fermentation of pig’s manure with litter from wheat straw in the mesophilic mode of fermentation. One category of bioreactors (control samples) was not exposed to influence of magnetic field, for the other, periodically were made treatment simultaneously with a low-frequency electromagnetic field and constant magnetic field synchronously with the process of mixing the substrate. The most significant results are: an experimental proof of effectiveness of the proposed method of intensification of the biogas output and increasing its quality, high accuracy of mathematical model of distribution the magnetic field in active zones of the stator-bioreactor system; assessment of the levels of consumption of nutrients by microorganisms from the substrate under the influence of the combined magnetic field and without influence of the magnetic field. The significance of obtained results lies in the fact that the proposed approach to intensification of the biogas output provides increase of the level production, the quality of biogas, and cumulative rate of methane output per unit of organic mass in the reactor.
... Among methanogens in all tanks, the most abundant species was acetoclastic Methanosaeta concilii. Methanosaeta grow in stable habitats characterized by low concentrations of acetate, due to their affinity for acetate [70,71]. McHugh and co-workers [72] investigated six different samples of anaerobic sludges, treating wastewater containing simple and complex compounds with low-and high-strength treatments at psychrophilic (10-14 °C), mesophilic (37 °C), and thermophilic (55 °C) temperatures. ...
... Among methanogens in all tanks, the most abundant species was acetoclastic Methanosaeta concilii. Methanosaeta grow in stable habitats characterized by low concentrations of acetate, due to their affinity for acetate [70,71]. McHugh and co-workers [72] investigated six different samples of anaerobic sludges, treating wastewater containing simple and complex compounds with low-and high-strength treatments at psychrophilic (10-14 • C), mesophilic (37 • C), and thermophilic (55 • C) temperatures. ...
Increasing worldwide milk manufacturing and dairy processing resulted in producing more effluents, and thus effective management of wastewater is now the most important issue. This study used a new design of a pilot plant-scale hybrid anaerobic labyrinth-flow bioreactor (AL-FB) to increase the efficiency of anaerobic biodegradation and biogas productivity and improve anaerobic microflora performance. In addition, effluent recirculation was used to boost the treatment of dairy wastewater. Metagenomic analyses of the anaerobic microbial community were performed. It was found that an organic loading rate (OLR) of 4.0–8.0 g COD/L·d contributed to the highest CH4 yield of 0.18 ± 0.01–0.23 ± 0.02 L CH4/g COD removed, which corresponded to a high COD removal of 87.5 ± 2.8–94.1 ± 1.3%. The evenest distribution of the microorganisms’ phyla determined the highest biogas production. In all tested samples, Bacteroidetes and Firmicutes abundance was the highest, and Archaea accounted for about 4%. Metagenomic studies showed that methane was mainly produced in acetoclastic methanogenesis; however, higher OLRs were more favorable for enhanced hydrogenotrophic methanogenesis. Effluent recirculation enhanced the overall treatment. Thus, at OLR of 10.0 g COD/L·d, the highest COD removal was 89.2 ± 0.4%, and methane production yield achieved 0.20 ± 0.01 L CH4/g COD removed, which was higher by 25% compared to the achievements without recirculation.
... The use of magnetic fields can influence the biological features as a result of the improvement of the activity of bacteria, which reduced the TDS of the 1000 Ω digester [55]. However, higher intensity and extensive retention time in a magnetic field can severely decrease the performance of a process, which is why the 1000 Ω digester did not reduce a significant amount of TDS after day 5 [47,56]. Instead, the digester with higher stability, i.e., 500 Ω digester, performed better as it revealed the lowest amount of TDS (0.2 ppm) present in the digester after day 30. ...
In this paper, the application of magnetite-nanoparticles and a microbial fuel cell (MFC) was studied on the anaerobic digestion (AD) of sewage sludge. The experimental setup included six 1 L biochemical methane potential (BMP) tests with different external resistors: (a) 100 Ω, (b) 300 Ω, (c) 500 Ω, (d) 800 Ω, (e) 1000 Ω, and (f) a control with no external resistor. The BMP tests were carried out using digesters with a working volume of 0.8 L fed with 0.5 L substrate, 0.3 L inoculum, and 0.53 g magnetite-nanoparticles. The results suggested that the ultimate biogas generation reached 692.7 mL/g VS fed in the 500 Ω digester, which was substantially greater than the 102.6 mL/g VS fed of the control. The electrochemical efficiency analysis also demonstrated higher coulombic efficiency (81.2%) and maximum power density (30.17 mW/ m 2) for the 500 Ω digester. The digester also revealed a higher maximum voltage generation of 0.431 V, which was approximately 12.7 times the 0.034 V of the lowest-performing MFC (100 Ω digester). In terms of contaminants removed, the best-performing digester was the digester with 500 Ω, which reduced contaminants by more than 89% on COD, TS, VS, TSS and color. In terms of cost-benefit analysis, this digester produced the highest annual energy profit (48.22 ZAR/kWh or 3.45 USD/kWh). This infers the application of magnetite-nanoparticles and MFC on the AD of sewage sludge is very promising for biogas production. The digester with an external resistor of 500 Ω showed a high potential for use in bioelectrochemical biogas generation and contaminant removal for sewage sludge.
... Nominal levels in the effluent were 277 ± 22 mgO 2 /dm 3 and 147 ± 17 mg/dm 3 , respectively. P2 (days [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] and P3 (days 31-45) had similar organic biodegradation rates, which were, respectively, 73.1 ± 1.7% and 75.8 ± 3.2% for COD and 80.7 ± 3.0% and 83.4 ± 4.7% for TOC. COD in the effluent did not exceed 100 mgO 2 /dm 3 , whereas TOC did not exceed 200 mg/dm 3 -significantly less than in P1 (Table 5). ...
The liquid fraction from the dewatering of digested sewage sludge (LF-DSS) represents a major processing complication for wastewater treatment facilities, thus necessitating new and effective methods of LF-DSS neutralization. This pilot-scale study examined the evolution of a Chlorella sp. monoculture into microalgal-bacterial granular sludge (M-BGS) during treatment of LF-DSS in a hybrid photo-bioreactor (H-PBR). The M-BGS reached a stable taxonomic and morphological structure after 60 days of H-PBR operation. The biomass was primarily composed of Chlorella sp., Microthrix parvicella, and type 1851 and 1701 filamentous bacteria. A greater abundance of bacteria led to a faster-growing M-BGS biomass (to a level of 4800 ± 503 mgTS/dm3), as well as improved TOC and COD removal from the LF-DSS (88.2 ± 7.2% and 84.1 ± 5.1%). The efficiency of N/P removal was comparable, since regardless of the composition and concentration of biomass, it ranged from 68.9 ± 3.1% to 71.3 ± 3.1% for N and from 54.2 ± 4.1% to 56, 2 ± 4.6% for P. As the M-BGS taxonomic structure evolved and the C/N ratio improved, so did the anaerobic digestion (AD) performance. Biogas yield from the M-BGS peaked at 531 ± 38 cm3/gVS (methane fraction = 66.2 ± 2.7%). It was found that final effects of AD were also strongly correlated with the N and TOC content in the substrate and pH value. A mature M-BGS significantly improved settleability and separability through filtration.
... . A high load of organic compounds can create a problem with the treatment, thus improper or insufficient treatment can enhance the processes of eutrophication and degradation of natural water reservoirs when wastewater is discharged into them [9]. ...
Production and consumption of confectionery products have increased worldwide, thus, effective management of wastewater produced is now an important issue. The confectionery high-load sewage was explored for biogas production in an innovative-design anaerobic reactor with labyrinth flow. The experimental studies were focused on determining the best technological parameters of anaerobic digestion for the effective removal of pollutants and obtaining high CH4 production efficiency. It was found that organic loading rate (OLR) of 5.0–6.0 g COD/L·d contributed to the highest CH4 generation of 94.7 ± 6.1 to 97.1 ± 5.1 L CH4/d, which corresponded to a high COD removal of 75.4 ± 1.5 to 75.0 ± 0.6%. Under such conditions the FOS/TAC ratio was below 0.4, indicating reactor stability, and pH was on the level of 7.15 ± 0.04 at OLR 5.0 g COD/L·d and 7.04 ± 0.07 at OLR 6.0 g COD/L·d.
... However, it is important to note that lowering pH of sewage sludge intended to be anaerobically digested can be detrimental to digestion performance [91]. Methanogenic bacteria are sensitive to changes in the environment and require neutral pH for optimal metabolic activity [92]. With this in mind, we used chlorides as Fe ion donors in our study, as they do not produce significant reductions in pH in pre-treated PSS. ...
Sewage sludge is successfully used in anaerobic digestion (AD). Although AD is a well-known, universal and widely recognized technology, there are factors that limit its widespread use, such as the presence of substances that are resistant to biodegradation, inhibit the fermentation process or are toxic to anaerobic microorganisms. Sewage sludge generated by the pharmaceutical sector is one such substance. Pharmaceutical sewage sludge (PSS) is characterized by high concentrations of biocides, including antibiotics and other compounds that have a negative effect on the anaerobic environment. The aim of the present research was to determine the feasibility of applying Advanced Oxidation Processes (AOP) harnessing Fenton's (Fe2+/H2O2) and Fenton-like (Fe3+/H2O2) reaction to PSS pre-treatment prior to AD. The method was analyzed in terms of its impact on limiting PSS toxicity and improving methane fermentation. The use of AOP led to a significant reduction of PSS toxicity from 53.3 ± 5.1% to 35.7 ± 3.2%, which had a direct impact on the taxonomic structure of anaerobic bacteria, and thus influenced biogas production efficiency and methane content. Correlations were found between PSS toxicity and the presence of Archaea and biogas yields in the Fe2+/H2O2 group. CH4 production ranged from 363.2 ± 11.9 cm3CH4/gVS in the control PSS to approximately 450 cm3/gVS. This was 445.7 ± 21.6 cm3CH4/gVS (1.5 gFe2+/dm3 and 6.0 gH2O2/dm3) and 453.6 ± 22.4 cm3CH4/gVS (2.0 gFe2+/dm3 and 8.0 gH2O2/dm3). The differences between these variants were not statistically significant. Therefore, due to the economical use of chemical reagents, the optimal tested dose was 1.5 gFe2+/6.0 gH2O2. The use of a Fenton-like reagent (Fe3+/H2O2) resulted in lower AD efficiency (max. 393.7 ± 12.1 cm3CH4/gVS), and no strong linear relationships between the analyzed variables were found. It is, therefore, a more difficult method to estimate the final effects. Research has proven that AOP can be used to improve the efficiency of AD of PSS.
... Disintegration of complex organic feedstocks can be achieved with the various, well explored methods of pre-treatment, which provide benefits, such as better biodegradability, higher biomethane yields, and greater mineralization of the digestate [32]. This helps reduce digester size, space requirements, and costs, while also improving cost-effectiveness [33]. Ultrasonic treatment has been one of the methods used to this end [34]. ...
Microalgae are considered to be very promising feedstocks for biomethane production. It has been shown that the structure of microalgal cell walls can be highly detrimental to the anaerobic digestibility of biomass. Therefore, there is a real need to seek ways to eliminate this problem. The aim of the present study was to assess the effect of ultrasonic disintegration of Scenedesmus sp. and Pinnularia sp. microalgal biomass on the performance and energy efficiency of anaerobic digestion. The pretreatment was successful in significantly increasing dissolved COD and TOC in the system. The highest CH4 yields were noted for Scenedesmus sp. sonicated for 150 s and 200 s, which produced 309 ± 13 cm3/gVS and 313 ± 15 cm3/gVS, respectively. The 50 s group performed the best in terms of net energy efficiency at 1.909 ± 0.20 Wh/gVS. Considerably poorer performance was noted for Pinnularia sp., with biomass yields and net energy gains peaking at CH4 250 ± 21 cm3/gVS and 0.943 ± 0.22 Wh/gVS, respectively. Notably, the latter value was inferior to even the non-pretreated biomass (which generated 1.394 ± 0.19 Wh/gVS).
