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.

Forest is an important vegetation type on the globe, and clearcutting is the main forest management method. This paper presents a process-based model developed to project the impact of forest growth and clearcutting on dissolved organic carbon (DOC) and total mercury (THg) export from forest-dominated watersheds over two forest-growing cycles. The modelling of THg is based on the observation that THg export from terrestrial to aquatic ecosystems occurs with the binding and subsequent in-stream transport of THg by DOC. From the results generated with the integrated model, DOC and THg export follows two main trends; (i) a multiple-year trend, associated with forest harvesting and re-growth patterns over the lifetime of the forest, and (ii) an annual trend, associated with the seasonal dynamics in forest litter production and decomposition. During a forest rotation, DOC and THg concentration decreases following clearcutting, reaches a minimum at about 15 years after forest regeneration and then gradually increases with forest ageing. Large debris pools left on site following clearcutting can provide a significant pulse in DOC production and within-watershed THg export during the first 2–3 years after harvest. In a single year, the integrated model predicts that DOC- and THg-concentration peaks after leaf fall in autumn, decreases to a minimum in April, increases to another maximum in June and finally decreases to a second minimum just before leaf fall. This seasonal cycle is repeated every year. Conifer species and wetland-dominated watersheds are anticipated to release a greater amount of DOC and THg to aquatic ecosystems than deciduous and dryland-dominated watersheds. The long-term and seasonal DOC production is consistent with field measurements.

Intermediate products from anaerobic fermentation, such as volatile fatty acids (VFA), are the preferred carbon sources for the production of added-value products, namely polyhydroxyalkanoates (PHA) or bioenergy. Organic fraction of municipal solid waste (OFMSW) can be valorized through the application of a hydrolytic-acidogenic stage, thus reducing its pollutant content and at the same time that it is obtaining high-value products (VFA). In this work, the anaerobic fermentation of OFMSW into VFA (production and profile) and the influence of both total solids (TS) content in the reactor and alkalinity addition were studied. The increase on TS content led to a decrease on the acidification degree whereas the increase on the alkalinity addition led to a higher degree of acidification. Hence, the highest degree of acidification (77.59 %) was obtained at the lowest TS content (5 %) and at the highest alkalinity addition (50 g CaCO3 L⁻¹). However, depending on the ultimate use of the produced VFA, the acidified residue presenting the highest VFA content (98.96 %) with higher propionic acid concentration, which is a more suitable VFA mixture for the production of high-quality PHA, was obtained at an intermediate TS content (8 %). From the response surfaces obtained, it was observed that all response variables (VFA production, degree of acidification, and effluent quality) presented a higher dependency on TS content than on initial alkalinity addition.

In this study, adsorption and biodegradation were exploited sequentially to remove the herbicide fenuron, the insecticide carbaryl and the estrogens 17β-estradiol (E2) and 4-tert-octylphenol (OP) from a municipal landfill leachate (MuLL). In the first step, we used spent coffee grounds, almond shells, a biochar and potato dextrose agar to adsorb the compounds spiked in MuLL at a concentration of 1 mg L⁻¹. After only 3 days, any adsorbent removed from MuLL the totality of E2 and OP, averagely more than 95 % of carbaryl and 62 % of fenuron (81 % after 7 days). In the second step, the adsorbents collected from MuLL after 7 days were inoculated with the fungi Bjerkandera adusta and Irpex lacteus, separately. After 7 days, the maximum degradation occurred for OP in any treatment being averagely 78 and 74 % using B. adusta and I. lacteus, respectively. After 15 days, the average percentages of fenuron, carbaryl, E2 and OP degraded were, respectively, 75, 76, 88 and 88 % using B. adusta, and 74, 79, 85 and 89 % using I. lacteus. Residual estrogenicity in the adsorbents, tested with the recombinant yeast assay, was strictly related to residual E2, thus indicating a negligible contribution from the other contaminants and/or degradation products. The 7-day treatment of MuLL with the adsorbents caused a significant abatement of MuLL phytotoxicity on flax (2.5 times seedling elongation with coffee grounds, compared to MuLL) and a huge stimulation of rapeseed respect to water (biomass almost doubled), thus suggesting a possible worthwhile recycling of this wastewater in agriculture.

Public concerns regarding the use of copper-based algaecide for controlling problematic algae may arise due to the risks it creates to non-target algae. To examine this concern, a series of comparative algal toxicity experiments were conducted to study effects of prokaryotic and eukaryotic algal cell densities on their responses to exposures of copper sulfate and copper-ethanolamine (Cu-EA). Microcystis aeruginosa and Pseudokirchneriella subcapitata were cultured separately in BG 11 medium to three initial cell densities (5 × 10⁴, 5 × 10⁵, and 5 × 10⁶ cells/mL). The 96-h EC₅₀ values of copper sulfate for M. aeruginosa at the three cell densities were 9, 63, and 112 μg Cu/L, respectively; and were 192, 1873, and 4619 μg Cu/L for P. subcapitata. The 96-h EC₅₀ values of Cu-EA were 101 and 2579 μg Cu/L for M. aeruginosa and P. subcapitata at 10⁶ cells/mL. The margin of safety (MOS) for P. subcapitata at 10⁴ cells/mL was 1.3, 0.9, and 0.8 when M. aeruginosa cell density was 10⁴, 10⁵, and 10⁶ cells/mL. This laboratory study suggests that applying copper-based algaecides to control problematic algae at a relatively low cell density would inhibit their growth with minimum impacts on non-target algae; risks to non-target algae would increase with increases of problematic algal cell density.

Fe₃O₄-CuO@montmorillonite was prepared using coprecipitation method, and its structure was determined by XRD, IR, and transmission electron micrograph (TEM). Montmorillonite in Fe₃O₄-CuO@montmorillonite nanocomposite allowed the silicate layer of montmorillonite to behave as a barrier, which prevented the agglomeration and natural crystallization of Fe₃O₄ and CuO. Furthermore, the chlorine dioxide (ClO₂) oxidative degradation of anthracene-contaminated soil was studied in detail using Fe₃O₄-CuO@montmorillonite as a magnetic heterogeneous catalyst. The operating parameters such as ClO₂ concentration, catalyst dosage, reaction time, and pH were evaluated. Compared with the conventional ClO₂ oxidation process without the catalyst, the ClO₂ catalytic oxidation system could significantly enhance the degradation efficiency. Under the optimal condition (anthracene concentration 89.8 mg/kg, water soil mass ratio 3:1, initial pH 7, ClO₂ concentration 1 mol/kg, catalyst dosage 1 g/kg, reaction time 30 min, and reaction temperature 25 °C), anthracene degradation efficiency achieved 96.2 %. The catalyst could be easily reused by magnetic separation and used at least 8 cycles without obvious loss of activity. The kinetic studies revealed that the ClO₂ catalytic oxidation degradation of anthracene-contaminated soil with Fe₃O₄-CuO@montmorillonite as catalyst followed pseudo-first-order kinetics with respect to ClO₂ concentration. Thus, this study showed potential application of ClO₂ catalytic oxidation process in remediation of organic pollutant-contaminated soil.

Wastewaters from civil and industrial use, which contain high concentration of heavy metals, pose the problem for their correct disposal. They cannot be directly discharged in sewage systems, as metal ions represent a serious problem not only for human health but also for the environment. In this paper, the removal of nickel, cobalt, chromium, and zinc ions from synthetic liquid wastes was carried out, by using a micellar-enhanced ultrafiltration (MEUF) process; an ultrafiltration (UF) membrane (a monotubular ceramic of molecular weight cutoff 210 kDa) together with sodium dodecyl sulfate (SDS) as an anionic surfactant was used, in a lab-scale experimental device. The synthetic liquid contained 10-mg/L metal ions (Cr, Zn, Co, Ni), while SDS concentration varied from values above and below critical micellar concentration (CMC). The experiments were carried out at room temperature (25 °C). Results achieved showed that SDS was able to bind metal ions, resulting in a strong increase of rejection coefficient, which reached highest values in case of SDS concentration below CMC, unexpectedly.

Due to their metal removal ability, bacterial biosorbents can be effectively used for the treatment of wastewaters containing heavy metals. Searching for bacterial biosorbents for hazardous heavy metals like cadmium is a pivotal for remediation efforts. The gene cadA, that mediates resistance to cadmium over an ATP-dependent efflux mechanism, provides a good target for the selection of potential cadmium biosorbents. For this reason, in this study, a 36-mer-oligonucleotide DNA probe based on the entire 3.5-kb BglII-XbaI fragment of cadA operon from staphylococcal plasmid pI258 was prepared by using Vector NTI Express software. Under the hybridization conditions of 46 °C, 50 % formamide, and 0.028 M NaCl, the designed cadA probe appeared to be highly specific to the cadA-positive Staphylococcus warneri and Delftia acidovorans isolates tested. The results indicated that the newly designed cadA-targeted DNA probe has potential as a specific, sensitive, and quantitative tool in selecting and in situ screening of potential cadmium biosorbents.

The As(V) extraction in the pH-dependent As(V)-Fe(III) precipitates and the corresponding interaction mechanism of As(V) with ferric iron coagulant were systematically investigated in this study. Generally, As(V) removal by coagulation was more susceptible to the influence of the solution pH than that of the coagulant dosage. There was a distinctively bell-shaped pattern for As(V) removal with increasing the solution pHᵢₙᵢ from 4.6 to 9.4 with varied mass ratios of Fe/As. Specifically, the removal efficiencies of As(V) were enhanced progressively with increasing pH from 4.6 to 6.2. However, As(V) removal declined appreciably as pH further increased to 9.4. The maximum uptake capacities of As(V) by the precipitates were 1.21, 1.10, and 0.95 mg As per mg Fe at pHᵢₙᵢ 6.2 with the Fe/As mass ratio of 0.6, 0.8, and 1.0, respectively. Approximately 99 % of sorbed amorphous hydrous and crystalline hydrous oxide-bound As(V) were extracted in bearing-As(V) precipitates at relevant pHᵢₙᵢ values (i.e., 5.0, 7.0, and 9.0), implying that the main mechanism governing As(V) removal process was forming the inner sphere complexes, which can cause much more powerful forces than chemical compounds. Moreover, it has been accounted well with the performances of floc coagulation for As(V) removal evidenced by the characterizations of the floc size distribution, the floc fractal dimension, and the Fourier transform infrared spectroscopy (FT-IR) spectra, respectively. Considering that As extraction can provide insights for understanding As speciation and mobility in settled precipitates, this study will definitely count much in predicting the long-term risks of As-Fe sediments to the natural environment.

Porous asphalt (PA), porous concrete (PC), and permeable inter-locking pavers (PICP) with sub-surface layers consisting of different gravel sizes (63, 40, and 12 mm) commonly used in the bedding, base, and sub-base layers of permeable pavements were investigated for their ability to remove total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN). The investigation focused on the individual surface and sub-surface layers of the three permeable pavements to “treat” these pollutants and how the physical design of these layers influences their water quality treatment performance. This assessment was conducted with a laboratory study, but performances were also compared to data obtained from a field-scale study of pollutant removal in PA, PC, and PICP. Pollutant removal by a sub-surface layer and the particle size distribution of outflow are dependent on both the thickness of the layer and the gravel size. Superior performance in removing pollutants was found in PC’s surface layer compared to the surface layers of PA and PICP. The lab-scale pavements and the field-scale pavements have similar performance in removing pollutants for TSS (87–95 %) and TP (75–89 %) but not for TN (3–10 % for lab-scale and 2–40 % for field-scale pavements). A simple mathematical model based on these results was developed to provide estimates of performance in the field.