Initial Pentachlorophenol Concentration Research Articles

Pentachlorophenol degradation in the heterogeneous catalytic o zonation process using Al2O3as a catalyst agent

In this study, the catalytic ozonation of pentachlorophenol (PCP) in the presence of aluminum oxide (Al2O3) and the formation of byproducts during ozonationhas been studied. Results showed that catalytic ozonation in the presence of Al2O3 can substantially enhance PCP degradation efficiency compared with the using only ozonation process. The influences of severalenvironmental parameters including pH of the solution, initial PCP concentration, dosage of Al2O3 and dissolved ozone concentration were also investigated. The highest degradation efficiency of PCP was achieved at conditions: pH 8, 1.87 g/LAl2O3, and 0.49 g/L dissolved ozone concentration. The catalytic activity of Al2O3 was linked to highly hydroxylated surface. The surface hydroxyl groups on Al2O3 were the active places during catalytic ozonation. According to the drastic changes in the color of solution during ozonationin this study and results of some previous researches, formation of the intermediate reaction products during ozonationwas verified.Free chloride ion released, which was favored at slightly alkaline solution, was also followed in catalytic ozonation process.

Pentachlorophenol degradation in the heterogeneous catalytic o zonation process using Al2O3as a catalyst agent

In this study, the catalytic ozonation of pentachlorophenol (PCP) in the presence of aluminum oxide (Al2O3) and the formation of byproducts during ozonation has been studied. Results showed that catalytic ozonation in the presence of Al2O3 can substantially enhance PCP degradation efficiency compared with the using only ozonation process. The influences of several environmental parameters including pH of the solution, initial PCP concentration, dosage of Al2O3 and dissolved ozone concentration were also investigated. The highest degradation efficiency of PCP was achieved at conditions: pH 8, 1.87 g/LAl2O3, and 0.49 g/L dissolved ozone concentration. The catalytic activity of Al2O3 was linked to highly hydroxylase surface. The surface hydroxyl groups on Al2O3 were the active places during catalytic ozonation. According to the drastic changes in the color of solution during ozonation this study and results of some previous researches, formation of the intermediate reaction products during ozonation was verified. Free chloride ion released, which was favored at slightly alkaline solution, was also followed in catalytic ozonation process.

Mineralization, kinetics, and degradation pathway of pentachlorophenol degradation from aqueous media via persulfate/dithionite process

The applicability of the dithionite/persulfate (DTN/PS) process for the degradation of pentachlorophenol (PCP) as an organic contaminant from aqueous solutions was investigated. Effective operational parameters, including the initial PCP concentration (25, 50, 100, and 150 mg/L), PS concentration (5, 10, 15, and 20 mg/L), DTN concentration (2.5, 5, 7, and 10 mg/L), solution pH (5, 7, 9, and 11), and reaction time (3, 5, 7, and 10 min) were investigated. To identify the influences of experimental factors involved in PCP degradation, an experimental design based on an orthogonal array was proposed using the Taguchi method. Based on the results, 97.28% of the PCP was removed at the optimal conditions (initial concentration of 25 mg/L, Na-PS (sodium persulfate) concentration of 20 mg/L, Na-DTN (sodium dithionite) concentration of 10 mg/L, pH of 11, and reaction time of 10 min) in the DTN/PS process. Moreover, COD and TOC removal rates were 75.2% and 41% in the DTN/PS process, respectively. An analysis of variance (ANOVA) indicated that PS is the most effective agent in removing PCP in the DTN/PS process. The compounds of phenol, 3,4-dichlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, oxalic acid, propionic acid, tetrachloro-o-benzoquinone, and butanedioic acid were identified as intermediates.

Whole-genome sequencing, genome mining, metabolic reconstruction and evolution of pentachlorophenol and other xenobiotic degradation pathways in Bacillus tropicus strain AOA-CPS1.

A pentachlorophenol degrading bacterium was isolated from effluent of a wastewater treatment plant in Durban, South Africa, and identified as Bacillus tropicus strain AOA-CPS1 (BtAOA). The isolate degraded 29% of pentachlorophenol (PCP) within 9 days at an initial PCP concentration of 100 mg L-1 and 62% of PCP when the initial concentration was set at 350 mg L-1. The whole-genome of BtAOA was sequenced using Pacific Biosciences RS II sequencer with the Single Molecule, Real-Time (SMRT) Link (version 7.0.1.66975) and analysed using the HGAP4-de-novo assembly application. The contigs were annotated at NCBI, RASTtk and PROKKA prokaryotic genome annotation pipelines. The BtAOA genome is comprised of a 5,246,860-bp chromosome and a 58,449-bp plasmid with a GC content of 35.4%. The metabolic reconstruction for BtAOA showed that the organism has been naturally exposed to various chlorophenolic compounds including PCP and other xenobiotics. The chromosome encodes genes for core processes, stress response and PCP catabolic genes. Analogues of PCP catabolic gene (cpsBDCAE, and p450) sequences were identified from the NCBI annotation data, PCR-amplified from the whole genome of BtAOA, cloned into pET15b expression vector, overexpressed in E. coli BL21 (DE3) expression host, purified and characterized. Sequence mining and comparative analysis of the metabolic reconstruction of the BtAOA genome with closely related strains suggests that the operon encoding the first two enzymes in the PCP degradation pathway were acquired from a pre-existing pterin-carbinolamine dehydratase subsystem. The other two enzymes were recruited via horizontal gene transfer (HGT) from the pool of hypothetical proteins with no previous specific function, while the last enzyme was recruited from pre-existing enzymes from the TCA or serine-glyoxalase cycle via HGT events. This study provides a comprehensive understanding of the role of BtAOA in PCP degradation and its potential exploitation for bioremediation of other xenobiotic compounds.

Adsorption-photocatalytic processes for removal of pentachlorophenol contaminant using FeNi3/SiO2/ZnO magnetic nanocomposite under simulated solar light irradiation.

The adsorption followed by photocatalytic degradation process was examined for the pentachlorophenol (PCP) removal from aqueous solution. These processes were accomplished by using FeNi3/SiO2/ZnO magnetic nanocomposite as an adsorbent-photocatalytic agent and under the irradiation of solar light. The magnetic nanocomposite used was first synthesized and then was characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating-sample magnetometer (VSM), and X-ray diffraction (XRD) spectroscopy. The PCP removal efficiency was tested for various factors, including pH, PCP concentration, and nanocomposite dose at different contact times. The characterization results of TEM, FE-SEM, and VSM analysis showed that the synthesized nanoparticles are amorphous and tend to agglomerate due to their high super-paramagnetic property. In addition, the EDX technique showed that the Zn and O elements had the highest weight percent in the synthesized nanocomposite, respectively. On the other hand, XRD analysis revealed that the crystalline size of the nanoparticles was about 42 nm. The kinetic of PCP degradation followed the pseudo-first-order model with R2 = 0.978. According to the results of the isotherm study, the adsorption of PCP onto the nanoparticles followed the Freundlich model. The results of adsorption-photocatalytic degradation experiments showed that 100% removal of PCP was obtained at optimum conditions of pH = 3, nanocomposite dose = 0.5 g/L, contact time = 180 min, and initial PCP concentration of 10 mg/L. Through the results obtained from this study, the adsorption process followed by solar light photocatalytic degradation process using FeNi3/SiO2/ZnO magnetic nanocomposite is found to be an efficacious treatment method for the removal of PCP contaminant from water and wastewater.

Performance of photocatalytic ozonation process for pentachlorophenol (PCP) removal in aqueous solution using graphene-TiO2 nanocomposite (UV/G-TiO2/O3).

The aim of this study was to evaluate the efficiency of photocatalytic ozonation process using graphene-dioxide titanium nanocomposite in removing Pentachlorophenol (PCP) from aqueous solutions. In this study, nanocomposites with graphene to TiO2(G/T) ratios of 1:10 and 1:20 were synthesized by hydrothermal method, and its characteristics were assessed using various analyses, SEM, XRD, FTIR, TEM, BET and TGA. In this process, the effects of parameters including O3 concentration (0.25-1.25mg/L), nanocomposite concentration (50-500mg/L), initial PCP concentration (10-100mg/L), and time (10-60min), were studied. The results showed that PCP removal efficiency was increased by decreasing solute concentration. Increasing nanocomposite dose to 100mg/L was led to an increase in efficiency (99.1%), but then a decreasing trend was observed. Increasing the concentration of ozone, up to specific value, also enhanced the efficiency but then had a negative effect on process efficiency. Furthermore, the optimum ratio of the catalyst was determined to be 1:20. The highest efficiency of the process for initial pentachlorophenol concentration of 100mg/L was obtained 98.82% in optimum conditions (catalyst dose of 100mg/L and 60min). It is concluded that the photocatalytic ozonation process using graphene-dioxide titanium nanocomposite had the highest efficiency in removal and mineralization of PCP.

Pentachlorophenol biodegradation in two-phase bioreactors operated with absorptive polymers: Box-Behnken experimental design and optimization by response surface methodology

The biodegradation of pentachlorophenol (PCP), the most toxic among chlorophenols, was extensively investigated in solid-liquid two-phase bioreactors (according to Box-Behnken experimental design) to demonstrate the feasibility of this technological platform. Process performance optimization for the subsequent scale up was also performed. The process was catalysed by an acclimated microbial consortium and the partitioning phase consisted of Hytrel 8206 polymer. The virtuous combination of polymer uptake/release and microbial biodegradation allowed achieving practically complete biodegradation efficiencies and rates in the range of 4.0–7.8mg/(L h) for PCP concentrations up to 100mg/L far above those previously tested. Detected biodegradation rates are one order of magnitude higher than the ones reported for suspended biomass reactors. A regression model based on 3 independent variables (initial PCP and biomass concentration and polymer-to-water ratio) was formulated to predict the volumetric biodegradation rate. The significance of independent variables and their interactions was tested by the analysis of variance (ANOVA) with 95% confidence limit. The model resulted adequate and the polymer-to-water ratio was identified as the most significant factor affecting the system response. Maximization of the biodegradation rate has been achieved for PCP concentration of 100mg/L, biomass concentration of 1 gVSS/L and polymer-to-water ratio of 9%.

Removal of Potential Toxic Inorganic and Organic Compounds from Contaminated Soils by Alkaline Leaching with Surfactant

ABSTRACTThe objective of this study was to evaluate the influence of soil parameters (total inorganic and organic carbon, pH, particle size distribution, initial contaminant levels) on the performance of a leaching process to remove As, Cr, Cu, pentachlorophenol (PCP), and polychlorodibenzo-dioxins and furans (PCDD/F) from the fine fractions (< 0.250 mm) of various contaminated soils. The chemical treatment, including three leaching steps (pulp density (PD) = 10% (w.w−1), [BW] = 3% (w.w−1), [NaOH] = 0.85 M, retention time (t) = 2 h and temperature (T) = 80°C) followed by two rinsing steps (PD = 10% (w.w−1), T = 20°C, t = 15 min), was optimized in previous works. Five soil samples (S1 to S5 – from different location on the same industrial site) were used to study the effect of the initial contaminant levels. The results showed good performance of the leaching process used to simultaneously remove PCP (96–98%) and PCDD/F (57–81%). These results also highlighted that the initial concentration of PCP and PCDD/F slightly influenced the performance of the leaching process. Subsequently, this leaching process was applied to three different soils (F1 to F3). The results showed that this process was efficient in removing PCP (50–86%) and PCDD/F (41–45%) regardless of the nature of the soil studied. However, the results also showed that the organic matter content and the particle size slightly influenced the efficiency of the leaching process to remove PCP.

Pentachlorophenol Removal from Water by Soybean Peroxidase and Iron(II) Salts Concerted Action

Soybean peroxidase (SBP) has been employed for the treatment of aqueous solutions containing pentachlorophenol (PCP) in the presence of hydrogen peroxide at pH range 5–7. Reaction carried out with 1 mg/L of PCP, 4 mg/L of H2O2, and 1.3 × 10−9 M of SBP showed a fast initial elimination of PCP (ca. 30% in 20 min), but the reaction does not go beyond the removal of 50% of the initial concentration of PCP. Modification in SBP and PCP amounts did not change the reaction profile and higher amounts of H2O2 were detrimental for the reaction. Addition of Fe(II) to the system resulted in an acceleration of the process to reach nearly complete PCP removal at pH 5 or 6; this is more probably due to a synergetic effect of the enzymatic process and Fenton reaction. However, experiments developed in tap water resulted in a lower PCP elimination, but this inconvenience can be partly overcome by leaving the tap water overnight in an open vessel before reaction.

Degradation of Pentachlorophenol in Aqueous Solution by the UV/ZrO2/H2O2 Photocatalytic Process

Pentachlorophenol (PCP), which is one of the resistant phenolic compounds, has been classified in the category of EPA’s priority pollutants due to its high toxicity and carcinogenic potential. Therefore, its removal from water and wastewater is very important. Various methods have been studied for removing the compound, among which advanced oxidation processes (AOPs) have attracted much attention because of ease of application and high efficiency. Thus the aim of this study was to investigate the efficiency of the UV/ZrO2/H2O2 process, as an AOP, for PCP removal from aquatic environments. The effects of several parameters such as ultraviolet (UV) exposure time, initial PCP concentration, pH, concentration of zirconium dioxide (ZrO2) nanoparticles, and H2O2 concentration were studied. Kinetics of the reaction was also detected. The concentration of the stated materials in the samples was determined using a spectrophotometer at 500 nm. The results showed that the highest efficiency (approximately 100%) was reached at optimized conditions of pH 6, contact time of 30 minutes, initial PCP concentration of 20 mg/L, the nanoparticles concentration of 0.1 g/L and H2O2 concentration of 14.7 mM/L. Also, the process followed the first order kinetics reaction. The obtained results illustrated that the UV/ZrO2/H2O2 process has a high ability in removing PCP.

Development and application of Fe3O4–Pd nanospheres as catalyst for electrochemical-heterogeneous Fenton process

Fe3O4 nanospheres with uniformly distributed Pd nanoparticles (Fe3O4–Pd) were prepared and used to catalyze the electrochemical-heterogeneous Fenton (EC-HF) degradation of pentachlorophenol (PCP). Synthesis of the catalyst was confirmed by X-ray diffraction and high-resolution transmission electron microscopy/energy-dispersive X-ray spectroscopy. The catalytic performance of the developed catalyst was assessed and the roles of Pd in the mechanism of Fe ion leaching and PCP degradation enhancement were elucidated. The conditions of 5V, pH 2.3, and 288K gave a removal efficiency of 100% within 30min with the catalyst, compared with 17.2% for the EC process alone. Pd nanoparticles altered the Fe leaching mechanism and enhanced both homogeneous and heterogeneous Fenton reactions when they were loaded on the Fe3O4 surface. The effects of operating conditions such as applied potential, pH, catalyst dose, solution temperature and initial PCP concentration were investigated. The results showed that a higher applied potential and solution temperature favored larger kinetic constants, whereas kinetic constants decreased with increasing solution pH. As the initial PCP concentration increased, the initial degradation rate increased while the kinetic constant decreased. The optimal catalyst dose was 50ppm. In addition, the Fe3O4–Pd reusability was evaluated.

Simultaneous adsorption and dechlorination of pentachlorophenol from effluent by Ni–ZVI magnetic biochar composites synthesized from paper mill sludge

The Ni–zero-valent iron magnetic biochar composites (Ni–ZVI-MBC) were synthesized from paper mill sludge and used as an adsorbent for the removal of pentachlorophenol (PCP) from the synthetic and real paper mill effluent. The synthesized Ni–ZVI-MBC was characterized and analyzed for the stability of Ni and ZVI particles in the biochar matrix. The Ni–ZVI-MBC involves simultaneous adsorption and dechlorination mechanism resulting in higher PCP removal efficiency. The presence of Ni as a catalyst in Ni–ZVI-MBC enhances the dechlorination rate and the adsorption of PCP by preventing the accumulation of PCP in the biochar matrix. The effect of operating parameters (solution pH, Ni loading, initial PCP concentration in the solution and temperature) on adsorption and dechlorination efficiency was studied. The exhausted Ni–ZVI-MBCs were used for the brick formation and the bricks showed good compressive strength and negligible heavy metal and PCP leaching.

Catalytic ozonation of pentachlorophenol in aqueous solutions using granular activated carbon

The efficiency of granular activated carbon (GAC) was investigated in this study as a catalyst for the elimination of pentachlorophenol (PCP) from contaminated streams in a laboratory-scale semi-batch reactor. The influence of important parameters including solution pH (2–10), radical scavenger (tert-butanol, 0.04 mol/L), catalyst dosage (0.416–8.33 g/L), initial PCP concentration (100–1000 mg/L) and ozone flow rate (2.3–12 mg/min) was examined on the efficiency of the catalytic ozonation process (COP) in degradation and mineralization of PCP in aqueous solution. The experimental results showed that catalytic ozonation with GAC was most effective at pH of 8 with ozone flow rate of 12 mg/min and a GAC dosage of 2 g. Compared to the sole ozonation process (SOP), the removal levels of PCP and COP were, 98, and 79 %, respectively. The degradation rate of kinetics was also investigated. The results showed that using a GAC catalyst in the ozonation of PCP produced an 8.33-fold increase in rate kinetic compared to the SOP under optimum conditions. Tert-butanol alcohol (TBA) was used as a radical scavenger. The results demonstrated that COP was affected less by TBA than by SOP. These findings suggested that GAC acts as a suitable catalyst in COP to remove refractory pollutants from aqueous solution.

Pentachlorophenol (PCP) adsorption from aqueous solution by activated carbons prepared from corn wastes

Corn wastes generated from starch and glucose production industry were used for the preparation of activated carbons. The prepared activated carbons and a commercial activated carbon were evaluated for their capability of adsorbing pentachlorophenol (PCP) from aqueous solution. Batch adsorption experiments were performed under different operating conditions including pH (2–8), adsorbent dosage (0.5–4.0 g/l), initial PCP concentration (10–100 mg/l), contact time (30–300 min), and temperature (25–45 °C). The kinetics and equilibrium models describing the adsorption of PCP by the prepared adsorbents were obtained. The adsorption of PCP by corn waste-based adsorbents was found to follow the second-order kinetics and the Freundlich equilibrium models. The intraparticle diffusion mechanism was successfully fitted to the obtained experimental data. Thermodynamic studies indicated that the adsorption process was exothermic. The adsorbents surface characterization revealed the presence of many functional groups capable of binding the adsorbate molecules. The study results suggest the possible use of corn wastes as a starting material for the production of activated carbon, thus lowering the costs of wastewater treatment processes.

Long-Term Anaerobic Mineralization of Pentachlorophenol in a Continuous-Flow System Using Only Lactate as an External Nutrient

A simple anaerobic upflow column system (15 cm long, 5 cm inner diameter) for complete pentachlorophenol (PCP) mineralization has been established using a microbial consortium requiring only lactate as the external nutrient. With lactate as an electron donor, PCP was dechlorinated to 3-chlorophenol (3-CP) and phenol. The degradation of 3-CP and phenol proceeded without an external electron acceptor, indicating fermentative or syntrophic characteristics. A tracer experiment using (14)C-U-ring-labeled PCP confirmed the conversion of PCP into CO(2) (54.1%), CH(4) (48.1%), and biomass (0.6%). The nitrogen required for degradation was supplied by N(2)-fixation, evidenced from the nitrogen balance and an acetylene reduction assay. A 16S rRNA gene library analysis showed that bottom of the upflow column harbored the potential dechlorinators, Dehalobacter and Desulfitobacterium, and the phenol/3-CP fermentative or syntrophic degraders, Cryptanaerobacter and Syntrophus. The nitrogen-fixing facultative anaerobes, Rhizobiales, were detected in the top of the upflow column, with other possible nitrogen-fixers at both bottom and top of the upflow column. The mineralization rate reached 1.96 μmoles L(-1) d(-1) for 50 μM of the initial PCP concentration: one of the highest efficiencies reported. This compact anaerobic mineralization system requiring no external supply of an electron acceptor would be useful for the remediation of chlorinated aromatic compounds under anaerobic conditions.

Catalytic wet air oxidation of pentachlorophenol over Ru/ZrO2 and Ru/ZrSiO2 catalysts

ZrSiO2 and ZrO2 supports loaded with active component Ru were unprecedentedly evaluated in catalytic wet air oxidation reaction of pentachlorophenol (PCP). The study results showed that the specific surface area of ZrSiO2 which was prepared by high temperature aging method was much larger than that of ZrO2, and it performed a better catalytic activity in catalytic wet air oxidation after being loaded with Ru. When the initial concentration of PCP was 125mgL−1, PCP conversion reached 92% after 90min under the low temperature and pressure conditions of 180°C and 0.1MPa oxygen partial pressure. PCP conversion was increased by raising reaction temperature, increasing oxygen partial pressure, reducing the initial concentration of PCP and prolonging reaction time. The kinetics study of PCP in catalytic wet air oxidation showed that the catalytic wet air oxidation reaction of PCP obeyed first order kinetic model and its Arrhenius activation energy was 96.98kJmol−1. The main intermediates of PCP in CWAO were acetic acid, oxalic acid and chlorine ion.

Photocatalytic degradation kinetics and mechanism of pentachlorophenol based on Superoxide radicals

The micron grade multi-metal oxide bismuth silicate (Bii 2SiO 20, BSO) was prepared by the chemical solution decomposition technique. Photocatalytic degradation of pentachlorophenol (PCP) was investigated in the presence of BSO under xenon lamp irradiation. The reaction kinetics followed pseudo first-order and the degradation ratio achieved 99.1% after 120 min at an initial PCP concentration of 2.0 mg/L. The pH decreased from 6.2 to 4.6 and the dechlorination ratio was 68.4% after 120 min at an initial PCP concentration of 8.0 mg/L. The results of electron spin resonance showed that Superoxide radical (O 2 ·−) was largely responsible for the photocatalytic degradation of PCP. Interestingly, this result was different from that of previous photocatalytic reactions where valence band holes or hydroxyl radicals played the role of major oxidants. Some aromatic compounds and aliphatic carboxylic acids were determined by GC/MS as the reaction intermediates, which indicated that O 2 ·− can attack the bond between the carbon and chlorine atoms to form less chlorinated aromatic compounds. The aromatic compounds were further oxidized by O 2 ·− to generate aliphatic carboxylic acids which can be finally mineralized to CO 2 and H 2O.

Degradation of pentachlorophenol with the presence of fermentable and non-fermentable co-substrates in a microbial fuel cell

Pentachlorophenol (PCP) was more rapidly degraded in acetate and glucose-fed microbial fuel cells (MFCs) than in open circuit controls, with removal rates of 0.12±0.01mg/Lh (14.8±1.0mg/g-VSS-h) in acetate-fed, and 0.08±0.01mg/Lh (6.9±0.8mg/g-VSS-h) in glucose-fed MFCs, at an initial PCP concentration of 15mg/L. A PCP of 15mg/L had no effect on power generation from acetate but power production was decreased with glucose. Coulombic balances indicate the predominant product was electricity (16.1±0.3%) in PCP-acetate MFCs, and lactate (19.8±3.3%) in PCP-glucose MFCs. Current generation accelerated the removal of PCP and co-substrates, as well as the degradation products in both PCP-acetate and PCP-glucose reactors. While 2,3,4,5-tetrachlorophenol was present in both reactors, tetrachlorohydroquinone was only found in PCP-acetate MFCs. These results demonstrate PCP degradation and power production were affected by current generation and the type of electron donor provided.

Interactions of synthetic Fe(II)–Fe(III) green rusts with pentachlorophenol under various experimental conditions

Sorption of pentachlorophenol (PCP) to three different green rusts (GRs) was studied versus time and initial PCP concentration at neutral pH. A competitive adsorption occurred when salicylate or silicate was present in the reaction medium. The monitoring of chloride formation and PCP byproducts indicated the absence of any possible reductive pathway in the PCP removal. All solid characterization showed that the PCP sorption in the presence or absence of foreign ligands did not alter the GR structure. Addition of nitrate (weak oxidant) involved a gradual release of PCP in solution from the sorbent solid. This is probably due to the oxidative transformation of GR into magnetite that sorbs less PCP. However, reaction with a strong oxidant (H 2O 2) involved both dechlorination and mineralization of PCP via oxidation reaction. HPLC and ion chromatography analysis, TOC and dissolved iron measurements showed that PCP had been degraded by heterogeneous Fenton-like reaction. Both X-ray diffraction analysis and Raman spectroscopy showed that the oxidation of GR may lead to magnetite (Fe 3O 4) or goethite (α-FeOOH), depending on the oxidant type. As green rusts have considerable potential in environmental applications, the influence of naturally occurring ligands and/or oxidants on the reactivity of green rusts should be considered.

The Effect of Lignite and Comamonas testosteroni on Pentachlorophenol Biodegradation and Soil Ecotoxicity

Biodegradation of pentachlorophenol (PCP) in soil by autochthonous microflora and in soil bioaugmented by the bacterial strain Comamonas testosteroni CCM 7530 was studied. Subsequent addition of lignite, an abundant source of humic acids, has also been investigated as possible sorbent for PCP immobilization. Biodegradation of PCP and number of colony-forming units were determined in the three types of soil, haplic chernozem, haplic fluvisol, and haplic arenosol, freshly spiked with PCP and amended with tested sorbent. The enhancing effect of sorbent addition and bioaugmentation on PCP biodegradation depended mainly on the soil type and the initial PCP concentration. Microbial activity resulted in biotransformation of PCP into certain potentially toxic substances, probably lower chlorinated phenols that are more soluble than PCP, and therefore more toxic toward present biota. Therefore, it was necessary to monitor soil ecotoxicity during biodegradation. Addition of lignite resulted in a significant improvement of PCP biodegradation and led to a considerable decrease of soil toxicity especially in bioaugmented soils. The method could potentially serve as a promising technique in remediation technology for reducing high initial PCP content in contaminated soils.