Elemental mercury production from contaminated riparian soil suspensions under air and nitrogen bubbling conditions.

The dynamic change of redox conditions is a key factor in emission of elemental mercury (Hg) from riparian soils. The objective of this study was to elucidate the influences of redox conditions on Hg emission from riparian soils. Soil suspension experiments were conducted to measure Hg emission from five Hg-contaminated soil samples in two redox conditions (i.

Microaerophilic Activated Sludge System for Ammonia Retention toward Recovery from High-Strength Nitrogenous Wastewater: Performance and Microbial Communities.

A transition to ammonia recovery from wastewater has started; however, a technology for sustainable nitrogen retention in the form of ammonia and organic carbon removal is still in development. This study validated a microaerophilic activated sludge (MAS) system to efficiently retain ammonia from high-strength nitrogenous wastewater. The MAS is based on conventional activated sludge (CAS) with aerobic and settling compartments.

Evaluation of Pollution Level, Spatial Distribution, and Ecological Effects of Antimony in Soils of Mining Areas: A Review.

The first global-scale assessment of Sb contamination in soil that was related to mining/smelting activities was conducted based on 91 articles that were published between 1989 and 2021. The geographical variation, the pollution level, the speciation, the influencing factors, and the environmental effects of Sb that were associated with mining/smelting-affected soils were analyzed. The high Sb values mainly occurred in developed (Poland, Italy, Spain, Portugal, New Zealand, Australia) and developing (China, Algeria, Slovakia) countries.

Combination of N Tracer and Microbial Analyses Discloses NO Sink Potential of the Anammox Community.

Although nitrogen removal by partial nitritation and anammox is more cost-effective than conventional nitrification and denitrification, one downside is the production and accumulation of nitrous oxide (NO). The potential exploitation of NO-reducing bacteria, which are resident members of anammox microbial communities, for NO mitigation would require more knowledge of their ecophysiology. This study investigated the phylogeny of resident NO-reducing bacteria in an anammox microbial community and quantified individually the processes of NO production and NO consumption.

Temperature and oxygen level determine N O respiration activities of heterotrophic N O-reducing bacteria: Biokinetic study.

Nitrous oxide (N O), a potent greenhouse gas, is reduced to N gas by N O-reducing bacteria (N ORB), a process which represents an N O sink in natural and engineered ecosystems. The N O sink activity by N ORB depends on temperature and O exposure, yet the specifics are not yet understood. This study explores the effects of temperature and oxygen exposure on biokinetics of pure culture N ORB.

Nonlinear response of methane release to increased trophic state levels coupled with microbial processes in shallow lakes.

Shallow lakes are a crucial source of methane (CH), a potent greenhouse gas, to the atmosphere. However, large uncertainties still exist regarding the response of CH emissions to the increasing trophic levels of lakes as well as the underlying mechanisms. Here, we investigate the CH emission flux from lakes with different trophic states in the middle and lower reaches of the Yangtze River basin, China to evaluate the effect of the trophic lake index (TLI) on CH emissions.

Exploration and enrichment of methane-oxidizing bacteria derived from a rice paddy field emitting highly concentrated methane.

Methane-oxidizing bacteria (MOB) possess the metabolic potential to assimilate the highly potent greenhouse gas, CH, and can also synthesize valuable products. Depending on their distinct and fastidious metabolic pathways, MOB are mainly divided into Type I and Type II; the latter are known as producers of polyhydroxyalkanoate (PHA). Despite the metabolic potential of MOB to synthesize PHA, the ecophysiology of MOB, especially under high CH flux conditions, is yet to be understood.

Eco-compatible biochar mitigates volatile fatty acids stress in high load thermophilic solid-state anaerobic reactors treating agricultural waste.

A high concentration of accumulated volatile fatty acids (VFAs) is one of the most important factors resulting in reactor failure during solid-state anaerobic digestion. In this study, the feedstock-to-inoculum (F/I) ratio (0.5, 2, 3, 4 and 6) and the recovery method after failure (biochar addition or inoculum addition) were investigated in batch solid-state anaerobic digestion fed with rice straw and pig urine.

Reducing geogenic arsenic leaching from excavated sedimentary soil using zero-valent iron amendment followed by dry magnetic separation: A case study.

Although the deep-layer sedimentary soils excavated from construction sites contain low level of geogenic arsenic (As), remediation is necessary when the As leachability exceeds the environmental standard (10 μg/L) in Japan. In this study, the zero-valent iron (ZVI) amendment followed by dry magnetic separation (ZVI-DMS) was implemented for the treatment of a geogenic As-contaminated alkaline sedimentary soil (pH 8.9; 7.

Enrichment, Isolation, and Characterization of High-Affinity NO-Reducing Bacteria in a Gas-Permeable Membrane Reactor.

The recent discovery of nitrous oxide (NO)-reducing bacteria suggests a potential biological sink for the potent greenhouse gas NO. For an application toward NO mitigation, characterization of more isolates will be required. Here, we describe the successful enrichment and isolation of high-affinity NO-reducing bacteria using a NO-fed reactor (NOFR).

Impact of turning waste on performance and energy balance in thermophilic solid-state anaerobic digestion of agricultural waste.

Mixing is an important operation in solid-state anaerobic digestion (SS-AD) to improve the mass transfer of the solid phase. This study proposed simple turning by loader in common garage-type digester without commonly used mixer or percolation system (simplified SS-AD). In simplified-SS-AD, turning is conducted in open condition.

Comparison of leachate percolation and immersion using different inoculation strategies in thermophilic solid-state anaerobic digestion of pig urine and rice straw.

Heterogeneous distribution of substrate and microorganisms and low mass transfer limit methane production dramatically in solid-state anaerobic digestion (SS-AD). To overcome this challenge, this study determined the optimal inoculation strategy (complete premix/slurry application) for reusing solid digestate as inoculum and the optimal leachate circulation method (percolation/immersion) using batch digestion. Initially, percolation and immersion (1 h per 3 days) were compared and the result shows that immersing rice straw into leachate was superior to leachate percolation in methane production.

Biokinetic Characterization and Activities of NO-Reducing Bacteria in Response to Various Oxygen Levels.

Nitrous oxide (NO)-reducing bacteria, which reduce NO to nitrogen in the absence of oxygen, are phylogenetically spread throughout various taxa and have a potential role as NO sinks in the environment. However, research on their physiological traits has been limited. In particular, their activities under microaerophilic and aerobic conditions, which severely inhibit NO reduction, remain poorly understood.

Immobilization of Azospira sp. strain I13 by gel entrapment for mitigation of NO from biological wastewater treatment plants: Biokinetic characterization and modeling.

Development of a strategy to mitigate nitrous oxide (NO) emitted from biological sources is important in the nexus of wastewater treatment and greenhouse gas emission. To this end, immobilization of NO-reducing bacteria as a biofilm has the potential to ameliorate oxygen (O) inhibition of the metabolic activity of the bacteria. We demonstrated the effectiveness of calcium alginate gel entrapment of the nosZ clade II type NO-reducing bacterium, Azospira sp.

Investigations of water-extractability of As in excavated urban soils using sequential leaching tests: Effect of testing parameters.

Excavated soils with low-level As contamination obtained from construction projects during city development have been of great concern in Japan. Water-extractable As represents the most easily mobilized and ecotoxicologically relevant fraction in the soil environment. In the present study, the water-extractability of As in excavated alkaline urban soils was assessed using sequential leaching tests (SLTs) with a focus on the effects of test parameters.

The influence of the total solid content on the stability of dry-thermophilic anaerobic digestion of rice straw and pig manure.

Dry anaerobic digestion is a promising technology for the recycling of agricultural waste to produce energy and fertilizer. Adding water to the substrate enables better handling and avoid inhibition caused by high total solid (TS) content in the reactor; however, it also increases leachate and operational costs. To assess the extent to which the amount of water added can be reduced, it was examined how the TS content in the reactor influenced the production of biogas.

Influence of feedstock-to-inoculum ratio on performance and microbial community succession during solid-state thermophilic anaerobic co-digestion of pig urine and rice straw.

This study investigated the effect of the feedstock-to-inoculum (F/I) ratio on performance of the solid-state anaerobic co-digestion of pig urine and rice straw inoculated with a solid digestate, and clarified the microbial community succession. A 44-day biochemical methane potential test at F/I ratios of 0.5, 1, 2 and 3 at 55 °C and a 35-day large-scale batch test at F/I ratios of 0.

Identification of hotspots for NO and NO production and consumption in counter- and co-diffusion biofilms for simultaneous nitrification and denitrification.

A membrane-aerated biofilm reactor (MABR) provides a counter-current substrate diffusion geometry in which oxygen is supplied from a gas-permeable membrane on which a biofilm is grown. This study hypothesized that an MABR would mitigate NO and NO emissions compared with those from a conventional biofilm reactor (CBR). Two laboratory-scale reactors, representing an MABR and CBR, were operated by feeding synthetic industrial wastewater.

Pollution potential leaching index as a tool to assess water leaching risk of arsenic in excavated urban soils.

Leaching of hazardous trace elements from excavated urban soils during construction of cities has received considerable attention in recent years in Japan. A new concept, the pollution potential leaching index (PPLI), was applied to assess the risk of arsenic (As) leaching from excavated soils. Sequential leaching tests (SLT) with two liquid-to-solid (L/S) ratios (10 and 20Lkg) were conducted to determine the PPLI values, which represent the critical cumulative L/S ratios at which the average As concentrations in the cumulative leachates are reduced to critical values (10 or 5µgL).

Counter-diffusion biofilms have lower NO emissions than co-diffusion biofilms during simultaneous nitrification and denitrification: Insights from depth-profile analysis.

The goal of this study was to investigate the effectiveness of a membrane-aerated biofilm reactor (MABR), a representative of counter-current substrate diffusion geometry, in mitigating nitrous oxide (NO) emission. Two laboratory-scale reactors with the same dimensions but distinct biofilm geometries, i.e.

Nitrous oxide production and mRNA expression analysis of nitrifying and denitrifying bacterial genes under floodwater disappearance and fertilizer application.

A pulse of nitrous oxide (NO) emission has been observed following the disappearance of floodwater by drainage. However, its mechanism is not well understood. We conducted a column study to clarify the mechanism for NO production during floodwater disappearance by using a microsensor and determining the bacterial gene expression.

Hybrid Nitrous Oxide Production from a Partial Nitrifying Bioreactor: Hydroxylamine Interactions with Nitrite.

The goal of this study was to elucidate the mechanisms of nitrous oxide (NO) production from a bioreactor for partial nitrification (PN). Ammonia-oxidizing bacteria (AOB) enriched from a sequencing batch reactor (SBR) were subjected to NO production pathway tests. The NO pathway test was initiated by supplying an inorganic medium to ensure an initial NH-N concentration of 160 mg-N/L, followed by NO (20 mg-N/L) and dual NHOH (each 17 mg-N/L) spikings to quantify isotopologs of gaseous NO (NO, NO, and NO).

Synthesis of CTAB intercalated graphene and its application for the adsorption of AR265 and AO7 dyes from water.

Environmental applications of graphene (GN) are limited by the occurrence of aggregation. Herein, graphene oxide (GO) was synthesized, reduced to GN by ascorbic acid, and intercalated with cetyltrimethylammonium bromide (CTAB). GN-CTAB was characterized by Boehm's titration, N adsorption/desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, Fluorescence spectrophotometry, X-ray diffraction and Scanning electron microscopy.