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Poor anode performance is one of the main bottlenecks in the development of microbial fuel cells (MFCs) for practical applications. Multilayered Ti 3 C 2 MXene (m -MXene) is an alternative anode modification material because of its high specific surface area and electrical conductivity. However, the multilayered structure, negatively charged surface, and electropositivity of m -MXene could limit its modification effects. In this work, we used a solution-phase flocculation method (ammonium ion method) to restack and aggregate MXene nanosheets as an anode modification material (n-MXene). The n-MXene-modified anode had a higher specific surface area, surface hydrophilicity and surface electropositivity than the m -MXene-modified anode. The n-MXene-modified anode obtained a maximum current density of 2.1 A m−2, which was 31.2% and 61.5% higher than that of the m -MXene-modified anode (1.6 A m−2) and bare carbon fiber cloth anode (1.3 A m−2). This improved anode performance was attributed to both the decrease in the charge transfer resistance and diffusion resistance, which were related to the increased quantity of biomass and microbial nanowire (or pili)-shaped filaments on the electrode surface. This work provides a simple and cost-effective approach to prepare MXene nanosheets for the modification of MFC anodes. [Display omitted] • An ammonium ion method was used to restack and aggregate of multi-layered MXene. • Modifying ammonium treated MXene increased hydrophilic and surface charge of anode. • Anode performance increased 61.5% with the modification of ammonium treated MXene. • Modifying ammonium treated MXene increased biomass and conductive matrix of biofilm. [ABSTRACT FROM AUTHOR]

Food waste fermentation liquid components, mainly lactate and volatile fatty acids (VFAs), can be used as alternative carbon sources to improve the nitrogen removal efficiency. To investigate the effects of carbon sources generated from food waste (FW) fermentation liquid on nitrogen removal for the treatment of high ammonium and high salt wastewater (HAHS), the lactate, acetate, propionate, butyrate, and their mixtures were added in activated sludge systems operating over 130-days. Lactate and butyrate inhibited nitrifiers by enriching polyphosphate accumulating organisms (PAOs), thus deteriorated nitrogen removal after a long-term period. When fed with acetate or propionate, the dominant glycogen accumulating organisms (GAOs) groups simultaneously realized nitrification and denitrification. The mixed carbon source enhanced microbial community robustness and the transformation of Polyhydroxyalkanoate (PHA), advancing nitrogen removal efficiency. Mixed carbon source of acetate-propionate was preferred, in which the coexisting groups of GAOs and PAOs enhanced the denitrification rate of denitrifiers and kept balancing with nitrifiers, where the highest denitrification rate (DNR) was 1.05 mg N/(h·g VSS) and the average TN removal efficiency was above 98% under the maximum nitrogen load of 0.48 kg N/(kg VSS·d). In addition, the primary pathways of nitrogen removal were heterotrophic nitrification and denitrification, since the autotrophic nitrifiers were inhibited by the free ammonium and salinity. This study illustrated the differences of nitrogen removal performance and mechanisms with fermentation liquid components as carbon sources processing of HAHS wastewater. [Display omitted] • Affinity of PAOs/GAOs with different carbon sources caused significant N removal. • Primary pathways of N removal were heterotrophic nitrification and denitrification. • Nitrifiers was inhibited by the enriched PAOs when feeding lactate and butyrate. • Mixed carbon source enhanced microbial community robustness and enhanced N removal. [ABSTRACT FROM AUTHOR]

Phytoremediation is an effective, green and economical technique. Different types of phytoremediation methods can be used for the reduction of heavy metal contaminations, such as phytoextraction, phytovolatilization, phytostabilization and phytofiltration. The biomass of plants and the bioavailability of heavy metals in soil are the key factors affecting the efficiency of phytoremediation. It's worth noting that the low remediation efficiency and the lack of effective disposal methods for contaminated biomass have limited its development and application. At present, biological, physical, chemical, agronomic and genetic approaches have been used to enhance phytoremediation. Disposal methods of contaminated biomass usually include pyrolysis, incineration, composting and compaction. They are effective, but are costly and have security problems. Improper disposal of contaminated biomass can lead to leaching of heavy metals. The leaching possibility of different forms of heavy metal in plants is different. Hence, it has great significance to explore the different forms of heavy metals in plants which can help to explore appropriate disposal methods. According to the challenges of phytoremediation, we put forward some views and recommendations for the sustainable and rapid development of phytoremediation technology. [Display omitted] • Low remediation efficiency and improper disposal of biomass limited phytoremediation. • Microbial and chemical additives are the main methods to enhance phytoremediation. • Exploring the different forms of metals in plants can help to dispose biomass properly. [ABSTRACT FROM AUTHOR]

Carcass decomposition could be considered as a common phenomenon in nature. However, during degradation processes, animal carcasses produce many toxic and harmful metabolites, posing potential ecological risks to water safety, thereby threatening human health. However, the metabolites produced by decomposition of animal corpses are not well understood. In this study, building on our previous baseline study of microbial community between the experimental groups (with animal carcasses) and control groups (without carcasses), the samples at the ultimate stage (19th day) of carcass decomposition were chosen to investigate the metabolic profiles and uncover the relationships between water quality, microbes and noxious metabolites in two types of water (Yellow River water and tap water) using fish as animal model by widely targeted metabolomics. Our results showed amino acid metabolomics, indole and its derivatives, and pyridine and pyridine derivatives mainly occurred in the corpse groups, suggesting that these metabolites are markers of carcass decomposition. And some noxious metabolites (e.g., polyamine, amines, and benzene and substituted derivatives) highly associated with carcass decomposition, which revealed new insights into how to investigate the hazard materials in water. And these noxious metabolites in the corpse groups were even increased 214543-fold in average compared with the control groups. Meanwhile, treatment was the most important factor affecting the water metabolites while microbiome contributed a small proportion to the metabolic profiles. Several opportunistic pathogenic genera Comamonas , Bacteriodes and Alcaligenes co-occurred most frequently with several kinds of polyamines and amines while some dominant genera Rhodoferax , Delftia and Brevundimonas had significant positive relationships with specific benzene and substituted derivatives. This work demonstrates that carcass decomposition causes water quality deterioration by producing various toxic metabolites, thus providing new insights into noxious metabolites when exposed to animal carcasses in aquatic environment. Image 1 • Many noxious metabolites were produced by carcass decomposition. • Different groups had distinguishing metabolites profiles. • Treatment was the most important factor effecting the water metabolites. • Some potential pathogens co-occurred frequently with several noxious metabolites. [ABSTRACT FROM AUTHOR]