The growing demand for new sources of water for irrigation has led to an increase in the practice of using treated wastewater in agricultural processes. Thus, in the present research, we have assessed the irrigation of a culture of eucalyptus with reclaimed wastewater. The sewage comes from domestic sources and was treated in a facultative lagoon. The culture of eucalyptus was assessed through plant diameter at breast height and total volume of wood produced. Soil contamination was determined through its salinization and the values of sodium adsorption ratio (SAR). The use of wastewater in irrigation has brought an increase of 82.9 % in productivity compared to traditional cultivation. This shows that in a same area of cultivation, practically double of the eucalyptus wood could be obtained and used in the most different industrial activities. In addition, it would prevent the entering of a large amount of nutrients in water bodies due to their recycling in the agricultural culture. In the period of 4 years of studies, SAR has always been below the values pointed by the literature as indicators of problems for the soil.

Detonations of military ordnance will leave various amounts of chemical residue on training ranges. Significant adverse ecological effects from these residues have not been documented except for ordnance containing white phosphorus. At a military training range in Alaska, USA, the deaths of thousands of waterfowl due to poisoning from white phosphorus ordnance prompted a two-decade-long investigation of the extent of the contamination, remediation technologies, and methods to assess and monitor the effectiveness of the remediation. This paper gives an overview of these investigations and provides the outcome of the remediation efforts.

Stressed communities show changes in energetics and nutrient demand and recovery. The evaluation of microbial communities energy demand can be measured by enzyme activities. Thus, by using such approaches, it might be possible to determine the microbial response to metal contaminations. Guanabara Bay surface sediments were sampled in 20 stations. Grain size, bioavailable metals, total organic carbon, total sulfur, dehydrogenase activity, esterase activities, viable bacterial cells, carbohydrates, lipids, and proteins were determined in all samples. Bioavailable metal concentration ranges from below detection limit in sandy stations in the entrance of the bay by up to the same order of magnitude as total concentrations obtained by other authors. Biopolymers were mainly lipids and carbohydrates, and minimum concentrations were also observed in sandy sediments. C:S ratio of 4.4 ± 1.3 (mean ± standard deviation) expresses the reduced tendency conditions of the bay, negatively correlated to viable bacteria cells (in order of 10⁷ cell g⁻¹). Esterase enzyme activities positively correlated with organic and fine sediment content. Stations with the highest metals and organic contents also have the highest esterase activities and dramatic decline of bacterial cells. In these locations occur better water renewal and subsequent aeration, which increases the efficiency of the organic matter oxidation and decreases matrix geochemical sequestration of metals and renders them bioavailable.

This study deals with the hydrogeochemical changes and metal(loid) attenuation processes along the extremely acidic Rio Tinto (SW Spain). The geochemistry of Tinto headwaters is determined by the variability of mining discharges due to different geological, geochemical and hydrological controls. Downstream of the mining area, a decrease in most dissolved element concentrations is recorded. However, not all elements decreased its concentration to the same extent, and even some did not decrease (e.g., Ba and Pb). A group of elements formed by Al, Cd, Co, Cr, Cu, Li, Mg, Mn, Ni and Zn behaved quasi-conservatively; mainly affected by dilution, except at the lower part of the catchment where seem to be affected by sorption/coprecipitation (e.g., Cd, Cu, and Zn) or mineral dissolution processes (e.g., Al, Mg). Iron and As exhibited a non-conservative behaviour due to ochre precipitation and sorption processes, respectively. A group of elements formed by Ca, Na, Sr and Li did not behave conservatively; waters were enriched in these elements by dissolutive reactions of carbonates and aluminosilicates from bedrocks. The behaviour of Pb in the Rio Tinto is complex; values fluctuate along the river course and its solubility may be related to the nature of Fe precipitates.

This work presents an evaluation of the remediation efficiency and of the environmental impact of a zero-valent iron commercial substrate used for the removal of heavy metals from groundwater in different conditions. A specific feature of the substrate is the presence of zero-valent iron (ZVI), organic carbon, and sulfate. The authors analyzed its composition and performances by means of batch tests in different boundary conditions. In detail, the efficacy was evaluated for metals (Cu, Cr, Pb, and Zn) and for nitrates and sulfates. Neutral and acidic pH values, imputable to dangerous waste landfill leachate or to acid mine drainage, were considered. The environmental impact of the substrate was also assessed for the investigated pHs. The product showed a high efficiency in the removal of metals (mainly described by a pseudo-second-order kinetic model), with a noticeable variability according to the pH of the polluted phase. Nitrate ion removal was inhibited by sulfates at all the considered pH values. Characterization and batch studies revealed that the substrate was a source of Mn, Cr, Pb, Cu, and sulfate ions, besides Fe. This study shows that the employment of an optimized amount of reagent, while achieving good performances, is essential to contain the leaching of undesirable substances into aqueous environment.

Water pollution through natural and anthropogenic activities has become a global problem causing short-and long-term impact on human and ecosystems. Substantial quantity of individual or mixtures of organic pollutants enter the surface water via point and nonpoint sources and thus affect the quality of freshwater. These pollutants are known to be toxic and difficult to remove by mere biological treatment. To date, most researches on the removal of organic pollutants from wastewater were based on the exploitation of individual treatment process. This single-treatment technology has inherent challenges and shortcomings with respect to efficiency and economics. Thus, application of two advanced treatment technologies characterized with high efficiency with respect to removal of primary and disinfection by-products in wastewater is desirable. This review article focuses on the application of integrated technologies such as electrohydraulic discharge with heterogeneous photocatalysts or sonophotocatalysis to remove target pollutants. The information gathered from more than 100 published articles, mostly laboratories studies, shows that process integration effectively remove and degrade recalcitrant toxic contaminants in wastewater better than single-technology processing. This review recommends an improvement on this technology (integrated electrohydraulic discharge with heterogeneous photocatalysts) viz-a-vis cost reduction in order to make it accessible and available in the rural and semi-urban settlement. Further recommendation includes development of an economic model to establish the cost implications of the combined technology. Proper monitoring, enforcement of the existing environmental regulations, and upgrading of current wastewater treatment plants with additional treatment steps such as photocatalysis and ozonation will greatly assist in the removal of environmental toxicants.

Sugarcane is a major crop in Brazil that generates huge amounts of organic residues that are usually left deposited in, or applied to the soil, and thereby affect the behavior of herbicides. This study assessed the effects of sugarcane residues (straw, ash, and compost) and residence time (“aging”) on the sorption of alachlor and diuron in two contrasting soils (LVd and LVAd), as well as the effects of these residues on the leaching of alachlor. Adding straw and compost had no effect, whereas adding ash significantly increased sorption of both herbicides. Aging (28 days) increased apparent sorption distribution coefficients (Kd,ₐₚₚvalues) by 1.2 to 2.3 times. Straw and ash amendments resulted in less leaching of alachlor (<1.0 % of the applied amount) than compost or control soil (~6 % of the applied amount). The straw retained ~80 % of the applied alachlor during leaching. Although this may be overrated due to an artifact of the methodology adopted, alachlor retention in the straw could not be predicted by the use of Kd,ₐₚₚ. The transport potential of alachlor may be overestimated if aging and sugarcane straw management are not factored into the models.

Particles derived from humic acid, as p(HA), are synthesized in a single step via a water-in-oil microemulsion system employing different cross-linkers such as divinylsulfone (DVS), glutaraldehyde (GA), epichlorohydrine (ECH), and adipochloride (AC). The different phenolic groups on humic moieties are connected via these cross-linkers to form particles. The prepared p(HA) particles were successfully used in the removal of toxic organo-phenolic such as phenol (Ph), 4-nitrophenol (4-NPh), 4-chlorophenol (4-CPh), 2-chlorophenol (2-CPh), and 2,3-dichlorophenol (2,3-CPh) from aqueous environments. Various parameters such as pH, contact time, reusability of particles, and the initial concentration of adsorbate are investigated. It is found that the absorption capacity of p(HA) particles for Ph is 180 mg/g, and the maximum absorption amount is obtained at pH 6. Furthermore, the reuse experiments are shown that p(HA) particles can release the absorbed Ph by the treatment of methanol, and an absorption capacity of 85 % is attainable up to five consecutive absorption and release cycles. p(HA) particles are characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) techniques.

Humic acid (HA) is ubiquitous in groundwater, and poses great influence on the biogeochemical controls on, as well as treatment of, contaminants. This study deals with the adsorption of HA on a bimetallic iron system, Cu/Fe, and its influence on the reduction of nitrobenzene in synthetic groundwater. The adsorption kinetics, isotherms, and enthalpy of HA on bimetallic Cu/Fe particles are investigated. Compared with the adsorption of HA on Fe⁰particles, the adsorption on Cu/Fe is faster than that on Fe⁰. The adsorption isotherms of HA at different pH values and temperatures show that the adsorption is always greater on Cu/Fe than on Fe⁰, and increases when the pH decreases and temperature increases. Moreover, the influences of pH and temperature on adsorption by Cu/Fe are less than those observed in adsorption on Fe⁰. The adsorption enthalpy on Cu/Fe is lower than that on Fe⁰, and both adsorptions are spontaneous and endothermic. Characterization of the corrosion products by SEM-EDX, XRD, and XPS reveals the appearance of maghemite (γ-Fe₂O₃) and magnetite (Fe₃O₄) on Cu/Fe with HA adsorption, which were more crystalline than those of Fe⁰, indicating that bimetallic Cu/Fe facilitated the formation of crystalline corrosion products. The adsorption of HA accelerates the release of iron ions but suppresses the reduction of nitrobenzene. Compared with Fe⁰, Cu/Fe accelerates the adsorption of HA and Cu/Fe increases the reduction of nitrobenzene. The suppression on nitrobenzene reduction increased with the increase in HA concentration.