Biomineralization of phosphorus during anaerobic treatment of distillery wastewaters.

This study addresses the pressing environmental concerns associated with the rapidly growing distillery industry, which is a significant contributor to wastewater generation. By focusing on the treatment of distillery wastewater using anaerobic digestion, this research explores the potential to convert organic materials into biofuels (methane). Moreover, the study aims to recover both methane and phosphorus from distillery wastewater in a single anaerobic reactor, which represents a novel and unexplored approach. Laboratory-scale experiments were conducted using mesophilic and thermophilic upflow anaerobic sludge blanket reactors. A key aspect of the study involved the implementation of a unique strategy: the mixing of centrate and spent caustic wastewater streams. This approach was intended to enhance treatment performance, manipulate the microbial community structure, and thereby optimizing the overall treatment performance. The integration of the centrate and spent caustic streams yielded remarkable co-benefits, resulting in significant biomethane production and efficient phosphorus precipitation. The study demonstrated a phosphorus removal efficiency of ∼60 % throughout the 130-140 days operation period. The recovery of phosphorus via the reactor sludge offers exciting opportunities for its utilization as a fertilizer or as a raw material within the phosphorus refinery industry. The biomethane produced during the treatment exhibits significant energy potential, estimated at 0.5 GJ/(m3 distillery wastewater).

Hybrid transformer convolutional neural network-based radiomics models for osteoporosis screening in routine CT.

OBJECTIVE: Early diagnosis of osteoporosis is crucial to prevent osteoporotic vertebral fracture and complications of spine surgery. We aimed to conduct a hybrid transformer convolutional neural network (HTCNN)-based radiomics model for osteoporosis screening in routine CT. METHODS: To investigate the HTCNN algorithm for vertebrae and trabecular segmentation, 92 training subjects and 45 test subjects were employed. Furthermore, we included 283 vertebral bodies and randomly divided them into the training cohort (n = 204) and test cohort (n = 79) for radiomics analysis. Area receiver operating characteristic curves (AUCs) and decision curve analysis (DCA) were applied to compare the performance and clinical value between radiomics models and Hounsfield Unit (HU) values to detect dual-energy X-ray absorptiometry (DXA) based osteoporosis. RESULTS: HTCNN algorithm revealed high precision for the segmentation of the vertebral body and trabecular compartment. In test sets, the mean dice scores reach 0.968 and 0.961. 12 features from the trabecular compartment and 15 features from the entire vertebral body were used to calculate the radiomics score (rad score). Compared with HU values and trabecular rad-score, the vertebrae rad-score suggested the best efficacy for osteoporosis and non-osteoporosis discrimination (training group: AUC = 0.95, 95%CI 0.91-0.99; test group: AUC = 0.97, 95%CI 0.93-1.00) and the differences were significant in test group according to the DeLong test (p < 0.05). CONCLUSIONS: This retrospective study demonstrated the superiority of the HTCNN-based vertebrae radiomics model for osteoporosis discrimination in routine CT.

LumVertCancNet: A novel 3D lumbar vertebral body cancellous bone location and segmentation method based on hybrid Swin-transformer.

Lumbar vertebral body cancellous bone location and segmentation is crucial in an automated lumbar spine processing pipeline. Accurate and reliable analysis of lumbar spine image is expected to advantage practical medical diagnosis and population-based analysis of bone strength. However, the design of automated algorithms for lumbar spine processing is demanding due to significant anatomical variations and scarcity of publicly available data. In recent years, convolutional neural network (CNN) and vision transformers (Vits) have been the de facto standard in medical image segmentation. Although adept at capturing global features, the inherent bias of locality and weight sharing of CNN constrains its capacity to model long-range dependency. In contrast, Vits excel at long-range dependency modeling, but they may not generalize well with limited datasets due to the lack of inductive biases inherent to CNN. In this paper, we propose a deep learning-based two-stage coarse-to-fine solution to address the problem of automatic location and segmentation of lumbar vertebral body cancellous bone. Specifically, in the first stage, a Swin-transformer based model is applied to predict the heatmap of lumbar vertebral body centroids. Considering the characteristic anatomical structure of lumbar spine, we propose a novel loss function called LumAnatomy loss, which enforces the order and bend of the predicted vertebral body centroids. To inherit the excellence of CNN and Vits while preventing their respective limitations, in the second stage, we propose an encoder-decoder network to segment the identified lumbar vertebral body cancellous bone, which consists of two parallel encoders, i.e., a Swin-transformer encoder and a CNN encoder. To enhance the combination of CNNs and Vits, we propose a novel multi-scale attention feature fusion module (MSA-FFM), which address issues that arise when fusing features given at different encoders. To tackle the issue of lack of data, we raise the first large-scale lumbar vertebral body cancellous bone segmentation dataset called LumVBCanSeg containing a total of 185 CT scans annotated at voxel level by 3 physicians. Extensive experimental results on the LumVBCanSeg dataset demonstrate the proposed algorithm outperform other state-of-the-art medical image segmentation methods. The data is publicly available at: https://zenodo.org/record/8181250. The implementation of the proposed method is available at: https://github.com/sia405yd/LumVertCancNet.

Switching from wet to dry anaerobic digestion of food waste with different dilution times under no mechanical mixing condition.

Previous research on anaerobic digestion of food waste has primarily focused on either wet or dry anaerobic digestion (AD), typically accompanied by continuous mechanical mixing. However, the necessary dilution rates and the extent of mixing required have yet to be addressed. In this study, we investigated switching from wet to dry AD of food waste without mechanical mixing, employing different dilution rates. Lab-scale anaerobic reactors were operated with dilution rates of 10, 5, and 2 times during Phases I (0-56 days), II (57-121 days), and III (122-209 days), respectively. The methane production rates were not significantly different (p > 0.05) across the dilution rates decreased from 10 to 2 times. Remarkably, the methane production in the anaerobic reactors exhibited fluctuations due to variations in feeding, with the methane production rate ranging from 2.0 to 2.7 g CH4-COD/(L d), without mechanical mixing, as the solids content transitioned from wet to near-dry digestion conditions (15 %, food waste). The distribution of sludge volatile solids concentrations remained uniform in the reactor, even at high solids concentrations of up to 15 %. A dynamic microbial community response to changes in dilution rates, with a shift from aceticlastic to hydrogenotrophic methanogenesis pathways. Syntrophic acetate oxidization bacteria (the genus Syner-01 (4.2-8.9 %) and f_Synergistaceae (3.6-4.2 %)) were highly enriched as switching from wet AD to dry AD. The study's findings provide crucial operational insights for anaerobic food waste treatment, potentially resulting in decreased water usage and operational costs, particularly in scenarios with low dilution rates and without mechanical mixing.

Picroside III Ameliorates Colitis in Mice: A Study Based on Colon Transcriptome and Fecal 16S Amplicon Profiling.

Picroside III (Pic), an iridoid glycoside derived from Picrorhiza scrophulariiflora, exhibits therapeutic potential in mending damage to the intestinal mucosa. This study aimed to explore Pic's regulatory impact on intestinal inflammation and the gut microbiota in mice with dextran sulfate sodium (DSS)-induced colitis. The findings revealed that pretreatment with Pic mitigated the DSS-induced escalation of the disease activity index (DAI), alleviated intestinal damage, and attenuated intestinal inflammation in mice. RNA-seq analysis, complemented by experimental validation, elucidated that Pic significantly hindered Akt phosphorylation in the colon tissues of colitis-afflicted mice. Furthermore, 16S rRNA sequencing demonstrated that Pic pretreatment effectively rectified microbial dysbiosis in colitis mice by elevating the abundance of Lactobacillus murinus and Lactobacillus gasseri. These observations suggest that Pic's efficacy in colitis treatment stems from its inhibition of intestinal inflammation via the suppression of the PI3K-Akt pathway and modulation of gut microbiota. This study contributes novel scientific insights into the potential application of Pic in the management of inflammatory bowel disease (IBD).

Designing carbon nanotube sponge/Au@MgO2 for surface-enhanced Raman scattering detection and fenton-like degradation of organic pollutants.

With the acceleration of industry and agriculture process, the massive emission of organic pollutants is a major problem which seriously restricts the sustainable development of society. Rapid enrichment, efficient degradation and sensitive detection are three key steps to solve the problem of organic pollutants, while developing a simple method integrating the above three capabilities is still a challenge. Herein, a three-dimensional carbon nanotube sponge decorated with magnesium peroxide and gold nanoparticles (CNTs/Au@MgO2 sponge) was prepared for surface enhanced Raman scattering (SERS) detection and degradation of aromatic organics by advanced oxidation processes. The CNTs/Au@MgO2 sponge with porous structures adsorbed molecules rapidly through π-π and electrostatic interaction, thus more aromatic molecules were driven to the hot-spot areas for highly sensitive SERS detection. A detection of limit with 9.09 × 10-9 M was achieved for rhodamine B (RhB). The adsorbed molecules were degraded by an advanced oxidation process utilizing hydrogen peroxide produced by MgO2 nanoparticles under acidic condition with 99% efficiency. In addition, the CNTs/Au@MgO2 sponge exhibited high reproducibility with the relative standard deviation (RSD) at 1395 cm-1 of approximately 6.25%. The results showed the sponge can be used to effectively track the concentration of pollutants during the degradation process and maintain the SERS activity by re-modifying Au@MgO2 nanomaterials. Furthermore, the proposed CNTs/Au@MgO2 sponge demonstrated the simultaneous functions of enrichment, degradation, and detection for aromatic pollutants, thus significantly expanding the potential applications of nanomaterials in environmental analysis and treatment.

Picroside III, an Active Ingredient of Picrorhiza scrophulariiflora, Ameliorates Experimental Colitis by Protecting Intestinal Barrier Integrity.

This study aims to explore the protective effects of Picroside III, an active ingredient of Picrorhiza scrophulariiflora, on the intestinal epithelial barrier in tumor necrosis factor-α (TNF-α) induced Caco-2 cells and dextran sulfate sodium (DSS) induced colitis in mice. Results show that Picroside III significantly alleviated clinical signs of colitis including body weight loss, disease activity index increase, colon shortening, and colon tissue damage. It also increased claudin-3, ZO-1 and occludin expressions and decreased claudin-2 expression in the colon tissues of mice with colitis. In vitro, Picroside III also significantly promoted wound healing, decreased the permeability of cell monolayer, upregulated the expressions of claudin-3, ZO-1 and occludin and downregulated the expression of claudin-2 in TNF-α treated Caco-2 cells. Mechanism studies show that Picroside III significantly promoted AMP-activated protein kinase (AMPK) phosphorylation in vitro and in vivo, and blockade with AMPK could significantly attenuate the upregulation of Picroside III in ZO-1 and occludin expressions and the downregulation of claudin-2 expression in TNF-α treated Caco-2 cells. In conclusion, this study demonstrates that Picroside III attenuated DSS-induced colitis by promoting colonic mucosal wound healing and epithelial barrier function recovery via the activation of AMPK.

Preparation and in vitro evaluation of hesperidin nanoparticles by antisolvent recrystallization in a double homogenate system.

Hesperidin nanoparticles (HNPs) were made for the first time employing an antisolvent recrystallization technique in a double homogenate system with positive and negative clockwise rotation in order to completely use the underutilized nutritional components in citrus peel. Dimethyl sulfoxide (DMSO), ethanol, and deionized water were used as the solvents and antisolvents in the hesperidin solution preparation. Hesperidin solution concentration of 60.26 mg/mL, homogenization speed of 8257 rpm, antisolvent-to-solvent volume ratio of 6.93 mL/mL, and homogenization time of 3.15 min were the ideal experimental conditions. HNPs have to be at least 72.24 nm in size. The structures of the produced hesperidin samples and the raw hesperidin powder were identical, according to the findings of the FTIR, XRD, and TG characterization tests. The HNP sample had an in vitro absorption rate that was 5.63 and 4.23 times greater than that of the raw hesperidin powder, respectively. It was discovered that DMSO was more suited than ethanol for creating HNP particles. In the realms of dietary supplements, therapeutic applications, and health promotion, the HNPs produced by the ARDH technology would be a potential formulation on increasing uses for a wider range of nutraceuticals (synergistic).

Extracting myricetin and dihydromyricetin simultaneously from Hovenia acerba seed by Ultrasound-Assisted extraction on a lab and small Pilot-Scale.

The flavonoids myricetin and dihydromyricetin are significant components of Hovenia acerba seed. In this work, myricetin and dihydromyricetin were extracted from Hovenia acerba seed using an ultrasound-assisted technique, and the extraction parameters were adjusted using the response surface design approach. HPLC was used to assess the yield of myricetin and dihydromyricetin. According to the data, myricetin and dihydromyricetin yields were 0.53 mg/g and 4.06 mg/g at a 60 % ethanol solution concentration, 180 W of ultrasonic irradiation power, a 20 mL/g ratio of liquid to solid, and a 40 °C optimal extraction temperature. The aforementioned findings are virtually in agreement with the experimental findings suggested by the model. The study mentioned above thus offers a means of separating and developing useful components of natural goods.

Exploring key factors in anaerobic syntrophic interactions: Biomass activity, microbial community, and morphology.

The present work evaluated the impacts of microbial communities, biomass activity and sludge morphology on anaerobic syntrophic reactions. Experiments were conducted using mature floc sludge and granular sludge under different food/microbes ratios, and with different sludge types (floc sludge, concentrated floc sludge and granular sludge) and sludge morphology (granules, vortexed granules, and granules with different particle sizes). The results show that the intact granules achieved the most effective syntrophic reaction among all sludge types. The granule structure facilitated the enrichment of syntrophic acetate oxidation bacteria (g_Syner-01 and g_Mesotoga) and methanogens, which corresponds to their superior specific methanogenic activity and high production of communication compounds. Despite the high diffusion and substrate uptake capacities, the disintegrated granules had low H2 consumption rates, which led to poor syntrophic activities. The results underline the importance of sludge spatial structures in promoting excellent syntrophic activities and the development of diverse microbial communities.

Conductive biofilms in up-flow anaerobic sludge blanket enhanced biomethane recovery from municipal sewage under ambient temperatures.

The feasibility of municipal sewage treatment in laboratory-scale up-flow anaerobic sludge blankets was investigated in this work. Unlike previous studies, granular activated carbon (conductive) or sponge (non-conductive) was introduced to hollow plastic balls as carriers and suspended in the middle and upper layers of the reactors. The two bioreactors were operated at four different hydraulic retention times (stepwise reduced from 24 h to 8 h) for 100 days at ∼18 °C. The conductive-amended treatment was more effective than the non-conductive treatment in enhancing reactor performance. Interestingly, in the reactor containing conductive carriers, microorganisms enriched in the conductive biofilm were also dominant in the suspended sludge. In the reactor containing sponge carriers, the dominant microorganisms differed between the non-conductive biofilm and the suspended sludge. This study underlines that the enrichment of functional microbial communities and the positive impacts of biofilm on suspended sludge are the keys to improving biomethane recovery.

Enhancing the resistance to H2S toxicity during anaerobic digestion of low-strength wastewater through granular activated carbon (GAC) addition.

Low-strength wastewater was treated using two laboratory-scale up-flow anaerobic sludge blankets (UASB) for 130 days under sulfate-reducing conditions. Granular activated carbon (GAC) was added to one of the reactors. The GAC addition increased the total chemical oxygen demand removal by 21-28% and total methane production by 32-78%. The sludge from the GAC-amended UASB showed higher specific methanogenic activities (SMA) and higher activities in the presence of H2S, indicating that the GAC addition enhanced the resistance of methanogens to H2S toxicity. Further, the microbial communities showed that the GAC addition shifted microbial communities. A robust syntrophic partnership between bacteria (i.e., Bacteroidetes_vadinHA17 and Trichococcus) and methanogens was established in the GAC-amended UASB. Sulfate-reducing bacteria (SRB) were enriched in the GAC biofilm, indicating the coexistence of competition and cooperation between SRB and methanogens. These findings provide significant insights regarding microbial community dynamics, especially SRB and methanogens, in a GAC-amended anaerobic digestion process under sulfate-reducing conditions.

Impacts of granular activated carbon addition on anaerobic granulation in blackwater treatment.

Upflow anaerobic sludge blanket (UASB) reactors, with or without granular activated carbon (GAC) amendment, were applied for blackwater treatment. The impact of GAC on the formation of granules and biomethane recovery was assessed. High organic loading rates (OLRs) up to 15.7 ± 2.1 kg COD/(m3d) were achieved with both reactors. Similar chemical oxygen demand (COD) removal and methane production rate were observed with OLRs ranging from 5.1 ± 1.0 to 9.3 ± 1.5 kg COD/(m3d). Under higher OLR conditions (13.6 ± 1.1 to 15.7 ± 2.1 kg COD/(m3d)), the GAC-amended UASB achieved a higher COD reduction than the UASB without GAC addition. Interestingly, volatile suspended solids (VSS) concentrations, granule size, and extracellular polymeric substance concentrations were lower in the GAC-amended UASB reactor as compared to the UASB without GAC. The methanogenesis activity of the granules in the GAC-amended UASB reactor was significantly higher than the methanogenesis activity of the UASB granules. The microbes o_Bacteroidales and Syntrophus were predominant in both reactors. The acetoclastic methanogens dominated in the UASB reactor without GAC addition; while hydrogenotrophic methanogens dominated in the GAC-UASB reactor. A phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) indicated that syntrophic acetate oxidation improved with GAC addition. The co-occurrence network indicated that interactions between dominant bacteria and archaea were higher in the GAC-amended UASB reactor than in the UASB reactor without GAC addition. This study demonstrated the improved blackwater treatment performance as a result of granulation in UASB with the addition of GAC.

Calcium hypochlorite pretreatment improves thermophilic digestion of waste activated sludge in an upflow anaerobic sludge blanket reactor.

Anaerobic wasted activated sludge (WAS) digestion has been widely applied to reduce sludge volume and generate bioenergy in the form of methane. However, anaerobic WAS digestion performance is often challenged with poor hydrolysis of biomass cellular structures. In the present study, the feasibility of using calcium hypochlorite (Ca(ClO)2) to improve the thermophilic digestion of WAS was studied. Two thermophilic upflow anaerobic sludge bed (UASB) reactors (one with and one without Ca(ClO)2 pretreatment) were operated for 120 days under low and high organic loading rate (OLR) conditions, corresponding hydraulic retention time (HRT) of 10 days and 6 days, respectively. Both reactors achieved satisfied performance during the studied period. Under the low OLR condition, Ca(ClO)2 pretreatment significantly improved WAS total volatile solids (VS) removal efficiency (from 48.06 ± 2.63% to 57.34 ± 3.54%) and methane yield (from 289.2 ± 27.6 to 362.2 ± 36.7 N mL/g VS). However, no significant improvement was observed under the high OLR condition. g_S1 and g_Fervidobacterium were predominant bacteria in the thermophilic UASB reactor fed with Ca(ClO)2 pretreated WAS. Methanosarcina was dominant archaea in both reactors. The treatment mechanism and application potential of using Ca(ClO)2 to enhance the WAS digestibility were further discussed.

Roles of granular activated carbon (GAC) and operational factors on active microbiome development in anaerobic reactors.

Ambient temperature municipal sewage was treated using two laboratory-scale up-flow anaerobic sludge blanket reactors for 225 days. Granular activated carbon (GAC) was added to one reactor to facilitate the development of direct interspecies electron transfer (DIET). The GAC addition increased total chemical oxygen demand removal by 5% - 18%. In addition to assessing the relative abundance of active amplicon sequence variants (ASVs), the mass balance model, the Mantel test, and the generalized linear models were applied to evaluate the dynamics of the active ASVs and the key operational factors controlling the bioreactor microbial community. These results demonstrated that, in addition to the GAC addition, extrinsic engineering operational factors played important roles in controlling (active) microbial communities. This study underlines the importance of taking a wholistic approach to assess microbial population dynamics. Reactor design and performance prediction should consider key engineering parameters when using DIET-based AD reactors in the future.

A new non-steady-state mass balance model for quantifying microbiome responses to disturbances in wastewater bioreactors.

Herein we proposed an ecology model, based on a non-steady-state mass balance (16S rRNA MiSeq reads normalized by volatile suspended solids), to quantify microbiome responses to disturbances in wastewater bioreactors. Rather than focusing on the most abundant microbial groups commonly used in the literature, the goal of the model was to identify active species within the community. The model incorporated the temporal changes of operational taxonomic units following a disturbance, through considering the density and type of genotypes in the influent entering the bioreactor, in the effluent leaving the bioreactor, growing in the bioreactor, and in the waste sludge discharged from the bioreactor continuously or instantaneously, as well as the prior microbial community and the sludge characteristics. One application of this model demonstrated that significant differences existed between the key populations responding to an increasing organic loading rate and the dominant species in a high-rate thermophilic upflow anaerobic sludge blanket reactor.

Calcium phosphate granules formation: Key to high rate of mesophilic UASB treatment of toilet wastewater.

Toilet wastewater, a rich source of organic matter and nutrients, can be treated anaerobically to recover energy and resources at mesophilic conditions (35 °C) using an upflow anaerobic sludge blanket (UASB) digester. However, low organic loading rates (OLR) have often been reported, which may be attributed to the flocs biomass applied in previous studies. In the present study, CaP granules were developed in the UASB reactor during the reactor operation of 250 days, which accounted for 89.2% of the UASB sludge, and had high VSS (25.9 ± 0.3 g/L) and high methanogenesis rates (0.34 ± 0.04 g CH4-COD/(gVSS·d)). An OLR of 16.0 g/(L·d) and a hydraulic retention time (HRT) of 0.25 days, were achieved, with a total chemical oxygen demand (COD) removal rate of 75.6 ± 6.0%, and a methane production rate of 8.4 ± 0.9 g CH4-COD/(L·d). The efficiency of the hydrolysis of organic substrates ranged from 32.6 ± 2.8% to 43.4 ± 1.4%. Microbial community analysis revealed that syntrophic bacteria Syntrophus, together with diverse H2-utilizing methanogens, proliferated; and eventually resulted in a hydrogenotrophic dominant pathway in the UASB reactor. The performance, mechanism of CaP granule formation, and the application of the process were discussed in detail. The present paper provided insight of high rate biomethane production from anaerobic toilet wastewater treatment.

A high-rate anaerobic biofilm reactor for biomethane recovery from source-separated blackwater at ambient temperature.

Anaerobic bioreactors for source-separated blackwater are mostly operated at low organic loading rates (OLRs) due to low biodegradability and the potential of ammonia inhibition. In this study, an anaerobic biofilm reactor having conductive carbon fibers as the media was investigated for the high-rate treatment of blackwater collected from vacuum toilets. The bioreactor was operated at different OLRs ranged from 0.77 to 3.01 g COD/L-d in four stages for a total operating period of ~ 250 days. With the increase of OLRs, the specific methane production rate increased from 105.3 to 304.6 ml/L-d with high methane content in biogas (75.5%-83%). The maximum methane yield was achieved at hydraulic retention time (HRT) of 15 days. Highest organics and suspended solids removal (80%-83%) were achieved at 20-days HRT, while increased OLRs resulted in diminished removal efficiencies. The state variables, including pH, total ammonia nitrogen, short-chain volatile fatty acids, and soluble chemical oxygen demand, indicated the system had a great capability to withstand the high OLRs. Microbial community analysis revealed that the high performance might be attributed to direct interspecies electron transfer (DIET) facilitated by potentially electroactive bacteria (e.g., Syntrophomonas, Clostridium) and electrotrophic archaea (e.g., Methanosaeta and Methanosarcina species) enriched on the carbon fibers. PRACTITIONER POINTS: An anaerobic biofilm reactor was investigated for biomethane recovery from source-separated blackwater. Conductive carbon fibers were utilized as the media to stimulate enrichment of potentially electroactive methanogenic communities. The bioreactor was operated at ambient temperature for over 250 days. High methane production rate and high-quality biogas were achieved at OLRs ranged from 0.77 to 3.01 g COD/L-d. Microbial community analysis suggested direct interspecies electron transfer (DIET) between specific electroactive bacteria and electrotrophic archaea.

Impacts of conductive materials on microbial community during syntrophic propionate oxidization for biomethane recovery.

Propionate is one of the most important intermediates in anaerobic digestion, and its degradation requires a syntrophic partnership between propionate-oxidizing bacteria and hydrogenotrophic methanogens. Anaerobic digestion efficiency can be improved by direct interspecies electron transfer (DIET) through conductive materials. This study aimed to investigate the effects of DIET on syntrophic propionate oxidization under room temperature (20°C) and reveal the syntrophic partners. Firstly, conventional anaerobic consortium and conductive material-enriched consortium were tested for DIET under high H2 partial pressure. The latter supplemented with granular activated carbon (GAC) can mitigate H2 inhibition through DIET. Secondly, a DIET consortium was enriched for testing GAC and magnetite, both showed DIET facilitation. Microbial communities in GAC- and magnetite-supplemented reactors were similar. Syntrophic propionate-oxidizing bacteria, for example, Smithella (3.9%-9.9%) and a genus from the family Syntrophaceae (1.9%-3.6%) and methanogens Methanobacterium (30.3%-75.2%), Methanolinea (8.5%-25.2%), Methanosaeta (11.4%-36.7%), and Candidatus Methanofastidiosum (3.6%-6.6%), were predominant. Functional genes for cell mobility and membrane transport (3.3% and 9.5% in control reactor) increased with GAC (3.7% and 11.1%, respectively) and magnetite (3.7% and 10.9%, respectively) addition. Syntrophic propionate-oxidizing bacteria and methanogenesis partners were revealed by co-occurrence network, for example, Methanobacterium with Smithella, Syntrophobacter, Dechloromonas, and Trichococcus, signifying the importance of the syntrophic partnership in DIET environment. PRACTITIONER POINTS: DIET improved syntrophic propionate oxidization under room temperature condition (20°C). Microbial communities were similar for GAC- and magnetite-supplemented reactors, different with control reactor. Syntrophic propionate-oxidizing bacteria and methanogenesis partners were revealed by co-occurrence network. Methanobacterium and Smithella, Syntrophobacter, Dechloromonas, and Trichococcus were correlated.

Key syntrophic partnerships identified in a granular activated carbon amended UASB treating municipal sewage under low temperature conditions.

Two laboratory-scale up-flow anaerobic sludge blankets (UASB) reactors, one with and one without granular activated carbon (GAC), were operated for municipal sewage treatment at low temperatures (16.5 ± 2.0 °C). During the 120-day operation, the GAC-amended reactor significantly enhanced COD removal (from 62% to 75%, P < 0.05) and methane production (from 87 to 218 mg CH4-COD/reactor/d) than the non-GAC reactor. Bacterial communities were significantly different between the two reactors (P < 0.05). Geobacter, a key indicator for direct interspecies electron transfer (DIET), had the highest differential score (LEfSe analysis), showing significantly higher abundances in the GAC-amended reactor (3.7-8.8%) than the non-GAC reactor (0.9-4.0%). GAC also enriched syntrophic bacteria, Syntrophomonas, Syntrophus and sulfate reducing bacteria. Methanobacterium dominated the archaeal community in the GAC-amended reactor sludge (35.7%) and GAC-biofilm (75.3%), and was less abundant in the non-GAC reactor (9.9%). It indicates that GAC enriched microbial syntrophic partners with potential electro-activities in the anaerobic digestion process.