The aim of this study was to evaluate the redox mediating capacity of anthraquinone-2,6-disulfonate (AQDS) immobilized on granular activated carbon (GAC) during the reductive decolorization of direct blue 71 (DB71) under microbial and chemical conditions. The immobilization of AQDS on GAC was conducted by adsorption, and it has obtained an uptake capacity of 0.227 mmol g⁻¹. The anchorage of AQDS on GAC improved its electron transfer capacity (ETC) up to 2.05 times higher than the raw material. Similarly, the addition of GAC-AQDS increased up to 1.75- and 1.16-fold the rate of decolorization (k d) of DB71 under microbial and chemical conditions, respectively, in comparison to the unmodified GAC. Surprisingly, a higher k d value was achieved in incubations without either GAC or GAC-AQDS because of the generation of aromatic amines, from the reduction DB71, taking into account that these species may act as a catalyst in the DB71 reduction process. In contrast, adsorption of aromatic amines on either GAC or GAC-AQDS decreased its redox mediating capacity as evidenced by spectrophotometric screenings of the decolorized solution and the supporting material. The development of materials with enhanced both redox and adsorption properties, as the GAC used in this study, offers a promising way to increase the redox conversion of recalcitrant pollutants commonly found in industrial wastewaters.

In the present paper, α-FeOOH and α-Fe(Al)OOH were prepared, and the adsorption of Cr(VI) on the two samples was investigated. The influence of pH, initial concentration, and some anions such as SO₄ ²⁻, H₂PO₄ ⁻, C₂O₄ ²⁻, CO₃ ²⁻, and SiO₃ ²⁻ on the adsorption of Cr(VI) on α-FeOOH and α-Fe(Al)OOH was studied by batch techniques. The results show that the adsorption capacity of Cr(VI) on α-Fe(Al)OOH increases with the introduction of aluminum, but decreases with the increase of pH. The adsorption irreversibility of Cr(VI) on α-Fe(Al)OOH is much higher than that on pure α-FeOOH. The adsorbed Cr(VI) species mainly exists in the form of *Fe(wk)-OHCrO₄ ²⁻ on the surface of the samples. With the presence of SiO₃ ²⁻, CO₃ ²⁻, C₂O₄ ²⁻, SO₄ ²⁻, and H₂PO₄ ⁻, the binding of Cr(VI) is inhibited by different degree. The inhibition of those anions is larger in the pure goethite than that in the Al-substituted goethite system. After Al was introduced into α-FeOOH, Cr(VI) ions are preferentially adsorbed on Al sites rather than Fe sites on α-Fe(Al)OOH.

A novel adsorbent was prepared by introducing xanthate group onto pristine multi-walled carbon nanotubes (MWCNTs) for removing Pb (II) from aqueous solution. The structure and property of xanthate-modified MWCNT (MWCNT-X) were detected by the technologies of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET). The investigation of various parameters, such as initial metal concentration, pH, contact time, and temperature, was taken to illustrate the adsorption behaviors of Pb (II) on MWCNT-X. Based on experimental data, Langmuir isotherm and pseudo-second-order kinetic provided a better correspondence to the adsorption process. The negative values of ΔG ᶿ and ΔH ᶿ indicated that the adsorption process is exothermic and spontaneous. Besides, the maximum uptake of MWCNT-X reached to 83.01 mg/g, which was much higher than that of pristine MWCNT and hydroxylated MWCNT (MWCNT-OH). Thus, the MWCNT-X can be potentially applied in heavy metal treatment.

Effect of harvesting and hydraulic retention time (HRT) on the performance of a sequencing batch reactor (SBR), growing a green alga Botoryococcus braunii, was investigated. In this continuous tertiary treatment, relieving limitations of light, inorganic carbon, nitrogen, and phosphorous can make photoautotrophy active through the rapid fixation of the building blocks into microalgal biomass together with heterotrophy promoted by organics and self-shading effect. Analysis of the results reveals that the control over CO₂ supply and the extension of solid retention time (SRT) are the keys to maintaining higher biomass productivity and better treatability in the mixotrophic SBR. Among HRTs tested, the shortest HRT of 2 days could demonstrate the best removal efficiencies of ammonia (98.8%) and total phosphorus (96.2%) while keeping the highest specific growth rate of 0.23 day⁻¹. Those results provide understanding on the impact of settling sequence, which extends SRT to 5~7 days and prevents significant limitations of light and essential building blocks. With the interplay between photoautotrophic and heterotrophic metabolisms of microalgae, this study identifies how the mixotrophic SBR perform resource recovery during tertiary treatment of livestock wastewater, and how limitation is associated with the effluent quality in the SBR.

Imazethapyr and imazapic are widely used in South Brazil to control weeds in rice fields, mainly through agricultural aviation. The environmental legislation requires that agricultural aviation companies have environmental licensing, which implies that the effluent treatment system must be compliant with the regulations of the Brazilian Ministry of Agriculture, which advises the use of an ozone-based system. An evaluation of the efficiency of this system through the analysis of the content of imazethapyr and imazapic (from the herbicide Only®) in the treatment of effluent with two distinct rates of ozone (1.0 and 2.0 g O₃/h) was performed. It was found that for each tank wash is generated an average volume of 132 L of effluent (112 L of water plus 20 L of surplus diluted spray solution). After the treatment with 1.0 and 2.0 g O₃/h, imazethapyr concentration decreased − 92.4 and − 95.2%, respectively. For imazapic, the concentration in the washing effluent decreased − 69.1 and − 80.1%, respectively. The results indicate that the system was effective in the treatment of the effluent containing residues of the herbicide Only®.

Imazalil (IMZ) is a widely used fungicide for the post-harvest treatment of citrus, classified as “likely to be carcinogenic in humans” for EPA, that can be only partially removed by conventional biological treatment. Consequently, specific or combined processes should be applied to prevent its release to the environment. Biological treatment with adapted microorganism consortium, photo-Fenton, and coupled biological photo-Fenton processes were tested as alternatives for the purification of water containing high concentration of the fungicide and the coadjutants present in the commercial formulation. IMZ-resistant consortium with the capacity to degrade IMZ in the presence of a C-rich co-substrate was isolated from sludge coming from a fruit packaging company wastewater treatment plant. This consortium was adapted to resist and degrade the organics present in photo-Fenton-oxidized IMZ water solution. Bacteria colonies from the consortia were isolated and identified. The effect of H₂O₂ initial concentration and dosage on IMZ degradation rate, average oxidation state (AOS), organic acid concentration, oxidation, and mineralization percentage after photo-Fenton process was determined. The application of biological treatment to the oxidized solutions notably decreased the total organic carbon (TOC) in solution. The effect of the oxidation degree, limited by H₂O₂ concentration and dosage, on the percentage of mineralization obtained after the biological treatment was determined and explained in terms of changes in AOS. The concentration of H₂O₂ necessary to eliminate IMZ by photo-Fenton and to reduce TOC and chemical oxygen demand (COD) by biological treatment, in order to allow the release of the effluents to rivers with different flows, was estimated.

Tetrachlorobisphenol A (TCBPA) is a widely used flame retardant and a potential endocrine disruptor. We estimated the role of the microbial community in degradation of TCBPA in river sediment from the vicinity of an E-waste processing facility. The effects of different anaerobic conditions on degradation efficiency of TCBPA were investigated, and differences in bacterial communities among these conditions were analyzed by 16S ribosomal RNA (rRNA) gene sequencing. The most effective dechlorination of TCBPA occurred under methanogenic conditions followed by electron donor-enhanced conditions and sulfate-reducing conditions with initial sulfate concentrations of 1, 10, and 20 mM. The extent of TCBPA removal under these conditions mentioned above was 65, 44, 43, 23, and 23%, respectively. 16S rRNA gene sequence analysis indicated that five dominant genera in the phylum Chloroflexi and another five species of Bacteroidetes, Chlorobi, and Firmicutes in these five systems were largely involved in TCBPA dechlorination. The initial sample had a total relative abundance of autochtonous potential dechlorinating bacteria of 12%. After 160 days, these values increased to 29–43% under above conditions. Addition of TCBPA decreased bacterial diversity. Efficiency of TCBPA degradation depends on the abundance and metabolism of dechlorinating bacterial guilds. The effectiveness of dechlorinating microbes in degradation of TCBPA was reduced by high sulfate concentrations.

Phthalic acid esters (PAEs) is a class of refractory organic compounds, widely used as additives or plasticizers in plastic industry. PAEs are ubiquitous endocrine-disrupting pollutants and can be degraded by microorganisms. The present study described the assimilation of four PAE mixture (dimethyl, diethyl, dipropyl, and dibutyl phthalate) by two bacillus species: Bacillus thuringiensis and Bacillus cereus, isolated from different agricultural soil and their consortium. Among which, the optimal degradation of 82–96% was achieved by B. thuringiensis. This is the first report on the metabolic breakdown of four basic PAE mixture. The optimum conditions for biodegradation were found to be pH 7, temperature 30 °C, inoculum size 10 mL, and concentration 400 mg/L. Moreover, the respective biodegradation followed the first-order kinetic model. Our results proffered supplementary confirmation of the wide spectrum of PAE utilization by B. thuringiensis and suggest the possibility of applying it for the remediation of PAE contamination waste.

Endosulfan, an organochlorine pesticide, has been applied ubiquitously worldwide. However, endosulfan has been identified as a type of persistent organic pollutants (POPs), and its ecotoxicity has drawn attentions from scientists. The present study was implemented to examine the effects of endosulfan on the diversity and structure of soil microorganism communities. A control treatment and three concentrations (0.1, 1.0, and 10.0 mg/kg) were set up in laboratory experiments and sampled on days 7, 14, 21, and 28. The results revealed that the populations of bacteria and actinomycetes decreased significantly after 1.0 and 10.0 mg/kg treatments and that the soil microbial biomass carbon (MBC) was increased by endosulfan compared with the control. Terminal restriction fragment length polymorphism (T-RFLP) results revealed that the soil bacterial diversity was decreased by endosulfan and that the soil microbial community structure became unstable after endosulfan application. Moreover, the results of a 16S rRNA clone library revealed that the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Spirochaetes, and Firmicutes showed an obvious advantage and closely relative. In conclusion, the results of the present study indicated that 0.1–10.0 mg/kg endosulfan showed obvious influences on the diversity and structure of the soil microbial community.

Although phosphorus (P) enrichment alone or in combination with other nutrients such as nitrogen (N) and potassium (K) due to anthropogenic activities may modify the nutrient pools and nutrient elemental ratios of terrestrial ecosystems, few studies have revealed the global effects of P alone or in combination with N and K enrichment on terrestrial ecosystems. In this study, we conducted a meta-analysis of the impacts of P addition alone or in combination with N and K on the C, N, and P pools and C/N/P ratios of plants, soils, and microbial biomass in terrestrial ecosystems. The results suggest that the following changes occurred: (1) P addition resulted in a significantly larger plant C pool, which was further enhanced when extra N and K were added. (2) The soil and microbial biomass C pools and the plant, soil, and microbial biomass N pools were minimally affected by P addition at the global scale but were noticeably affected when N and K were simultaneously added. (3) The P pools of the plants, soil, and microbial biomass were significantly and consistently enhanced by the addition of P, NP, and NPK. (4) The plant C/N, N/P, and C/P ratios were significantly reduced when P was added, while the C/N/P ratios in the soil and microbial biomass were minimally affected. These results, which show the inconsistent responses of plant, soil, and microbial biomass nutrient pools and elemental ratios to P, NP, and NPK addition, improve our understanding of terrestrial ecosystem functions under global change scenarios.