This work focuses on the performance of a primary facultative pond, in a full-scale waste stabilization pond system, located in a temperate climate region (average air temperature in winter, 7.7°C; spring and autumn, 14.0°C; and summer, 19.9°C) in Puerto Madryn city—Argentine Patagonia (42°45′S; 65°05′W). Experimental work was conducted for 43 months in seven sampling points. During the experimental time frame, the influent flow rate increased from 12,000 to 15,500 m3/day; the surface organic loading ranged from 55 to 68 kg BOD5/ha·day and the theoretical retention time decreased from 31 to 24 days. The results indicate that a primary facultative pond performing in this region, to keep predominant facultative conditions and acceptable filtered biochemical oxygen demand (BOD5) removal, should be loaded with an organic loading rate of up to 60 kg BOD5/ha·day. The flow and organic loading increase affected the ammonium removal process, extending the period time in which ammonium removal was less than 50% and nitrate was not detectable; at first, this period occurred during winter strictly and then covered part of autumn and part of spring, too. Ammonium removal was clearly temperature dependent and directly related to chlorophyll a and nitrate concentrations (i.e. higher ammonia removals were reported under summer conditions when chlorophyll a and nitrate concentrations were higher), but was not linked with high pH values. The ammonium volatilization as a predominant removal process could be discarded, while ammonium nitrification–denitrification and algal nitrogen uptake seems to be the dominant mechanisms.

To provide good quality of drinking water, a biological system to remove ammonium-nitrogen (NH₄-N) from groundwater was studied in this research. The NH₄-N removal system consists of two attached growth reactors: one for nitrification and the other for hydrogenotrophic denitrification (H. denitrification). The nitrification reactor, fed by the NH₄-N contained water, could remove NH₄-N without any need of aeration. The nitrification efficiency was increased by reactor length; the highest efficiency of 92 % was achieved at the longest reactor of 100 cm. A high Fe in groundwater affected the reactor performance by decreasing the efficiency, while a low inorganic carbon (IC) had no effects. Despite of good efficiency in terms of NH₄-N removal, the nitrification reactor increased the concentration of NO₃-N in its effluent. To treat the NO₃-N, a H. denitrification reactor was set up after the nitrification reactor. Efficiency of the H. denitrification reactor was enhanced by increasing H₂ flow rates. The efficiencies were 3, 27, and 90 % for 30, 50, and 70 mL/min of H₂ flow rates, respectively. It was also found that the NO₃-N contained water (water from the nitrification reactor) had to supply IC (i.e., NaHCO₃ or CO₂) for efficient H. denitrification; however, an on-site reactor showed that it can be achieved even without IC addition. The treated water contained low NH₄-N and NO₃-N of <1.5 and <11.3 mg/L, respectively, which comply with drinking water standards. The good performance of the reactors in terms of high efficiency, no aeration need, and low H₂ supply indicated appropriateness of the system for groundwater treatment.

Plant growth-promoting rhizobacteria (PGPR) play an important role in the biodegradation of natural and xenobiotic organic compounds in soil. They can also alter heavy metal bioavailability and contribute to phytoremediation in the presence or absence of synthetic metal chelating agents. In this study, the inhibitory effect of Cd2+ and Ni2+ at different concentrations of Ca2+ and Mg2+, and the influence of the widely used chelator EDTA on growth of the PGPR Pseudomonas brassicacearum in a mineral salt medium with a mixture of four main plant exudates (glucose, fructose, citrate, succinate) was investigated. Therefore, the bacteriostatic effect of Cd2+, Ni2+ and EDTA on the maximum specific growth rate and the determination of EC50 values was used to quantify inhibitory impact. At high concentrations of Ca2+ (800 μmol L-1) and Mg2+ (1,250 μmol L-1), only a small inhibitory effect of Cd2+ and Ni2+ on growth of P. brassicacearum was observed (EC50 Cd2+, 18,849 ±â€‰80 μmol L−1; EC50 Ni2+, 3,578 ±â€‰1,002 μmol L−1). The inhibition was much greater at low concentrations of Ca2+ (25 μmol L−1) and Mg2+ (100 μmol L−1) (EC50 Cd2+, 85 ±â€‰0.5 μmol L−1 and EC Ni2+, 62 ±â€‰1.8 μmol L−1). For the chosen model system, a competitive effect of the ions Cd2+ and Ca2+ on the one hand and Ni2+ and Mg2+ on the other hand can be deduced. However, the toxicity of both, Cd2+ and Ni2+, could be significantly reduced by addition of EDTA, but if this chelating agent was added in stoichiometric excess to the cations, it also exhibited an inhibitory effect on growth of P. brassicacearum.

Co(II) adsorption on high-purity amorphous Fe–Mn binary oxide adsorbent was investigated. The Co(II) adsorption behavior of this synthetic material was studied and discussed as a function of contact time, pH and initial concentration. The Langmuir and Freundlich isotherm models were applied to fit the Co(II) adsorption data on Fe–Mn binary oxide with mesoporous particles of irregular surface morphology and a specific surface area of 201.8 m² g⁻¹ with a maximum capacity of 32.25 mg g⁻¹. Various kinetic models applied to the adsorption rate data of the Co(II) ion were evaluated. The results show that the pseudo-second order and the intra-particle mass transfer diffusion models correlated best with the experimental rate data. The adsorption activation energy was found to be 9.07 kJ mol⁻¹ indicating that it corresponds to a physical adsorption. The evaluated thermodynamics parameters of the adsorption values indicated the endothermic and spontaneous nature of the adsorption. The results obtained confirmed that Fe–Mn binary oxide had the potential to be utilized as a low-cost and relatively effective adsorbent for Co(II) removal from wastewater.

This study examined the potential for Fe mobilization and greenhouse gas (GHG, e.g. CO₂, and CH₄) evolution in SEQ soils associated with a range of plantation forestry practices and water-logged conditions. Intact, 30-cm-deep soil cores collected from representative sites were saturated and incubated for 35 days in the laboratory, with leachate and headspace gas samples periodically collected. Minimal Fe dissolution was observed in well-drained sand soils associated with mature, first-rotation Pinus and organic Fe complexation, whereas progressive Fe dissolution occurred over 14 days in clear-felled and replanted Pinus soils with low organic matter and non-crystalline Fe fractions. Both CO₂ and CH₄ effluxes were relatively lower in clear-felled and replanted soils compared with mature, first-rotation Pinus soils, despite the lack of statistically significant variations in total GHG effluxes associated with different forestry practices. Fe dissolution and GHG evolution in low-lying, water-logged soils adjacent to riparian and estuarine, native-vegetation buffer zones were impacted by mineral and physical soil properties. Highest levels of dissolved Fe and GHG effluxes resulted from saturation of riparian loam soils with high Fe and clay content, as well as abundant organic material and Fe-metabolizing bacteria. Results indicate Pinus forestry practices such as clear-felling and replanting may elevate Fe mobilization while decreasing CO₂ and CH₄ emissions from well-drained, SEQ plantation soils upon heavy flooding. Prolonged water-logging accelerates bacterially mediated Fe cycling in low-lying, clay-rich soils, leading to substantial Fe dissolution, organic matter mineralization, and CH₄ production in riparian native-vegetation buffer zones.

The capacity of an iron-modified zeolite was evaluated for the removal of two dyes (red 5 and yellow 6) use in foodstuff; the regeneration of the dye-saturated materials was also considered. The zeolitic material (clynoptilolite type) was treated with sodium chloride (Na-Ze) and then with ferric chloride (Fe-Ze). The sorption kinetics and isotherms were evaluated, considering the effect of pH on the sorption processes. Sorption–regeneration cycles using iron-modified zeolitic material were performed. The sorption kinetics showed that the sodium-modified zeolitic material removed neither red 5 nor yellow 6 dyes, while the iron-modified zeolitic material removed both dyes; the equilibrium time was reached in 48 h for yellow 6, and it was almost reached in the same time for red 5, the removal percentage for red 5 was 89.4 % and for yellow 6 was 96.7 %. The experimental data showed best adjustment to the pseudo-first-order model (Lagergren), which is based on a superficial reaction. The sorption capacities obtained by the sorption isotherms were 1.6 and 1.7 mg/g for red 5 and yellow 6, respectively. The experimental data were best adjusted to the Langmuir–Freundlich model which indicates that the sorption takes place on a heterogeneous material. It was also observed that the sorption capacities increase as the pH decreases. The results on the desorption processes showed that the best regenerator agent was Fenton’s reagent; the capacities increased in each sorption–regeneration cycle using this reagent; for the red 5, the sorption percentage was 73.6 % in the first cycle and 96.3 % in the third cycle and for yellow 6, the removal percentage was 66.7 % in the first cycle and 80.5 % in the second.

The present work investigated the ability of inactive brown seaweed, Turbinaria conoides, to biosorb aluminum(III) and cadmium(II) ions in both single and binary systems. Initial experiments were undertaken to determine the influence of pH and biosorption isotherms of each metallic ion. Owing to the presence of carboxylic groups, T. conoides exhibited high uptake capacity towards Al(III) and Cd(II) through ion-exchange mechanism. In the case of Al(III), T. conoides exhibited maximum biosorption at pH 4 with a capacity of 2.37 mmol/g, whereas the highest Cd(II) biosorption occurred at pH 5 with a capacity of 0.96 mmol/g. For both metal ions, T. conoides exhibited fast kinetics. Several models were used to describe isotherm (Langmuir, Freundlich, Redlich-Peterson, and Toth) and kinetic (pseudo-first and pseudo-second order) data. Desorption and reuse of T. conoides biomass in three repeated cycles was successful with 0.1 M HCl as elutant. In binary systems, the presence of Cd(II) severely affected Al(III) uptake by T. conoides. Compared to single-solute systems, Al(III) uptake was reduced to 56% compared to only 27% for Cd(II). Based on the model parameters regressed from the respective monometal systems, multicomponent Langmuir and Freundlich models were used to predict binary (Al + Cd) system of which the multicomponent Freundlich model was able to describe with good accuracy.

This study was carried out to examine the phytotoxicity and oxidant stress by CuO and ZnO nanoparticles (NPs) in Cumumis sativus and the characterization of CuO and ZnO NP suspensions. We estimated the bioaccumulation of CuO and ZnO NP in plant, reactive oxygen species enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activities in plant tissue of root, and observed CuO and ZnO NPs with transmission electron microscopy. We found that the seedling biomass significantly decreased to 75% and 35% of that of control at 1,000 mg/L of CuO and ZnO NPs, respectively. The bioavailability and oxidant stress potential of plants exposed to metal oxide particles were dependent in the size, concentration, and species of the NPs. The median inhibition concentrations of CuO and ZnO NPs were 376 and 215 mg/L, respectively. In transmission electron microscopy, CuO and ZnO NPs greatly adhered to the root cell wall, and NPs were observed in the root cells. Another finding indicated that both CuO and ZnO NPs caused statistically significant increase in SOD, CAT, and POD activities and significant increase at 100 mg/L concentration levels. These results indicated that NPs alter both phytotoxicity and oxidative stress in plant assays. We further suggest that the oxidative stress markers appear to be a good predator of potential future toxicity of nanoparticles.

Sensitivity to magnesium chloride (MgCl2) was assessed on five common roadside tree species by maintaining soil concentrations at 0-, 400-, 800-, or 1,600-ppm chloride via MgCl2 solution over four growing seasons. Evaluations of growth, leaf retention, foliar damage, and ion concentrations were conducted. Water potentials were measured on two species. Foliar chloride and magnesium concentrations were positively correlated with foliar damage in all species. Conifers exhibited mild damage during the first growing season but moderate to severe damage during the first winter and second growing season. The two highest MgCl2 treatments caused leaf loss, severe damage, or mortality of Douglas-fir, lodgepole, and ponderosa pines after two seasons of treatments and of limber pine after four seasons. Aspen also displayed foliar damage and crown loss but abscised damaged leaves and flushed asymptomatic leaves throughout the growing seasons. The highest treatment caused mortality of aspen in 4 years. Approximately 13,000–17,000-ppm foliar chloride was associated with severe damage in conifers but ranged from 13,000- to 33,000-ppm in fully necrotic leaves. Aspen foliage contained the highest concentrations of chloride (24,000–36,000-ppm), and limber pine leaves had the lowest (<14,200-ppm). Although MgCl2 caused reductions in leaf water potential, aspen and ponderosa pine did not appear to be under substantial moisture stress and continued to take up ions. Mortality of common roadside tree species in 2 to 4 years can occur due to high MgCl2 soil concentrations, and transportation officials should consider these implications in their management plans.

Polybrominated diphenyl ethers (PBDEs) and perfluorinated compounds (PFCs) are both classes of persistent organic pollutants with potential major health and environmental concerns. Many PBDE- and PFC-containing products are ultimately discarded in landfills. In samples from 28 landfills and dumpsites across Canada, PBDEs and PFCs were detected in almost all landfill leachate samples, with concentrations up to 1,020 and 21,300 ng/L, respectively. Mean concentrations were 166 ng/L for PBDEs and 2,950 ng/L for PFCs. Landfill leachates from southern Canada generally had greater concentrations of PBDEs and PFCs than those from northern Canada. The dominant compounds were decabromodiphenyl ether (BDE-209) (mean contribution 52 %) for the PBDEs and perfluorohexanoic acid (mean contribution 25 %) for the PFCs. There were strong correlations for some compounds within each contaminant class, such as the major congeners in the penta-BDE commercial mix (BDE-47, BDE-99, and BDE-100). Estimated average ∑PBDE and ∑PFC loadings from an urban landfill to the environment were calculated to be 3.5 and 62 tonnes/year, respectively.