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[Display omitted] • EEM-PARAFAC revealed the protein-like fraction drove the sulfate reduction process. • Sulfide boosted SOB activity by regulating electron transfer and oxidative stress. • SRB and HDB, in cooperation with SOB, were the key species and main ARGs hosts. • Assimilatory sulfate reduction pathway was closely associated with ARGs spread. This study proposed the double-edged sword effects of sulfate reduction process on nitrogen removal and antibiotic resistance genes (ARGs) transmission in sulfur autotrophic denitrification system. Excitation-emission matrix-parallel factor analysis identified the protein-like fraction in soluble microbial products as main endogenous organic matter driving the sulfate reduction process. The resultant sulfide tended to serve as bacterial modulators, augmenting electron transfer processes and mitigating oxidative stress, thereby enhancing sulfur oxidizing bacteria (SOB) activity, rather than extra electron donors. The cooperation between SOB and heterotroph (sulfate reducing bacteria (SRB) and heterotrophic denitrification bacteria (HDB)) were responsible for advanced nitrogen removal, facilitated by multiple metabolic pathways including denitrification, sulfur oxidation, and sulfate reduction. However, SRB and HDB were potential ARGs hosts and assimilatory sulfate reduction pathway positively contributed to ARGs spread. Overall, the sulfate reduction process in sulfur autotrophic denitrification system boosted nitrogen removal process, but also increased the risk of ARGs transmission. [ABSTRACT FROM AUTHOR]

[Display omitted] • XG induced a new biogenic iron-based nanomaterial with high stability and activity. • BX-FeS preformed high U(VI) removal capacity in real uranium wastewater. • BX-FeS can withstand a wide pH (3.0–9.0) during the process of U(VI) removal. • Bacteria drove highly active BX-FeS regeneration, inhibiting secondary pollution. • The primary mechanism for U(VI) removal was reduction using ≡S2- as a main reductant. The high efficiency, economy, sustainability and no secondary pollution of U(VI) removal is an important and challenging topic for U(VI) wastewater treatment. Here, the regenerable biohybrids with xanthan gum (XG) stabilized biogenic mackinawite nanoparticles (BX-FeS) were prepared, where XG acted as carrier facilitated the Fe2+ attachment and induced the low size, high stability and activity of nearly spherical FeS nanoparticles. Results showed that BX-FeS kept high activity after storing two years and good performance for U(VI) removal in broad pH range and co-existence of ions, and had greater removal efficiency (97.9 %) than biogenic B-FeS (67.1 %). Moreover, BX-FeS preformed high adsorption capacity in uranium wastewater (658.0 mg/g), and lower cost compared with zerovalent-iron and silica gel. Importantly, BX-FeS maintained high activity within three regeneration cycles driven by Desulfovibrio desulfuricans , inhibited the secondary pollution (Fe3+, SO 4 2-) of reaction. This study provides a new strategy for sustainable and efficient treatment of U(VI) wastewater. [ABSTRACT FROM AUTHOR]

The biogenetic sulfidation of zero-valent iron (BS-ZVI) by sulfate-reducing bacteria (SRB) has been demonstrated to enhance the reactivity of ZVI. However, long-term performance of BS-ZVI and related mechanism were still unknown. Therefore, columns containing sponge iron and SRB are built to prepare BS-ZVI in-situ and study its long-term performance. Over 80 % of NO 3 ‾ was reduced to NH 4 + by in-situ BS-ZVI within 140 days, which was higher than the sole ZVI treatment (40 %-60 %). The bonding of ZVI and FeS x was in-situ firstly and finally loaded on ZVI. The reduction of Fe(III) by S(-II) and SRB contributed to the formation of FeS x , which improved the electrons transfer. Moreover, BS-ZVI enhanced the enzymes activity of SRB, thus accelerating the metabolic transformation of lactic acid to acetic acid. The accumulation of acetic acid enhanced the removal efficiency of NO 3 ‾ through the dissolution of passivation layer. Overall, this study demonstrated a reactivity enhancement of ZVI through biogenetic sulfidation, which provided a new alternative method for the remediation of groundwater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

[Display omitted] • Performance of BE-UASB treating high-sulfate methanolic wastewater was evaluated. • BE-UASB exhibited COD removal of 93.6 % with 1.4-fold CH 4 yield of control. • Humics as main components of EPS on electrodes benefited the electron transfer. • Electrocatalysis induced synergy between Acetobacterium and SRB to reduce SO 4 2−. • BE-UASB restructured MPA to alleviate the competition with SRB for electron donors. A bioelectrochemical upflow anaerobic sludge blanket (BE-UASB) was constructed and compared with the traditional UASB to investigate the role of bioelectrocatalysis in modulating methanogenesis and sulfidogensis involved within anaerobic treatment of high-sulfate methanolic wastewater (COD/SO 4 2− ratio ≤ 2). Methane production rate for BE-UASB was 1.4 times higher than that of the single UASB, while SO 4 2− removal stabilized at 16.7%. Bioelectrocatalysis selectively enriched key functional anaerobes and stimulated the secretion of extracellular polymeric substances, especially humic acids favoring electron transfer, thereby accelerating the electroactive biofilms development of electrodes. Methanomethylovorans was the dominant genus (35%) to directly convert methanol to CH 4. Methanobacterium as CO 2 electroreduction methane-producing archaea appeared only on electrodes. Acetobacterium exhibited anode-dependence, which provided acetate for sulfate-reducing bacteria (norank Syntrophobacteraceae and Desulfomicrobium) through synergistic coexistence. This study confirmed that BE-UASB regulated the microbial ecology to achieve efficient removal and energy recovery of high-sulfate methanolic wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Intermittent electrical mode raised CH 4 yield by 21.0 ± 0.1 % in sulfate conditions. • Intermittent electrostimulation increased substrate competition among methanogens. • Electro-biofilm exhibited excellent electron transfer and electrochemical activity. • Cytochrome gene abundance increased by 67.3 ± 2.5 % in intermittent electrical mode. • Enhanced DIET-induced syntrophic methanogenesis outcompeted sulfidogenesis. Methane recovery and organics removal in sulfate (SO 4 2−)-rich wastewater anaerobic digestion are hindered by electron competition between methanogenesis and sulfidogenesis. Here, intermittently electrostimulated bioelectrodes were developed to facilitate direct interspecies electron transfer (DIET)-driven syntrophic methanogenesis, increasing substrate competition among methanogenic archaea (MA). By optimising the electrochemical environment, MA was able to employ electron transfer more efficiently than sulfate-reducing bacteria (SRB), resulting in significant methane accumulation (58.1 ± 1.0 mL-CH 4 /m3 reactor) and COD removal (90.5 ± 0.5 %) at lower COD/SO 4 2− ratio. Intermittent electrostimulation improved the metabolic pathway for electroactive bacteria to utilize acetate and direct electrons to electrotrophic MA, decreasing SRB abundance and affecting the sulfate reduction pathway. Intermittently electrostimulated biofilms significantly increased gene levels of key enzymes in electron transport for cytochrome and e-pili biosynthesis, crucial for DIET, demonstrating enhanced DIET-driven syntrophic methanogenesis. This study provides a strategic approach to optimize methanogenesis in sulfate-rich wastewater anaerobic digestion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe@C maintained methane productivity at 0.23–0.27L/gCOD under COD/SO 4 2- ratio of 3.0. • Inhibited propionate degradation and sulfate reduction were mitigated by Fe@C dosing. • Fe@C decreased EPS secretion and promoted mass transfer efficiency of sludge. • Fe@C accelerated microbial community succession and alteration of dominant SRB. • Increased sulfate concentration inhibited MM-CoA metabolism of propionate degradation. This study evaluated the reflection of long-term anaerobic system exposed to sulfate and propionate. Fe@C was found to efficiently mitigate anaerobic sulfate inhibition and enhance propionate degradation. With influent propionate of 12000mgCOD/L and COD/SO 4 2- ratio of 3.0, methane productivity and sulfate removal were only 0.06 ± 0.02L/gCOD and 63 %, respectively. Fe@C helped recover methane productivity to 0.23 ± 0.03L/gCOD, and remove sulfate completely. After alleviating sulfate stress, less organic substrate was utilized to form extracellular polymeric substances for self-protection, which enhanced mass transfer in anaerobic sludge. Microbial community succession, especially for alteration of key sulfate-reducing bacteria and propionate-oxidizing bacteria, was driven by Fe@C, thus enhancing sulfate reduction and propionate degradation. Acetotrophic Methanothrix and hydrogenotrophic unclassified_f_Methanoregulaceae were enriched to promote methanogenesis. Regarding propionate metabolism, inhibited methylmalonyl-CoA degradation was a limiting step under sulfate stress, and was mitigated by Fe@C. Overall, this study provides perspective on Fe@C's future application on sulfate and propionate rich wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • PFSF was developed by loading sulfur on polyurethane foam. • PFSF exhibited superior denitrification performance compared to Na 2 S 2 O 3. • The PFSF system showed synergies among ADB and SRB, reducing sulfate production. • The better economics of PFSF indicated its suitability for wastewater treatment. Sulfur-driven autotrophic denitrification (SdAD) is a promising nitrogen removing process, but its applications were generally constrained by conventional electron donors (i.e., thiosulfate (Na 2 S 2 O 3)) with high valence and limited bioavailability. Herein, an immobilized electron donor by loading elemental sulfur on the surface of polyurethane foam (PFSF) was developed, and its feasibility for SdAD was investigated. The denitrification efficiency of PFSF was 97.3%, higher than that of Na 2 S 2 O 3 (91.1%). Functional microorganisms (i.e., Thiobacillus and Sulfurimonas) and their metabolic activities (i.e., nir and nor) were substantially enhanced by PFSF. PFSF resulted in the enrichment of sulfate-reducing bacteria, which can reduce sulfate (SO 4 2−). It attenuated the inhibitory effect of SO 4 2−, whereas the generated product (hydrogen sulfide) also served as an electron donor for SdAD. According to the economic evaluation, PFSF exhibited strong market potential. This study proposes an efficient and low-cost immobilized electron donor for SdAD and provides theoretical support to its practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heavy metal removal by SRB was predicted by machine learning. • The CatBoost model had the best predictive performance for the four metals. • pH, temperature, C/S ratio, and SO 4 2− were critical for HM removal. • The important features of different HM models were compared. A robust modeling approach for predicting heavy metal removal by sulfate-reducing bacteria (SRB) is currently missing. In this study, four machine learning models were constructed and compared to predict the removal of Cd, Cu, Pb, and Zn as individual ions by SRB. The CatBoost model exhibited the best predictive performance across the four subsets, achieving R2 values of 0.83, 0.91, 0.92, and 0.83 for the Cd, Cu, Pb, and Zn models, respectively. Feature analysis revealed that temperature, pH, sulfate concentration, and C/S (the mass ratio of chemical oxygen demand to sulfate) had significant impacts on the outcomes. These features exhibited the most effective metal removal at 35 °C and sulfate concentrations of 1000–1200 mg/L, with variations observed in pH and C/S ratios. This study introduced a new modeling approach for predicting the treatment of metal-containing wastewater by SRB, offering guidance for optimizing operational parameters in the biological sulfidogenic process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Increase of PFAS level adversely affected the AD system and microbial activity. • PFOA led to higher impacts on AD performance and microbial activity than PFOS. • Archaeal group was more vulnerable to both PFOA and PFOS than bacterial group. • PFOA induced changes in microbial community by their toxicity. • PFOS induced changes in microbial community by their toxicity and functional group. Per- and polyfluoroalkyl substances (PFASs) are recalcitrant organic pollutants, which accumulate widely in aquatic and solid matrices. Anaerobic digestion (AD) is one of possible options to manage organic wastes containing PFASs, however, the impacts of different types of PFAS on AD remains unclear. This study aimed to critically investigate the effects of two representative PFAS compounds, i.e., perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), on the AD performance and microbial community structure. 100 mg/L of both PFOA and PFOS considerably inhibited the AD performance and changed the microbial community structure. Especially, PFOA was more toxic to bacterial and archaeal activity than PFOS, which was reflected in AD performance. In addition, the sulfonic acid group in PFOS affected the changes in microbial community structure by inducing abundant sulfate reducing bacteria (i.e., Desulfobacterota). This study provides a significant reference to the response of AD system on different PFAS types and dosage. [ABSTRACT FROM AUTHOR]

[Display omitted] • The r-/K-selection theory was applied to anaerobic digestion with sulfate reduction. • The rapid-filling mode enabled reactors to exhibit a fast reaction rate. • The operational mode altered the ethanol metabolic pathway. • The effect of operational mode on bioreactors depended on types of organic carbon. • R-strategists Desulfomicrobium and K-strategists Geobacter were enriched. Anaerobic digestion (AD) is promising for treating high-strength wastewater. However, the effect of operational parameters on microbial communities of AD with sulfate is not yet fully understood. To explore this, four reactors were operated under rapid- and slow-filling modes with different organic carbons. Reactors in the rapid-filling mode generally exhibited a fast kinetic property. For example, the degradation of ethanol was 4.6 times faster in ASBR ER than in ASBR ES , and the degradation of acetate was 11.2 times faster in ASBR AR than in ASBR AS. Nevertheless, reactors in the slow-filling mode could mitigate propionate accumulation when using ethanol as organic carbon. Taxonomic and functional analysis further supported that rapid- and slow-filling modes were suitable for the growth of r-strategists (e.g., Desulfomicrobium) and K-strategists (e.g., Geobacter), respectively. Overall, this study provides valuable insights into microbial interactions of AD processes with sulfate through the application of the r/K selection theory. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) was introduced to Enterococcus avium strain BY7 sulfate-reducing bacteria culture as a carrier, GO was partially reduced by SRB to reduced graphene oxide (rGO). The rGO could further self-assemble Enterococcus avium strain BY7 sulfate-reducing bacteria to form BY-rGO particles. Growth and sulfate reduction activity of strain BY7 was promoted by rGO, which probably due to the protective effect of rGO, and enhanced electron transfer by rGO as electron shuttle. Effects of pH and temperature variance on strain BY-rGO were remarkably weakened, growth and sulfate reduction were observed from pH 2.0 to 12.0, and from 10 to 45 °C, respectively. Metal toxicity to BY7 strain SRB was sharply decreased in BY-rGO particles and heavy metal removal was remarkably accelerated (up to 50%). The immobilization methods established in this study might open a new way for the application of SRBs, especially under extreme environmental conditions. [ABSTRACT FROM AUTHOR]

High sulfur content in excess sludge impacts the production of biomethane during anaerobic digestion, meanwhile leads to hydrogen sulfide (H 2 S) formation in biogas. Effect of initial sludge pH on H 2 S formation during batch mesophilic anaerobic digestion of slaughterhouse wastewater sludge was studied in this paper. The results demonstrated that when the initial sludge pH increased from 6.5 to 8.0, the biogas production increased by 10.1%, the methane production increased by 64.1%, while the H 2 S content in biogas decreased by 44.7%. The higher initial sludge pH inhibited the competition of sulfate-reducing bacteria with methane-producing bacteria, and thus benefitted the growth of methanogens. Positive correlation was found between the relative abundance of Desulfomicrobium and H 2 S production, as well as the relative abundance of Methanosarcina and methane production. More sulfates and organic sulfur were transferred to solid and liquid rather than H 2 S formation at a high initial pH. [ABSTRACT FROM AUTHOR]

A novel strategy for acclimation to ammonia stress was implemented by stimulating a high ammonia-ammonium-pH environment in a high-solid anaerobic digestion (AD) system in this study. Three semi-continuously stirred anaerobic reactors performed well over the whole study period under mesophilic conditions, especially in experimental group (R-2) when accommodated from acclimation period which the maximum total ammonia nitrogen (TAN) and free ammonia nitrogen (FAN) increased to 4921 and 2996 mg/L, respectively. Moreover, when it accommodated the high ammonia-ammonium-pH system, the daily biogas production and methane content were similar to those in R-1 (the blank control to R-2), but the hydrogen sulfide (H 2 S) content lower than the blank control. Moreover, mechanistic studies showed that high ammonia stress enhanced the activity of coenzyme F 420 . The results of real-time fluorescent quantitative polymerase chain reaction (PCR) showed that ammonia stress decreased the abundance of sulfate-reducing bacteria and increased the abundance of methane-producing archaea. [ABSTRACT FROM AUTHOR]

The biogas generated from anaerobic digestion (AD) also includes undesirable by-product such as hydrogen sulfide (H 2 S), which must be removed before the biogas can be used as a clean energy source. Therefore, it is necessary to find an appropriate strategy to simultaneously enhance the methane yield and reduce H 2 S production. An efficient strategy—pretreating sludge at pH 10 for 8 d and adjusting the system at neutral pH to produce methane for 20 d—is reported for the synchronous enhancement of methane production and reduction of H 2 S production during AD. The experimental results showed that the cumulative methane yield was 861.2 ± 6.1 mL/g volatile solids (VS) of sludge pretreated at pH 10 in semi-continuous stirred anaerobic reactors for 84 d, an increase of 49.6% over the yield in the control. Meanwhile, the cumulative production of H 2 S was 144.1 × 10 −4 mL/g VS, 54.2% lower than that in the control. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effect of sulfate-reducing bacteria on performance of a mixed culture microbial electrosynthesis system (MES). The two-chamber MESs were operated under different cathode potentials (−0.5, −0.6, −0.7, and −0.8 V) with or without addition of 6 mM sulfate. At −0.7 V, acetate production and electrons harvesting in the MES with the sulfate addition were 31.81 mM and 5152 C, respectively, which improved by 2.7 and 2.4 times compared to that without sulfate. With sulfate, the biomass, proportion of live cells, and electrochemical activity of cathode biofilm were enhanced at all the potentials. At −0.7 V, the relative abundance of Acetobacterium and Desulfovibrionaceae was 14.2% and 36.7% with sulfate, respectively, compared to 17.4% and 7.3% without sulfate. At −0.7 and −0.8 V, the sulfate-reducing bacteria can promote the electron transfer of cathode biofilm and enhance the acetate production. [ABSTRACT FROM AUTHOR]

Microorganisms from an anaerobic methane oxidizing sediment were enriched with methane gas as the substrate in a biotrickling filter (BTF) using thiosulfate as electron acceptor for 213 days. Thiosulfate disproportionation to sulfate and sulfide were the dominating sulfur conversion process in the BTF and the sulfide production rate was 0.5 mmol l −1 day −1 . A specific group of sulfate reducing bacteria (SRB), belonging to the Desulforsarcina/Desulfococcus group, was enriched in the BTF. The BTF biomass showed maximum sulfate reduction rate (0.38 mmol l −1 day −1 ) with methane as sole electron donor, measured in the absence of thiosulfate in the BTF. Therefore, a BTF fed with thiosulfate as electron acceptor can be used to enrich SRB of the DSS group and activate the inoculum for anaerobic oxidation of methane coupled to sulfate reduction. [ABSTRACT FROM AUTHOR]

Direct interspecies electron transfer (DIET) is an alternative to syntrophic metabolism in natural carbon cycle as well as in anaerobic digesters, but its function in anaerobic treatment of sulfate-containing wastewater have not yet to be described. Here, conductive stainless steel was added into anaerobic digesters for treating sulfate-containing wastewater to investigate the potential role of DIET in the response to the sulfate impact. Results showed that adding the conductive stainless steel made the anaerobic digestion less affected by the sulfate reduction than adding insulative plastic material. With adding stainless steel, methane production of the digesters increased by 7.5%-24.6%. Microbial analysis showed that the dissimilatory Fe (III) reducers like Geobacter species were enriched on the surface of the stainless steel. These results implied that the potential DIET of methanogenesis was established associating with stainless steel to outcompete the sulfate reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrical voltage (EV) enhanced CH 4 production by 30 % and sulfate removal by 40 %. • High energy recovery for EV-applied reactor supports the practical applicability. • The abundance of sulfate-reducing bacteria was increased by 1.5 times in EVR. • The abundance of Dsr and hydrogenase genes was >50 % higher in EV-applied. • F-type ATPase gene expression was increased by (x3) in the archaeal community. Treatment of sulfate-rich wastewater with high methane recovery is a major concern due to sulfide inhibition. Here, an electrical voltage (EV) aims to enhance methanogenesis and sulfidogenesis to treat sulfate-rich wastewater. Two (control and EV-applied) reactors were operated with a gradual decrease in chemical oxygen demand (COD)/SO 4 2− ratios (CSR). EV-applied reactor (EVR) demonstrated an increase of ∼30 % in methane production and ∼40 % in sulfate removal, compared to the control till CSR of 2.0. At CSR 1.0, the control failed, while EVR still exhibited a stable performance of 50 % COD-methane recovery. Microbial community results showed that the relative abundance of sulfate-reducing bacteria in EVR was 1.5 times higher than the control. Furthermore, higher relative abundance of dissimilatory sulfate reductase (>50 %) and Ni/Fe hydrogenase (x15) genes demonstrated an improved tolerance against H 2 S toxicity. This study highlights the importance of EV application by minimizing the byproduct inhibition in sulfate-rich wastewater. [ABSTRACT FROM AUTHOR]

This study systematically evaluated the effect of ferric iron on sulfate reduction to sulfide, feed digestion and fermentation, methane production, and populations of select ruminal microbes using in vitro rumen cultures. Ferric oxide (Fe 2 O 3 ) and ferric citrate (C 6 H 5 FeO 7 ) at six concentrations (0, 25, 50, 100, 150, and 200 mg/L as Fe 3+ ) were tested. Ferric iron decreased production of both H 2 S gas in culture headspace (up to 71.9%) and aqueous sulfide (up to 80.8%), without adversely affecting other fermentation parameters, with ferric citrate being more effective than ferric oxide. Total archaeal population was increased by ferric citrate, but methane production was not affected significantly. The population of sulfate reducing bacteria was affected differently by ferric oxide than by ferric citrate. The results of this study could guide future in vivo studies to develop effective solutions to abate sulfur-associated polioencephalomalacia in cattle fed high-sulfur diet such as dried distiller’s grains with solubles. [ABSTRACT FROM AUTHOR]

This study reports that the obligate anaerobic microorganism, Desulfovibrio desulfuricans , a predominant sulfate-reducing bacterium (SRB) in soils and sediments, can produce nanoscale bacterial appendages for extracellular electron transfer. These nanofilaments were electrically-conductive (5.81 S·m −1 ) and allowed SRBs to directly colonize the surface of insoluble or solid electron acceptors. Thus, the direct extracellular electron transfer to the insoluble electrode in the microbial fuel cell (MFC) was possible without inorganic electron-shuttling mediators. The production of nanofilaments was stimulated when only insoluble electron acceptors were available for cellular respiration. These results suggest that when availability of a soluble electron acceptor for SRBs (SO 4 2− ) is limited, D. desulfuricans initiates the production of conductive nanofilaments as an alternative strategy to transfer electrons to insoluble electron acceptors. The findings of this study contribute to understanding of the role of SRBs in the biotransformation of various substances in soils and sediments and in the MFC. [ABSTRACT FROM AUTHOR]

Sulfate-reducing bacteria (SRB) are widely existed in oil production system, and its H 2 S product inhibits rhamnolipid producing bacteria. In-situ production of rhamnolipid is promising for microbial enhanced oil recovery. Inhibition of SRB, removal of H 2 S and production of rhamnolipid by recombinant Pseudomonas stutzeri Rhl were investigated. Strain Rhl can simultaneously remove S 2− (>92%) and produce rhamnolipid (>136 mg/l) under S 2− stress below 33.3 mg/l. Rhl reduced the SRB numbers from 10 9 to 10 5 cells/ml, and the production of H 2 S was delayed and decreased to below 2 mg/l. Rhl also produced rhamnolipid and removed S 2− under laboratory simulated oil reservoir conditions. High-throughput sequencing data demonstrated that addition of strain Rhl significantly changed the original microbial communities of oilfield production water and decreased the species and abundance of SRB. Bioaugmentation of strain Rhl in oilfield is promising for simultaneous control of SRB, removal of S 2− and enhance oil recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • Granular sludge successfully aggregated performing hydrogenotrophic denitrification. • Granular sludge reactor achieved highest NRR of 0.42 ± 0.04 kgN/(m3·d) at 30 °C. • Granular sludge reactor had stable operation with groundwater and low temperature. • Granular sludge reactor showed higher NRR than fixed-bed biofilm reactor. • Dominant genera of granular sludge were Hydrogenophaga and Comamonas , Hydrogenotrophic denitrification (HD) is a promising autotrophic biological process for advanced nitrogen removal, while sludge granulation was seldom reported. This study aimed to cultivate granular sludge to improve capacity and stability of HD process. The resulting HD granular sludge performed high nitrogen removal rate (NRR) of 0.42 ± 0.0.4 kgN/(m3·d) with low accumulation of nitrite and nitrous oxide emission. HD granular sludge reactor performed over 3 times higher NRR compared to that in HD fixed-bed biofilm reactor (0.13 ± 0.01 kgN/(m3·d). Besides, granular sludge reactor could treat groundwater well even at the low temperature of 15 °C. The dominant genera were Hydrogenophaga and Comamonas in granular sludge, and Dechloromonas in biofilm. Noticeably, sulfate in the groundwater stimulated the growth of sulfur converting microbes with increasing abundances of sulfite reductase gene and sulfate-reducing bacteria Desulfovibrio. This study highlights the potential implementation of HD process in granular sludge reactor for advance nitrogen removal from impaired groundwater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Superior viability performance of SRB bio-cathode biofilm than non-C 4 -HSL addition. • More efficient and quick sulfate reduction was achieved by C 4 -HSL addition. • Extracellular polymers' secretion promotes uniform biofilms forming due to C 4 -HSL. • Acidogenic fermentation bacteria co-metabolized with SRB improve sulfate reduction. Signaling molecules are useful in biofilm formation, but the mechanism for biofilm construction still needs to be explored. In this study, a signaling molecule, N -butyryl- l -Homoserine lactone (C 4 -HSL), was supplied to enhance the construction of the sulfate-reducing bacteria (SRB) bio-cathode biofilm in microbial electrolysis cell (MEC). The sulfate reduction efficiency was more than 90% in less time under the system with C 4 -HSL addition. The analysis of SRB bio-cathode biofilms indicated that the activity, distribution, microbial population, and secretion of extracellular polymers prompted by C 4 -HSL, which accelerate the sulfate reduction, in particular for the assimilatory sulfate reduction pathway. Specifically, the relative abundance of acidogenic fermentation bacteria increased, and Desulfovibrio was co-metabolized with acidogenic fermentation bacteria. This knowledge will help to reveal the potential of signaling molecules to enhance the SRB bio-cathode biofilm MEC construction and improve the performance of treating sulfate-containing wastewater. [ABSTRACT FROM AUTHOR]

Extracellular polymeric substances (EPS) play an important role in the treatment of acid mine drainage (AMD) by sulfate-reducing bacteria (SRB). In this paper, Desulfovibrio desulfuricans was used as the test strain to explore the effect of heavy metals on the components and adsorption ability of EPS. Fourier-transform infrared (FTIR) spectroscopy analysis results showed that heavy metals did not influence the type of functional groups of EPS. Potentiometric titration results indicated that the acidic constants (p K a ) of the EPS fell into three ranges of 3.5–4.0, 5.9–6.7, and 8.9–9.8. The adsorption site concentrations of the surface functional groups also increased. Adsorption results suggested that EPS had a specific binding affinity for the dosed heavy metal, and that EPS extracted from the Zn 2+ -dosed system had a higher binding affinity for all heavy metals. Additionally, Zn 2+ decreased the inhibitory effects of Cd 2+ and Cu 2+ on the SRB. [ABSTRACT FROM AUTHOR]

Simultaneous removal of COD, SO 4 2− and NO 3 − and recovery of elemental sulfur (S 0 ) were evaluated in a four-compartment anaerobic baffled reactor (ABR) with separated functional units of sulfate reduction (SR) and denitrifying sulfide removal (DSR). Optimal SO 4 2− -S/NO 3 − -N ratio was evaluated as 5:5, with a substantial improvement of S 0 recovery maintained at 79.1%, one of the highest level ever reported; meanwhile, removal rates of COD, SO 4 2− and NO 3 − were approached at 71.9%, 92.9% and 98.6%, respectively. Nitrate served as a key factor to control the shift of SR and DSR related populations, with the possible involvement of Thauera sp. during SR and Sulfurovum sp. or Acidiferrobacter sp. during DSR, respectively. DsrB and aprA genes were the most abundant during SR and DSR processes, respectively. Cylindrical-type ABR with the improved elemental sulfur recovery was recommended to deal with sulfate and nitrate-laden wastewater under the optimized SO 4 2− /NO 3 − ratio. [ABSTRACT FROM AUTHOR]

The effects of three types of dietary sulfur on in vitro fermentation characteristics, sulfide production, methane production, and microbial populations at two different buffer capacities were examined using in vitro rumen cultures. Addition of dry distilled grain with soluble (DDGS) generally decreased total gas production, degradation of dry matter and neutral detergent fiber, and concentration of total volatile fatty acids, while increasing ammonia concentration. High buffering capacity alleviated these adverse effects on fermentation. Increased sulfur content resulted in decreased methane emission, but total Archaea population was not changed significantly. The population of sulfate reducing bacteria was increased in a sulfur type-dependent manner. These results suggest that types of dietary sulfur and buffering capacity can affect rumen fermentation and sulfide production. Diet buffering capacity, and probably alkalinity, may be increased to alleviate some of the adverse effects associated with feeding DDGS at high levels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sulfite-based pretreatment remarkably promoted VFAs production from microalgae. • Acetate proportion of 54.5% was obtained at 200 mg S/L with time of day 8. • More and relatively easy biodegradable organics were released into liquid phase. • Sulfite-induced sulfate-reducing bacteria facilitated the acetate generation pathway. • β-glucanase, β-glucosidase, and acetate kinase activities were accelerated. Volatile fatty acids (VFAs) production from anaerobic fermentation of microalgae is generally constrained by low organics solubilization and poor substrate-availability. In this study, sulfite-based pretreatment was developed to overcome such situation. Experimental results showed that the maximum concentration of VFAs (467.5 mg COD/g VSS) and corresponding acetate proportion (54.5%) was obtained at 200 mg sulfite-S/L with fermentation time of day 8, which was respectively 2.1- and 1.9-fold of control. It was found that after sulfite pretreatment, more and relatively easy biodegradable organics were released into liquid phase, providing available substrate for acid-producing bacteria. The rigid cell wall of microalgae was destroyed, evidenced by the decreased particle size and increased surface area, which made the microalgae more accessible for subsequent hydrolysis and acidification. Meanwhile, the sulfite-induced sulfate-reducing bacteria facilitated the acetate generation pathway. The accelerated activities of β-glucanase, β-glucosidase, and acetate kinase involved in anaerobic fermentation further validated the above results. [ABSTRACT FROM AUTHOR]

Highlights: [•] Graphite felt electrode was treated by electrochemical oxidation. [•] The treated anode facilitated formation of electrogenic biofilm. [•] Strong hydrogen and/or peptide bonds contributed to bacterial attachment. [•] Cytochrome c of D. desulfuricans was efficiently bound to the electrode and transferred electrons directly. [ABSTRACT FROM AUTHOR]

Highlights: [•] Integrated simultaneous desulfurization and denitrification process is tested. [•] ISDD reaches high removals of sulfate, sulfide and COD in single reactor. [•] Strains were identified for SRB, hNRB and aNRB for ISDD reactor. [•] Optimal C/S ratio to maximize ISDD performance was noted. [ABSTRACT FROM AUTHOR]

Highlights: [•] Microbial fuel cell with SRB+SOB anodic biofilm treats sulfate+lactate wastewater. [•] Tested MFC efficiently converted sulfate to elemental sulfur. [•] Electrochemical analyses showed that sulfide is dominating species for performance. [•] Form sulfide diffused to SOB cell for conversion to sulfur and excess electrons. [•] Short diffusional distance of sulfide ions between cells enhances MFC performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Haloalkaliphilic microorganisms were used to reduce sulfate and nitrate. [•] Sulfide concentration reached up to 703mg/l. [•] There was no sulfide inhibition to haloalkaliphilic microorganisms. [•] Bacterial community of haloalkaliphilic bioreactor was studied. [Copyright &y& Elsevier]

Highlights: [•] Hematite and gypsum in the mixture promote anaerobic degradation of substrate. [•] Hematite and gypsum in the mixture reduce the GHG releasing. [•] Addition of hematite increases the anaerobic digestion process. [•] Iron oxide precipitates and eliminate the negative impact of S2−. [•] Ca2+ released from gypsum generates calcite. [ABSTRACT FROM AUTHOR]

An anoxic biocathode was developed using sulfate-reducing bacteria (SRB) consortium on activated carbon fabric (ACF) and the effect of stainless steel (SS) mesh as additional current collector was investigated. Improved performance of biocathode was observed with SS mesh leading to nearly five folds increase in power density (from 4.79 to 23.11 mW/m 2 ) and threefolds increase in current density (from 75 to 250 mA/m 2 ). Enhanced redox currents and lower Tafel slopes observed from cyclic voltammograms of ACF with SS mesh indicated the positive role of uniform electron collecting points. Differential pulse voltammetry technique was employed as an additional tool to assess the redox carriers involved in bioelectrochemical reactions. SRB biocathode was also tested for reduction of volatile fatty acids (VFA) present in the fermentation effluent stream and the results indicated the possibility of integration of this system with anaerobic fermentation for efficient product recovery. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sb(V) removal from Sb mine drainage using SRB was studied. [•] SRB are effective in removing Sb from water. [•] Sb(V) removed by SRB is due to Sb(V) reduction to Sb(III) and formation of Sb2S3. [•] Element sulfur was generated during Sb(V) reduction by SRB. [Copyright &y& Elsevier]

Highlights: [•] MPA predominated in COD and electrons utilization in high sulfate situation. [•] At HRT of 6h, methane yield reached 0.23L/gCOD with COD removal above 80%. [•] Methane was generated by Methanosaeta concilii GP6 with acetate as substrate. [•] Sulfate was mainly reduced by Desulfovibrio species with ethanol as substrate. [•] SRB accounted for 17.6% in bacteria and all belonged to incomplete oxidizers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cu/Fe bimetallic can enhance Cu2+ and Zn2+ removal and SRB resistance for metals. [•] High level metal removal efficiency maintained at wide range pH in SRB–Cu/Fe system. [•] The first time found that SRB–Cu/Fe preferable to SRB–Fe0 for Cu2+ and Zn2+ removal. [•] 97.9% Zn2+ and 97.2% Cu2+ reduction efficiency was obtained within the first 24h. [•] Heavy metals reduction in SRB–Cu/Fe system was feasible and effective. [Copyright &y& Elsevier]

Abstract: The treatment of Cr(VI) containing textile wastewater was studied in ethanol and glucose-fed sulfate-reducing fluidized bed reactors at 35°C for around 250days. The synthetic wastewater contained Cr(VI) (5–45mgL−1), azo dye (Remazol Brilliant Violet 5R) (100–200mgL−1), sulfate (2000mgL−1) and ethanol or glucose (2000mgL−1 chemical oxygen demand (COD)). The robustness of two FBRs was assessed under varying Cr(VI) and azo dye loadings. Both reactors performed well in terms of COD, sulfate, color and Cr(VI) removals. However, ethanol-fed FBR performed better than glucose-fed one. The COD, sulfate, chromium and color removals at the highest Cr(VI) concentration (45mgL−1) in ethanol-fed FBR were around 75%, 95%, 93%, and 99%, respectively. Further increase in influent Cr(VI) concentration adversely effected reactor performance. The COD, sulfate, chromium and color removals at 45mgL−1 Cr(VI) in glucose-fed FBR were around 60%, 50%, 93%, and 76%, respectively. [Copyright &y& Elsevier]

The leaching and/or accumulation of trace elements in sulfate reducing granular sludge systems was investigated. Two thermophilic up-flow anaerobic sludge bed (UASB) reactors operated at pH 5 were fed with sucrose (4 g COD l reactor −1 d −1 ) and sulfate at different COD/SO 4 2− ratios. During the start-up of such acidogenic systems, an initial leaching of trace elements from the inoculum sludge occurred regardless of trace elements supplementation in the reactor influent. The granular sludge maintained the physical structure despite high Fe leaching. After start-up and nonetheless the acidic conditions, Co, Ni, Cu, Zn, Mo and Se were retained or accumulated by the sludge when added. Particularly, Ni and Co accumulated in the carbonates and exchangeable fractions ensuring potential bioavailability. Otherwise, the initial stock in the inoculum sludge sufficed to operate the process for nearly 1 year without supplementation of trace elements and no significant sludge wash-out occurred. [ABSTRACT FROM AUTHOR]

Abstract: Biological treatment of sulfate-laden wastewater consists of two separate reactors to reduce sulfate to sulfide by sulfate-reducing bacteria (SRB) and to oxidize sulfide to sulfur (S0) by sulfide oxidation bacteria (SOB). To have SRB+SOB in a single reactor faced difficulty of low S0 conversion. This study for the first time revealed that dissolved oxygen (DO) level can be used to manipulate SRB+SOB reactions in a single reactor. This work demonstrated successful operation of an integrated SRB+SOB reactor under micro-aerobic condition. At DO=0.10–0.12mgl−1, since the activities of SOB were enhanced by limited oxygen, the removal efficiency for sulfate reached 81.5% and the recovery of S0 peaked at 71.8%, higher than those reported in literature. At increased DO, chemical oxidation of sulfide with molecular oxygen competed with SOB so conversion of S0 started to decline. At DO>0.30mgl−1 activities of SRB were inhibited, leading to failure of the SRB+SOB reactor. [Copyright &y& Elsevier]

Abstract: A denitrification reactor packed with wood as a carbon source was operated using synthetic inorganic wastewater. The maximum denitrification rate was 62.4g-/m3/day at HRT of 24h. The nitrate removal continued after 1500days. The denitrification efficiency was assumed to enhance sulfur denitrification via wood degradation by sulfate reduction. The achieved sulfate reduction rate was 468mg-/kg-dry weight wood/day after 419days of operation. The sulfate reduction rate in the deep-layer biofilm inside the wood was higher than that in the total biofilm inside the wood. The sulfate-reducing bacteria segregated inside the wood. This study suggested that Desulfobulbus spp. and Desulfomicrobium spp. grown in the deep-layer degraded the wood incompletely, and the produced organic acids were utilized by the heterotrophic denitrifying bacteria, Desulfobacter spp. and Desulfonema spp., grown in the surface layer, and that these surface bacteria complete the degradation of the organic acids from the wood. [ABSTRACT FROM AUTHOR]

Abstract: The present study was conducted to investigate the chromium(VI), COD and sulphate removal efficiency from aqueous solution and treatment of real effluent (CETP) in a small scale bioreactor using sulphate reducing bacteria consortium. Effect of different hydraulic retention times (HRTs), initial metal concentrations, various carbon sources and temperatures were studied on removal of chromium(VI), COD and sulphate. Maximum chromium(VI) and sulphate removal was found to be 96.0% and 82.0%, respectively, at initial concentration of 50mgl−1 using lactate as carbon source. However, highest COD removal was 36.2% in medium containing fructose as the carbon source and electron donor. NADH dependent chromate reductase activity was not observed which indicated the anaerobic consortium. Initially consortium medium with a strong negative oxidation reduction potential indicated the reducing activity. The FTIR spectrum of the sulphate reducing bacteria consortium clearly shows the existence of the sulphate ions and signifies that sulfate reducing bacteria have used sulfate during the growth phase. [ABSTRACT FROM AUTHOR]

Abstract: The performance of a sulfidogenic bioreactor and the response of bacterial populations to influent alkalinity changes were investigated. The bioreactor reached 40% of sulfate removal efficiency (SRE) with 0mgl−1 of alkalinity, and single-stranded conformation polymorphism profiles showed that some members of Bacteroides, Dysgonomonas, Sporobacter, Quinella, and Citrobacter became dominant populations. 16S rRNA gene library analysis indicated that the Actinobacteria group increased from 0% in seed to 23% in sludge. An increase in alkalinity to 1300mgl−1 led to a rapid increase of SRE to 65% and changes in the bacterial community. Sequences representing Dysgonomonas, Raoultella, Kluyvera, and Phascolarctobacterium were now found. When alkalinity was deceased to 0mgl−1, SRE dropped and the bands representing Raoultella, Kluyvera, and Phascolarctobacterium disappeared, while bands representing Clostridium appeared. A second cycle of low/high alkalinity did not result in obvious changes to the bacterial community. These results indicate that the sulfidogenic bioreactor favored higher influent alkalinity and that the different functional microbial populations responded well to the alkalinity changes. [ABSTRACT FROM AUTHOR]

Abstract: The effect of a sulfate reducing bacteria immobilized in polyvinyl alcohol (PVA) on simultaneous sulfate reduction and copper removal was investigated. Batch experiments were designed using central composite design (CCD) with two parameters, i.e. the copper concentration (10–100mg/L), and the quantity of immobilized SRB in culture solution (19–235mg of VSS/L). Response surface methodology (RSM) was used to model the experimental data, and to identify optimal conditions for the maximum sulfate reduction and copper removal. Under optimum condition, i.e. ∼138.5mg VSS/L of sulfate reducing bacteria immobilized in PVA, and ∼51.5mg/L of copper, the maximum sulfate reduction rate was 1.57d−1 as based on the first-order kinetic equation. The data demonstrate that immobilizing sulfate reducing bacteria in PVA can enhance copper removal and the resistance of the bacteria towards copper toxicity. [Copyright &y& Elsevier]