Magnetic and electric field accelerate Phytoextraction of copper Lemna minor duckweed

Cupric ions inducing dynamic hormesis in duckweed systems for swine wastewater treatment: Quantification, modelling and mechanisms

Hormesis has attracted close attention of environmental and toxicological communities over the past decades. Most studies focused on the hormesis induced by stressors in the aspect of their biotoxicity to organisms, while little research was conducted on hormesis in the aspect of biological wastewater treatment process. In this study, removal of NH₄⁺-N and Cu²⁺ by S. polyrrhiza under long-term Cu²⁺ exposure at environmentally relevant concentrations in swine wastewater was investigated. Removal efficiencies of NH₄⁺-N by duckweeds at 0.0, 0.1, 0.5, 1.0, 2.0 and 4.0 mg/L Cu²⁺ were 81.6 %, 83.7 %, 89.4 %, 74.9 %, 61.8 % and 45.1 % on day 28, however, during the initial period of cultivation (0-4 days), such hormetic effect was not observed, indicating time-dependent feature of hormesis in NH₄⁺-N removal. The modified logistic growth model was applied to describe long-term hormesis induced by Cu²⁺ on NH₄⁺-N removal and it suggested that the optimal copper exposure for ammonium removal was 0.48 mg/L. More importantly, it was found that previous exposure to low doses of Cu²⁺ (0-1 mg/L) could enhance NH₄⁺-N removal performance under the second exposure. Cu²⁺ above 1 mg/L could switch copper bioaccumulation pattern from the Langmiur-irreversible type to reversible one, indicating risk of secondary pollution. Six components including freshly-produced humic-like substances, lignin, fulvic acid-protein complex, free amino acid-like substances, tyrosine-like substance and soluble amino acid-like substances in duckweeds were detected by parallel factor (PARAFAC) model detected. Principle component analysis (PCA) conducted on PARAFAC components suggested that enhanced synthesis of protein and growth factors intracellularly at low dose stimulation improved ammonia uptake from the environment. This study provided a novel strategy to improve treatment performance of duckweeds for copper contaminated wastewater and helped understand biochemical responses and their roles in evolutionary adaptive strategies to stresses.

New energy approaches to the use of waste biosorbents of microalgae Chlorella kessleri (Chlorellaceae, Chlorellales)

The use of microalgae Chlorella kessleri VKPM A1-11 ARM (RF, NPO Algobiotechnology) for environmental and energy purposes is considered. The results of our study of the use of C. kessleri microalgae biomass as a biosorbent to purify model wastewater from Cu2+ ions under static conditions are presented. Biosorption is a promising technology for the treatment of industrial effluents containing various heavy metal compounds, but the issues of economic benefits of using biosorbents, their environmental safety and the cost of disposal of used sorbents are subject to much discussion. The paper proposes to dispose the used biosorbent formed after wastewater treatment from copper as an additional fuel. The copper concentration in the filtrate was determined by colorimetric analysis with sodium diethyldithiocarbamate. The cleaning efficiency and sorption capacity of the dry mass of C. kessleri were obtained by calculation. The maximum sorption capacity for Cu2+ ions was 4.2 mg/g. The purification efficiency reached 87% at the initial concentration of Cu2+ ions being 97 mg/l. Tests to estimate the specific heat of combustion of C. kessleri biomass and used biosorbents based thereon were carried out by the calorimetric method using a bomb calorimeter. The specific heats of combustion were 22,125 kJ/kg and 21,674 kJ/kg, respectively. A comparison of these values with traditional energy carriers is given. A technological scheme has been developed for a waste-free cycle of using C. kessleri to treat wastewater from industrial enterprises with the production of several valuable resources as end products, such as purified water, energy resources, fertilizers, and recycled metals. The obtained results of our study can be applied in technologies for post-treatment of wastewater from various industrial enterprises using biological non-waste resources.

Graphene Oxide-Chitosan Composites for Water Treatment from Copper Cations

This paper considers modern sorption materials for wastewater treatment. The literature data on wastewater treatment with materials based on graphene and chitosan are presented. The production and application of composite sorbents is discussed. It is shown that a promising application of graphene oxide (GO) as a filler enhances the mechanical and sorption properties of the polymer matrix. The biopolymer chitosan (Ch) is a challenging matrix for GO, having unique sorption, chelate-forming, ion-exchange, and complex-forming properties. Composite adsorbents based on graphene oxide and chitosan have a high extraction efficiency of heavy and radioactive metals, dyes, and pharmaceutical compounds dorzolamide and tetracycline. GO-Ch composites with various ratios of chitosan and graphene oxide (2–7%) were formed by drop granulation. The composites obtained were investigated in terms of the ability to extract copper cations from the effluents, and it was shown that the composite having the content of GO:Ch = 55.5:44.5% (by mass in dry granules) had the best sorption and mechanical properties. This sample had high purification efficiency from copper cations (96%) and the required mechanical properties (attrition ≤ 0.4%, grindability ≤ 4%). For this sample, the influence of various factors (pH, sorbent dosage, temperature, and time of sorption) on sorption processes were studied. The best conditions for the sorption processes by the GO-Ch sorbent were determined. The sorbent dosage was 20 g/L, the sorption time was 20 min, and the temperature was 20 ± 2 °C, pH = 7. The adsorption isotherm was plotted and the maximum sorption capacity of copper cations A = 58.5 mg/g was determined. Microstructural and infrared (IR) spectroscopy studies of GO-Ch composites showed the presence of a porous surface and OH- and C=O functional groups. A mechanism for the extraction of copper cations due to physical sorption of the porous surface by GO-Ch composites, and due to chemisorption processes by functional groups, was proposed. The sorption properties for methylene blue and iodine absorption, and the specific surface area of the GO-Ch samples, were determined. The spent sorbent is proposed to be used as a soil improver.

Biogas Potential Assessment of the Composite Mixture from Duckweed Biomass

The article presents the research results of anaerobic digestion processes in bioreactors of composite mixtures based on initial and residual biomass of Lemna minor duckweed and additives: inoculum (manure), food waste, and spent sorbents to determine biogas potential (biogas volume, methane content). Duckweed Lemna minor, which is widespread in freshwater reservoirs, is one of the promising aquatic vegetation species for energy use. Residual biomass is obtained by chemically extracting valuable components from the primary product. The purpose of the research was to evaluate the possibility of the energy potential of residual biomass of Lemna minor to reduce the consumption of fossil fuels and reduce greenhouse gas emissions. This is in line with the International Energy Agency (IEA) scenarios for the reduction of environmental impact. The obtained results confirm the feasibility of using this type of waste for biogas/biomethane production. The recommendations on the optimal composition of the mixture based on the residual biomass of Lemna minor, which will allow for an increase in biogas production, are given. The obtained data can be used in the design of bioreactors.