Microbial desalination cells (MDCs) have been studied for contaminant removal from wastewater and salinity reduction in saline water. However, in an MDC wastewater treatment and desalination occurs in different streams, and high salinity of the treated wastewater creates challenges for wastewater reuse. Herein, a single-stream MDC (SMDC) with four chambers was developed for simultaneous organic removal and desalination in the same synthetic wastewater. This SMDC could achieve a desalination rate of 12.2–31.5 mg L⁻¹ h⁻¹ and remove more than 90 % of the organics and 75 % of NH₄⁺-N; the pH imbalance between the anode and cathode chambers was also reduced. Several strategies such as controlling catholyte pH, increasing influent COD concentration, adopting the batch mode, applying external voltage, and increasing the alkalinity of wastewater were investigated for improving the SMDC performance. Under a condition of 0.4 V external voltage, anolyte pH adjustment, and a batch mode, the SMDC decreased the wastewater salinity from 1.45 to below 0.75 mS cm⁻¹, which met the salinity standard of wastewater for irrigation. Those results encourage further development of the SMDC technology for sustainable wastewater treatment and reuse.

Acid drainage is an environmental liability that impacts the quality of surface waters. However, the precipitation of iron and aluminum oxy/hydroxides decreases the concentration of dissolved toxic metals (such as arsenic) in rivers that receive acid drainage. Additionally, hydrodynamic factors (e.g., flow velocity fields and mixing ratios) control incomplete chemical mixing. Despite the occurrence of incomplete mixing in streams, its role on the fate and transport of contaminants has not been explored. We analyzed these processes at the Azufre River (pH 2)–Caracarani River (pH 8.6) confluence, northern Chile. We performed cross-sectional measurements of pH, turbidity, and particle size distributions and sampled water and suspended solids to analyze iron, aluminum, and arsenic. To complement field measurements, mixing experiments and geochemical modeling were performed. We found that there were distinct mixing zones on the field that promoted the precipitation of iron phases (pH >3) or the precipitation of iron and aluminum phases (pH ∼5). While iron phases immobilized arsenic by sorption (up to 8700 mg kg⁻¹ of arsenic concentration in the solid phase), aluminum contributed to produce particles with the capacity to resist shear stress (strength factors ∼90 %). More than 50 % of the total arsenic was removed from the aqueous phase within 100 m from the junction point, suggesting settling of iron and aluminum particles. These results showed that incomplete mixing was a controlling factor in the fate and transport of arsenic. Fluvial confluences receiving acid drainage are natural reactors that can attenuate toxic metals. A better understanding of the chemical-hydrodynamic interactions in fluvial confluences can lead to new strategies for enhanced attenuation of toxic metals.

The study examined the individual and combined effects of potassium ferrate(VI) additions and freeze-thaw conditioning for the treatment and dewatering of sludge samples. The first part of the experiments, using primary sludge, compared potassium ferrate(VI) additions prior to freeze-thaw treatment (pretreatment) versus potassium ferrate(VI) additions following freeze-thaw treatment (posttreatment). A low dose (LD) of 1.0 g/L and a high dose (HD) of 10.0 g/L of potassium ferrate(VI) were evaluated along with a freezing temperature of −20 °C and freezing periods of 1, 8 and 15 days. Following the designated freezing period, the samples were removed from the freezer and thawed at room temperature for 12 h. The second part of the study, using anaerobically digested sludge, evaluated the effects of potassium ferrate(VI) pretreatment, using LD = 0.5 g/L and HD = 5.0 g/L, and used simulated drainage beds to separate meltwater from the sludge cake during the thawing period. The study demonstrated that stand-alone freeze-thaw can reduce faecal coliform by >3-log after being frozen for only 1 day, and pretreatment with potassium ferrate(VI) can be used to improve the effects of freeze-thaw on faecal coliform inactivation in sludge. Furthermore, the drainability of the sludge following freeze-thaw was not significantly deteriorated when potassium ferrate(VI) was added to the sludge prior to freezing, despite greater than fourfold increases in the concentrations of soluble proteins and soluble carbohydrates. The meltwater collected during the sludge thawing was approximately 85 % of the initial sludge volume. When 5 g/L of potassium ferrate(VI) was added to the sludge prior to freezing, the meltwater collected had <0.28 MPN/mL faecal coliform, the turbidity was <10 NTU and the pH was 9.1. Pretreatment with potassium ferrate(VI) also reduced the concentration of faecal coliform in the sludge cake, suggesting that freeze-thaw coupled with potassium ferrate(VI) additions can be used to stabilise sludge and reduce sludge volume.

The kinetic trend for Cu extraction from contaminated soil through ethylenediamine-N,N′-disuccinic acid (EDDS)-enhanced soil washing is investigated. Long-term tests are conducted over 96 h at five different values of EDDS-Cu (M) molar ratio (mol/mol) and five different values of liquid-to-soil (L/S) ratio (v/w). The overall Cu extraction efficiency at different M ratios ranges from ≃47 to ≃60 % as the ratio increases from stoichiometric values to EDDS excess (M = 50). An increase in the L/S ratio generally leads to the Cu extraction efficiency decrease, from ≃60 % (L/S = 5) to ≃49 % (L/S = 45). The highest decrease of Cu extraction yield is observed while increasing the L/S ratio from 5 to 15, with negligible differences occurring as the L/S ratio increases further. The collected data show a two-step kinetic tendency during the extraction process, first characterized by a fast extraction kinetic which is followed by a slow extraction step. Two sets of experimental data are used for calibration and validation of a two-step mathematical model used to simulate Cu mobilization efficiency as a function of treatment time and M ratio. The proposed model is a useful tool for Cu extraction efficiency prediction and can be applied to improve the decision-making process regarding the EDDS-enhanced soil washing approach.

Herein, an efficient nano TiO₂-functionalized graphene oxide nanocomposite photocatalyst was readily prepared, using an ordinary solvothermal technique. It was noted that the as-prepared nanocomposite yielded a quadruple degradation capacity of the previously reported P25-graphene composite photocatalyst towards methylene blue (MB). To elucidate this, the Brunauer–Emmett–Teller (BET)-specific surface area, conductivity, and water contact angle measurements were all carried out. It was found out that graphene oxide was endowed with nontrivial photocatalytic activity by increasing its content in the nanocomposite (from 1/100 to 1/9, with respect to the dosage of nano TiO₂). Overall, the nano TiO₂-functionalized graphene oxide nanocomposite is a promising candidate in applications of environment remediation.

Recently, persulfate (PS) has been applied to the oxidation of organic contaminants in wastewater, groundwater, and soil. However, PS requires activation by UV light, heat, transition metal, or pH control to be useful. In particular, transition metals are able to rapidly activate PS to sulfate radical. However, it is difficult to control the concentration of transition metal solution in an environmental setting. In this study, the potential of an electrochemical reaction using an iron anode to activate PS was investigated with phenol as a model contaminant. Based on Faraday’s law, Fe(II) generated by the electrochemical reaction was regularly supplied to the solution to activate PS to sulfate radical. The activation of PS was influenced by current intensity; however, excess Fe(II) decreased the oxidation rate of phenol because anodic oxidation-generated Fe(II) also scavenged sulfate radical. However, the electrochemical reaction using the iron anode could be readily controlled to supply an optimal amount of Fe(II) for activation of PS. Therefore, it is expected that this electrochemical process using an iron anode could be useful for the effective removal of phenol.

The previous studies indicated that Tychonema-like strains from Lake Erhai could release geosmin so that the species was listed as the potential harmful cyanobacteria influencing the drinking water safety around Lake Erhai. But, the dynamics and biological information of this species were too limited. In this study, the polyphasic approach was used to reveal its biological characterization and the dynamics in Lake Erhai. The characters of trichomes, including filaments with solitary or bundle state, reddish-brown or blue-green color, planktonic habitat, and presence of keritomized content, were examined by the microscopic method. The 16S rDNA sequences of these strains were used for phylogenetic analysis and molecular identification. The strains were morphologically classified as Tychonema bourrellyi, and geosmin and β-ionone were identified as the major volatile substances using gas chromatography–mass spectrometry (GC-MS) analysis. No strains of T. bourrellyi were found to produce microcystin by the HPLC and mcy gene approaches. Cell numbers at 12 sampling sites in Lake Erhai were shown as an average of 3 × 10⁴ cells L⁻¹ in 2009 and 2010. The obvious peaks occurred in July and August each year. This was the first report on occurrence of T. bourrellyi from outside of Europe, and T. bourrellyi was also a newly recorded species in China. Such a result demonstrated that T. bourrellyi could distribute extending from cold waters in North Europe to the warm waters in subtropical regions. It was interesting to observe the coincidence of the occurrence of T. bourrellyi with slightly eutrophicated waters since Lake Erhai had been regarded as an early phase of eutrophicated lake.

The Platanus fruit fibers (PFFs) with unique hollow tubular structures were successfully utilized in the preparation of an efficient oil sorbents for the first time by chemical modification with acetic anhydride. The structure and morphology of the pristine PFFs (p-PFFs) and acetylated PFFs (a-PFFs) were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The effects of acetic anhydride to PFFs ratio, catalyst concentration, reaction temperature, and time on the weight percent gain (WPG) and oil sorption capacity were particularly investigated in detail. The results showed the hydrophobic modification of p-PFFs contributed to the enhancement of the sorption capacity of a-PFFs for various oils and organic solvents. The sorption kinetic analysis indicated the oil sorption data were fitted well with a pseudo-second-order kinetic model. And the oil-filled a-PFFs exhibited high oil retention ability with less than 30 % of the sorbed oil lost after 2-h dripping. Moreover, a-PFFs showed little loss of initial sorption capacities after eight sorbing/desorbing cycles with the recovery of sorbents by n-hexane extraction. The natural renewable a-PFFs are proved to be a promising candidate for large-scale removal of spilled oils from water.

This study aims at understanding characteristics of current traffic pollution at roadsides and to assess the use of magnetic parameters for a cost-efficient monitoring concept. We conducted a systematic monitoring study of roadside pollution at three sites in southern Germany and one site at Lanzhou/China. For this purpose, we installed ground-based monitoring boxes filled with clean quartz sand at different distances (1, 2, and 4 m) from the road. Mass-specific magnetic susceptibility (χ), heavy metal (HM) contents, and polycyclic aromatic hydrocarbon (PAH) concentrations all showed decreasing values with distance to the roadside. The temporal variations over 2 years of monitoring reveal an overall increasing trend but differences in depth migration due to seasonal effects (i.e., precipitation). A magnetite-like phase turned out to be responsible for the enhancement of χ. Significant positive correlations between χ and total PAHs as well as HMs for the German sites suggest that χ—which can be measured fast and convenient—can be used as a proxy for traffic-derived PAH and HM pollution. However, in the much drier region of Lanzhou, the relationship of χ with HMs is much weaker, which might be caused by specific materials used in road construction and heavy vehicles. From the obtained results, we conclude that an appropriate roadside monitoring procedure based on magnetic signatures should best use a single thin (1–2 cm) layer of clean quartz sand protected against lateral material translocation.

Phytoextraction has been proposed as an alternative remediation technology for heavy metal contamination, and it is well known that chelators may alter the toxicity of heavy metals and the bioavailability in plants. Our previous work demonstrated that an adsorbent-column chromatography can effectively separate melanoidin-like product (MLP) from sugarcane molasses. The aim of this study was to examine the chelating property of MLP and to evaluate the facilitatory influence on the phytoextraction efficiency of Japanese radish. The result showed that MLP binds to all the metal ions examined and the binding capacity of MLP toward Cu²⁺ seems to be the highest among them. The metal detoxification by MLP followed the order of Pb²⁺ > Zn²⁺ > Ni²⁺ > Cu²⁺ > Fe²⁺ > Cd²⁺ > Co²⁺. Furthermore, in the phytoextraction experiment using copper sulfate, the application of MLP accelerated the detoxification of copper and the bioavailability in radish sprouts. Thus, these results suggest that MLP possesses the potential for an accelerator of phytoextraction in the copper-contaminated media.