Raluca Maria Hlihor

Experimental analysis and mathematical prediction of Cd(II) removal by biosorption using support vector machines and genetic algorithms

We investigated the bioremoval of Cd(II) in batch mode, using dead and living biomass of Trichoderma viride. Kinetic studies revealed three distinct stages of the biosorption process. The pseudo-second order model and the Langmuir model described well the kinetics and equilibrium of the biosorption process, with a determination coefficient, R(2)>0.99. The value of the mean free energy of adsorption, E, is less than 16 kJ/mol at 25 °C, suggesting that, at low temperature, the dominant process involved in Cd(II) biosorption by dead T. viride is the chemical ion-exchange. With the temperature increasing to 40-50 °C, E values are above 16 kJ/mol, showing that the particle diffusion mechanism could play an important role in Cd(II) biosorption. The studies on T. viride growth in Cd(II) solutions and its bioaccumulation performance showed that the living biomass was able to bioaccumulate 100% Cd(II) from a 50 mg/L solution at pH 6.0. The influence of pH, biomass dosage, metal concentration, contact time and temperature on the bioremoval efficiency was evaluated to further assess the biosorption capability of the dead biosorbent. These complex influences were correlated by means of a modeling procedure consisting in data driven approach in which the principles of artificial intelligence were applied with the help of support vector machines (SVM), combined with genetic algorithms (GA). According to our data, the optimal working conditions for the removal of 98.91% Cd(II) by T. viride were found for an aqueous solution containing 26.11 mg/L Cd(II) as follows: pH 6.0, contact time of 3833 min, 8 g/L biosorbent, temperature 46.5 °C. The complete characterization of bioremoval parameters indicates that T. viride is an excellent material to treat wastewater containing low concentrations of metal.

Rhizobacteria and plant symbiosis in heavy metal uptake and its implications for soil bioremediation

Certain species of plants can benefit from synergistic effects with plant growth-promoting rhizobacteria (PGPR) that improve plant growth and metal accumulation, mitigating toxic effects on plants and increasing their tolerance to heavy metals. The application of PGPR as biofertilizers and atmospheric nitrogen fixators contributes considerably to the intensification of the phytoremediation process. In this paper, we have built a system consisting of rhizospheric Azotobacter microbial populations and Lepidium sativum plants, growing in solutions containing heavy metals in various concentrations. We examined the ability of the organisms to grow in symbiosis so as to stimulate the plant growth and enhance its tolerance to Cr(VI) and Cd(II), to ultimately provide a reliable phytoremediation system. The study was developed at the laboratory level and, at this stage, does not assess the inherent interactions under real conditions occurring in contaminated fields with autochthonous microflora and under different pedoclimatic conditions and environmental stresses. Azotobacter sp. bacteria could indeed stimulate the average germination efficiency of Lepidium sativum by almost 7%, average root length by 22%, average stem length by 34% and dry biomass by 53%. The growth of L. sativum has been affected to a greater extent in Cd(II) solutions due its higher toxicity compared to that of Cr(VI). The reduced tolerance index (TI, %) indicated that plant growth in symbiosis with PGPR was however affected by heavy metal toxicity, while the tolerance of the plant to heavy metals was enhanced in the bacteria-plant system. A methodology based on artificial neural networks (ANNs) and differential evolution (DE), specifically a neuro-evolutionary approach, was applied to model germination rates, dry biomass and root/stem length and proving the robustness of the experimental data. The errors associated with all four variables are small and the correlation coefficients higher than 0.98, which indicate that the selected models can efficiently predict the experimental data.

Potential of biosorption and bioaccumulation processes for heavy metals removal in bioreactors

Environmental contamination with heavy metals, especially of soils and water, became a significant problem because most of them are toxic to the living organisms, non-degradable and persistent in the contaminated media. Physico-chemical methods, such as chemical precipitation, electrochemical treatment, filtration, ion exchange, evaporation, reverse osmosis and membrane technologies are currently the most used methods to remove heavy metal ions from wastewaters. Bioremediation technologies, which are known to be environmentally sound natural processes, have become attractive alternatives to the conventional methods. Among these, biosorption and bioaccumulation address various interactions and concentration of toxic metals in either living (bioaccumulation) or non-living (biosorption) biomass. The aim of this paper is to emphasize the proficiency of biosorption and bioaccumulation processes applied in different types of bioreactors (stirred tank, fixed bed, fluidized-bed and air-lift) using various microorganisms for the removal of heavy metals from contaminated effluents.

Monitoring pesticides degradation in apple fruits and potential effects of residues on human health

AbstractThe behaviour of 12 pesticides used in the treatment of a variety of apples in areal conditions from a Romanian orchard is studied, considering recommended dosages, different stages of fruit development, environmental and atmospheric conditions. Five treatments were applied in recommended dosage considering the phenological growth phases, at 23 days intervals between treatments. Pesticides degraded quickly in apples during the first days, when 30–50% from the initial concentration is lost. Pesticides residues at harvesting were below the Maximum Residue Level (MRL) in European Union, excepting tebuconazole and chlorothalonil. The estimated lifetime exposure dose was calculated based on pesticide concentrations in apples at harvesting, and average fruit consumption of 197.08 g/ person/day in EU-27 during 2011. These doses for adults and children were below the reference dose (RfD) for each pesticide, suggesting a negligible risks for consumers. Hazard indices below 1 demonstrate that the studied pe...

Environmental Bioremediation by Biosorption and Bioaccumulation: Principles and Applications

The historical and everyday environmental pollution generates numerous impacts on the environmental quality and human health. Anthropogenic activities, in particular the industrial and agricultural systems, release in the environment large quantities of pollutants of inorganic and organic nature, which can be transported, immobilized, degraded, or bioaccumulated in the environmental compartments (water, air, soil) and in the ecological components (plants, animals). From there, they are easily available to humans through the food chain. This is why numerous efforts have been invested for the reduction and/or removal of pollution from the environment, together with preventive actions. Diverse physico-chemical and biological options and processes were applied to remove and/or transform different kind of pollutants (heavy metals, dyes, persistent organic pollutants) from the environment. Physico-chemical processes including chemical precipitation, ion exchange, adsorption, membrane separation, coagulation, flocculation, flotation, electrochemical technologies, etc. were applied for the mobilization, immobilization, or degradation of various pollutants. However, some of these processes, although with fast results in some cases, proved to be less efficient and more expensive than bioremediation-based processes. The biological applications, considered as low-cost alternatives, gained more and more the interest of scientists and stakeholders for ensuring a sustainable environmental remediation. This work discusses some current aspects and perspectives in the environmental bioremediation by biosorption and bioaccumulation, which exploit the potential of non-living and living biomass to immobilize and biodegrade persistent contaminants. A focus on past and present studies addressing the bioremediation of both inorganic and organic pollutants, their bioavailability in the environment, mechanisms, and impacts of environmental factors on the removal efficiency by biosorption and bioaccumulation was considered. Various biosorbents for the removal of these contaminants, such as agricultural or industrial wastes, microbial-based biomass (bacteria, fungi), algae, and plant-based biomass, are considered from impact, tolerance to persistent pollutants, effectiveness, and cost perspectives. This approach contributes to a better understanding of biological processes, so as to overcome the technical barriers in the application of biosorption and bioaccumulation processes that delay the commercialization and to increase their scale-up potential for practical applications.

The role of Arthrobacter viscosus in the removal of Pb(II) from aqueous solutions

The aim of this paper was to establish the optimum parameters for the biosorption of Pb(II) by dead and living Arthrobacter viscosus biomass from aqueous solution. It was found that at an initial pH of 4 and 26 °C, the dead biomass was able to remove 97% of 100 mg/L Pb(II), while the living biomass removed 96% of 100 mg/L Pb(II) at an initial pH of 6 and 28 ± 2 °C. The results were modeled using various kinetic and isotherm models so as to find out the mechanism of Pb(II) removal by A. viscosus. The modeling results indicated that Pb(II) biosorption by A. viscosus was based on a chemical reaction and that sorption occurred at the functional groups on the surface of the biomass. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX) analyses confirmed these findings. The suitability of living biomass as biosorbent in the form of a biofilm immobilized on star-shaped polyethylene supports was also demonstrated. The results suggest that the use of dead and living A. viscosus for the removal of Pb(II) from aqueous solutions is an effective alternative, considering that up to now it has only been used in the form of biofilms supported on different zeolites.

Bioremediation: An Overview on Current Practices, Advances, and New Perspectives in Environmental Pollution Treatment

We would like to extend our gratitude to all the authors who submitted their work for consideration in our special issue and to reviewers for their critical feedback. Contributions of Raluca Maria Hlihor and Maria Gavrilescu to this special issue were supported by a grant of the Romanian National Authority for Scientific Research,CNCS-UEFISCDI (Project no. PN-III-P4-ID-PCE-2016-0683, Contract no. 65/2017). Teresa Tavares’ contribution is supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the research project PTDC/AAG-TEC/5269/2014, the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of NORTE 2020 (Programa Operacional Regional do Norte).

Comparison of Rhodotorula sp. and Bacillus megaterium in the removal of cadmium ions from liquid effluents

Abstract This study compares the capacity of Rhodotorula sp. and Bacillus megaterium for Cd(II) removal considering the influence of operating parameters (pH, biosorbent dosage, contact time, temperature, initial metal concentration in solution). The highest Cd(II) uptake of 14.2 mg/g by Rhodotorula sp. was exhibited at 30°C, when working at pH 6 and with 5 g/l biosorbent dosage, after 48 h of contact time. In these conditions, a removal efficiency of 85% was obtained. Similar outcomes were obtained for B. megaterium (15.1 mg/g, 90%) at 35°C, pH 4 and 3 g/l biosorbent dosage, considered as the optimum set of parameters, equilibrium being achieved for a contact time of 20 min. The possible interaction mechanisms between the biosorbents and Cd(II) were evaluated through point of zero charge (pHpzc), Fourier transform infrared (FTIR), spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX). Data were modeled using pseudo-first and pseudo-second order kinetic models and Langmuir and Freundlich isotherms models. Further studies considered a modeling approach based on linear regression with Durbin-Watson statistics, while the accuracy and precision of experiments were evaluated by ANOVA.

Life cycle assessment of paper manufacturing: Environmental and human health impacts

The reduction of production waste impact started to be an important subject in the context of industrial development. In the last years the authorities became to be interested in the reduction of impacts generated by the large amount of waste, by recycling or reuse in processes. In this context, the present study is developed to help decision makers to take the best decision regarding the management of production waste from paper manufacturing so as to mitigate its impacts. According to the results obtained after an analysis of the production waste conducted in the Life Cycle Analysis (LCA) framework, the recycling of this type of waste can reduce considerable the impact on the environment and human health by reducing tree cutting and increasing the absorption capacity of CO2 from the environment.

Overview of human health hazards posed by pesticides in plant products

Pesticides use, one of the hottest topics nowadays when it comes to human health, started to be a serious concern to consumers considering their known harmful effects. This paper provides a short overview on pesticides application and their corresponding maximum residue levels (MRLs) in plant products, risks associated to human health and steps in conducting a human health risk assessment. The procedure of assessing the MRLs is discussed and a methodology of assessing human health risks to pesticides is considered based on currently existing framework provided by USEPA. This analysis highlights the requisite of continuous monitoring programmes of pesticide residues in plant products, and deep knowledge of their toxic effects and assessment strategies necessary in human health risk estimation and mitigation.