Enhancement of the germination and growth of Panicum miliaceum and Brassica juncea in Cd- and Zn-contaminated soil inoculated with heavy-metal-tolerant Leifsonia sp. ZP3.

The addition of plant-growth-promoting bacteria (PGPB) to heavy-metal-contaminated soils can significantly improve plant growth and productivity. This study isolated heavy-metal-tolerant bacteria with growth-promoting traits and investigated their inoculation effects on the germination rates and growth of millet (Panicum miliaceum) and mustard (Brassica juncea) in Cd- and Zn-contaminated soil. Leifsonia sp. ZP3, which is resistant to Cd (0.5 mM) and Zn (1 mM), was isolated from forest soil. The ZP3 strain exhibited plant-growth-promoting activity, including indole-3-acetic acid production, phosphate solubilization, catalase activity, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging. In soil contaminated with low concentrations of Cd (0.232 ± 0.006 mM) and Zn (6.376 ± 0.256 mM), ZP3 inoculation significantly increased the germination rates of millet and mustard 8.35- and 31.60-fold, respectively, compared to the non-inoculated control group, while the shoot and root lengths of millet increased 1.77- and 4.44-fold (p < 0.05). The chlorophyll content and seedling vigor index were also 4.40 and 18.78 times higher in the ZP3-treated group than in the control group (p < 0.05). The shoot length of mustard increased 1.89-fold, and the seedling vigor index improved 53.11-fold with the addition of ZP3 to the contaminated soil (p < 0.05). In soil contaminated with high concentrations of Cd and Zn (0.327 ± 0.016 and 8.448 ± 0.250 mM, respectively), ZP3 inoculation led to a 1.98-fold increase in the shoot length and a 2.07-fold improvement in the seedling vigor index compared to the control (p < 0.05). The heavy-metal-tolerant bacterium ZP3 isolated in this study thus represents a promising microbial resource for improving the efficiency of phytoremediation in Cd- and Zn-contaminated soil.

Interferometric Imaging, and Beam-Formed Study of a Moving Type-IV Radio Burst with LOFAR.

Type-IV radio bursts have been studied for over 50 years. However, the specifics of the radio emission mechanisms is still an open question. In order to provide more information about the emission mechanisms, we studied a moving Type-IV radio burst with fine structures (spike group) by using the high-resolution capability of the Low-Frequency Array (LOFAR) on August 25, 2014. We present a comparison of Nançay Radioheliograph (NRH) and the first LOFAR imaging data of the Type-IV radio burst. The degree of circular polarization (DCP) is calculated at frequencies in the range 20 - 180 MHz using LOFAR data, and it was found that the value of DCP gradually increased during the event, with values of 20 - 30%. LOFAR interferometric data were combined with white-light observations in order to track the propagation of this Type-IV burst. The kinematics shows a westward motion of the radio sources, slower than the CME leading edge. The dynamic spectrum of LOFAR shows a large number of fine structures with durations of less than 1 s and high brightness temperatures ( T B ), i.e., 10 12 - 10 13 K. The gradual increase of DCP supports gyrosynchrotron emission as the most plausible mechanism for the Type IV. However, coherent emissions such as Electron Cyclotron Maser (ECM) instability may be responsible for small-scale fine structures. Countless fine structures altogether were responsible for such high T B . Supplementary Information: The online version contains supplementary material available at 10.1007/s11207-022-02042-0.

Evaluation of rhizoremediation and methane emission in diesel-contaminated soil cultivated with tall fescue (Festuca arundinacea).

Rhizoremediation, CH4 emission, and bacterial community dynamics were evaluated in diesel-contaminated soil cultivated with tall fescue via a pot experiment. At the beginning of the experiment, total petroleum hydrocarbons (TPHs) removal efficiency was 30.2% in tall fescue-cultivated soil, which was significantly higher than that of unplanted soil (19.4%). However, when compost was added as a soil amendment, TPHs removal efficiency increased to 39.2% in tall fescue-cultivated soil. Interestingly, potential CH4 emissions were more affected by the initial diesel concentration than by compost addition or tall fescue planting. Specifically, the potential CH4 emission was approximately 3.8 times higher in the treatment with the highest initial diesel concentration (T-WC38) than that of the treatment with the lowest initial diesel concentration (T-WC5). Functional gene analysis revealed that TPHs removal had a linear correlation with the alkB/16S gene ratio, whereas potential CH4 emission had a linear correlation with pmoA gene copy numbers. Initial diesel concentrations in soil also affected bacterial community structures and the genera Rhizobium, Halothiobacillus, and Geobacter were found to be positively linked to diesel-contaminated soil rhizoremediation. Therefore, this study provides useful insights into the development of strategies to enhance rhizoremediation efficiency and CH4 emission mitigation in diesel-contaminated soils.

Dynamics of bacterial functional genes and community structures during rhizoremediation of diesel-contaminated compost-amended soil.

The objective of this study was to characterize the effects of organic soil amendment (compost) on bacterial populations associated with petroleum hydrocarbon (PH) degradation and nitrous oxide (N2O) dynamics via pot experiments. Soil was artificially contaminated with diesel oil at total petroleum hydrocarbon (TPH) concentration of 30,000 mg·kg-soil-1 and compost was mixed with the contaminated soil at a 1:9 ratio (w/w). Maize seedlings were planted in each pot and a total of ten pots with two treatments (compost-amended and unamended) were prepared. The pot experiment was conducted for 85 days. The compost-amended soil had a significantly higher TPH removal efficiency (51.1%) than unamended soil (21.4%). Additionally, the relative abundance of the alkB gene, which is associated with PH degradation, was higher in the compost-amended soil than in the unamended soil. Similarly, cnorB and nosZ (which are associated with nitric oxide (NO) and N2O reduction, respectively) were also highly upregulated in the compost-amended soil. Moreover, the compost-amended soil exhibited higher richness and evenness indices, indicating that bacterial diversity was higher in the amended soil than in the unamended soil. Therefore, our findings may contribute to the development of strategies to enhance remediation efficiency and greenhouse gas mitigation during the rhizoremediation of diesel-contaminated soils.

Effect of upflow and downflow baffle configuration on particulate matter removal in a mirror-symmetrical multi-compartment scrubber.

Control over particulate matter (PM) emission from grilling is required for improving public health and air quality. The performance of mirror-symmetrical multi-compartment scrubbers with an upflow (U-type) and downflow baffle (D-type) configuration was evaluated for PM emission control from grilling at a flow rate of 30 m3 min-1. The PM removal efficiency of the U-type scrubber was the highest when the water level was 8 cm (95.6%), and the pressure drops recorded at the water levels of 6, 8 and 10 cm were 103, 122 and 153 mmH2O, respectively. Although PM removal efficiency of the D-type scrubber was over 91.0% at the water levels of 8, 10 and 12 cm, the pressure drops were 124, 142 and 185 mmH2O, respectively. A comprehensive evaluation of the water volume, pressure drop and PM removal performance, as well as device size, revealed that the U-type scrubber with a PM removal efficiency of 92% or higher and a pressure drop of 122 mmH2O or lower at the water levels of 6-8 cm was more economical for removing PM from grilling gas than the D-type scrubber.

Emission characteristics of particulate matter, odors, and volatile organic compounds from the grilling of pork.

Meat-grilling restaurants are considered to be residential emission sources of air pollutants. To investigate the emission characteristics of particulate matter (PM), odors, and volatile organic compounds (VOCs) from the grilling of meat, a grilling apparatus equipped with butane gas burners was used to grill pork belly and marinated pork ribs in a laboratory setting. When grilling the pork belly, the emission factor for PM with a diameter of 2.5 µm or below (PM2.5) was 754 mg-PM·kg-meat-1, accounting for 99% of total suspended particles (TSPs), while that of the marinated pork ribs was 137 mg-PM·kg-meat-1 (96% of TSPs). Ammonia and acetaldehyde were the most common odors emitted during grilling at 43-88 mg·kg-meat-1 and 22-30 mg·kg-meat-1, respectively. Aldehydes were the most significant contributor to total odor intensity (36%-67%). Benzene, vinyl acetate, and hexene were the most abundant VOCs for the pork belly, while butane, vinyl acetate, and n-dodecane were the most abundant for the marinated ribs. Among the VOCs emitted from the pork grilling process, hexene, butane, and toluene were the dominant ozone precursors. The information obtained in this study is useful for furthering the understanding of the characteristics of air pollutants emitted from actual meat-grilling restaurants. Additionally, knowledge of the PM, odor, and VOC emission characteristics and their emission factors is useful for establishing management strategies for air pollutants from meat-grilling restaurants.

Characterization of sludge reduction and bacterial community dynamics in a pilot-scale multi-stage digester system with prolonged sludge retention time.

Sludge reduction performance and bacterial community dynamics in a pilot-scale multi-stage digester system with prolonged sludge retention time were characterized. Throughout the operation period of 281 days, the total loading sludge and the total digested sludge were 4700 and 3300 kg-MLSS. After 114 days of operation, the residual MLSS (RMLSS) in the reactors for sludge treatment was maintained at 18-25 kg-RMLSS m-3, and the sludge reduction efficiency achieved 95% under the F/M ratio (kg-loading MLSS kg-RMLSS-1) of less than 0.018. Also, among the sludge components, both fixed suspended solids and volatile suspended solids were reduced. Based on the sludge reduction performance and the RNA-based bacterial community characteristics, the combined action of the maintenance metabolism, lysis-cryptic growth, and particulate inorganic matter is proposed as the sludge reduction mechanism in the multi-stage sludge treatment process.

Characterization of nitrous oxide reduction by Azospira sp. HJ23 isolated from advanced wastewater treatment sludge.

A new nitrous oxide (N2O)-reducing bacterium was isolated from a consortium that was enriched using advanced wastewater treatment sludge as an inoculum and N2O as the sole nitrogen source. The isolated facultative anaerobe was identified as Azospira sp. HJ23. Azospira sp. HJ23 exhibited optimum N2O-reducing activity with a C/N ratio of 62 at pH 6 in the temperature range of 37 °C to 40 °C. The optimum carbon source for N2O reduction was a mixture of glucose and acetate. The maximum rate of N2O reduction by Azospira sp. HJ23 was 4.8 mmol·g-dry cell-1·h-1, and its N2O-reducing activity was higher than other known N2O reducers. Azospira sp. HJ23 possessed several functional genes for denitrification. These included narG (NO3- reductase), nirK (NO2- reductase), norB (NO reductase), and nosZ (N2O reductase) genes. These results suggest that Azospira sp. HJ23 can be applied in the denitrification process to minimalize N2O emission.

Evaluation of denitrification performance and bacterial community of a sequencing batch reactor under intermittent aeration.

Effects of operational parameters (initial nitrite concentration, initial nitrate concentration, carbon source, and COD/N ratio) on denitrification performance was evaluated using a sequencing batch reactor (SBR) under intermittent aeration. Complete denitrification was observed without N2O accumulation when the initial nitrite concentration was 100-500 mg-N·L-1. When the initial nitrate concentration was 75-300 mg-N·L-1, 95-96% of NO3--N was completely reduced to N2 gas. Acetate was the most effective sole carbon source for the complete denitrification of the SBR under intermittent aeration, and 99% of NO3--N was reduced to N2 gas. The optimum COD/N ratio was 8-12 for the complete denitrification, while NO2- accumulation was observed at low COD/N ratios of 1 and 2. In this study, N2O accumulation was not observed during the denitrification process regardless of operational condition. Paracoccus (15-68%), a representative aerobic denitrifying bacterium, was dominant in the SBR during the denitrification process, and the intermittent aeration condition could affect the abundance of Paracoccus in this study.

Removal of particulate matter from pork belly grilling gas using an orifice wet scrubber.

Grilling restaurants are a major contributor to airborne particulate matter (PM) in metropolitan areas. In this study, the removal of PM during the grilling of pork belly using an orifice scrubber, which is a form of gas-induced spray scrubber, was assessed. During grilling, the particle mass concentration was the highest for 1.0 < PM ≤ 2.5 µm (55.5% of total PM emissions), followed by 0.5 < PM ≤ 1.0 (27.1%), PM ≤ 0.5 (10.7%), and PM > 2.5 µm (7.0%). The PM removal efficiency of the orifice scrubber at a gas flow of 4.5 m3 min-1 was > 99.7% for PM ≥ 2.5 µm, 89.4% for 1.0 < PM ≤ 2.5 µm, 62.1% for 0.5 < PM ≤ 1.0, and 36.5% for PM ≤ 0.5 µm. Although further research is necessary to optimize its use, the orifice scrubber offers a user-friendly technology for the control of PM in small grilling restaurants because of its simple design, uncomplicated operation, and satisfactory PM removal performance.

Effects of Chronic Intake of a Low Concentration of Taurine on Physical Strength and Body Composition in Mice.

Most studies of taurine on athletic performance have been conducted at acute and high doses in rodents. These doses and duration of administration are not reasonable for normal human life. Thus, it is not valid to extrapolate these animal results to people. Dose and duration that mimic human use of taurine in normal life can help to clarify the taurine effect in humans. This study investigated whether long-term, low-dose taurine (2% taurine drinking water for 25 weeks), similar to normal taurine intake in humans, can affect endurance exercise and body composition. Twenty ICR mice were divided into two groups. The control group received normal drinking water, and the taurine treated group received 2% taurine drinking water for 25 weeks. The mice were evaluated for body composition by mass and for physical strength by treadmill exhaustion and suspension tests. The supply of chronic 2% taurine drinking water has a slight effect on weight gain. In body composition analysis, a slight increase in body weight was due to an increase in muscle mass, not an increase in body fat. However, taurine ingestion did not increase endurance exercise. In conclusion, these results indirectly suggest that acute, high-dose taurine treatment is better than long-term, low-dose treatment to increase athletic performance.

Effects of carbon source, C/N ratio, nitrate, temperature, and pH on N2O emission and functional denitrifying genes during heterotrophic denitrification.

The effects of operational parameters such as carbon source, C/N ratio, initial nitrate concentration, temperature, and pH value on heterotrophic denitrification and functional denitrifying genes were evaluated. When methanol was used as the sole carbon source, complete denitrification was performed in a short time without nitrous oxide (N2O) emission. Complete denitrification was performed at high C/N ratios (5.14 and 12.85) and low initial nitrate concentrations (75.9 and 151.6 mg N L-1). The denitrification rate was not temperature-sensitive in the range of 25-35 °C, but tended to decrease at a low pH of 5-6. The relationships between N2O emission and functional genes under various operational conditions were investigated by Pearson correlation and association network analyses. The C/N ratio was a key factor for N2O emission during the heterotrophic denitrification process. This information on the denitrification performance and its association with functional gene dynamics under various operational conditions is useful for N2O mitigation strategies for wastewater treatment processes.

Design and shelf stability assessment of bacterial agents for simultaneous removal of methane and odors.

Two types of solid bacterial agents for the simultaneous removal of methane and odor were designed using humic soil (De-MO-1) and the mixture of humic soil and tobermolite (De-MO-2) as biocarriers. The bacterial consortium, having the removability of methane and dimethyl sulfide (DMS), was immobilized in the biocarriers, and then stored at room temperature for 375 days without additional treatment. Although the lag period, of which the incubation time required for removing methane and DMS, tended to increase over the storage period, the removability of methane and DMS was maintained during 375 days in both bacterial agents. Key bacteria associated with the removal of methane and odors (Streptomyces, Promicromonospora, Paracoccus, Lysobacter, Sphingopyxis and Methylosystis) could keep their abundance during the storage period. The richness and evenness values of the bacterial communities in De-MO-1 and De-MO-2 ranged 4.89 ∼ 6.50 and 0.89 ∼ 0.98, respectively, indicating that high bacterial diversity was maintained during the storage period. The results suggest that De-MO-1 and De-MO-2, designed for the simultaneous removal of methane and odors, had shelf stabilities over one year.

Two-Dimensional Solar Wind Speeds from 6 to 26 Solar Radii in Solar Cycle 24 by Using Fourier Filtering.

Measurement of the solar wind speed near the Sun is important for understanding the acceleration mechanism of the solar wind. In this Letter, we determine 2D solar wind speeds from 6 to 26 solar radii by applying Fourier motion filters to SOHO/LASCO C3 movies observed from 1999 to 2010. Our method successfully reproduces the original flow speeds in the artificially generated data as well as streamer blobs. We measure 2D solar wind speeds from one-day to one-year timescales and their variation in solar cycle 24. We find that the solar wind speeds at timescales longer than a month in the solar maximum period are relatively uniform in the azimuthal direction, while they are clearly bimodal in the minimum period, as expected from the Ulysses observations and interplanetary radio scintillation reconstruction. The bimodal structure appears at around 2006, becomes most distinctive in 2009, and abruptly disappears in 2010. The radial evolution of the solar wind speeds resembles the Parker's solar wind solution.

Odor mitigation and bacterial community dynamics in on-site biocovers at a sanitary landfill in South Korea.

Unpleasant odors emitted from landfills have been caused environmental and societal problems. For odor abatement, two pilot-scale biocovers were installed at a sanitary landfill site in South Korea. Biocovers PBC1 and PBC2 comprised a soil mixture with different ratios of earthworm casts as an inoculum source and were operated for 240 days. Their odor removal efficiencies were evaluated, and their bacterial community structures were characterized using pyrosequencing. In addition, the correlation between odor removability and bacterial community dynamics was assessed using network analysis. The removal efficiency of complex odor intensity in the two biocovers ranged from 81.1% to 97.8%. Removal efficiencies of sulfur-containing odors (hydrogen sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide), which contributed most to complex odor intensity, were greater than 91% in both biocovers. Despite the fluctuations in ambient temperature (-8.2 to 31.3 °C) and inlet complex odor intensity (10,000-42,748 of odor dilution ratio), biocovers PBC1 and PBC2 displayed stable deodorizing performance. A high ratio of earthworm casts as an inoculum source led to high odor removability during the first 25 days of operation, but different mixing ratios of earthworm casts did not significantly affect overall odor removability. A bacterial community analysis showed that Methylobacter, Arthrobacter, Acinetobacter, Rhodanobacter, and Pedobacter were the dominant genera in both biocovers. Network analysis results indicated that Steroidobacter, Cystobacter, Methylosarcina, Solirubrobacter, and Pseudoxanthomonas increased in relative abundance with time and were major contributors to odor removal, although these bacteria had a relatively low abundance compared to the overall bacterial community. These data contribute to a more comprehensive understanding of the relationship between bacterial community dynamics and deodorizing performance in biocovers.

Extended local similarity analysis (eLSA) reveals unique associations between bacterial community structure and odor emission during pig carcasses decomposition.

Soil burial and composting methods have been widely used for the disposal of pig carcasses. The relationship between bacterial community structure and odor emission was examined using extended local similarity analysis (eLSA) during the degradation of pig carcasses in soil and compost. In soil, Hyphomicrobium, Niastella, Rhodanobacter, Polaromonas, Dokdonella and Mesorhizobium were associated with the emission of sulfur-containing odors such as hydrogen sulfide, methyl mercaptan and dimethyl disulfide. Sphingomonas, Rhodanobacter, Mesorhizobium, Dokdonella, Leucobacter and Truepera were associated with the emission of nitrogen-containing odors including ammonia and trimetylamine. In compost, however, Carnobacteriaceae, Lachnospiaceae and Clostridiales were highly correlated with the emission of sulfur-containing odors, while Rumincoccaceae was associated with the emission of nitrogen-containing odors. The emission of organic acids was closely related to Massilia, Sphaerobacter and Bradyrhizobiaceae in soil, but to Actinobacteria, Sporacetigenium, Micromonosporaceae and Solirubrobacteriales in compost. This study suggests that network analysis using eLSA is a useful strategy for exploring the mechanisms of odor emission during biodegradation of pig carcasses.

Relationship of nutrient dynamics and bacterial community structure at the water-sediment interface using a benthic chamber experiment.

The relationships between nutrient dynamics and the bacterial community at the water-sediment interface were investigated using the results of nutrient release fluxes, bacterial communities examined by 16S rRNA pyrosequencing and canonical correlation analysis (CCA) accompanied by lab-scale benthic chamber experiment. The nutrient release fluxes from the sediments into the water were as follows: -3.832 to 12.157 mg m-2 d-1 for total phosphorus, 0.049 to 9.993 mg m-2 d-1 for PO4-P, -2.011 to 41.699 mg m-2 d-1 for total nitrogen, -7.915 to -0.074 mg m-2 d-1 for NH3-N, and -17.940 to 1.209 mg m-2 d-1 for NO3-N. To evaluate the relationship between the bacterial communities and environmental variables, CCA was conducted in three representative conditions: in the overlying water, in the sediment at a depth of 0-5 cm, and in the sediment at a depth of 5-15 cm. CCA results showed that environmental variables such as nutrient release fluxes (TN, NH4, NO3, TP, and PO4) and water chemical parameters (pH, DO, COD, and temperature) were highly correlated with the bacterial communities. From the results of the nutrient release fluxes and the bacterial community, this study proposed the hypothesis for bacteria involved in the nutrient dynamics at the interface between water and sediment. In the sediment, sulfate-reducing bacteria (SRB) such as Desulfatibacillum, Desulfobacterium, Desulfomicrobium, and Desulfosalsimonas are expected to contribute to the decomposition of organic matter, and release of ammonia (NH4+) and phosphate (PO43-). The PO43- released into the water layer was observed by the positive fluxes of PO43-. The NH4+ released from the sediment was rapidly oxidized by the methane-oxidizing bacteria (MOB). This study observed in the water layer dominantly abundant MOB of Methylobacillus, Methylobacter, Methylocaldum, and Methylophilus. The nitrate (NO3-) accumulation caused by the oxidation environment of the water layer moved back to the sediment, which led to the relatively large negative fluxes of NO3-, compared to the small negative fluxes of NH4+.

Effects of nitrate and sulfate on the performance and bacterial community structure of membrane-less single-chamber air-cathode microbial fuel cells.

Membrane-less, single-chamber, air-cathode, microbial fuel cells (ML-SC MFCs) have attracted attention as being suitable for wastewater treatment. In this study, the effects of nitrate and sulfate on the performance of ML-SC MFCs and their bacterial structures were evaluated. The maximum power density increased after nitrate addition from 8.6 mW·m-2 to 14.0 mW·m-2, while it decreased after sulfate addition from 11.5 mW·m-2 to 7.7 mW·m-2. The chemical oxygen demand removal efficiencies remained at more than 90% regardless of the nitrate or sulfate additions. The nitrate was removed completely (93.0%) in the ML-SC MFC, while the sulfate removal efficiency was relatively low (17.6%). Clostridium (23.1%), Petrimonas (20.0%), and unclassified Rhodocyclaceae (6.2%) were dominant on the anode before the addition of nitrate or sulfate. After the addition of nitrate, Clostridium was still the most dominant on the anode (23.6%), but Petrimonas significantly decreased (6.0%) and unclassified Rhodocyclaceae increased (17.1%). After the addition of sulfate, the amount of Clostridium almost doubled in the composition on the anode (43.2%), while Petrimonas decreased (5.5%). The bacterial community on the cathode was similar to that on the anode after the addition of nitrate. However, Desulfovibrio was remarkably dominant on the cathode (32.9%) after the addition of sulfate. These results promote a deeper understanding of the effects of nitrate or sulfate on the ML-SC MFCs' performance and their bacterial community.

Performance evaluation of an on-site biocomplex textile as an alternative daily cover in a sanitary landfill, South Korea.

The performance of a biocomplex textile prototype was evaluated as an alternative daily cover at an operational landfill site to mitigate odors and methane. The biocomplex textile prototype consisted of two layers of nonwoven fabric and biocarrier immobilized microorganisms and showed excellent removal of odors and methane compared to landfill cover soil. The complex odor intensity (odor dilution ratio (ODR)) on the surface of landfill cover soil was 1,000-10,000 ODR (average of 4,204 ODR), whereas it was 5-250 ODR (average of 55 ODR) on the surface of biocomplex textile. Hydrogen sulfide, which contributes a significant odor intensity, had an average concentration on the biocomplex textile of 8.64 parts-per-billion (ppb), compared to 1733.21 ppb on the landfill cover soil. The biocomplex textile also showed effective methane removal with methane concentrations of 0-1.2% (average of 0.3%) on the biocomplex textile compared to 0-20% (average of 5.3%) on the landfill cover soil. Bacterial community diversity in the biocomplex textile increased with time until an operating period of 66 days, after which diversity indices were maintained at a constant level. The dominant species were the methanotrophs Methylocaldum and Methylobacter, and the non-methanotrophs Acinetobacter, Serpens, Ohtaekwangia, and Actinophytocola. These results demonstrate that on-site biocomplex textile is a suitable alternative daily cover to mitigate odors and methane in landfills.

Process contribution evaluation for COD removal and energy production from molasses wastewater in a BioH2-BioCH4-MFC-integrated system.

In this study, a three-stage-integrated process using the hydrogenic process (BioH2), methanogenic process (BioCH4), and a microbial fuel cell (MFC) was operated using molasses wastewater. The contribution of individual processes to chemical oxygen demand (COD) removal and energy production was evaluated. The three-stage integration system was operated at molasses of 20 g-COD L-1, and each process achieved hydrogen production rate of 1.1 ± 0.24 L-H2 L-1 day-1, methane production rate of 311 ± 18.94 mL-CH4 L-1 day-1, and production rate per electrode surface area of 10.8 ± 1.4 g m-2 day-1. The three-stage integration system generated energy production of 32.32 kJ g-COD-1 and achieved COD removal of 98 %. The contribution of BioH2, BioCH4, and the MFC reactor was 20.8, 72.2, and, 7.0 % of the total COD removal, and 18.7, 81.2, and 0.16 % of the total energy production, respectively. The continuous stirred-tank reactor BioH2 at HRT of 1 day, up-flow anaerobic sludge blanket BioCH4 at HRT of 2 days, and MFC reactor at HRT of 3 days were decided in 1:2:3 ratios of working volume under hydraulic retention time consideration. This integration system can be applied to various configurations depending on target wastewater inputs, and it is expected to enhance energy recovery and reduce environmental impact of the final effluent.