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[Display omitted] • ssPBR was a reliable way to purify water quality and generate profit for WWTPs. • P discharge thresholds of secondary effluent would increase after using ssPBR. • The ssPBR for algae culture with sequential batch operation could perform steadily. • N of 15 mg/L and P of 1.5 ∼ 3.0 mg/L were optimal concentrations for ssPBR operation. • Carriers in the ssPBR contributed to the efficient growth and metabolism of algae. Nitrogen (N) and phosphorus (P) absorbed by algae in the suspended-solid phase photobioreactor (ssPBR) have emerged as an efficient pathway to purify the effluent of wastewater treatment plants (WWTPs). However, the key operational parameters of the ssPBR need to be optimized. In this study, the stability of the system after sequential batch operations and the efficiency under various influent P concentrations were evaluated. The results demonstrated that the ssPBR maintained a high N/P removal efficiency of 96 % and 98 %, respectively, after 5 cycles. When N was kept at 15 mg/L and P ranged from 1.5 to 3.0 mg/L, the system yielded plenty of algae products and guaranteed the effluent quality that met the discharge standards. Notably, the carriers were a key contributor to the high metabolism of algae and high performance. This work provided theoretical ideas and technical guidance for effluent quality improvement in WWTPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effects of reflux ratios from 50% to 500% on the performance of EGSB were evaluated. • The reflux ratios of 100% and 200% were beneficial for the performance of EGSB. • The dominant microbes and AHLs in different layers of the EGSB were identified. • C 4 -HSL and C 8 -HSL were regarded as the potential AHLs in the formation of AnGS. • 3-oxo-C 6 -HSL and 3-oxo-C 14 -HSL were significantly related with methanogenesis. Performance of anaerobic sludge and microbial social behaviors in an expanded granular sludge bed (EGSB) were evaluated by increasing reflux ratio from 50% to 500% stage by stage, with a constant influent chemical oxygen demand (COD) of 5500 mg/L at hydraulic retention time 12 h. The results indicated that the reflux ratio of 100% − 200% was more favorable for the EGSB with a methane production of 2.4 m3/m3·d. It was found that acyl-homoserine lactones (AHLs)-mediated quorum sensing (QS) could balance various microbial populations in the anaerobic digestion process. C 4 -HSL and C 8 -HSL were identified as the specific AHLs in enhancing granulation of anaerobic sludge by stimulating protein secretion into extracellular polymeric substances (EPS). 3-oxo-C 6 -HSL and 3-oxo-C 14 -HSL were verified for the enhancement of methanogenesis. The present study showed a novel perspective on the performance of EGSB with reflux ratios based on the AHLs-mediated QS. [ABSTRACT FROM AUTHOR]

[Display omitted] • A UASB suffered from a shock loading was restored by stage-to-stage OLR regulation. • Balance among functional populations was reestablished in the restoration process. • Performance of functional populations was closely related to specific AHLs secretion. • C 4 -HSL was found as the most dominant AHLs for EPS secretion and AFBs growth. • 3-oxoC 6 -HSL was found as the key signal molecule in enhancing methanogens. To understand the microbial social behaviors regulated by acyl-homoserine lactones (AHLs) in the upflow anaerobic sludge blanket (UASB) during the restored process after a shock loading, the correlation analyses of AHLs and components of extracellular polymeric substances (EPS), AHLs genes and microbes, and AHLs and microbes were investigated. The results showed that the performance could be restored by regulating influent organic loading rate stage-by-stage. A variation in microbial community and endogenous AHLs was also found during the restoration process. It was found that C 14 -HSL had improved the synthesis of protein in EPS and resulted in better aggregation of microbes. C 4 -HSL, as well as C 8 -HSL and 3-oxoC 14 -HSL, could prompt the metabolism of acidogenic fermentation bacteria. While 3-oxoC 6 -HSL was identified as the key signal molecule in enhancing methanogenesis. The present work advanced the understanding of microbial social behaviors and provided an attractive strategy for the restoration of anaerobic digestion after shock loadings. [ABSTRACT FROM AUTHOR]

Metagenomic comparisons of microbial profiles were conducted to investigate differences between the samples from steady (Day 42), ammonium-adjusting (Day 63), and ammonium-stressed (Day 102) periods during the 110-day operation of a high solid anaerobic digester of sewage sludge. Comparing to the steady period, biogas production was slightly inhibited after ammonium adjustment, during which the microbes showed higher abundance in 6 of the total 22 ammonium-related genes. In addition, among the 19 amino-acid-related genes, 9 genes involved in amino acid generation and utilization were reduced, which partially revealed the reason of deterioration of volatile solids (VSs) degradation following ammonium stress. Furthermore, although the acetoclastic pathway was to some extent inhibited with the decrease of biogas amount and content, no enhancement of genes involved in hydrogenotrophic methanogenesis was observed, elucidating the distinct role of ammonium stress in directing bacterial community structure toward the enhanced syntrophic acetate oxidation reaction. [ABSTRACT FROM AUTHOR]

Highlights • Specific QS signals of various populations in anaerobic digestion were identified. • Most AHLs in anaerobic digestion were secreted in starvation conditions. • The specific QS signals induced the K -strategy of populations to survive. • The QS regulated cooperation among populations in resource-limited situations. • Profiles of AHLs indicated the performance of anaerobic digestion processes. Abstract A series of dominant functional floras involved in anaerobic digestion was obtained by subculturing anaerobic sludge with specific substrates, respectively, and their specific quorum sensing signals (AHLs) were identified. It was found that most of the AHLs were secreted in starvation of the functional floras. One or two AHLs were found to have a significant positive correlation with the behavior of hydrolytic-fermentative bacteria, homoacetogens, syntrophic propionate-oxidizing bacteria, syntrophic butyrate-oxidizing bacteria and aceticlastic methanogens, respectively. Hydrogenotrophic methanogens had a various self-organization means and broader relations with the other populations, which was induced by six AHLs at least. Performance of an upflow anaerobic sludge blanket in the startup process revealed that the dominant populations involved in anaerobic digestion would secret specific AHLs to induce K -strategy in resource-limited situation for reproduction and regulating their cooperation. This work presents a novel perspective on the social behaviors of microbial populations in anaerobic digestion. [ABSTRACT FROM AUTHOR]

Bicarbonate (HCO 3 − ) has been extensively researched as a buffer in anaerobic digestion. The effect of HCO 3 − concentration on syntrophic butyrate oxidation process was evaluated by batch culturing of anaerobic activated sludge, and the mechanism was further revealed by the changes of Gibbs free energy (Δ G ) and the interspecies transfers of electron and proton. The results showed that butyrate degradation rate was enhanced by 32.07% when the supplement of HCO 3 − increased from 0 to 0.20 mol/L. However, methane production and acetate degradation were strongly inhibited by HCO 3 − more than 0.10 mol/L. More function of HCO 3 − was found as 1) decreasing the Δ G of syntrophic methanogenesis of butyrate while increasing the Δ G of methanogenesis of acetate, 2) enriching M. harundinacea and M. concilii , 3) increasing the diffusion rate of protons between the syntrophic consortia. This work would increase the anaerobic digestion efficiency by enhancing the interaction of the syntrophic consortia. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel MV-mediated CEF system is proposed for efficient butanol production. • Methyl viologen supplement inhibits H 2 formation and enhances butanol production. • Exogenous butyric acid enhances butanol production in the MV-mediated CEF system. • Butanol selectivity from co-substrates of glucose and butyric acid achieves 90.44%. Butanol production by solventogenic Clostridia shows great potential to combat the energy crisis, but is still challenged by low butanol selectivity and high downstream cost. In this study, a novel cathodic electro-fermentation (CEF) system mediated by methyl viologen (MV) was proposed and sequentially optimized to obtain highly selective butanol production. Under the optimal conditions (−0.60 V cathode potential, 0.50 mM MV, 30 g/L glucose), 7.17 ± 0.55 g/L butanol production were achieved with the yield of 0.32 ± 0.02 g/g. With the supplement of 4 g/L butyric acid as co-substrate, butanol production further improved to 13.14 ± 1.14 g/L with butanol yield and selectivity as high as 0.43 ± 0.01 g/g and 90.44 ± 1.66%, respectively. The polarized electrode enabled the unbalanced fermentation towards butanol formation and MV further inhibited hydrogen production, both of which contributed to the high-level butanol production and selectivity. The MV-mediated CEF system is a promising approach for cost-effective bio-butanol production. [ABSTRACT FROM AUTHOR]

Abstract: The effective disposal of redundant straw is a significant work for environmental protection and full utilization of resource. In this work, the wheat straw has been modified by etherification to prepare a kind of quaternary ammonium straw adsorbents. The adsorption behaviors of the modified straw for methyl orange (MO) and acid green 25(AG25) were studied in both batch and column systems. The adsorption capacity of the straw for both dyes improved evidently after modification. The maximal MO and AG25 uptakes were more than 300 and 950mgg−1, respectively. Furthermore, the adsorption equilibrium, kinetics and column studies all indicated that the adsorption behavior was a monolayer chemical adsorption with an ion-exchange process. In addition, after adsorption of anionic dyes, the used adsorbents were successfully applied to adsorb a cationic dye directly at suitable conditions in the secondary adsorption. This was due to the altered surface structures of the used adsorbents. [Copyright &y& Elsevier]

[Display omitted] • A novel NR-mediated CEF system of Clostridium beijerinckii was constructed. • The enhanced H 2 yield of 206.53 mL/g was 71.4% higher than the open circuit system. • The enhanced butanol yield of 0.30 g/g was 172.7% higher than the OC system. • The polarized electrode was responsible for the effective H 2 production. • The additional neutral red induced more carbon source and electrons to form butanol. To enhance the co-production of butanol and hydrogen by the acetone-butanol-ethanol (ABE) fermentation of Clostridium beijerinckii , a novel cathodic electro-fermentation (CEF) system was constructed with neutral red (NR) as electron mediator. With the mediation of NR, production of butanol and hydrogen from glucose in the CEF system achieved 5.49 ± 0.28 g/L and 3.74 ± 0.16 L/L, 569.5% and 325.0% higher than that in the open circuit (OC) system, respectively. The butanol and hydrogen yield of 0.30 ± 0.02 g/g and 206.53 ± 8.20 mL/g was 172.7% and 71.4% higher than that in the OC system, respectively. The effective co-production of butanol and hydrogen in the NR-mediated CEF system was attributed to the cooperation of the introduced polarized electrode and the additional NR. With the control of the polarized electrode, a feasible ORP was available for the effective hydrogen production. And the additional NR had induced more carbon source and electrons to the synthesis of butanol. [ABSTRACT FROM AUTHOR]