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The coexistence of microplastics (MPs) and heavy metals in sediments has caused a potential threat to sediment biota. However, differences in the effects of MPs and heavy metals on microbes and plants in sediments under different sediment conditions remain unclear. Hence, we investigated the influence of polyethylene (PE) and polylactic acid (PLA) MPs on microbial community structure, Pb bioavailability, and wheatgrass traits under sequential incubation of sediments (i.e., flood, drainage, and planting stages). Results showed that the sediment enzyme activities presented a dose-dependent effect of MPs. Besides, 10 % PLA MPs significantly increased the F1 fractions in three stages by 11.13 %, 30.10 %, and 17.26 %, respectively, thus resulting in higher Pb mobility and biotoxicity. MPs altered sediment bacterial composition and structures, and bacterial community differences were evident in different incubation stages. Moreover, the co-exposure of PLA MPs and Pb significantly decreased the shoot length and total biomass of wheatgrass and correspondingly activated the antioxidant enzyme activity. Further correlation analysis demonstrated that community structure induced by MPs was mainly driven by sediment enzyme activity. This study contributes to elucidating the combined effects of MPs and heavy metals on sediment ecosystems under different sediment conditions. [Display omitted] • Effects on enzyme activities varied with MPs types and sediment conditions. • 10 % PLA MPs significantly increased the bioavailability of Pb in sediment. • MPs reduced the complexity and stability of bacterial co-occurrence networks. • Co-exposure PLA MPs and Pb exhibited stronger negative impact on wheatgrass growth. • The bacterial structures were mainly driven by sediment enzyme activities. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are able to interact with diverse contaminants in sediments. However, the impacts of MPs on sediment properties and bacterial community structure in heavy metal-contaminated sediments remain unclear. In this study, we investigated the adsorption of Pb(II) by sediment-MPs mixtures and the effects of different concentration MPs on sediment enzyme activities, DOM fractions, and Pb bioavailability in riverine sediments, and further explored the response of sediment microbial community to Pb in the presence of MPs. The results indicated that the addition of MPs significantly decreased the adsorption amount of Pb(II) by sediments, especially decreased by 12.6% at 10% MPs treatment. Besides, the changes in enzyme activities, DOM fractions exhibited dose-dependent effects of MPs. The higher level of MPs (5% and 10%) tends to transform Pb into more bioavailable fractions in sediments. Also, MPs amendment was observed to alter sediment bacterial community structures, and community differences were evident in the uncontaminated and lead-contaminated sediments. Therein, significant increase of Bacteroidota , Proteobacteria and decrease of Firmicutes abundance in Pb-contaminated sediment at the phylum level were observed. These findings are expected to provide comprehensive information for assessing the combined ecological risks of heavy metals and MPs in riverine sediments. [Display omitted] • The adsorption capacity of sediment for Pb(II) decreased with the content of MPs. • The changes in sediment enzyme activities and DOC structures varied with MPs concentration. • High doses of MPs increased the bioavailability of Pb in sediments. • MPs had a greater impact on bacterial community in Pb-contaminated sediments. [ABSTRACT FROM AUTHOR]

Due to the mass production and daily use of plastic products, the potential toxicity of microplastics to the water environment has attracted worldwide attention. In this work, the effect of typical microplastics (PET) on the performance of activated sludge from membrane bioreactors (MBR) was evaluated. The impacts on biological removal efficiency were unconspicuous with continuous dosing of 60 particles/L. However, further investigations revealed that PET particle accumulation caused adverse impacts on settleability and dewaterability. The SVI value increased from 53.3 ml/g MLSS to 69.9 ml/g MLSS and the CST in the PET reactor increased by 22%. Nevertheless, hydrophobicity was reduced by 49.2%. Mechanism studies exposed that the PET microplastics accumulation improved extracellular polymeric substances (EPS) from 116.96 mg/L to 138.70 mg/L and caused cell membrane damage. The abundance and diversity of microbial community reduced in activated sludge in PET reactor compared with control reactor. These phenomena revealed a possible hypothesis that the microplastic particles increased EPS and cytotoxicity of activated sludge. However, the rate of transmembrane pressure (TMP) build-up was significantly mitigated in PET-MBR compared to that in a control-MBR (1.27 folds), which attributes that physical scour of particles may still alleviate membrane contamination in MBR. • Membrane biofouling was alleviated due to physical scouring of PET particles. • The physicochemical properties of sludge were changed after long-term PET exposure. • Accumulation of PET particles caused EPS secretion and cell membrane damage. • Long-term exposure to PET changed the microbial community of MBR system. [ABSTRACT FROM AUTHOR]

• PSB could release VFAs inhibition and recover biogas production effectively. • PSB bioaugmentation could maintain the microbial diversity of the system. • Light could accelerate the consuming speed of VFAs with or without PSB addition. • Adding PSB to release VFAs inhibition might be a cost-effective choice. The accumulation of volatile fatty acids (VFAs) can decrease reactor pH and inhibit methane-producing process. For the first time, photosynthetic bacteria (PSB) were used to recover from VFAs inhibition (pH 6.0) of an anaerobic digestion system. After adding PSB for 12 days with and without light condition, the methane content recovered from 33.3% to 60.5% and from 32.1% to 59.3%, respectively; the pH increased to 7.1 and 6.8, respectively, the system alkalinity rapidly increased to 2238 and 1921 mg/L, respectively; the sCOD decreased from 5600 to 995 mg/L and from 5575 to 2025 mg/L, respectively; and the contents of formic acid, acetic acid, propionic acid and total VFA were greatly reduced. Microbial analysis found that PSB bioaugmentation could maintain microbial diversity of the system. PSB bioaugmentation could effectively relieve acids accumulation and stimulate methane production especially under light condition. It is also found that light could accelerate recovery with or without bioaugmentation. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a process widely exist in bacteria, which refers to the cell-cell communication through secretion and sensing the specific chemical signal molecules named autoinducers. This review demonstrated recent research progresses on the specific impacts of signal molecules in the granular sludge reactors, such corresponding exogenous strategies contained the addition of QS signal molecules, QS-related enzymes and bacteria associated with QS process. Accordingly, the correlation between QS signaling molecule content and sludge granulation (including the formation and stability) was assumed, the comprehensive conclusion elucidated that some QS signals (acyl-homoserine lactone and Autoinducer 2) can accelerate the growth of particle diameter, the production of extracellular polymeric substance (EPS), microbial adhesion and change the microbiome structure. But diffusable signal factor (DSF) acted as a significant disincentive to the formation and stability of GS. As a result, it deserved serious attention on the value and role of QS signals in the GS. This review attempts to illuminate the potential method for addressing the main bottleneck: to accelerate the formation of granules and keep the high stability of GS for a long-term reactor. Therefore, review discussed the possible trends of GS: QS and intercellular/intracellular signaling which can lay a theoretical foundation for mechanism of GS formation and stability, would be of practical significance for further application in the future. Image 10514 • Particle diameter in the granules were relative to the variety of signal molecules. • The production of EPS was enhanced by AHLs and AI-2 and reduced by DSF. • Augmentation of signal molecules changed the microbial community in the granules. • Mechanism of signal molecules functioned in granules could be effectively applied. [ABSTRACT FROM AUTHOR]

• Microbial community dynamics are analyzed under the condition of exogenous QQ. • The change of sludge's biofouling propensity is investigated when adding exogenous QQ. • Exogenous QQ can reduce the species diversities of MBRs, especially in the short term. • Exogenous QQ can enhance biofouling propensity of sludge itself in the short term. • The enhancing of biofouling propensity of sludge depends on the dynamics of situ QS and QQ bacteria. Recently, bacterial quorum quenching (QQ) has been proven as a novel approach for biofouling mitigation in membrane bioreactors (MBRs). The information about microbial community is vital for the development of QQ strategies. Also, the change of microbial community may affect the biofouling propensity of sludge. In this study, the effects of exogenous QQ on microbial community dynamics in MBRs were investigated, along with biofouling propensity of activated sludge. QQ MBR dosed with exogenous QQ bacteria exhibited a better anti-biofouling, whereas the wastewater treatment performance was almost no difference compared with control MBR. As for the microbial community, exogenous QQ had an impact on both the bacterial diversities and community composition, especially for the quorum sensing (QS) and QQ bacteria in situ. The addition of exogenous QQ could reduce the QQ ability of sludge itself in the short term, and enhance its biofouling propensity. These findings provided new insights for the development of QQ strategies. [ABSTRACT FROM AUTHOR]

• The microbial community in wastewater play an important role in current generation. • The presence of aerobic bacteria in the sample reduces the current generation. • The anode needs to be cultured by the same source of water a prior measurement. • Pretreatment of bacteria before testing may improve the accuracy and reliability. • Two ways to reduce the systemic error in testing wastewater were firstly proposed. Microbial fuel cells (MFCs) based sensors had been studied in measuring biochemical oxygen demand (BOD) or the equivalent chemical oxygen demand (COD) recently. Limited attention has been paid to the effect of the microbial communities in wastewater on the responses of these sensors. This study systematically evaluated, for the first time, the effect of wastewater samples from a variety of sources on the electrical response of a micro-fabricated double-chamber MFC device. It was found that the response of the MFC is positively correlated with the bacterial composition, in particular electroactive bacteria. The presence of aerobic bacteria in the sample reduces the current generation. These findings indicated that the bacterial content of the water sample could be a significant interference source and must be considered in the use of µMFC-based sensors. Filtering samples may be effective in improving the reliability of these microsensors. [ABSTRACT FROM AUTHOR]