Plant-assisted sediment microbial fuel cells (SMFCs) are emerging as promising green energy technologies with potential applications in wastewater treatment and biosensing in open-environment systems. However, their practical implementation is limited by their inherently low voltage output. A common strategy to enhance the voltage involves stacking multiple unit cells in series; however, such configurations often suffer from voltage reversal (VR), which disrupts system stability and reduces the overall output voltage. Herein, a strategy is presented to mitigate VR in stacked water lettuce-assisted SMFCs (WL-SMFCs) by tuning the anodic surface area. A theoretical framework was first developed to relate electrical parameters to the anodic surface area, predicting that increasing the anodic surface area of the terminal unit would enhance the overall stack voltage. This prediction was experimentally validated by using a laboratory-scale stack of series-connected WL-SMFC units. When the anodic surface area of the terminal unit was increased to match the total anodic surface area of all other units combined, the VR was significantly reduced. In two-, three-, and four-unit stacks, VR decreased by 70%, 57%, and 54%, respectively. Electrochemical impedance spectroscopic analysis confirms the corresponding increase in anodic storage charge (C) to 318.25 +/- 12.35 (670 +/- 26), 453.08 +/- 12.12 (964 +/- 26), and 422.92 +/- 9.39 (872 +/- 19) from the unit value of 240.58 +/- 25.65 (523 +/- 55) with respective capacitance (pF) values shown in brackets. This anodic surface area tuning approach offers a technically simple, self-sustaining, and cost-effective solution for alleviating VR, thereby enhancing the feasibility of SMFCs for open-environment applications.

Sediment microbial fuel cells (SMFCs) are emerging as a promising green energy technology with enormous application potential for wastewater treatment and linked electrical energy production. However, the practical application of these devices is challenged by their low-performance factors pertaining to the imbalanced electrolyte and oxygen levels and weak cathodic functions in open environment conditions. This study explored to address the poor performance of the SMFC by coupling it with a free-floating aquatic plant, Water lettuce. Growth of the plant balanced the catholyte pH in the range of 7.2-7.6, increased the ionic conductivity by 60 %, stabilized the sub-surface water oxygen level, and boosted the cathodic potential by similar to 102 mV and similar to 49 mV in open and close circuit operations mode, respectively. The cumulative effect of these inputs led to producing a power density of 22.45 mW/m(2) and a current density of 136.84 mA/m(2) at 2 k Omega and 50 Omega loads, respectively. The enhanced cathodic performance was also attributed to the colonization of Water lettuce root bacteria as biofilm on the cathode that supported catalytic oxygen reduction on the graphite electrode. Metagenonic analysis indicated the biofilm is created mostly by aerobic microbes such as Ferrovibrio terrae, Comamonas aquatic, Achromobacter xylosoxidans, Hydrogenophaga taeniospiralis etc. bearing catalase enzyme, Pannonibacter phragmitetus, Streptococcus pyogenes, Streptococcus mutans etc. bearing heme enzyme and these microbes synergistically catalysed cathodic reduction reactions. This study demonstrated the positive role of Water lettuce in boosting the power performance of SMFC mainly by activating the cathodic functions of the setup.

Remediation of aged petroleum hydrocarbon (A-PHC) contamination is hindered by the recalcitrance of pollutants and the disruption of soil microbial networks. The efficacy of biochar amendments relies on balancing two opposing functions of contaminant adsorption and microbial biostimulation. Here, we propose a microecological threshold framework to resolve this trade-off. By investigating biochar application rates (0 %-5.5 %), we identified a critical threshold at approximately 1 %, where weak stimulation optimally balanced substrate bioavailability with microbial activation. This condition sustained high microbial diversity and fostered cooperative, circular network architectures, resulting in a 50.86 %-83.60 % enhancement in A-PHC degradation compared to controls. Conversely, supra-threshold dosages, while initially stimulating activity, triggered a collapse in diversity and the formation of competitive networks, ultimately stalling degradation. Community assembly analysis revealed a shift from deterministic filtering to stochastic, interaction-driven processes under threshold-optimized conditions. Spectroscopic evidence confirmed that enhanced biodegradation was driven by active microbial transformation of dissolved organic matter, distinct from the abiotic adsorption dominance observed at higher dosages. These findings validate the microecological threshold as a critical parameter for precision bioremediation, shifting the focus from simple pollutant reduction to the reconstruction of functional ecosystem networks.

The work investigated the combined effect of pyrocatechol (0.001n and 0.1n) with KMnO4 (0.001n and 0.01n) on the Lemna minor. The range of ratios of equivalent concentrations of metal ion and pyrocatechol was from 1:100 to 10:1. It was shown that individual solutions of pyrocatechol exhibited a pronounced damaging effect towards L. minor starting from a concentration of 0.1n, and KMnO4 – from 0.01n. It was revealed that the toxic effect of a 0.1n solution of pyrocatechol decreased with the addition of 0.01n and, to a greater extent, 0.001n solutions of KMnO4. A significant reduction in the damaging effect of 0.01n KMnO4 solution was established when adding 0.001n pyrocatechol to a 10-fold excess of the equivalent concentration of potassium permanganate (2.0-2.4 times). On the contrary, the yield of electrolytes increased in equinormal 0.001 n mixtures of solutions of pyrocatechol and a metal compared to individual solutions. Based on the toxicological data, analysis of UV-VIS spectra, an attempt was made to explain the mechanisms of interaction between pyrocatechol and KMnO4 during their action on plant. The data can be useful for understanding the processes of self-purification of water bodies, be of interest when using plants to clean water bodies, predicting environmental risks.

The possibility of selective Cu and Zn leaching from the sample of old pyrite tailings, which is one of the most widespread types of solid waste forming during non-ferrous metal production, using sulfuric acid solutions and water was studied. It was shown that water leaching provided selective extraction of Cu and Zn and comparatively low iron ion extraction. At the same time, acid leaching provided the obtainment of pregnant solutions with high ferric ion concentration, which can be used for oxidative leaching of substandard copper concentrates. Water and acid leaching also provided increased Au recovery by cyanidation. The results suggest that acid leaching can be an effective approach for processing old flotation tailings, which allows the extraction of base metals from these wastes and treating flotation tailings for subsequent cyanidation. Effective flotation treatment methods should also provide environmental load reduction, which is caused by the long-term storage of metal-bearing wastes.

Environmental pollution is becoming ubiquitous; it has a negative impact on ecosystem diversity and worsens the quality of human life. This review discusses the possibility of applying the plant microbial fuel cells (PMFCs) technology for concurrent processes of electricity generation and the purification of water and soil ecosystems from organic pollutants, particularly from synthetic surfactants and heavy metals. The review describes PMFCs’ functioning mechanisms and highlights the issues of PMFCs’ environmental application. Generally, this work summarizes different approaches to PMFC development and to the potential usage of such hybrid bioelectrochemical systems for environmental protection.

The study examined the concentration dynamics of naphthalene, with its initial concentrations of 1, 2, and 3 g/L in synthetic wastewater. The initial number of Bacillus megaterium MK64-1 cells in the medium amounted to 1.7×107 CFU/mL. On day 14 of the experiment, the concentration of naphthalene decreased to hundredths of a gram, while the microbial count increased to 109 CFU/mL (at the initial naphthalene concentrations of 1 and 2 g/L) and 1011 CFU/mL (at the initial naphthalene concentration of 3 g/L). After 14 days, the medium pH decreased by an average of 0.7 units (from 8.56 to 7.86) in both test and control media, with the addition of a microbial suspension. During this time, the redox potential of the medium increased by an average of 70 mV in the test media. Quite a strong direct correlation (p < 0.05) was found between the initial concentration and the amount of pollutant degraded by bacteria. The determination of dehydrogenase activity in Bacillus megaterium by means of two methods (with 2,3,5-triphenyltetrazolium chloride and methylene blue), as well as microbial sensitivity to hydrocarbon concentrations of 1, 2, and 3 g/L via the disk-diffusion method, showed no toxic effect of the analyzed pollutant concentrations on bacteria under the experimental conditions. The obtained results indicate the ability of Bacillus megaterium strain MK64-1 to biodegrade naphthalene.

This study explores the combined toxic effect of Mn(II) and resorcinol (0.01 n and 0.2 n) on duckweed (Lemna minor). During the acute experiments, the plants released electrolytes into the aquatic environment after 30 min of exposure to the toxicants, indicating a disruption of tissue permeability as a test response. The experiments showed that the toxicity of the equinormal mixtures of resorcinol and Mn(II) (0.2 n each) increased relative to their single solutions. This was observed both in the freshly prepared solutions and in the solutions stored for 20 h prior to the experiments. The change in the UV absorption spectra indicates that there was complexation or other interaction between resorcinol and Mn(II) at equinormal concentrations (0.01 n). At the Mn(II) : resorcinol ratio of 1:20 (0.01 n Mn(II) and 0.2 n resorcinol), the toxicity of the system to duckweed decreased compared to the separate effects of these substances. The results obtained highlight the importance of considering the interactions between heavy metals and phenolic compounds when assessing the quality of aquatic environments.

Results of studying the main types of surfactants effect on earthworms Eisenia fetida andrey (Bouche, 1972) are presented. The worms were tested for survival and preference-avoidance behavioral reactions. Earthworms avoided sodium dodecyl sulfate (SDS) at 0.02 g/kg and above, cetyltrimethylammonium bromide - at 0.1 g/kg and above, and polysorbate 80 - at 30 mL/kg and above. The 100% mortality of earthworms occurred at 0.001, 0.01 and 0.02 g/kg of SDS on day 30, at 1 g/kg - on day 25, and at 1 g/kg - on day 2 of the experiment. & Scy;etyltrimethylammonium bromide at 0.001 and 0.01 g/kg caused the 100% mortality of worms on day 30; at 0.1 g/kg - on day 25; at 0.5 g/kg - on day 5; and at 1.0 g/kg already on day 2 of the experiment. The 100% mortality of worms occurred at 0.1, 1 and 10 mL/kg of polysorbate 80 on day 30 of incubation; at 20 or 30 mL/kg - on day 20; at 50 mL/kg - on day 10 of experience. The following toxicity series (both in terms of g/L and in terms of g/mol) of the tested surfactants for earthworms was constructed on the basis of the results obtained (increasing toxicity): polysorbate 80 (non-ionic surfactant) < cetrimonium bromide (cationic surfactant) < sodium dodecyl sulfate (anion-active surfactant).

In order to determine optimum and ecologically acceptable conditions for aromatic amines (benzidine was chosen as an example) elimination by chara algae Nitella sp. a multi-factor experiment has been undertaken. The benzidine elimination process by chara algae was studied by variation of four factors, such as benzidine initial concentration in water solution, algae biomass, temperature, time and at the interaction of these factors as well. A mathematical model adequately describing the benzidine elimination process by chara algae at the optimal conditions has been obtained by means of design of experiments method. Suggested model might be useful for obtaining the data important for hydro botanical treatment facilities design and self-cleaning processes understanding.

The paper shows that oil pollution of gray forest and soddy-podzolic soils led to a decrease in capillary water capacity, plasticity and solid phase of soils. As a result of the introduction of the nonionic surfactant tween-80 into the oil-contaminated soil, these indicators were partially restored, but their values remained lower than in soil samples subjected to oil treatment. The obtained materials allow us to speak about the fundamental possibility of using surfactants for the remediation of oil-contaminated soils.

The change in capillary moisture capacity of gray forest soil was analyzed at various levels of oil and diesel fuel contamination (50, 150 and 300 ml/kg), as well as as a result of reagent treatment of contaminated soil samples using the nonionic surfactant Tween-80. The concentration of Tween-80 in the wash solutions was 1, 5 and 10 g/L. The ratio of the system components was: 100 g of soil: 400 ml of water: 100 ml of washing solution. Treatment of oil-contaminated soil with washing solutions was carried out for 1 hour with continuous stirring (60 rpm) and a temperature of 20 °C. Contamination of gray forest soils with oil and diesel fuel has led to a decrease in capillary moisture capacity. Thus, the moisture capacity indicator moved from the category “best” (40-50% according to the classification of Kaczynski, 1965) to “satisfactory” (25-30%) or “unsatisfactory” (less than 25%). After washing oil-contaminated soils with surfactant solutions, the values of capillary moisture capacity were restored from the level of “unsatisfactory” to “good” or “best”, although they remained somewhat lower than the level of the parameter of the original (uncontaminated) soil. The results obtained demonstrated an improvement in the studied and so important (in terms of yield) agrophysical parameter of oil-contaminated soil after its treatment with Tween-80. This confirms the prospects of using reagent treatment of oil-contaminated soils using this nonionic surfactant. At the indicated ratio soil: aqueous phase : washing solution, and the contamination level is up to 150 ml/kg (oil) and 300 ml/kg (diesel fuel), the optimal concentration for washing contaminated soil is 5 g/l Tween-80. When reclaiming soils contaminated with oil at a concentration of 300 ml/kg, it is recommended to increase the concentration of surfactants in washing solutions to 10 g/l.

The unique ecosystem of Lake Baikal is composed of diverse and mainly endemic flora and fauna. The sponge fauna of Baikal is represented by two families, endemic Lubomirskiidae and cosmopolitan Spongillidae. In recent years, the situation with Lake Baikal has been characterized as catastrophic, especially in the littoral zone. There are numerous reports about the suppressed state of Baikal sponges and a decrease in the magnitudes of their populations in many lake areas. Scientists insist that not only nature-conservative, but also nature-restoring measures are required. This review discusses the basic known sponge cultivation techniques and approaches. Four main approaches to the ex situ and in situ sponge cultivation in the global practice are described in the most detail: (1) cultivation from larvae, (2) cultivation from primmorphs (sponge cell cultures), (3) cultivation from resting stages (gemmules and reduction bodies), and (4) cultivation from explants (fragments of living tissues detached from a parent organism). Attempts to use the described common approaches for the cultivation of Baikal sponges are also discussed. Based on the analysis of existing publications, we assume that the use of the most effective of the abovementioned approaches will make it possible to develop a technology for cultivating Baikal sponges.

The adhesion of microorganisms on various surfaces plays a crucial role in many biotechnological processes. A widespread component of wastewater is the anion-active surfactant sodium dodecyl sulfate (SDS). Surfactants have a significant influence on all interfacial reactions, including those occurring in microbial fuel-cell technology. The work set out to study the effect of sodium dodecyl sulfate on the sorption of cells of the Micrococcus luteus 1 strain (which has electrogenic activity in microbial fuel cells) on the surface of various carbon-containing electrode materials used in biological fuel cell technology: 1) carbon tissue; 2) carbon felt; 3) crushed graphite contact trolleybus inserts (summer); 4) birch activated carbon. Using spectrophotometry and microscopy methods, the presence of sodium dodecyl sulfate in the concentration range of 10–200 mg/l was shown to increase the sorption of Micrococcus luteus 1-i cells on the surfaces of the tested carbon materials under experimental conditions. The maximum increase in sorption during 2 hours of exposure was detected when 100 mg/l of this surfactant was applied: for birch activated carbon – 21%; for carbon fabric – 26%; for carbon felt relative to the control (without surfactant) – 24%. The results demonstrate a sufficiently effective adhesion of Micrococcus luteus 1-i cells to various carbon materials, including in the presence of fairly high concentrations of sodium dodecyl sulfate, confirming the prospects of this strain for use in various types of microbial fuel cells.

The effect on the survival of the yeast S. cerevisiae of mixtures of diesel fuel (summer variety) with four representatives of different classes of surfactants – cationic (cetyltrimethylammonium bromide), anionic (sodium dodecyl sulfate), nonionic (Tween-80) and polymeric (polyvinyl alcohol) – was studied. It was shown that diesel fuel and two representatives of the classes of anionic and cationic surfactants (sodium dodecyl sulfate and cetyltrimethylammonium bromide) in the mixture exhibited higher toxicity than when exposed individually. At the same time, the toxicity of diesel fuel mixed with a nonionic surfactant (Tween- 80) and a polymer surfactant (polyvinyl alcohol) was comparable to their individual toxicity.

We studied the physicochemical and electrochemical characteristics of microbial fuel cells (MFCs) with a new proton-exchange membrane. It was synthesized on the basis of zeolite-doped polyvinyl alcohol cross-linked with sulfosuccinic acid (PVA-SSA-BEA). An MF-4SK industrial membrane (Plastpolymer, Russia) was used as a comparative sample. Various sugars were added as substrates (glucose, arabinose, galactose, xylose). The role of the bioagent was performed by the strain Micrococcus luteus 1-i. MFCs with PVA-SSA-BEA and MF-4SK membranes showed rather close electrochemical characteristics. A higher electricity output was performed with the addition of glucose, galactose, the lowest-with the use of xylose. The data obtained indicate that the proposed PVA-SSA-BEA membrane is promising for use as an alternative to proton-exchange membranes widely used in fuel cell technology.

The toxic effects of Fe2+ ions and resorcinol on Lemna minor in their joint presence in the aquatic environment were studied. The test response in the bioassay of solutions of Fe2+, resorcinol, and their mixtures was a violation of the permeability of duckweed membranes. This parameter was estimated from the change in the electrical conductivity of the aquatic medium in which the plant was placed, exposed to the toxicant in the acute experiment (30 min). It was found that the addition of both an equinormal concentration of Fe(II) (0.1n) and a five-fold deficiency (0.02n) to a 0.1n solution of resorcinol reduced the toxicity of resorcinol. Most likely, the effect obtained can be achieved by the formation of a new, less toxic compound (probably of a complex nature). The test used in the work, based on the assessment of the permeability of cell membranes under the action of toxicants, once again proved to be a promising tool for analyzing the combined toxicity of phenolic compounds and metal ions in relation to plant organisms.

The discharge of toxic chemicals into water bodies and their linked detrimental effects on health is a global concern. Phytoremediation, an environment-friendly plant-based technology, has gained intensive interest over the last decades. For the aquatic phytoremediation process, the commonly available duckweeds have recently attracted significant attention due to their capacity to grow in diverse ecological niches, fast growth characteristics, suitable morphology for easy han-dling of biomass, and capacity to remove and detoxify various potential toxic elements and com-pounds. This review presents the progress of duckweed-assisted aquatic phytoremediation of toxic chemicals. A brief background of general phytoremediation processes, including the different phy-toremediation methods and advances in understanding their underlying mechanisms, has been described. A summary of different approaches commonly practiced to assess the growth of the plants and their metal removal capacity in the phytoremediation process has also been included. A vast majority of studies have established that duckweed is an efficient plant catalyst to accumu-late toxic heavy metals and organic contaminants, such as pesticides, fluorides, toxins, and aromatic compounds, reducing their toxicity from water bodies. The potential of this plant-based phytoremediation process for its downstream applications in generating value-added products for the rural economy and industrial interest has been identified.