Fe₂O₃/γ-Al₂O₃catalysts were prepared using the wet impregnation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption. The continuous catalytic wet hydrogen peroxide oxidation of an aqueous phenol solution over Fe₂O₃/γ-Al₂O₃was studied in a fixed-bed reactor. The effects of several factors, such as the weight hourly space velocity (WHSV), particle size, reaction temperature, H₂O₂concentration, and initial pH, were studied to optimize the operation conditions for phenol mineralization. For a 1 g L⁻¹phenolic aqueous solution, the phenol was nearly completely removed and chemical oxygen demand (COD) removal was approximately 92 % at steady-state conditions with a WHSV of 2.4 × 10⁻² gPₕOH h⁻¹ gcₐₜ⁻¹at 80 °C with 5.1 g L⁻¹H₂O₂. The long-term stability of the Fe₂O₃/γ-Al₂O₃catalyst was also investigated for the continuous treatment of phenolic water. The removal of phenol and COD exhibited a slowly decreasing trend, which was primarily due to the complexation of active sites with acid organic compounds and the adsorption of intermediate products. The deposition of organic carbon and Fe leached from the catalyst had a small role in the partial deactivation of the catalyst. The Fe leached from the catalyst partially contributed to the phenol removal during a short run. However, this contribution could be neglected after 36 h because the Fe leached from the catalyst decreased to approximately 5 mg L⁻¹.

Methane production by methanogenic microbes under anaerobic condition is affected by the types of fertilizers, which determine carbon availability, used in rice fields. In addition, irrigation management controls oxygen availability in soil. Thus, irrigation management and types of fertilizers are major driving forces for methane emission in rice fields. While these factors affect paddy microbial communities over the course of cultivation, little is known about the effects of fertilizers and irrigation conditions on initial paddy microbial communities. In this study, we investigated the initial impacts of fertilizers and irrigation systems on paddy microbial communities and methane emission. At early stages of rice cultivation (2 weeks after transplanting 15-day-old rice seedlings), a high amount of methane was emitted from rice fertilized with swine manure. In addition, pre-transplantation flooding increased methane emission by 30 %. Although these conditions did not affect the overall paddy soil microbial communities, 126 operational taxonomic units (OTUs) were found to be significantly more abundant in paddy soils fertilized with swine manure. These OTUs included archaeal methanogenic species and bacterial substrate providers for biomethane production. Shared-OTU analysis with swine fecal microbial communities indicated swine manure as the origin of key methane-producing microbes. In conclusion, the applications of swine manure and permanent flooding irrigation introduce active methane producers and enhance methane emission, respectively, and should therefore be avoided.

The cyanobacterial bloom in water has adversely affected water quality, local economies, and human health. Therefore, the removal and restricting the growth of harmful algae are of particular interest. In this study, ZnO–montmorillonite that could flocculate and restrict the growth of Microcystis aeruginosa, used as a probe of cyanobacterial, was prepared by hydrothermal solution intercalation method and characterized by means of XRD, IR, and TEM. In ZnO–montmorillonite, ZnO nanoparticles were either embedded in the interlayer space of montmorillonite or dispersed on montmorillonite surface. The determinations of chlorophyll a levels, total soluble protein content, and malondialdehyde concentration demonstrated that ZnO–montmorillonite had stronger flocculation effect on M. aeruginosa compared with natural montmorillonite and ZnO under visible light and had a better photocatalytic degradation effect on M. aeruginosa than ZnO under UV irradiation after 1 h. Under UV, 95 % removal efficiency was achieved for M. aeruginosa in 1 h using 50 mg L⁻¹ZnO–montmorillonite, and the proliferation of M. aeruginosa was totally inhibited due to the high photocatalytic activity and absorption flocculation ability of ZnO–montmorillonite. Furthermore, the cell structure was irreversibly damaged and the cell lysed. The synergy of absorption flocculation and photocatalysis of ZnO–montmorillonite promoted the removal of M. aeruginosa.

The ability of untreated and acid-treated biomass from Pistia stratiotes (PL and APL, respectively) and Eichhornia crassipes (ELS and AELS, respectively) to remove color from anaerobically digested sugar cane stillage (ADS) was investigated. The effects of pH (3–8), particle size (< 0.75, 0.75–1, 1–4 mm), and biomass concentration (5–15 g/L) on decolorization of ADS were assessed using untreated biomass. After acid modification of biomass (acid-treated), the effects of pH (3–8), biomass concentration (6–10 g/L), time (20–480 min), and ADS dilution (non-diluted, 1:2, 1:10, 1:20) on color removal from ADS were evaluated. Scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR) analyses were also performed. A clear effect of particle size on ADS decolorization was found (21.04 ± 0.75 and 27.87 ± 0.30 % for 0.75–1 and <0.75 mm, respectively, for ELS; 31.65 ± 0.23 and 37.82 ± 0.53 for 1–4 and 0.75–1 mm, respectively, for PL). Decolorization also increased when the untreated biomass concentration was higher (15.41 ± 0.3 and 27.89 ± 0.2 % for 5 and 10 g/L, respectively, for ELS; 15.61 ± 0.11 and 33.06 ± 1.09 % for 5 and 10 g/L, respectively, for PL). The use of acid-treated biomass enhanced the effect of pH on color removal (48.30 ± 1.27 and 12.96 ± 0.27 % for pH of 3 and 7, respectively, for AELS; 47.11 ± 1.72 and 6.62 ± 0.21 % for pH of 3 and 7, respectively, for APL). The highest rate of color removal obtained using acid-treated biomass was 55.58 ± 1.82 and 56 ± 0.77 % for AELS and APL, respectively. The FTIR spectra analysis suggested the electrostatic attraction between protonated carboxylic groups on biomass and anionic colored compounds as being one of the adsorption mechanisms for ADS decolorization. The use of dry biomass from invasive macrophytes is an effective alternative for color removal from ADS.

This study aimed to decolourise different dyes using two Klebsiella strains (Bz4 and Rz7) in different concentrations and incubation conditions. Azo (Evans blue (EB)) and triphenylmethane (brilliant green (BG)) dyes were used individually and in mixture. The toxicity of the biotransformation products was estimated. Both strains had a significant potential to decolourise the dyes in the fluorone, azo and triphenylmethane classes. The type and concentration of dye affects the decolourisation effectiveness. Differences in the dye removal potential were observed particularly in the main experiment. The best results were obtained for Bz4 in the samples with EB (up to 95.4 %) and dye mixture (up to 99 %) and for Rz7 with BG (100 %). The living and dead biomass of the strain Bz4 highly absorbs the dyes. Significant effect of the process conditions was noticed for both strains. The best results were obtained in static and semistatic samples (89–99 %) for the removal of EB and a mixture of dyes and in static samples (100 %) for BG. The decrease in zootoxicity (from class IV/V) was noticed in all samples with living biomass of the strain Bz4 (to class III/IV) and in samples with single dyes for Rz7 (to class III/IV). The decrease in phytotoxicity (from class III/IV) was noticed for Bz4 in the samples with BG and a mixture (to class III) and for Rz7 in the samples with BG (to class III). The process conditions did not affect the changes in toxicity after the process.

Dielectric barrier discharges (DBDs) were utilized for the remediation of soil contaminated with p-nitrophenol (PNP). The effect of treatment time, applied discharge voltage, initial PNP concentration, pH of contaminated soil, and airflow rate were investigated in this study. The results showed that 63.2 % of the PNP in the contaminated soil was degraded in 50 min with a voltage of 38.2 kV with no airflow. This degradation reaction followed the first order reaction kinetics. The degradation by ozone alone was compared with the plasma treatment to identify the role of ozone. Chromatographic analysis was applied to monitor the intermediates produced during the oxidation process, and the main byproducts were maleic acid, p-benzoquinone, 4-nitrocatechol, methanoic acid, acetic acid, oxalic acid, NO₂ ⁻, and NO₃ ⁻. Possible pathways for the degradation of PNP in this system were deduced, which would provide evidence for the researches about the remediation of soils polluted by organic pollutants.

Grass from municipal roadside verges is a potential yet largely unused resource for bioenergy recovery, which is mainly due to its unknown elemental composition. Therefore, we measured the concentration of 16 elements (Ca, K, Mg, N, Na, P, S, Al, Cd, Cl, Cr, Cu, Mn, Pb, Si and Zn) in a material from the city of Kassel harvested in different management intensities. The element concentrations were mainly close to reference values of agricultural or nature conservation grassland and usually within the range of literature data. Concentrations of most elements, including heavy metals, were below limiting values. Only N and Cl concentrations in the raw material exceeded the limiting values for combustion, but washing and dewatering of the biomass with the “integrated generation of solid fuel and biogas from biomass” technique resulted in concentrations in the press cake well below the limiting values. Considering the element concentrations of grass from urban roadside verges, utilisation for energy recovery may be possible, provided an appropriate technology is applied.

Leachate from unlined or leaky landfills can create groundwater contaminant plumes that last decades to centuries. Understanding the dynamics of leachate movement in space and time is essential for monitoring, planning and management, and assessment of risk to groundwater and surface-water resources. Over a 23.4-year period (1986–2010), the spatial extent of the Norman Landfill leachate plume increased at a rate of 7800 m²/year and expanded by 878 %, from an area of 20,800 m²in 1986 to 203,400 m²in 2010. A linear plume velocity of 40.2 m/year was calculated that compared favorably to a groundwater-seepage velocity of 55.2 m/year. Plume-scale hydraulic conductivity values representative of actual hydrogeological conditions in the alluvium ranged from 7.0 × 10⁻⁵to 7.5 × 10⁻⁴ m/s, with a median of 2.0 × 10⁻⁴ m/s. Analyses of field-measured and calculated plume-scale hydraulic conductivity distributions indicate that the upper percentiles of field-measured values should be considered to assess rates of plume-scale migration, spreading, and biodegradation. A pattern of increasing Cl⁻concentrations during dry periods and decreasing Cl⁻concentrations during wet periods was observed in groundwater beneath the landfill. The opposite occurred in groundwater downgradient from the landfill; that is, Cl⁻concentrations in groundwater downgradient from the landfill decreased during dry periods and increased during wet periods. This pattern of changing Cl⁻concentrations in response to wet and dry periods indicates that the landfill retains or absorbs leachate during dry periods and produces lower concentrated leachate downgradient. During wet periods, the landfill receives more recharge which dilutes leachate in the landfill but increases leachate migration from the landfill and produces a more concentrated contaminant plume. This approach of quantifying plume expansion, migration, and concentration during variable hydrologic conditions provides increased understanding of plume behavior and migration potential and may be applied at less monitored landfill sites to evaluate potential risks of contamination to downgradient receptors.

The phenolics and high organic content present in palm oil mill effluent are the major contributors to its dark brown color, toxicity, and antimicrobial properties. In this study, ten white rot fungi were screened for their potential in the dephenolization and decolorization of treated palm oil mill effluent (TPOME) in solid and liquid state cultures. Among them, Trametes hirsuta strain AK 04 was found to be more tolerant to high TPOME concentrations and showed the highest phenolics and color removal activities. This strain was immobilized onto oil palm fibers (OPFs) and appeared more resistant to inhibitory compounds such as phenolics in TPOME than the free cell culture. The OPF-immobilized fungus was able to effectively remove phenolics and color of TPOME without effluent dilution and addition of nutrients. The activities of laccase and manganese peroxidase were found during dephenolization and decolorization processes. Moreover, the degradation rate of immobilized fungus could be accelerated by pretreatment of phenolics with phenol-degrading bacteria. This method improved the fungal dephenolization and decolorization simultaneously up to 82.2 ± 3.8 % and 87.1 ± 1.1 % after 8 days of incubation. Therefore, a two-stage biological process containing phenol-degrading bacteria and OPF-immobilized fungus could be a feasible and economical method for simultaneous improvement of dephenolization and decolorization of TPOME.

Effects of pH, As species, and Fe/Mn minerals on the fractions of adsorbed As in aquifer sediments were evaluated. Kinetic data showed that As adsorption was controlled by diffusion through the external film. Isothermal data of both As(III) and As(V) fitted the Langmuir isotherm well, revealing a monolayer adsorption process. Sequential extraction demonstrated that water-soluble As and non-specifically sorbed As were the major fractions of adsorbed As. Assessing the relationship between the Freundlich K F and the increases in the amounts of As fractions showed that the pH played a key role in weakly adsorbed As, especially water-soluble As. Although inorganic As species converted each other during the adsorption processes, more non-specifically sorbed As was adsorbed in As(V)-treated sediment than in As(III)-treated sediment, showing that the electrostatic selectivity controlled the non-specific adsorption. Additionally, specifically sorbed As and As associated with the amorphous phases were predominated by Fe/Mn minerals, especially Fe(III) (hydr)oxides. These results suggested that pH, As species, and Fe/Mn minerals would regulate the As fractions in aquifer sediments, and therefore control As cycling in aquifer systems.