Evaluating the stability and performance of a novel core-shell ZVI@C-montmorillonite particle for anaerobic treatment of chloramphenicol wastewater

Assessing the long-term impact of incorporating GAC and Fe&G mediators for enhancing phenol containing simulated wastewater treatment in UASB reactor

Phenol containing wastewater (PCW) is highly toxic and difficult to be treated by traditional methods. This study utilized granular activated carbon (GAC) and Fe (Sponge iron) &GAC (Fe&G) in a laboratory-scale UASB reactor to mitigate the toxicity of phenol containing simulated wastewater (PCSW) and enhance treatment performance. Compared with GAC, Fe&G mediators achieves approximately 7 % and 24 % higher removal rates for COD and phenolic compounds, respectively. The methane accumulation in Fe&G group was about 10 % higher than that in GAC group and 22 % higher than that in blank group. Microbial analysis showed that compared with GAC, Fe&G mediators could enrich Petronas and Methanothrix to intensify Direct Interspecies Electron Transfer (DIET) to augment PCSW treatment and boost methane production. PICRUSt analysis showed that these mediators enriched key genes such as TCA cycle and CO2 methanogenesis pathway to improve microbial resistance to PCSW toxicity and enhance microbial metabolism. This study provides a new method for anaerobic treatment of highly polluted industrial wastewater.

Synchronous nitrogen and sulfur removal in sulfur-coated iron carbon micro-electrolytic fillers: Exploring the synergy between sulfur autotrophic denitrification and iron-carbon micro-electrolysis

Sulfur autotrophic denitrification (SAD) is a promising technology for nitrogen removal, particularly suitable for low carbon-to-nitrogen wastewater without additional carbon sources. However, SAD inevitably generates significant amounts of SO42-. To address this issue, combining SAD with iron-carbon micro-electrolysis technology, which can reduce sulfate, provides electron donors for autotrophic denitrification and facilitates sulfur cycling. Nonetheless, extensive iron precipitation can cause clogging and exert toxic effects on microorganisms. Herein, a sulfur-coated iron carbon micro-electrolytic filler (Fe-C@S) was established to achieve higher removal efficiency of NO3--N (97 %) and SO42- (99 %), less NO2--N was produced (<6 mg·L-1), and the role of sulfur shell in Fe-C@S was systematically evaluated. Furthermore, when comparing the Fe-C@S filler with traditional sulfur fillers (TS) and mixed systems combining TS with iron-carbon fillers (TS-ICME), it becomes evident that the Fe-C@S exhibits dual capabilities in nitrogen removal and sulfur recycling. This effectively addresses the issues of excessive SO42- concentration in effluents and the tendency of iron-carbon fillers to harden. Moreover, the Fe-C@S demonstrates nitrogen and sulfur removal performance in continuous landfill leachate experiments. Additionally, the dominant bacteria within the Fe-C@S comprise more electrophilic denitrifying bacteria (18.2 %), its stable and efficient performance in nitrogen and sulfur removal even under low current conditions.

Superior selectivity for efficiently reductive degradation of hydrophobic organic pollutants in strongly competitive systems

Highly toxic halo-/nitro-substituted organics, often in low concentrations and with high hydrophobicity, make it difficult to obtain electrons for reduction when strongly electron-competing substances (e.g., O2, H+/H2O, NO3-) coexist. To address this barrier, we devised a new strategy to modify microscale zero-valent aluminum (mZVAl) with graphene (GE) by one-pot ball-milling for GE@mZVAl, which exhibits 99 % selective removal of halo-/nitro-substituted organic pollutants (e.g., carbon tetrachloride (CT), trichloroethylene (TCE), p-nitrophenol (PNP) and p-nitrochlorobenzene (p-NCB)) in the presence of multiple competing inorganics (O2, H+/H2O, Cr(VI), NO3- and BrO3-) and interfering ions (Cl-, CO32-, SO42- and PO43-). Notably, due to the fact that the side-reaction of H2 evolution and second-passivation are significantly suppressed, the electron utilization efficiency for organics degradation reaches an impressive 96 %, even under harsh pH conditions (3-11). GE@mZVAl contains an Al-C interface with a high concentration of C-O, which can form active sites for organics and perform selective electron transfer. Meanwhile, the organophilic catalyst GE also hinders the exposure of AlOH+/Al0 sites to shield the competing and interfering of inorganic substances. As a highly selective reduction system, this work may yield innovative insights for the selective removal of hydrophobic refractory pollutants in complex water matrices.

Electromagnetic field coupled vertical flow constructed wetlands for rural sewage treatment: Performance, microbial community characteristics and metabolic pathways

Rural sewage management has been a long and difficult task. To overcome this problem, there is an urgent need for efficient, low-maintenance, low-consumption treatment technologies. In this study, an electromagnetic field coupled vertical flow constructed wetland (EMC-VFCW) and a vertical flow constructed wetland (VFCW) were constructed, and the removal performance, microbial changes, and metabolic pathways of both were investigated. The results demonstrated that the EMC-VFCW system achieved removal rates of 88.68% for COD, 92.89% for TP, 83.39% for NH4+-N, and 94.60% for NO3--N. SEM analysis revealed that the lysis of the filler surface in the EMC-VFCW system was rougher and had an increased number of active sites, which provided conditions for microbial attachment. High-throughput sequencing revealed that the EMC-VFCW system was enriched with a greater abundance of microorganisms, including Proteobacteria, Betaproteobacteria, and Acinetobacter, indicating that the presence of the electromagnetic field increased the amount of bacteria associated with phosphate removal and denitrogenation. A KEGG analysis suggested that during decontamination, the electromagnetic field might have released signal molecules that promoted energy metabolism, stimulated membrane transport, and accelerated nitrogen metabolism in the EMC-VFCW system. Additionally, the presence of the electromagnetic field altered nitrogen metabolism pathways and increased the relative abundance of denitrification-related genes (nirB, nirS, nirK). Moreover, the electromagnetic field improved the relationships among microorganisms, nitrogen metabolism functional genes, and pollutant removal in the EMC-VFCW system. Therefore, this study offers valuable insights into the performance and mechanisms of rural sewage disposal.

Enhancement of anaerobic treatment of antibiotic pharmaceutical wastewater through the development of iron-based and carbon-based materials: A critical review

The extensive use of antibiotics has created an urgent need to address antibiotic wastewater treatment, posing significant challenges for environmental protection and public health. Recent advances in the efficacy and mechanisms of conductive materials (CMs) for enhancing the anaerobic biological treatment of antibiotic pharmaceutical wastewater are reviewed. For the first time, the focus is on the various application forms of iron-based and carbon-based CMs in strengthening the anaerobic methanogenic system. This includes the use of single CMs such as zero-valent iron (ZVI), magnetite, biochar (BC), activated carbon (AC), and graphene (GP), as well as iron-based and carbon-based composite CMs with diverse structures. These structures include mixed, surface-loaded, and core-shell combinations, reflecting the development of CMs. Iron-based and carbon-based CMs promote the rapid removal of antibiotics through adsorption and enhanced biodegradation. They also mitigate the inhibitory effects of toxic pollutants on microbial activity and reduce the expression of antibiotic resistance genes (ARGs). Additionally, as effective electron carriers, these CMs enrich microorganisms with direct interspecies electron transfer (DIET) functions, accelerate interspecies electron transfer, and facilitate the conversion of organic matter into methane. Finally, this review proposes the use of advanced molecular detection technologies to clarify microbial ecology and metabolic mechanisms, along with microscopic characterization techniques for the modification of CMs. These methods can provide more direct evidence to analyze the mechanisms underlying the cooperative anaerobic treatment of refractory organic wastewater by CMs and microorganisms.

Magnetite encapsulated in carbon shell particles (Fe3O4@C) to boost anaerobic methanogenesis of chloramphenicol wastewater

Magnetite (Fe3O4) is extensively applied to enhance efficacy of anaerobic biological treatment systems designed for refractory wastewater. However, the interaction between magnetite, organic pollutants and microorganisms in digestion solution is constrained by magnetic attraction. To overcome this limitation and prevent magnetite aggregation, the core-shell composite materials with carbon outer layer enveloping magnetite core particles (Fe3O4@C) were developed. The impact of Fe3O4@C with varying Fe3O4 mass ratios on the anaerobic methanogenesis capability in the treatment of chloramphenicol (CAP) wastewater was investigated. Experimental results demonstrated that Fe3O4@C not only enhanced chemical oxygen demand (COD) removal efficiency and biogas production by 2.42-13.18% and by 7.53%-23.25%, respectively, but also reduced the inhibition of microbial activity caused by toxic substances and the secretion of extracellular polymeric substances (EPS) by microorganisms responding to adverse environments. The reinforcing capability of Fe3O4@C increased with the rise in Fe3O4 content. Furthermore, High-throughput pyrosequencing illustrated that Fe3O4@C enhanced the relative abundance of Methanobacterium, a hydrogen-utilizing methanogen capable of participating in direct interspecies electron transfer (DIET), by 5%. Metagenomic analysis indicated that Fe3O4@C improved the decomposition of complex organics into simpler compounds by elevating functional genes encoding key enzymes associated with organic matter metabolism, acetogenesis, and hydrogenophilic methanogenesis pathways. These findings suggest that Fe3O4@C have the potential to strengthen both the hydrogenophilic methanogenesis and DIET processes. This insight offers a novel perspective on the anaerobic bioaugmentation of high-concentration refractory organic wastewater.

Refractory degradable dissolved organic matter (R-DOM) driving nitrogen removal by the electric field coupled iron‑carbon biofilter (E-ICBF): Performance and microbial mechanisms

Researches on the advanced nitrogen (N) removal of municipal tailwater always overlooked the value of refractory degradable dissolved organic matter (R-DOM). In this study, a novel electric field coupled iron‑carbon biofilter (E-ICBF) was utilized to explore the performance and microbial changes with polyethylene glycol (PEG) as the representative R-DOM. Results demonstrated that the removal efficiencies of E-ICBF for nitrate nitrogen (NO3--N), ammonia nitrogen (NH4+-N), and total nitrogen (TN) improved by 28.76 %, 12.96 %, and 28.45 %, compared to quartz sand biofilter (SBF). Moreover, removal efficiencies of NO3--N and TN in E-ICBF with R-DOM went up by 12.11 % and 14.02 % compared to methanol. Additionally, both PEG and the electric field reduced the microbial richness and diversity. However, PEG promoted the increase of denitrifying bacteria abundance including unclassified_f_Comamonadaceae, Thauera, and unclassified_f_Gallionellaceae. The electric field improved the abundances of genes related to N removal (hao, nasC, nasA, nifH, nifD, nifK) and PEG further enhanced the effect. The abundances of key enzymes [EC:1.7.5.1], [EC:1.7.2.1], [EC:1.7.2.4], and [EC:1.7.2.5] decreased due to the addition of PEG and the electric field mitigated the negative influence. Additionally, the electric field changed relationships between microorganisms and pollutant removal, and improved interspecific relationships between denitrifying bacterial genera and other genera in E-ICBF.

Effects of Fe/Fe-Mn oxides loaded biochar on anaerobic degradation of typical phenolic compounds in coal gasification wastewater: Performance and mechanism

In this study, two kinds of magnetic biochar (BC) were synthesized by loading Fe (FeBC) and Fe-Mn oxides (FMBC) and their effects on anaerobic phenolics degradation were investigated. Compared with BC/FMBC, FeBC addition achieved the superior phenolics biodegradation even for 3,5-xylenol. Compared with control, FeBC addition enhanced CH4 production by 100.1 % with the lag time shortened from 9.5 days to 6.6 days while it increased to 11.2 days with FMBC addition. FeBC addition activated adsorption-biodegradation and Fe (III) reduction with the improved electron transfer activity, adenosine triphosphate and cytochrome C concentrations. Abundant phenol degrading bacteria, electroactive bacteria, syntrophic partners could be enriched by FeBC addition, contributing to the enhanced benzoyl-CoA and methanogenesis pathways. However, this enhancement was inhibited by FMBC addition owing to the accumulation of reactive oxygen species. This study provided novel insights into the application of magnetic BC to enhanced anaerobic treatment of phenolic wastewater.