Treatment of groundwater containing Mn(II), Fe(II), As(III) and Sb(III) by bioaugmented quartz-sand filters

Algae promotes the biogenic oxidation of Mn(II) by accelerated extracellular superoxide production

Microbial manganese (Mn) oxidation, predominantly occurs within the anaerobic-aerobic interfaces, plays an important role in environmental pollution remediation. The anaerobic-aerobic transition zones, notably riparian and lakeside zones, are hotspots for algae-bacteria interactions. Here, we adopted a Mn(II)-oxidizing bacterium Pseudomonas sp. QJX-1 to investigate the impact of algae on microbial Mn(II) oxidation and verify the underlying mechanisms. Interestingly, we achieved a remarkable enhancement in bacterial Mn(II)-oxidizing activity within the algae-bacteria co-culture, despite the inability to oxidize Mn(II) for the algae used in this study. In addition, the bacterial density almost remains constant in the presence of algal cells. Therefore, the increased Mn(II) oxidation by QJX-1 in the presence of algae cannot be due to the increased biomass. Within this co-culture system, the Mn(II) oxidation rate surged to an impressive 0.23 mg/L/h, in stark contrast to 0.02 mg/L/h recorded within pure QJX-1 system. The presence of algae could inhibit the Fe-S cluster activity of QJX-1 by the produced active substance in co-culture, and result in the acceleration of extracellular superoxide production due to the impairment of electron transfer functions located in QJX-1 cell membranes. Moreover, elevated peroxidase gene expression and heightened extracellular catalase activity not only expedited Mn(II) ions oxidation but also facilitated conversion of intermediate Mn(III) ions into microbial Mn oxides, achieved through the degradation of hydrogen peroxide. Therefore, the acceleration of extracellular superoxide production and the decomposition of hydrogen peroxide are identified as the principal mechanisms behind the observed enhancement in Mn(II) oxidation within algae-bacteria co-cultures. Our findings highlight the need to consider the effect of algae on microbial Mn(II) oxidation, which plays an important role in the environmental pollution remediation.

Influence of microbial inoculation site on trichloroethylene degradation in electrokinetic-enhanced bioremediation of low-permeability soils

The integration of electrokinetic and bioremediation (EK-BIO) represents an innovative approach for addressing trichloroethylene (TCE) contamination in low-permeability soil. However, there remains a knowledge gap in the impact of the inoculation approach on TCE dechlorination and the microbial response with the presence of co-existing substances. In this study, four 1-dimensional columns were constructed with different inoculation treatments. Monitoring the operation conditions revealed that a stabilization period (∼40 days) was required to reduce voltage fluctuation. The group with inoculation into the soil middle (Group B) exhibited the highest TCE dechlorination efficiency, achieving a TCE removal rate of 84%, which was 1.1-3.2 fold higher compared to the others. Among degraded products in Group B, 39% was ethylene. The physicochemical properties of the post-soil at different regions illustrated that dechlorination coincided with the Fe(III) and SO42- reduction, meaning that the EK-BIO system promoted the formation of a reducing environment. Microbial community analysis demonstrated that Dehalococcoides was only detected in the treatment of injection at soil middle or near the cathode, with abundance enriched by 2.1%-7.2%. The principal components analysis indicated that the inoculation approach significantly affected the evolution of functional bacteria. Quantitative polymerase chain reaction (qPCR) analysis demonstrated that Group B exhibited at least 2.8 and 4.2-fold higher copies of functional genes (tceA, vcrA) than those of other groups. In conclusion, this study contributes to the development of effective strategies for enhancing TCE biodechlorination in the EK-BIO system, which is particularly beneficial for the remediation of low-permeability soils.

Study on mechanism of removal of sudden Tetracycline by compound modified biological sand filtration process

The removal of tetracycline from the sewage plant effluents through advanced treatment methods is key to controlling tetracycline levels in the water environment. In this study, modified quartz sands (QS) were used in a biological sand filter to remove tetracycline. The modified QS, with different surface characteristics, were prepared using glass etching technology combined with subsequent chemical modification methods, including hydroxylation treatment, metal ion modification, and amino modification. The adsorption efficiency of hydroxylated QS was higher than that of metal ion modified and amino modified QS, with adsorption efficiencies of 20.4331 mg/kg, 12.8736 mg/kg, and 10.1737 mg/kg, respectively. Results indicated that QS primarily reduce tetracycline through adsorption. Adsorption on ordinary QS fit the pseudo-first-order kinetic model, while adsorption on other modified QS and biofilm-coated QS fit the pseudo-second-order kinetics model. Biodegradation was identified as another mechanism for tetracycline reduction, which fit the zero-order kinetic model. Pseudomonas alcaligenes and unclassified Pseudomonas accounted for 96.6% of the total tetracycline-degrading bacteria. This study elucidates the effectiveness and mechanisms of five types of QS in treating tetracycline from sewage plant effluents. It provides a novel method for tetracycline reduction in real-world wastewater scenarios.

Divalent manganese stimulates the removal of nitrate by anaerobic sludge

This study investigated the effect of different concentrations of Mn2+ on the removal of nitrate by anaerobic sludge and changes in the microbial communities through batch experiments. The results showed that the addition of Mn2+ promoted nitrate removal by anaerobic sludge; the nitrate was completely removed within 6 d in the treatment group with >5 mM Mn2+. With the increase in Mn2+, the concentration of nitrite and nitrous oxide increased in the first 4 d and then decreased to 0 μM after 8 d of incubation. The increasing tendency of ammonium increased firstly and then decreased with the addition of Mn2+ compared to A. Moreover, the Mn2+ removal efficiency gradually decreased with the increase of Mn2+ concentration. The changes of microflora structure in sludge before and after adding Mn2+ were analyzed, and the results revealed that the microbial communities in the sludge may have evolved towards an energy-efficient association of short-cut nitrification, denitrification, and anaerobic ammonia oxidation after adding Mn2+. Mn2+ stimulated the removal of nitrate by anaerobic sludge mainly by promoting the growth of PHOS-HE36.

Removal of toxic metal Cd (II) by Serratia bozhouensis CdIW2 using in moving bed biofilm reactor (MBBR)

The use of bioreactor technology to treat industrial wastewater containing heavy metals has created new perspectives. Cadmium metal is one of the toxic heavy metals that have harmful effects on human health and the environment. This research work presents a comprehensive approach for aqueous cadmium removal through biosorption in a moving bed biofilm reactor (MBBR). The bacterium resistant to Cd(II) (350 mg/L) CdIW2 was selected among 8 cadmium tolerant bacteria isolated from the industrial wastewater of the metal industry. 16S rRNA gene and phenotypic analysis showed that the bacterium CdIW2 is similar to Serratia bozhouensis. The highest biosorption capacity of 65.79 mg/g was acquired in optimal conditions (30 min, pH = 6, 0.5 g/L, and 35 °C). The biosorption of the CdIW2 strain was consistent with the Langmuir isotherm and the pseudo-second order kinetic and showed the process's spontaneous thermodynamic and endothermic results. The removal rate 91.74% of MBBR in batch mode was obtained in 72 h and 10 mg/L of Cd(II). Furthermore, continuous mode bioreactor analysis has shown high efficiency at intel loading rates of 6-36 mg/L. day for cadmium removal. The second order kinetic (Grau) was chosen as the suitable model for modeling the MBBR process. Although several studies have evaluated the removal of various types of heavy metals, none of the studies involved the use of a metal-resistant strain in an MBBR bioreactor.

Efficient utilization of biogenic manganese oxides in bioaugmentation columns for remediation of thallium(I) contaminated groundwater

Little attention has been paid to the in situ-generated biogenic manganese oxides (BMnOx) for practical implementation in continuous groundwater remediation systems. The enrichment effects of manganese oxidizing bacteria (MOB) in bioaugmentation columns and the in situ-generated BMnOx for continuous thallium(I) (Tl(I)) removal from groundwater were investigated. Results indicated that Pseudomonas Putida MnB1 (strain MnB1) attached on the groundwater sediments (GS) can achieve a maximum of 97.37 % Mn(II) oxidation and generate 29.6 mg/L BMnOx, which was superior than that of traditional quartz sand (QS). The in situ-generated BMnOx in MOB_GS column effectively removed 10-100 μg/L Tl(I) under the interference of high concentrations of Fe(II) and Mn(II) in groundwater. Distinctive microbial enrichment effects occurred in the bioaugmentation columns under the competition of indigenous microbes in groundwater. The release of Mn(II) from the BMnOx inhibited with the decrease in Tl(I) removal efficiency. XAFS analysis revealed Tl(I) was effectively adsorbed by BMnOx and Mn-O octahedra with Tl-O tetrahedral coordination existed in BMnOx. This study provides an in-depth understanding of the in situ-generated BMnOx for the Tl(I) removal and contributes to the application of BMnOx in groundwater remediation.

Application of manganese oxides in wastewater treatment: Biogeochemical Mn cycling driven by bacteria

Manganese oxides (MnOx) are recognized as a strongest oxidant and adsorbent, of which composites have been proved to be effective in the removal of contaminants from wastewater. This review provides a comprehensive analysis of Mn biochemistry in water environment including Mn oxidation and Mn reduction. The recent research on the application of MnOx in the wastewater treatment was summarized, including the involvement of organic micropollutant degradation, the transformation of nitrogen and phosphorus, the fate of sulfur and the methane mitigation. In addition to the adsorption capacity, the Mn cycling mediated by Mn(II) oxidizing bacteria and Mn(IV) reducing bacteria is the driving force for the MnOx utilization. The common category, characteristics and functions of Mn microorganisms in recent studies were also reviewed. Finally, the discussion on the influence factors, microbial response, reaction mechanism and potential risk of MnOx application in pollutants' transformation were proposed, which might be the promising opportunities for the future investigation of MnOx application in wastewater treatment.

Detoxification and metabolism of glyphosate by a Pseudomonas sp. via biogenic manganese oxidation

Biogenic manganese oxides (BMO) are widely distributed in groundwater and provides promise for adsorbing and oxidizing a wide range of micropollutants, however, the continuous biodegradation and bioavailability of micropollutants via cycle biogenic Mn(II) oxidation remains to be elucidated. In this study, glyphosate was degraded and to serve as the nutrient source by a Pseudomonas sp. QJX-1. The addition of glyphosate will not affect the Mn(II) oxidation function of the strain but will affect its Mn(II) oxidation process and effect. The glyphosate degradation products could further be used as the C, N and P sources for bacterium growth. Analysis of the RNA-seq data suggested that Mn(II) oxidation driven by oxidoreductases for glyphosate degradation. The long-term column experiments using biological Mn(II) cycling to realize continuous detoxification and metabolism of glyphosate, and thus revealed the synergism effects of biological and chemical conversion on toxic micropollutants and continuous metabolism in an aquatic ecosystem.

Removal of pharmaceutical in a biogenic/chemical manganese oxide system driven by manganese-oxidizing bacteria with humic acids as sole carbon source

Bioaugmented sand filtration has attracted considerable attention because it can effectively remove contaminants in drinking water without additional chemical reagent addition. In this study, a synthesized chemical manganese dioxide (MnO₂)-coated quartz sand (MnQS) and biogenic manganese oxide (BioMnO_x) composite system was proposed to simultaneously remove typical pharmaceutical contaminants and Mn²⁺. We demonstrated a manganese-oxidizing bacterium, Pseudomonas sp. QJX-1, could oxidize Mn²⁺ to generate BioMnO_x using humic acids (HA) as sole carbon source. The coaction of MnQS, QJX-1, and the generated BioMnO_x in simultaneously removing caffeine and Mn²⁺ in the presence of HA was evaluated. We found a synergistic effect between them. MnQS and BioMnO_x together significantly increased the caffeine removal efficiency from 32.8% (MnQS alone) and 21.5% (BioMnO_x alone) to 61.2%. Meanwhile, Mn²⁺ leaked from MnQS was rapidly oxidized by QJX-1 to regenerate reactive BioMnO_x, which was beneficial for continuous contaminant removal and system stability. Different degradation intermediates of caffeine oxidized by MnQS and BioMnO_x were detected by LC-QTOF-MS analysis, which implied that caffeine was oxidized by a different pathway. Overall, this work promotes the potential application of bioaugmented sand filtration in pharmaceutical removal in the presence of natural organic matter in drinking water.

A review: Manganese-driven bioprocess for simultaneous removal of nitrogen and organic contaminants from polluted waters

Water pollutants, such as nitrate and organics have received much attention for their harms to ecological environment and human health. The redox transformation between Mn(Ⅱ) and Mn(Ⅳ) for nitrogen and organics removal have been recognized for a long time. Mn(Ⅱ) can act as inorganic electron donor to drive autotrophic denitrification so as to realize simultaneous removal of Mn(Ⅱ), nitrate and organic pollutants. Mn oxides (MnOx) also play an important role in the adsorption and degradation of some organic contaminants and they can change or create new oxidation pathways in the nitrogen cycle. Herein, this paper provides a comprehensive review of nitrogen and organic contaminants removal pathways through applying Mn(Ⅱ) or MnOx as forerunners. The main current knowledge, developments and applications, pollutants removal efficiency, as well as microbiology and biochemistry mechanisms are summarized. Also reviewed the effects of factors such as the carbon source, the environmental factors and operation conditions have on the process. Research gaps and application potential are further proposed and discussed. Overall, Mn-based biotechnology towards advanced wastewater treatment has a promising prospect, which can achieve simultaneous removal of nitrogen and organic contaminants, and minimize sludge production.

Reinforcement of Calcareous Sands by Stimulation of Native Microorganisms Induced Mineralization

Calcareous sand is a special soil formed by the accumulation of carbonate fragments. Its compressibility is caused by a high void ratio and breakable particles. Because of its high carbonate content and weak cementation, its load-bearing capacity is limited. In this study, the optimal stimulation solution was obtained with response surface methodology. Then, the effect of reinforcing calcareous sand was analysed with unconfined compressive strength (UCS) tests, calcium carbonate content tests, microscopy and microbial community analyses. The components and concentrations of the optimal stimulation solution were as follows: sodium acetate (38.00 mM), ammonium chloride (124.24 mM), yeast extract (0.46 g/L), urea (333 mM), and nickel chloride (0.01 mM), and the pH was 8.75. After the calcareous sand was treated with the optimal stimulation scheme, the urease activity was 6.1891 mM urea/min, the calcium carbonate production was 8.40%, and the UCS was 770 kPa, which constituted increases of 71.41%, 35.40%, and 83.33%, respectively, compared with the initial scheme. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses showed that calcium carbonate crystals were formed between the particles of the calcareous sand after the reaction, and the calcium carbonate crystals were mainly calcite. Urease-producing microorganisms became the dominant species in calcareous sand after treatment. This study showed that biostimulation-induced mineralization is feasible for reinforcing calcareous sand.

Fe(II) oxygenation inhibits bacterial Mn(II) oxidation by P. putida MnB1 in groundwater under O2-perturbed conditions

Bacterial Mn(II) oxidation plays a crucial role in Mn cycling and the associated biogeochemistry in natural waters and is of practical concern in the clean-up of excess Mn from drinking water. Fe(II) usually occurring together with Mn(II) in groundwater is oxidized prior to Mn(II) when perturbed by O₂, but the impact of Fe(II) oxygenation on the subsequent bacterial Mn(II) oxidation remains unknown. Here we demonstrated that Fe(II) oxygenation largely inhibited the Mn(II)-oxidizing ability of MnB1 belong to Pseudomonas putida which is ubiquitous in groundwater. The mechanisms of the inhibition varied under different Fe(II) concentrations. At high Fe(II) concentrations (≥ 1 mM), the inhibition of bacterial Mn(II) oxidation was mainly because of cell death caused by intracelluar reactive oxygen species. At low Fe(II) concentrations (≤ 0.05 mM), the inhibition of bacterial Mn(II) oxidation was attributed to Fe(III) oxyhydroxides generated from Fe(II) oxygenation. Fe(III) oxyhydroxides attached to cell surface and damaged the cell membrane, resulting in the influx of dissolved Fe into the cell. Transcriptomic analysis revealed that the intracellular Fe suppressed the transcription initiation process and the subsequent generation of multicopper oxidases which were responsible for Mn(II) oxidation. These findings implicate that the inhibition effect of Fe(II) oxygenation on bacterial Mn(II) oxidation should be considered in groundwater-surface water interaction zone and the biological treatment of Fe-Mn containing drinking water.

Microbial ecology of biofiltration used for producing safe drinking water

Abstract

Biofiltration is a water purification technology playing a pivotal role in producing safe drinking water. This technology attracts many interests worldwide due to its advantages, such as no addition of chemicals, a low energy input, and a high removal efficiency of organic compounds, undesirable taste and odours, and pathogens. The current review describes the microbial ecology of three biofiltration processes that are routinely used in drinking water treatment plants, i.e. (i) rapid sand filtration (RSF), (ii) granular activated carbon filtration (GACF), and (iii) slow sand filtration (SSF). We summarised and compared the characteristics, removal performance, and corresponding (newly revealed) mechanisms of the three biofiltration processes. Specifically, the microbial ecology of the different biofilter processes and the role of microbial communities in removing nutrients, organic compounds, and pathogens were reviewed. Finally, we highlight the limitations and challenges in the study of biofiltration in drinking water production, and propose future perspectives for obtaining a comprehensive understanding of the microbial ecology of biofiltration, which is needed to promote and optimise its further application.

Key points

• Biofilters are composed of complex microbiomes, primarily shaped by water quality.

• Conventional biofilters contribute to address safety challenges in drinking water.

• Studies may underestimate the active/functional role of microbiomes in biofilters.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-12013-x.

Antimony redox processes in the environment: A critical review of associated oxidants and reductants

The environmental behavior of antimony (Sb) has recently received greater attention due to the increasing global use of Sb in a range of industrial applications. Although present at trace levels in most natural systems, elevated Sb concentrations in aquatic and terrestrial environments may result from anthropogenic activities. The mobility and toxicity of Sb largely depend on its speciation, which is dependent to a large extent on its oxidation state. To a certain extent, our understanding of the environmental behavior of Sb has been informed by studies of the environmental behavior of arsenic (As), as Sb and As have somewhat similar chemical properties. However, recently it has become evident that the speciation of Sb and As, especially in the context of redox reactions, may be fundamentally different. Therefore, it is crucial to study the biogeochemical processes impacting Sb redox transformations to understand the behavior of Sb in natural and engineered environments. Currently, there is a growing body of literature involving the speciation, mobility, toxicity, and remediation of Sb, and several reviews on these general topics are available; however, a comprehensive review focused on Sb environmental redox chemistry is lacking. This paper provides a review of research conducted within the past two decades examining the redox chemistry of Sb in aquatic and terrestrial environments and identifies knowledge gaps that need to be addressed to develop a better understanding of Sb biogeochemistry for improved management of Sb in natural and engineered systems.

Application oriented bioaugmentation processes: Mechanism, performance improvement and scale-up

Bioaugmentation is an optimization method with great potential to improve the treatment effect by introducing specific strains into the biological treatment system. In this study, a comprehensive review of the mechanism of bioaugmentation from the aspect of microbial community structure, the optimization methods facilitating application as well as feasible approaches of scale-up application has been provided. The different contribution of indigenous and exogenous strains was critically analyzed, the relationship between microbial community variation and system performance was clarified. Operation regulation and immobilization technologies are effective methods to deal with the possible failure of bioaugmentation. The gradual expansion from lab-scale, pilot scale to full-scale, the transformation and upgrading of wastewater treatment plants through the combination of direct dosing and biofilm, and the application of side-stream reactors are feasible ways to realize the full-scale application. The future challenges and prospects in this field were also proposed.

Review on heterogeneous oxidation and adsorption for arsenic removal from drinking water

The long term exposure of arsenic via drinking water has resulted in wide occurrence of arsenisim globally, and the oxidation of the non-ionic arsenite (As(III)) to negatively-charged arsenate (As(V)) is of crucial importance for the promising removal of arsenic. The chemical oxidants of ozone, chlorine, chlorine dioxide, and potassium permanganate may achieve this goal; however, their application in developing countries is sometimes restricted by the complicate operation and high cost. This review paper focuses on the heterogeneous oxidation of As(III) by solid oxidants such as manganese oxide, and the adsorption of As(V) accordingly. Manganese oxide may be prepared by both chemical and biological methods to achieve good oxidation performance towards As(III). Additionally, manganese oxide may be combined with other metal oxides, e.g., iron oxide, to improve the adsorption capability towards As(V). Furthermore, manganese oxide may be coated onto porous materials of metal organic frameworks to develop novel adsorbents for arsenic removal. To achieve the application in engineering works, the adsorbents granulation may be achieved by drying and calcination, agglomeration, and the active components may also be in situ coated onto the porous materials to maintain the oxidation and adsorption activities as much as possible. The novel adsorbents with heterogeneous oxidation and adsorption capability may be carefully designed for the removal of arsenic in household purifiers, community-level decentralized small systems, and the large-scale drinking water treatment plants (DWTPs). This review provides insight into the fundamental studies on novel adsorbents, the development of innovative technologies, and the demonstration engineering works involved in the heterogeneous oxidation and adsorption, and may be practically valuable for the arsenic pollution control globally.

Human health risk assessment of groundwater nitrate at a two geomorphic units transition zone in northern China

To assess groundwater nitrate contamination and its human health risks, 489 unconfined groundwater samples were collected and analyzed from Zhangjiakou, northern China. The spatial distribution of principle hydrogeochemical results showed that the average concentrations of ions in descend order was HCO₃^-, SO₄^2-, Na⁺, Ca²⁺, Cl^-, NO₃^-, Mg²⁺ and K⁺, among which the NO₃^- concentrations were between 0.25 and 536.73 mg/L with an average of 29.72 mg/L. In total, 167 out of 489 samples (~ 34%) exceeded the recommended concentration of 20 mg/L in Quality Standard for Groundwater of China. The high NO₃^- concentration groundwater mainly located in the northern part and near the boundary of the two geomorphic units. As revealed by statistical analysis, the groundwater chemistry was more significantly affected by anthropogenic sources than by the geogenic sources. Moreover, human health risks of groundwater nitrate through oral and dermal exposure pathways were assessed by model, the results showed that about 60%, 50%, 32% and 26% of the area exceeded the acceptable level (total health index>1) for infants, children, adult males and females, respectively. The health risks for different groups of people varied significantly, ranked: infants> children> adult males>adult females, suggesting that younger people are more susceptible to nitrate contamination, while females are more resistant to nitrate contamination than males. To ensure the drinking water safety in Zhangjiakou and its downstream areas, proper management and treatment of groundwater will be necessary to avoid the health risks associated with nitrate contamination.

Simultaneous removal of nitrate, manganese, and tetracycline by Zoogloea sp. MFQ7: Adsorption mechanism of tetracycline by biological precipitation

A Mn(II) oxidizing-denitrifying and tetracycline (TC) removal bacterium Zoogloea sp. MFQ7 was isolated in this study. Nitrogen removal was 83.49% by nitrogen balance experiment. The maximum removal efficiencies of nitrate, Mn(II), and TC by strain MFQ7 within 96 h was 100.00, 74.56, and 63.59% at C/N of 2.0, pH of 7.0, Mn(II) of 20 mg L^-1, temperature of 30.0 °C, and TC of 0.2 mg L^-1. SEM illustrated that biogenic manganese oxides (BMO) was petal-like, XRD and XPS analyses confirmed that MnO₂ was the main component of BMO. Besides, the maximum adsorption capacity of BMO for TC was 52.21 mg g^-1. FTIR detected the changes in TC adsorption by BMO. Pseudo-second-order model (R² = 0.994) explained the adsorption kinetics of TC on BMO and Langmuir isotherm model (R² = 0.983) suggested that it was homogeneous adsorption, thermodynamics data (ΔG < 0, ΔH = 18.31 kJ mol^-1, ΔS = 72.8 J (mol*K)^-1) confirmed that adsorption was endothermic and spontaneous.

Anoxic storage to promote arsenic removal with groundwater-native iron

Storage containers are usually used to provide a constant water head in decentralized, community groundwater treatment systems for the removal of iron (Fe) and arsenic (As). However, the commonly practiced aeration prior to storage assists in rapid and complete Fe²⁺ oxidation, resulting in poor As removal, despite sufficient native-Fe²⁺ in the source water. In this study, it was found that application of anoxic storage enhanced As removal from groundwater, containing ≥300 µg/L of As(III) and 2.33 mg/L of Fe²⁺ in an As affected village of Rajshahi district in Bangladesh. Although the oxidation of Fe²⁺ and As(III) during oxic storage was considerably faster, the As/Fe removal ratio was higher during anoxic storage (61-80±5 µgAs/mgFe) compared to the oxic storage (45±5 µgAs/mgFe). This higher As removal efficacy in anoxic storage containers could not be attributed to the speciation of As, since As(V) concentrations were higher during oxic storage due to more favorable abiotic (As(III) oxidation by O₂ and Fenton-like intermediates) and biotic (As(III) oxidizing bacteria, e.g., Sideroxydans, Gallionella, Hydrogenophaga) conditions. The continuous, in-situ hydrous ferric oxide floc formation during flow-through operation, and the favorable lower pH aiding higher sorption capacities for the gradually formed As(V) likely contributed to the improved performance in the anoxic storage containers.

Efficient removal of nitrate, manganese, and tetracycline by a polyvinyl alcohol/sodium alginate with sponge cube immobilized bioreactor

The co-existence of nitrate, manganese (Mn), and antibiotics are of a wide concern. In this study, a denitrifying and manganese-oxidizing Zoogloea Q7 bacterium was immobilized using polyvinyl alcohol/sodium alginate with sponge cube (PVA/SA@sponge cube) in the reactor. The optimal operation parameters of the bioreactor were explored. Maximum nitrate, Mn(II), and tetracycline (TC) removal efficiencies of 93.00, 72.34, and 57.32% were achieved with HRT of 10 h, pH of 6.5, Mn(II) concentration of 20 mg L^-1, and TC of 1 mg L^-1, respectively. Fluorescence excitation-emission matrix (EEM) proved that the microorganism in the bioreactor was greatly active. Scanning electron microscope (SEM) images demonstrated that Zoogloea Q7 was commendably immobilized on the novel material. X-ray diffraction (XRD) analysis suggested that the bioprecipitate was mainly composed of MnO₂ and MnCO_3. Through high-throughput analysis, Zoogloea sp. Q7 was considered to be the dominant bacteria present in the bioreactor.

Characterization and mechanism of Mn(II)-based mixotrophic denitrifying bacterium (Cupriavidus sp. HY129) in remediation of nitrate (NO3--N) and manganese (Mn(II)) contaminated groundwater

The co-contamination of groundwater with nitrate (NO₃^--N) and manganese (Mn(II)) is a global issue that needs to be efficiently remediated. In this research, a novel denitrifying and manganese-oxidizing strain HY129 was isolated from the sediments sample of a drinking water and identified as Cupriavidus sp. HY129. The remediation ability of strain HY129 regarding the nitrate and Mn(II) pollution were investigated. The removal efficiency of nitrate and Mn(II) were 99.81% (0.229 mgL^-1 h^-1) and 87.24% (0.233 mgL^-1 h^-1) in bacterial culture after 72 h, respectively. Moreover, the addition of Mn(II) significantly enhanced the denitrification process, while excessive concentration of Mn(II) caused more NO₂^--N accumulation. The impacts of adsorption and oxidation activity on Mn(II) removal were investigated. Protein in extracellular polymeric substance (EPS) which produced in the Mn-oxidizing process was speculated to be the main cause of extracellular adsorption of Mn(II). Characterization of biogenic manganese oxides (BMO) confirmed the formation of high-valent manganese and the trapping experiment with sodium pyrophosphate (NaPP) demonstrated the existence of Mn(III)-intermediates. Furthermore, multicopper oxidase gene amplification provided evidence for the molecular biology of Mn(II) oxidation by strain HY129.

Impact of algal organic matter on the performance, cyanotoxin removal, and biofilms of biologically-active filtration systems

The occurrence of harmful algal blooms dominated by toxic cyanobacteria has induced continuous loadings of algal organic matter (AOM) and toxins in drinking water treatment plants. However, the impact of AOM on the active biofilms and microbial community structures of biologically-active filtration (BAF), which directly affects the contaminant removal, is not well understood. In this study, we systematically examined the effects of AOM on BAF performance and bacterial biofilm formation over 240 days, tracing the removal of specific AOM components, a cyanotoxin [microcystin-LR (MC-LR)], and microbial community responses. The component analysis (excitation and emission matrix analysis) results for AOM revealed that terrestrial humic-like substances showed the highest removal among all the identified components and were strongly correlated to MC-LR removal. In addition, reduced empty bed contact time and deactivation of biofilms significantly decreased BAF performances for both AOM and MC-LR. The active biofilm, bacterial community structure, and mlrA gene (involved in microcystin degradation) abundance demonstrated that bacterial biofilm composition responded to AOM and MC-LR, in which Rhodocyclaceae, Saprospiraceae, and Comamonadaceae were dominant. In addition, MC-LR biodegradation appeared to be more active at the top than at the bottom layer in BAF. Overall, this study provides deeper insights into the role of biofilms and filter operation on the fate of AOM and MC-LR in BAF.

Simultaneous removal of iron and manganese from acid mine drainage by acclimated bacteria

A bacterial consortium for efficient decontamination of high-concentration Fe-Mn acid mine drainage (AMD) was successfully isolated. The removal efficiencies of Fe and Mn were effective, reaching 99.8 % and 98.6 %, respectively. High-throughput sequencing of the 16S rRNA genes demonstrated that the microbial community had changed substantially during the treatment. The Fe-Mn oxidizing bacteria Flavobacterium, Brevundimonas, Stenotrophomonas and Thermomonas became dominant genera, suggesting that they might play vital roles in Fe and Mn removal. Moreover, the pH of culture increased obviously after incubation, which was benefit for depositing Fe and Mn from AMD. The specific surface area of the biogenic Fe-Mn oxides was 108-121 m²/g, and the surface contained reactive oxygen functional groups (-OH and -COOH), which also improved Fe and Mn removal efficiency. Thus, this study provides an alternative method to treat AMD containing high concentrations of Fe and Mn.

Effect of Cobalt, Cadmium and Manganese on Nitrogen Removal Capacity of Arthrobacter arilaitensis Y-10

The aim of this study was to investigate the possibility of a simultaneous nitrification–denitrification hypothermic bacterium for applying in Cd(II), Co(II), and Mn(II)-contaminated wastewater. The influence of Cd(II), Co(II), and Mn(II) on the inorganic nitrogen removal capacity of the hypothermia bacterium Arthrobacter arilaitensis Y-10 was determined. The experimental results demonstrated that low concentration of Cd(II) (2.5 mg/L) exhibited no significant impact on bioremediation of ammonium. The nitrate and nitrite removal activities of strain Y-10 were enhanced by 0.1 and 0.25 mg/L of Cd(II), but hindered by more than 0.25 and 0.5 mg/L of Cd(II), respectively. However, the cell growth and denitrification activity ceased immediately once Co(II) was supplemented. In terms of Mn(II), no conspicuous inhibitory impact on ammonium bioremediation was observed even if Mn(II) concentration reached as high as 30 mg/L. The bioremediation of nitrates and nitrites was significantly improved by 0.5 mg/L of Mn(II), and then dropped sharply along with the increase of Mn(II). The order of the degree of inhibitory influence of the three heavy metal ions on the nitrogen bioremediation ability of strain Y-10 was Co(II) > Cd(II) > Mn(II). All the results highlighted that the heterotrophic nitrification was less sensitive to the inhibitory effects of Cd(II), Co(II), and Mn(II) relative to aerobic denitrification.

Mineral Materials Coated with and Consisting of MnOx-Characteristics and Application of Filter Media for Groundwater Treatment: A Review

For groundwater treatment, the technologies involving oxidation on MnOx filter bed are beneficial, common, and effectively used. The presence of MnOx is the mutual feature of filter media, both MnOx-coated mineral materials like quartz sand and gravel, chalcedonite, diatomite, glauconite, zeolite, or anthracite along with consisting of MnOx manganese ores. This review is based on the analysis of research and review papers, commercial data sheets, and standards. The paper aimed to provide new suggestions and useful information for further investigation of MnOx filter media for groundwater treatment. The presented compilations are based on the characteristics of coatings, methods, and conditions of its obtaining and type of filter media. The relationship between the properties of MnOx amendments and the obtained purification effects as well as the commonly used commercial products, their features, and applications have been discussed. The paper concludes by mentioning about improving catalytic/adsorption properties of non-reactive siliceous media opposed to ion-exchange minerals and about possible significance of birnessite type manganese oxide for water treatment. Research needs related to the assessment of the use MnOx filter media to heavy metals removal from groundwater in field operations and to standardize methodology of testing MnOx filter media for water treatment were identified.

Metagenomics Unravels Differential Microbiome Composition and Metabolic Potential in Rapid Sand Filters Purifying Surface Water Versus Groundwater

Designed for retaining suspended particles, rapid sand filters (RSFs) are widely used in drinking water treatment. There is increasing evidence that microbial processes within RSFs contribute to the transformation and removal of organic carbon, nitrogen, and metal pollutants. Here, we linked microbial composition and functional profiles with the treatment performance of 12 different RSFs that significantly removed influent ammonium and manganese (Mn). Metagenomic analyses showed that chemoautotrophic or methanotrophic bacteria were prevalent in the groundwater filters, and chemoheterotrophic bacteria encoding more carbohydrate- and xenobiotic-metabolizing genes were more abundant in the surface water filters. Approximately 92% of ammonium was transformed into nitrate, with a critical contribution from comammox Nitrospira. The composition of comammox amoA differed between groundwater and surface water filters, with clade A dominating groundwater filters (78.0 ± 12.0%) and clade B dominating surface water filters (91.9 ± 8.9%). Further, we identified six bacterial genera encoding known Mn(II)-oxidizing genes in the RSFs, with Pseudomonas accounting for 71.1%. These Mn(II)-oxidizing bacteria might promote Mn(II) oxidation and thus increase the removal of influent Mn. Overall, our study gave a comprehensive investigation of microbiome in RSFs and highlighted the roles of comammox and Mn(II)-oxidizing bacteria in water purification.

Multiple organic substrates support Mn(II) removal with enrichment of Mn(II)-oxidizing bacteria

Three different organic substrates, K-medium, sterilized activated sludge (SAS), and methanol, were examined for utility as substrates for enriching manganese-oxidizing bacteria (MnOB) in an open bioreactor. The differences in Mn(II) oxidation performance between the substrates were investigated using three down-flow hanging sponge (DHS) reactors continuously treating artificial Mn(II)-containing water over 131 days. The results revealed that all three substrates were useful for enriching MnOB. Surprisingly, we observed only slight differences in Mn(II) removal between the substrates. The highest Mn(II) removal rate for the SAS-supplied reactor was 0.41 kg Mn⋅m^-3⋅d^-1, which was greater than that of K-medium, although the SAS performance was unstable. In contrast, the methanol-supplied reactor had more stable performance and the highest Mn(II) removal rate. We conclude that multiple genera of Comamonas, Pseudomonas, Mycobacterium, Nocardia and Hyphomicrobium play a role in Mn(II) oxidation and that their relative predominance was dependent on the substrate. Moreover, the initial inclusion of abiotic-MnO₂ in the reactors promoted early MnOB enrichment.

Single molecule sequencing reveals response of manganese-oxidizing microbiome to different biofilter media in drinking water systems

Rapid sand biofiltration (RSBF) is widely used for the removal of contaminants from drinking water treatment systems. Biofilm microbiomes in the biofilter media play essential roles in biotransformation of contaminants, but is not comprehensively understood. This study reports on Mn(II) oxidation and the core microbiomes in magnetite sand RSBF (MagS-RSBF) and manganese sand RSBF (MnS-RSBF). MnS-RSBF showed a relatively higher Mn(II) removal rate (40-91.2%) than MagS-RSBF during the start-up. MagS-RSBF and MnS-RSBF had similar Mn(II) removal rates (94.13% and 99.16%) over stable operation for 80 days. Mn(II) removal rates at different depths in the MnS-RSBF reactor significantly changed with operation time, and the filter in the upper layer of MnS-RSBF made the largest contribution to Mn(II) oxidation once operation had stabilized. PacBio single molecule sequencing of full-length 16S rRNA gene indicated that biofilter medium had a significant impact on the core microbiomes of the biofilms from the two biofilters. The magnetite sand biofilter facilitated the enrichment of Mn(II)-oxidizing biofilms. The dominant populations consisted of Pedomicrobium, Pseudomonas, and Hyphomicrobium in the RSBF, which have been affiliated with putative manganese-oxidizing bacteria (MnOB). The relative abundance of Pedomicrobium manganicum increased with operation time in both RSBF reactors. In addition, Nordella oligomobilis and Derxia gummosa were statistically correlated with Mn(II) oxidation. Species-species co-occurrence networks indicated that the microbiome of MnS-RSBF had more complex correlations than that of MagS-RSBF, implying that biofilter medium substantially shaped the microbial community in the RSBF. Hyphomicrobium and nitrite-oxidizing Nitrospira moscoviensis were positively correlated. The core microbiomes' composition of both RSBF reactors converged over operation time. A hybrid biofilter medium with magnetite sand and manganese sand may therefore be best in rapid sand filtration for Mn(II) oxidation.

Performance and microbial community of simultaneous removal of NO3--N, Cd2+ and Ca2+ in MBBR

A moving-bed biofilm reactor (MBBR) containing immobilized Acinetobacter sp.CN86 was operated to investigate the simultaneous denitrification, bio-mineralization and cadmium removal performance. Effects of hydraulic residence time (HRT) (4 h, 6 h and 8 h), pH (6.0, 7.0 and 8.0) and influent Cd²⁺ concentrations (10 mg/L, 30 mg/L and 50 mg/L) were assessed on the simultaneous removal of nitrate, Cd²⁺ and Ca²⁺. Results indicate that the highest pollutant removal efficiency (98.33% (1.866 mg/L·h) for NO₃^--N; 99.36% (1.242 mg/L·h) for Cd²⁺; 68.80% (15.480 mg/L·h) for Ca²⁺) was achieved under the conditions of a hydraulic residence time of 8 h, pH of 7.0 and initial Cd²⁺ concentration of 10 mg/L. Analyses of microbial distribution and community structures showed that Acinetobacter sp.CN86 was the main contributor (occupy 15.3% at the species level) to the effective removal of multiple pollutants in the MBBR. In addition, the main gas and precipitation components in the biofilm reactor were identified by gas chromatography, scanning electron microscope, and X-ray diffraction analyses.

Biological, biochemical and genotoxic effects of Sb in the midge Chironomus sancticaroli Strixino and Strixino, 1981 (Diptera: Chironomidae)

In aquatic systems, antimony (Sb) is found in the water column and associated with sediment particles being bioavailable to organisms. Consequently, toxic effects have been detected in benthic invertebrates, but the toxicity after Sb exposure in Chironomidae have not been investigated. Were investigated DNA damage, activities of cholinesterase (ChE), alpha and beta esterase (EST-α, EST-β), glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD) and lipid peroxidation after acute (48 h) and subchronic exposure (8 d). We also investigated the effects of subchronic (8 d) on development of larvae and chronic (25 d) Sb exposure on emergence and size of adults of Chironomus sancticaroli. Were analyze Sb nominal concentrations ranged from 0.5 to 800 μg.L^-1. Genotoxic effects occurred at higher concentrations upon acute (50, 800 μg.L^-1) and subchronic exposure (50 μg.L^-1). Acute exposure increased ChE, EST-α, EST-β, and GST activities. Subchronic Sb exposure increased EST-α activity at 0.2 μg.L^-1 and GST activity at 5 μg.L^-1. CAT activity increased at all concentrations while increasing lipid peroxidation levels were observed (1 μg.L^-1, 5 μg.L^-1 and 50 μg.L^-1), indicating oxidative stress. All concentrations of Sb delayed larval development and decreased the number of emerging adults. At high concentrations (50, 500, 800 μg.L^-1), the emerging adults were smaller. In conclusion, these varying genotoxic, biochemical and biological effects of Sb make a notable impact on the reproduction and population dynamics of C. sancticaroli.

Mesoporous zirconia nanostructures (MZN) for adsorption of As(III) and As(V) from aqueous solutions

Mesoporous zirconia nanostructures (MZN) were synthesized by hydrothermal method to efficiently remove highly mobile and toxic arsenite (As(III)) and arsenate (As(V)) from aqueous solutions. The as-synthesized MZN were characterized by Brunauer-Emmett-Teller (BET), X-Ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM), and Energy-dispersive X-ray spectroscopy (EDX) techniques. The batch adsorption experimental results showed that the As(III) and As(V) removal capacities of the MZN were 105.03 and 110.29 mg/g, respectively, under neutral pH conditions, which were better than many recently reported adsorbents. The adsorption behavior of As(III) and As(V) on the MZN could be well described by pseudo-second-order and Langmuir isotherms models. Moreover, As(III) and As(V) adsorption on the MZN was spontaneous and endothermic. Some of the common co-existing ions had slightly affected the arsenic removal proficiency of MZN. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the adsorption mechanism of As(III) and As(V) on the as-synthesized MZN. The as-synthesized MZN demonstrated quite fast and good treatment of simulated real arsenic (As(III,V)) contaminated water. This study suggested that the as-synthesized MZN are potential candidate for practical applications of As(III) and As(V) removal from the aqueous solutions.

Biostimulation of carbonate precipitation process in soil for copper immobilization

The urease-based microbially induced carbonate precipitation (MICP) is known as effective remediation strategy in soil metals remediation; however, all related studies confined to bioaugmentation. In the present study, biostimulation process was adopted for the first time in accelerating MICP in copper (Cu) immobilization in soil. The abundance, composition, and diversity of the bacterial community after biostimulation were assessed with MiSeq Illumina sequencing analysis that confirmed number and types of ureolytic and calcifying bacteria grown significantly leading to MICP process, compared to untreated soil. The results demonstrated that biostimulation induced calcite precipitation in soil that immobilized Cu mainly in carbonated fraction of soil, while soluble-exchangeable fraction decreased from 45.54 mg kg^-1 to 1.55 mg kg^-1 Cu in soil. Scanning electron microscopy (SEM) cum energy-dispersive X-ray spectroscopy (EDX) evaluated structure and elemental composition in Cu immobilization after biostimulation. Fourier Transform-Infra Red (FTIR) spectroscopy depicted functional chemical groups involved in copper immobilization, while X-Ray Diffraction (XRD) identified main crystalline phases or biominerals formed during biostimulation in order to carryout Cu remediation from soil.

Natural Attenuation of Mn(II) in Metal Refinery Wastewater: Microbial Community Structure Analysis and Isolation of a New Mn(II)-Oxidizing Bacterium Pseudomonas sp. SK3

Natural attenuation of Mn(II) was observed inside the metal refinery wastewater pipeline, accompanying dark brown-colored mineralization (mostly MnIVO2 with some MnIII2O3 and Fe2O3) on the inner pipe surface. The Mn-deposit hosted the bacterial community comprised of Hyphomicrobium sp. (22.1%), Magnetospirillum sp. (3.2%), Geobacter sp. (0.3%), Bacillus sp. (0.18%), Pseudomonas sp. (0.03%), and non-metal-metabolizing bacteria (74.2%). Culture enrichment of the Mn-deposit led to the isolation of a new heterotrophic Mn(II)-oxidizer Pseudomonas sp. SK3, with its closest relative Ps. resinovorans (with 98.4% 16S rRNA gene sequence identity), which was previously unknown as an Mn(II)-oxidizer. Oxidation of up to 100 mg/L Mn(II) was readily initiated and completed by isolate SK3, even in the presence of high contents of MgSO4 (a typical solute in metal refinery wastewaters). Additional Cu(II) facilitated Mn(II) oxidation by isolate SK3 (implying the involvement of multicopper oxidase enzyme), allowing a 2-fold greater Mn removal rate, compared to the well-studied Mn(II)-oxidizer Ps. putida MnB1. Poorly crystalline biogenic birnessite was formed by isolate SK3 via one-electron transfer oxidation, gradually raising the Mn AOS (average oxidation state) to 3.80 in 72 h. Together with its efficient in vitro Mn(II) oxidation behavior, a high Mn AOS level of 3.75 was observed with the pipeline Mn-deposit sample collected in situ. The overall results, including the microbial community structure analysis of the pipeline sample, suggest that the natural Mn(II) attenuation phenomenon was characterized by robust in situ activity of Mn(II) oxidizers (including strain SK3) for continuous generation of Mn(IV). This likely synergistically facilitated chemical Mn(II)/Mn(IV) synproportionation for effective Mn removal in the complex ecosystem established in this artificial pipeline structure. The potential utility of isolate SK3 is illustrated for further industrial application in metal refinery wastewater treatment processes.

Environmental Bacteria Involved in Manganese(II) Oxidation and Removal From Groundwater

The presence of iron (Fe) and manganese (Mn) in groundwater is an important concern in populations that use it as source of drinking water. The ingestion of high concentrations of these metals may affect human health. In addition, these metals cause aesthetic and organoleptic problems that affect water quality and also induce corrosion in distribution networks, generating operational and system maintenance problems. Biological sand filter systems are widely used to remove Fe and Mn from groundwater since they are a cost-effective technology and minimize the use of chemical oxidants. In this work, the bacterial communities of two biological water treatment plants from Argentina, exposed to long term presence of Mn(II) and with a high Mn(II) removal efficiency, were characterized using 16S rRNA gene Illumina sequencing. Several selective media were used to culture Mn-oxidizing bacteria (MOB) and a large number of known MOB and several isolates that have never been reported before as MOB were cultivated. These bacteria were characterized to select those with the highest Mn(II) oxidation and biofilm formation capacities and also those that can oxidize Mn(II) at different environmental growth conditions. In addition, studies were performed to determine if the selected MOB were able to oxidize Mn(II) present in groundwater while immobilized on sand. This work allowed the isolation of several bacterial strains adequate to develop an inoculum applicable to improve Mn(II) removal efficiency of sand filter water treatment plants.

Fe(ii) and Mn(ii) removal by Ca(ii)–manganite (γ-MnOOH)-modified red mud granules in water

In this study, a material (DLRMG) was synthesized by modifying Ca²⁺ and manganite (γ-MnOOH) on red mud granules (RMG), which were the main raw materials derived from industrial alumina. Moreover, a series of experiments were conducted on the adsorption of Fe²⁺ and Mn²⁺ in underground water. The prepared samples were analyzed by X-ray diffraction (XRD), thermogravimetric analysis-differential thermal analysis (TG-DTA), zeta potential analysis, BET and scanning electron microscopy (SEM); the concentration of the effluent was found to be of acceptable standard after the treatment. DLRMG continued to treat fluoride wastewater even after the saturated adsorption of Fe²⁺ and Mn²⁺, and the results clearly showed that the treatment was effective. Overall, the problems of red mud stockpile and pollution in China would be effectively controlled by DLRMG.

The use of the waste of aluminum industry to prepare effective polluted materials for the treatment of underground water.

Removal of micropollutants and cyanobacteria from drinking water using KMnO4 pre-oxidation coupled with bioaugmentation

Increasing micropollutant and cyanobacterial contamination of drinking water threatens human health worldwide. However, these contaminates are not efficiently removed by common drinking water treatment processes, and thus additional treatments are frequently required. Recent investigations have demonstrated that KMnO₄ pre-oxidation can efficiently remove some micropollutants and cyanobacteria but the release of cyanobacterial toxins and Mn²⁺ limit its use. To overcome these problems, we proposed a KMnO₄ pre-oxidation coupled with bioaugmentation (e.g., sand filtration) method to treat micropollutant- and cyanobacteria-laden water. We used 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP-4, a common micropollutant in drinking water sources) and Microcystis aeruginosa (a widely distributed cyanobacterial species) as model pollutants to verify the feasibility of the proposed method. Results revealed that KMnO₄ pre-oxidation efficiently removed existing natural organic matter and Microcystis aeruginosa but failed to remove BP-4 and released Mn²⁺ and microcystin-LR (MC-LR) during treatment. Following the addition of a manganese-oxidizing bacterial strain (Pseudomonas sp. QJX-1) to the KMnO₄-treated solution, we found that the bacteria could transform Mn²⁺ to Mn(III&IV) oxides, with the formed Mn oxides then able to remove BP-4 and MC-LR. Overall, the proposed method exhibited advantages in the removal of natural organic matter (i.e., decreasing disinfection byproduct formation), micropollutants, and cyanobacteria as well as preventing the release of Mn²⁺, and thus may be considered a good alternative for treating polluted drinking water.

Antimony contamination, consequences and removal techniques: A review

A significant amount of antimony (Sb) enters into the environment every year because of the wide use of Sb compounds in industry and agriculture. The exposure to Sb, either direct consumption of Sb or indirectly, may be fatal to the human health because both antimony and antimonide are toxic. Firstly, the introduction of Sb chemistry, distribution and health threats are presented in this review, which is essential to the removal techniques. Then, we provide the recent and common techniques to remove Sb, including adsorption, coagulation/flocculation, membrane separation, electrochemical methods, ion exchange and extraction. Removal techniques concentrate on the advantages, drawbacks, economical efficiency and the recent achievements of each technique. We also take an overall consideration of experimental conditions, comparison criteria, and economic aspects.

A Genomic Outlook on Bioremediation: The Case of Arsenic Removal

Microorganisms play a major role in biogeochemical cycles. As such they are attractive candidates for developing new or improving existing biotechnological applications, in order to deal with the accumulation and pollution of organic and inorganic compounds. Their ability to participate in bioremediation processes mainly depends on their capacity to metabolize toxic elements and catalyze reactions resulting in, for example, precipitation, biotransformation, dissolution, or sequestration. The contribution of genomics may be of prime importance to a thorough understanding of these metabolisms and the interactions of microorganisms with pollutants at the level of both single species and microbial communities. Such approaches should pave the way for the utilization of microorganisms to design new, efficient and environmentally sound remediation strategies, as exemplified by the case of arsenic contamination, which has been declared as a major risk for human health in various parts of the world.

The first Taxus rhizosphere microbiome revealed by shotgun metagenomic sequencing

In the present study, the shotgun high throughput metagenomic sequencing was implemented to globally capture the features of Taxus rhizosphere microbiome. Total reads could be assigned to 6925 species belonging to 113 bacteria phyla and 301 species of nine fungi phyla. For archaea and virus, 263 and 134 species were for the first time identified, respectively. More than 720,000 Unigenes were identified by clean reads assembly. The top five assigned phyla were Actinobacteria (363,941 Unigenes), Proteobacteria (182,053), Acidobacteria (44,527), Ascomycota (fungi; 18,267), and Chloroflexi (15,539). KEGG analysis predicted numerous functional genes; 7101 Unigenes belong to "Xenobiotics biodegradation and metabolism." A total of 12,040 Unigenes involved in defense mechanisms (e.g., xenobiotic metabolism) were annotated by eggNOG. Talaromyces addition could influence not only the diversity and structure of microbial communities of Taxus rhizosphere, but also the relative abundance of functional genes, including metabolic genes, antibiotic resistant genes, and genes involved in pathogen-host interaction, bacterial virulence, and bacterial secretion system. The structure and function of rhizosphere microbiome could be sensitive to non-native microbe addition, which could impact on the pollutant degradation. This study, complementary to the amplicon sequencing, more objectively reflects the native microbiome of Taxus rhizosphere and its response to environmental pressure, and lays a foundation for potential combination of phytoremediation and bioaugmentation.

Benzophenone-4 Promotes the Growth of a Pseudomonas sp. and Biogenic Oxidation of Mn(II)

Interactions between microbes and micropollutants (MPs) play a crucial role in water purification or treatment. Current studies have generally focused on the direct degradation or cometabolism of MPs. Considering the increasing interest in and importance of the roles of MPs in microbial metabolism, we adopted an Mn(II)-oxidizing Pseudomonas sp. QJX-1 using tyrosine (Tyr) as the sole carbon and nitrogen source to investigate the effects of seven MPs on its growth and function. Six MPs exhibited an inhibition effect on bacterial growth and Mn(II) oxidation. Only benzophenone-4 (BP-4) promoted the growth of QJX-1 and biogenic oxidation Mn(II), but its concentration was not directly coupled to growth, which was unexpected. RNA-seq data suggested that the addition of BP-4 did not significantly change the basic metabolic function of QJX-1, but stimulated the upregulation of the pyruvate and gluconeogenesis metabolic pathways of Tyr for QJX-1 growth. Furthermore, protein identification and extracellular superoxide detection indicated that Mn(II) oxidation was largely driven by the formation of superoxide in response to Tyr starvation; the acceleration of superoxide production, due to BP-4 accelerating Tyr consumption, was responsible for the promotion effect of BP-4 on QJX-1 Mn(II) oxidation. Our findings highlight the dual effects that MPs can have on the growth and function of a single strain in aquatic ecosystem, i.e., the coexistence of inhibition and promotion.

Simultaneous Oxidation and Sequestration of As(III) from Water by Using Redox Polymer-Based Fe(III) Oxide Nanocomposite

Water decontamination from As(III) is an urgent but still challenging task. Herein, we fabricated a bifunctional nanocomposite HFO@PS-Cl for highly efficient removal of As(III), with active chlorine covalently binding spherical polystyrene host for in situ oxidation of As(III) to As(V), and Fe(III) hydroxide (HFO) nanoparticles (NPs) embedded inside for specific As(V) removal. HFO@PS-Cl could work effectively in a wide pH range (5-9), and other substances like sulfate, chloride, bicarbonate, silicate, and humic acid exert insignificant effect on As(III) removal. As(III) sequestration is realized via two pathways, that is, oxidation to As(V) by the active chlorine followed by specific As(V) adsorption onto HFO NPs, and As(III) adsorption onto HFO NPs followed by oxidation to As(V). The exhausted HFO@PS-Cl could be refreshed for cyclic runs with insignificant capacity loss by the combined regeneration strategy, that is, alkaline solution to rinse the adsorbed As(V) and NaClO solution to renew the host oxidation capability. In addition, fixed-bed experiments demonstrated that the HFO@PS-Cl column could generate >1760 bed volume (BV) effluent from a synthetic As(III)-containing groundwater to meet the drinking water standard (<10 μg As/L), whereas other two HFO nanocomposites, HFO@PS-N and HFO@D201 could only generate 450 and 600 BV effluents under otherwise identical conditions.