Using an indoor microcosm assay, we analyzed the biodegradation of total petroleum hydrocarbons (TPHs) by autochthonous bacterial populations in mining soil in the presence of a surfactant (Tween 80). The kinetic behavior of TPH biodegradation involved fast and slow stages. Initially, heterotrophic and hydrocarbonoclastic bacteria increased in abundance by an order of magnitude, but both groups decreased to close to their initial population sizes by the end of experiment. The most efficient final biodegradation (61.5 %) was achieved using soil with 0.5 % added surfactant. Polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) were used to analyze changes in the bacterial community structure. During the fast biodegradation phase, bacterial species richness as indicated by DGGE profiles was reduced after long periods of TPH biodegradation with exposure to Tween 80. The distribution of families was modified, but no particular pattern could be identified. The main bacterial genera were Acinetobacter, Pedomicrobium, Halomonas, Rhizobium, Cryobacterium, Pseudomonas, Lysobacter, Thermomonas, and Stenotrophomonas. Acinetobacter exhibited the highest species richness and was the most abundant and persistent genus, followed by Pedomicrobium and Rhizobium. Decreasing TPH biodegradation can be attributed to a reduction in the microbial population and the disappearance of most of the initial bacterial genera. The correlation between TPH biodegradation and microbial population dynamics helps explain long bioremediation times and can facilitate actions for increasing bioremediation efficiency.

In this study, the genotoxic and histopathological effects of olive-mill wastewater (OMW) on the tissue cells of Lepomis gibbosus were investigated. The fish were caught from Topçam dam lake (Çine/Aydın) and were exposed to the wastewater in 50-L aquariums which contained 0.5 % OMW for 3–5 and 7 days. In genotoxic investigations, a statistically significant increase was observed in the frequency of micronuclei in the L. gibbosus in experimental groups. As a result of the exposure to OMW, histopathological findings which showed a parallel increase with the amount of exposure in the gill, liver and muscle tissues were determined. In the gills, disruption of lamellae shape, shortening and breakage of primary and secondary lamellae, fusion and branching, separation in the secondary lamellae epithelium, ballooning dilation, hyperplasia in support cells and increase in mucus cells were observed. In the parenchyma of the liver, a difference in local staining, focal necrosis, haemorrhaging in necrotic areas, oedema of blood vessels, expansion in sinusoids, congestion and dilation in portal veins, deterioration of vessel walls, cytoplasmic vacuolization in hepatocytes, pyknotic nuclei, decrease in glycogen storage in hepatocytes near the central vein and aggregates of melanomacrophages were also observed. The necrosis in muscle bundles, widespread oedema between myofibrils, degeneration and separation in some muscle groups, decrease in glycogen content, intramuscular oedema and atrophy in the myofibers were determined in the experimental groups.

Environmental pollution by pentachlorophenol (PCP) is a critical concern worldwide, and microbial bioremediation could constitute an ecologically friendly solution. The main objectives of this study were at first to clarify the factors, affecting the ability and efficiency of PCP biodegradation by the bacterium isolate P6, and secondly to optimize the condition of using P6 for PCP bioremediation. The PCP mineralizing bacterium was isolated from the contaminated forest soil of Tunisia, and it was identified as Citrobacter freundii (C. freundii), by using conventional and molecular characteristics. The HPLC and spectroscopic analysis were used to investigate the PCP degradation and the biomass formation by this isolate P6. The main results showed that P6 was able to degrade or to transform more than 98 % of 640 mg/l PCP afterwards 168 h in mineral salt medium (MSM). As well, the optimal aerobic growth conditions of P6 in MSM include essentially the range of pH (4 ≤ pH ≤ 9) and of temperature (25 °C < temperature < 30 °C). The addition of glucose as extra carbon sources has an effect to enhance the PCP biodegradation. On the other side, this isolate of C. freundii is capable to remove or transform around 95.33 % of PCP added in the sterilized soil suspension supplemented with PCP and adjusted to a final concentration of around 400 mg/l during 2 weeks of incubation at 25 °C. This last result argues in favor of the use of this strain P6 of C. freundii as a microbial tool of remediation of PCP-contaminated site.

The capacities of a biosurfactant producing and polycyclic aromatic hydrocarbon (PAH) utilizing bacterium, namely, strain 1C, isolated from an Algerian contaminated soil, were investigated. Strain 1C belonged to the Paenibacillus genus and was closely related to the specie Paenibacillus popilliae, with 16S rRNA gene sequence similarity of 98.4 %. It was able to produce biosurfactant using olive oil as substrate. The biosurfactant production was shown by surface tension (32.6 mN/m) after 24 h of incubation at 45 °C and 150 rpm. The biosurfactant(s) retained its properties during exposure to elevated temperatures (70 °C), relatively high salinity (20 % NaCl), and a wide range of pH values (2–10). The infrared spectroscopy (FTIR) revealed that its chemical structure belonged to lipopeptide class. The critical micelle concentration (CMC) of this biosurfactant was about 0.5 g/l with 29.4 mN/m. In addition, the surface active compound(s) produced by strain 1C enhanced PAH solubility and showed a significant antimicrobial activity against pathogens. In addition to its biosurfactant production, strain 1C was shown to be able to utilize PAHs as the sole carbon and energy sources. Strain 1C as hydrocarbonoclastic bacteria and its interesting surface active agent may be used for cleaning the environments polluted with polyaromatic hydrocarbons.

The aim of this study was to investigate the removal and recovery of hexavalent chromium (Cr(VI)) from industrial plating wastewater using anion exchanger Kanecaron SA fibers in batch systems. The surface morphology and physicochemical properties of the fiber were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), and Fourier transform infrared spectroscopy (FT-IR). The removal efficiency was affected by the solution pH and showed a plateau formation decreasing on both sides of pH 4. The Cr(VI) uptake on Kanecaron SA fibers was rapidly increased in the first 10 min, and the kinetic data fit well to the Elovich model. Isotherm model analysis demonstrates that the Redlich-Peterson model suitably describes the equilibrium data, and the maximum adsorption capacity (Q ₘ) from the Langmuir model was 87.366 mg/g for Cr(VI) in distilled water, 117.977 mg/g for total Cr, and 57.101 mg/g for Cr(VI) in wastewater. Additionally, the Cr(III) contained in the plating wastewater was removed by the Kanecaron SA fibers, while the other heavy metals were not removed. Thermodynamic analysis indicates that Cr(VI) adsorption to Kanecaron SA fibers decreased with increasing temperature from 10 to 50 °C, indicating the spontaneous and exothermic nature of the sorption process. The removal efficiency was maintained above 80 % during four regeneration cycles.

To improve the denitrification characteristics of anaerobic denitrifying bacteria and obviate the disadvantage of use of explosive hydrogen gas, tourmaline, a polar mineral, was added to the hydrogenotrophic denitrification system in this study. Microbial reduction of nitrate in the presence of tourmaline was evaluated to assess the promotion effect of tourmaline on nitrate biodegradation. The experiment results demonstrated that tourmaline speeded up the cultivation process of bacteria from 65 to 36 days. After domestication of the bacteria, nitrate (50 mg NO₃ ⁻–N L⁻¹) was completely removed within 3 days in the combined tourmaline–bacteria system, and the generated nitrite was also removed within 8 days. The reduction rate in this system is higher relative to that in the bacteria system alone. Efficient removal of nitrate by tourmaline-supported anaerobic bacteria (without external hydrogen input) indicated that tourmaline might act as the sole hydrogen donor to sustain autotrophic denitrification. Besides the production of hydrogen, the promoted activity of anaerobic denitrifying bacteria might be caused by the change of water properties, e.g., the pH of aqueous solutions was altered to about 8.0 and the oxidation–reduction potential decreased by 62 % in the tourmaline system. The distinctive effects of tourmaline on bacteria were related to its electric properties.

Escherichia coli (E. coli) contamination of groundwater (GW) and surface water (SW) occurs significantly through the subsurface from onsite wastewater treatment systems (OWTSs). However, E. coli transport in the subsurface remains inadequately characterized at the field scale, especially within the vadose zone. Therefore, the aim of this research is to investigate the impact of groundwater fluctuations (e.g., recharging, discharging conditions) and variable conditions in the vadose zone (e.g., pulses of E. coli flux) by characterizing E. coli fate and transport in a linked surface water-soil water-groundwater system (SW-SoW-GW). In particular, this study characterizes the impact of flow regimes on E. coli transport in the subsurface and evaluates the sensitivity of parameters that control the transport of E. coli in the SW-SoW-GW system. This study was conducted in Lake Granbury, which is an important water supply in north-central Texas providing water for over 250,000 people. Results showed that there was less removal of E. coli during groundwater recharge events as compared to GW discharge events. Also, groundwater and surface water systems largely control E. coli transport in the subsurface; however, temporal variability of E. coli can be explained by linking the SW-SoW-GW system. Moreover, sensitivity analysis revealed that saturated water content of the soil, total retention rate coefficient, and hydraulic conductivity are important parameters for E. coli transport in the subsurface.

The adsorption of ethyl acetate, a volatile organic compound, on activated carbons, synthesized from various precursors based on by-products and waste materials—polymer, biomass, coal tar pitch—was studied. The activated carbons were prepared by thermochemical treatment of the precursors, carbonization, and subsequent activation with water vapor. Surface and textural properties of obtained carbon adsorbents were characterized by low-temperature N₂ adsorption, Boehm’s method, etc. The activated carbons are distinguished by relatively high surface area and developed pore structure. The adsorption investigations were performed with water solutions of ethyl acetate, and the obtained results fit well the Langmuir model, as well as the Freundlich model. All activated carbons demonstrated considerably high adsorption capacity in the range 160–450 mg/g. The obtained data indicate that the adsorption ability of activated carbon toward ethyl acetate depends on the surface area, and it increases with increasing the content of mesopores, where ethyl acetate molecules are preferably adsorbed.

Seven full-scale wastewater treatment plants were investigated to highlight the effectiveness of each treatment stage on removing Escherichia coli. The primary sedimentation achieved an average E. coli removal efficiency of 30.5% which was much lower than the suspended solids (58%), thus, revealing the absence of a linear relationship between the two parameters. Biological processes proved to be very important in the removal of E. coli through adsorption inside the sludge flocs and complex decay (mortality). In biological processes with a long retention time, such as activated sludge denitrification-nitrification, the decay was very important, whereas in the more traditional activated sludge process, without nitrification, the contribution of adsorption and mortality was quite balanced. Overall, the mechanical-biological treatment achieved a removal efficiency of 91.8–96.5% depending on the process. Additional removal can be achieved by disinfection. The effectiveness of E. coli removal with sodium hypochlorite was strictly depended on the product of residual chlorine (C R) with the contact time (t). The experimental curve fitted the Collins model well, with a standard deviation of less than 7%.

Carbamazepine is one of the pharmaceutical compounds frequently detected in the receiving waters and water bodies. The main objective of this study was to develop a quadratic model to predict carbamazepine (CBZ) photocatalytic removal through a response surface methodology. A factorial plan (linear model; 2⁴ experiments) was used to determine the contribution of individual factors (pH, CBZ concentration, photocatalyst concentration, and treatment time) and interactions among the factors. Pollutant concentration and treatment time were found to be the most important parameters influencing the oxidation rate, with respective contributions of 19.22 and 71.55 %. Central composite methodology was then applied to determine the optimal experimental parameters for CBZ oxidation. The highest percentage of CBZ removed was 94.67 ± 0.51 %, recorded using a pH of 5, a minimal CBZ concentration of 10 mg/L, a photocatalyst concentration of 1.14 g/L, and a treatment time of 90 min. The effects of different anions (NO₃ ⁻ and SO₄ ²⁻) and cations (Cu²⁺, Cr³⁺, Zn²⁺) were also studied. Copper was found to have both catalytic and inhibitory effects on CBZ removal rate.