Possibility of Using Phenol- and 2,4-Dichlorophenol-Degrading Strain, Rhodococcus erythropolis 17S, for Treatment of Industrial Wastewater

Actinobacteria isolated from wastewater treatment plants located in the east-north of Algeria able to degrade pesticides

The pollution of water resources by pesticides poses serious problems for public health and the environment. In this study, Actinobacteria strains were isolated from three wastewater treatment plants (WWTPs) and were screened for their ability to degrade 17 pesticide compounds. Preliminary screening of 13 of the isolates of Actinobacteria allowed the selection of 12 strains with potential for the degradation of nine different pesticides as sole carbon source, including aliette, for which there are no previous reports of biodegradation. Evaluation of the bacterial growth and degradation kinetics of the pesticides 2,4-dichlorophenol (2,4-DCP) and thiamethoxam (tiam) by selected Actinobacteria strains was performed in liquid media. Strains Streptomyces sp. ML and Streptomyces sp. OV were able to degrade 45% of 2,4-DCP (50 mg/l) as the sole carbon source in 30 days and 84% of thiamethoxam (35 mg/l) in the presence of 10 mM of glucose in 18 days. The biodegradation of thiamethoxam by Actinobacteria strains was reported for the first time in this study. These strains are promising for use in bioremediation of ecosystems polluted by this type of pesticides.

Application of a fluidized three-dimensional electrochemical reactor with Ti/SnO2-Sb/β-PbO2 anode and granular activated carbon particles for degradation and mineralization of 2,4-dichlorophenol: Process optimization and degradation pathway

A three-dimensional electrochemical reactor with Ti/SnO₂-Sb/β-PbO₂ anode and granular activated carbon (3DER-GAC) particle electrodes were used for degradation of 2,4-dichlorophenol (2,4-DCP). Process modeling and optimization were performed using an orthogonal central composite design (OCCD) and genetic algorithm (GA), respectively. Ti/SnO₂-Sb/β-PbO₂ anode was prepared by electrochemical deposition method and then its properties were studied by FESEM, EDX, XRD, Linear sweep voltammetry and accelerated lifetime test techniques. The results showed that lead oxide was precipitated as highly compact pyramidal clusters in the form of β-PbO₂ on the electrode surface. In addition, the prepared anode had high stability (170 h) and oxygen evolution potential (2.32 V). A robust quadratic model (p-value < 0.0001 and R² > 0.99) was developed to predict the 2,4-DCP removal efficiency in the 3DER-GAC system. Under optimal conditions (pH = 4.98, Na₂SO₄ concentration = 0.07 M, current density = 35 mA cm^-2, GAC amount = 25 g and reaction time = 50 min), the removal efficiency of 2,4-DCP in the 3DER-GAC system and the separate electrochemical degradation process (without GAC particle electrode) were 99.8 and 71%, respectively. At a reaction time of 80 min, the TOC removal efficiencies in the 3DER-GAC and the separate electrochemical degradation system were 100 and 57.5%, respectively. Accordingly, the energy consumed in these two systems was calculated to be 0.81 and 1.57 kWh g^-1 TOC, respectively. Based on the results of LC-MS analysis, possible degradation pathways of 2,4-DCP were proposed. Trimerization and ring opening reactions were the two dominant mechanisms in 2,4-DCP degradation.

A new Rhodococcus aetherivorans strain isolated from lubricant-contaminated soil as a prospective phenol-biodegrading agent

Microbe-based decontamination of phenol-polluted environments has significant advantages over physical and chemical approaches by being relatively cheaper and ensuring complete phenol degradation. There is a need to search for commercially prospective bacterial strains that are resistant to phenol and other co-pollutants, e.g. oil hydrocarbons, in contaminated environments, and able to carry out efficient phenol biodegradation at a variable range of concentrations. This research characterizes the phenol-biodegrading ability of a new actinobacteria strain isolated from a lubricant-contaminated soil environment. Phenotypic and phylogenetic analyses showed that the novel strain UCM Ac-603 belonged to the species Rhodococcus aetherivorans, and phenol degrading ability was quantitatively characterized for the first time. R. aetherivorans UCM Ac-603 tolerated and assimilated phenol (100% of supplied concentration) and various hydrocarbons (56.2–94.4%) as sole carbon sources. Additional nutrient supplementation was not required for degradation and this organism could grow at a phenol concentration of 500 mg L⁻¹ without inhibition. Complete phenol assimilation occurred after 4 days at an initial concentration of 1750 mg L⁻¹ for freely-suspended cells and at 2000 mg L⁻¹ for vermiculite-immobilized cells: 99.9% assimilation of phenol was possible from a total concentration of 3000 mg L⁻¹ supplied at daily fractional phenol additions of 750 mg L⁻¹ over 4 days. In terms of phenol degradation rates, R. aetherivorans UCM Ac-602 showed efficient phenol degradation over a wide range of initial concentrations with the rates (e.g. 35.7 mg L⁻¹ h⁻¹ at 500 mg L⁻¹ phenol, and 18.2 mg L⁻¹ h⁻¹ at 1750 mg L⁻¹ phenol) significantly exceeding (1.2–5 times) reported data for almost all other phenol-assimilating bacteria. Such efficient phenol degradation ability compared to currently known strains and other beneficial characteristics of R. aetherivorans UCM Ac-602 suggest it is a promising candidate for bioremediation of phenol-contaminated environments.