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The interplay of Fe(II) oxidation and Fe(III) bio-reduction occurs widely in both natural and engineered redox-dynamic systems. This study aimed to unravel the impact of Fe(II) oxidation by O 2 in the presence of iron-reducing bacteria on subsequent Fe(III) bio-reduction. Mixed solutions of Fe 2+ (0.1–0.5 mM) and Shewanella oneidensis strain MR-1 (MR-1, 2.0 × 10 7  CFU/mL) at neutral pH were first exposed to laboratory air for Fe(II) oxidation and bacterial inactivation, and then the resultant Fe(III) suspensions were switched to anoxic conditions for bio-reduction by the surviving bacteria. In the oxidation step, the coexisting MR-1 was inactivated by 0.8–1.71 orders of magnitude within 60 min. In the subsequent bio-reduction step, the resultant Fe(III) was bio-reduced by the surviving MR-1. Bio-reduction of the resultant Fe(III) by the surviving MR-1 was 1.8–2.5 times faster than that of the Fe(III) that was produced from Fe 2+ oxidation without MR-1 by fresh MR-1 cells at 2.0 × 10 7  CFU/mL. Although MR-1 inactivation during Fe(II) oxidation may inhibit Fe(III) bio-reduction, the increase in bio-availability of the resultant Fe(III) and the residual reactivity of dead cells led to net enhancement of bio-reduction under the tested conditions. Lepidocrocite was the sole Fe(III) mineral that was produced from Fe 2+ oxidation without MR-1, while 19% ferrihydrite was produced from Fe 2+ oxidation in the presence of MR-1. The formation of low-crystallinity ferrihydrite accounts for the increase in bio-availability of the Fe(III) minerals. The findings of this study highlight an important but overlooked impact underlying the interplay of Fe(II) oxidation and Fe(III) bio-reduction. [ABSTRACT FROM AUTHOR]

The aim of this article is to introduce the methodology of disease burden (DB) to quantify the health impact of microbial regrowth during wastewater reuse, using the case study of a decentralized water reuse system in Xi'an Si-yuan University, located in Xi'an, China. Based on field investigation findings, Escherichia coli ( E. coli ), Salmonella and rotavirus were selected as typical regrowth pathogens causing potential health hazards during the reuse of reclaimed water. Subsequently, major exposure routes including sprinkler irrigation, landscape fountains and toilet flushing were identified. Mathematical models were established to build the relationship between exposure dose and disease burden by calculating the disability adjusted life year (DALY). Results of disease burden for this case study show that DALYs attributed to E. coli were significantly greater than those caused by other pathogens, and DALYs associated with sprinkler irrigation were higher than those originating from other routes. A correlation between exposure dose and disease was obtained by introducing a modified calculation of morbidity, which can extend the assessment endpoint of health risk to disease burden from the conventional infection rate. [ABSTRACT FROM AUTHOR]

Groundwater table fluctuation during natural and anthropogenic processes can facilitate the interaction between oxygen (O 2) from the unsaturated zone and ferrous iron (Fe2+) from the saturated zone. In light of previous findings that Fe(III)-reducing bacteria can be killed by the reactive oxidants produced from Fe2+ oxidation under static oxic conditions, we hypothesize that Fe(III)-reducing bacteria will be attenuated during groundwater table fluctuations. To test this hypothesis, this study explored the variations of cell numbers of Shewanella oneidensis strain MR-1 (MR-1), a typical strain of Fe(III)-reducing bacteria, together with dissolved oxygen (DO) and Fe2+, at different points during controlled groundwater table fluctuations in a sand column. The results showed that, during the rise of the water table, O 2 in the pore air was entrapped by the deoxygenated groundwater, and Fe2+ in the groundwater was oxidized by the entrapped O 2. In this process, 1.40–2.42 orders of magnitude of viable MR-1 cells were killed at different points in the column. Further investigation proposed that the death of MR-1 is caused by the production of intracellular reactive oxidants, such as O 2 •− and OH•, from the oxidation of adsorbed/absorbed Fe2+ instead of by bulk reactive oxidants, such as OH• and Fe(IV), produced from the oxidation of aqueous Fe2+. The findings here provide new insights for Fe biogeochemical cycling in the redox-dynamic zone. Unlabelled Image • Fe(III)-reducing bacterium MR-1 was attenuated during the rise of groundwater table. • Fe2+ oxidation killed MR-1 during the rise of groundwater table. • Intracellular reactive oxidants might be the main reason for MR-1 death. • Intracellular reactive oxidants were produced from adsorbed Fe2+ oxidation. [ABSTRACT FROM AUTHOR]

Disability adjusted life year (DALY) has been widely used since 1990s for evaluating global and/or regional burden of diseases. As many environmental pollutants are hazardous to human health, DALY is also recognized as an indicator to quantify the health impact of environmental pollution related to disease burden. Based on literature reviews, this article aims to give an overview of the applicable methodologies and research directions for using DALY as a tool for quantitative assessment of environmental pollution. With an introduction of the methodological framework of DALY, the requirements on data collection and manipulation for quantifying disease burdens are summarized. Regarding environmental pollutants hazardous to human beings, health effect/risk evaluation is indispensable for transforming pollution data into disease data through exposure and dose–response analyses which need careful selection of models and determination of parameters. Following the methodological discussions, real cases are analyzed with attention paid to chemical pollutants and pathogens usually encountered in environmental pollution. It can be seen from existing studies that DALY is advantageous over conventional environmental impact assessment for quantification and comparison of the risks resulted from environmental pollution. However, further studies are still required to standardize the methods of health effect evaluation regarding varied pollutants under varied circumstances before DALY calculation. [ABSTRACT FROM AUTHOR]

An effective early warning tool is of great administrative and social significance to the containment and control of an epidemic. Facing the unprecedented global public health crisis caused by COVID-19, wastewater-based epidemiology (WBE) has been given high expectations as a promising surveillance complement to clinical testing which had been plagued by limited capacity and turnaround time. In particular, recent studies have highlighted the role WBE may play in being a part of the early warning system. In this study, we briefly discussed the basics of the concept, the benefits and critical points of such an application, the challenges faced by the scientific community, the progress made so far, and what awaits to be addressed by future studies to make the concept work. We identified that the shedding dynamics of infected individuals, especially in the form of a mathematical shedding model, and the back-calculation of the number of active shedders from observed viral load are the major bottlenecks of WBE application in the COVID-19 pandemic that deserve more attention, and the sampling strategy (location, timing, and interval) needs to be optimized to fit the purpose and scope of the WBE project. Unlabelled Image • Wastewater surveillance has the potential for combatting the COVID-19 pandemic. • Early warning can be given by monitoring wastewater viral load. • Fecal shedding dynamics is still largely unclear and needs proper modeling. • Back-calculation is critical to the feasibility of WBE. [ABSTRACT FROM AUTHOR]

A series of ordered mesoporous Fe Mn bimetal oxides (OMFMs) were fabricated by using a novel inverse micelle method, and the texture, nanostructure and interface chemistry properties of OMFMs were closely correlated to the calcination temperature. Due to the amorphous regular inner-connected nanostructure and bimetallic synergistic effect, the obtained OMFMs exhibited superior arsenic sequestration performance than pure mesoporous Fe oxides (PMF) and Mn oxides (PMM). The optimum ratio of Fe/Mn and calcination temperature for arsenic removal was 3/1 and 350 °C (OMFM-3), and the maximum As(III) and As(V) adsorption capacities of OMFM-3 were 174.59 and 134.58 mg/g, respectively. Solution pH value negligibly affected the uptake of arsenic (ranged from 3.0 to 7.0), while SiO 3 2−/PO 4 3− ions and humic acid (HA) displayed significant inhibitory effect on arsenic removal by OMFM-3. According to the mechanism of arsenic removal, which simultaneously analyzed the arsenic redox transformation in aqueous phase and on solid phase interface, it was concluded that manganese oxides in OMFM-3 mainly played the role as a remarkable As(III) oxidant in water, whereas iron oxides dominantly acted as an excellent arsenic species adsorbent. Finally, the prominent arsenic sequestration behavior and performance in surface water suggested that OMFM-3 could be a promising and hopeful candidate for arsenic-contaminated (especially As(III)) surface water and groundwater remediation and treatment. Unlabelled Image • A series of OMFMs were successfully fabricated via a novel inverse micelle method. • Calcination temperature affected the nanostructure and surface chemistry of OMFMs. • SiO 3 2−/PO 4 3− ions and HA significantly influenced on both As(III) and As(V) removal. • Redox transformation of arsenic in liquid-solid phase was simultaneously investigated. • Respective role of Fe/Mn oxides in OMFM-3 for arsenic removal was identified. [ABSTRACT FROM AUTHOR]

Pore size is one of the most important properties in the successful operation of membrane-based bioprocesses for the treatment of municipal wastewater. The characteristics of two anaerobic membrane bioreactors (AnMBRs), one with a hollow fiber membrane of 0.4 μm pore size (AnMBR1), and the other with a membrane of 0.05 μm pore size (AnMBR2) were investigated for the treatment of real municipal wastewater at room temperature (25 °C) under varied hydraulic retention times (HRTs). Process performance was evaluated in terms of organic removal efficiency, biogas production and membrane filtration behaviours during a long-term continuous operation. Both AnMBRs showed good organic removal performance with COD and BOD removal efficiencies of around 89% and 93%, respectively. High energy recovery potential was achieved, with the biogas yield ranging between 0.20 and 0.26 L-gas/g-COD rem and a methane content of approximately 75%. The differences in the membrane filtration behaviours in the two AnMBRs included different permeate flux and total filtration resistance (R t). In the AnMBR with a 0.4 μm pore size membrane, an average R t of 1.08 × 10^12 m−1 was obtained even when the permeate flux was a high 0.274 m/day, while a higher average R t of 1.51 × 10^12 m−1 was observed in the AnMBR with 0.05 μm pore size membrane even when the flux was a low 0.148 m/day. The off-line membrane cleaning strategy used for AnMBR1 indicated that the membrane restoration efficiency was 90.2%. Unlabelled Image • Two AnMBRs with different pore size membranes treated municipal wastewater. • Average COD and BOD removal efficiencies reached 89% and 93%. • Biogas yield was 0.20–0.26 L-gas/g-COD rem with CH 4 content of 75%. • Membrane with 0.4 μm pore size was more appropriate than 0.05 μm. • Membrane restoration efficiency of 90.2% was achieved by the off-line cleaning. [ABSTRACT FROM AUTHOR]

Oxygen can enter into reductive aquifer through natural and artificial processes. However, the joint response of groundwater chemistry and functional microbial communities to oxygenation is not well understood due to the gap between taxonomic and functional microbial composition. Here, two wells named CZK15 and CZK22 at the second confined aquifer in Central China were in situ aerated, and the chemical parameters of groundwater and microbial communities in bio-trapping sand sediment were analysed during aeration. The microbial metabolic functions related to C, N, S, Fe transformation were predicted by Functional Annotation of Prokaryotic Taxa (FAPROTAX) approach and some key functional genes, such as phe , nah , narG , and soxB were verified by the real-time quantitative Polymerase Chain Reaction (qPCR) method. The biomass was promoted, microbial diversity fluctuated, and microbial composition changed remarkably with aeration mainly constrained by reduction-oxidation (redox) variation and SO 4 2− concentration. Among functional microbes, aerobic chemoheterotrophs including aromatic compound degraders (also especially for relative abundance of phe and some nah gene) and methylotrophs are dramatically enriched interpreting dissolved oxygen (DO) consumption and total organic carbon (TOC) decomposing in sediment. Whilst fermenters and methanogen expectedly decreased during aeration. Denitrifying microbes and narG gene relative abundance increased corresponding to the NO 3 − increase after aeration, while microbes for N 2 fixation, ammonification, and nitrification decreased relating to the source of NH 4 +. The sulfide oxidation causing increased SO 4 2− was reflected by the blooming of sulfur-oxidizing microbes and soxB gene. Some sulfate reducers persisted in sediment after aeration due to sufficient SO 4 2− as substrate. Fe(II) was mainly chemically oxidized as iron-oxidizing microbes were of low abundance and tended to decrease with aeration. The iron-reducing bacteria Geobacteraceae increased with aeration corresponding to the increased Fe(III) oxides formation. The findings of this study could have important implications in understanding the biogeochemical behaviours with cyclic redox conditions. Unlabelled Image • Well aeration causes chemical variation and transformation of C, N, S, and Fe. • Aeration greatly changes microbial biomass, diversity and taxonomic composition. • Redox condition and SO 4 2− mainly constrains microbial community evolution. • Function annotation and proving by FAPROTAX and qPCR interpret microbial role • Responses of chemistry and functional microbe to aeration are combined. [ABSTRACT FROM AUTHOR]