This paper presents a study of the combined process of adsorption and biodegradation in solid biologically activated carbon (AC) for the removal of salicylic acid aimed at determining the influence of the presence of biofilm on the process. Adsorption on AC and biodegradation of free cell cultures were studied separately so as to compare their performance with that of the combined biosorption system. The formation of bacterial biofilm on the surface of the carbon was investigated. The study was carried out using a range of synthetic solutions containing between 15 and 500 mg/L salicylic acid simulating an industrial effluent from the pharmaceutical industry. An individual bacterium, Pseudomonas putida (DSM 4478), was used to study the differentiated effects. Filtrasorb 400 and GAC 830 ACs were used in the adsorption processes and Filtrasorb 400 in the biofilm formation and combined biosorption processes. As regards, combined adsorption/biodegradation results indicated that the bioactivated carbon system outperformed the combination of conventional AC and biological water treatment processes when working with high pollutant concentrations.

A novel high-capacity phosphate removal adsorbent of graphene nanosheets (GNS) supported lanthanum hydroxide (LaOH) is prepared. The phosphate adsorption performance for GNS-LaOH is examined by a batch adsorption method from aqueous solutions. The Freundlich and Langmuir models are used to simulate the sorption equilibrium, which reveal that the Langmuir model has a better correlation with the experimental data. The maximum adsorption capacity is calculated to be 41.96 mg/g. The kinetic data from the adsorption of phosphate is suggested as the pseudo-second-order model, and the multi-linearity adsorption process is observed in the intraparticle diffusion model, indicating that a chemisorption process is dominant in the adsorption of phosphate. The phosphate adsorption mechanism is explored by analyzing the Fourier transform infrared spectroscopy (FT-IR) and the relationship between the adsorption amount and the pH value of phosphate solution. Ligand exchange and electrostatic and Lewis acid–base interactions are determined to be three main factors for phosphate adsorption.

This contribution is concerned with the comparison of the efficiency of the removal of four pure neonicotinoid active ingredients (AIs) and their commercial formulations (CFs) from aqueous solutions by using different advanced oxidation processes at the pH 2.8. The AIs of thiamethoxam and imidacloprid, and their CFs (Actara and Confidor), having a nitroguanidine functional group, exhibited low persistence to photolysis. In contrast to them, thiacloprid and acetamiprid and their CFs (Calypso and Mospilan), containing a cyanoimine functional group, were stable during the UV irradiation period. As expected, the degradation rate of the studied neonicotinoids increased significantly in the combined action of UV radiation and H₂O₂. In the case of thiacloprid and acetamiprid and their CFs, the reaction of the OH radicals formed and molecules of these insecticides was the major destruction pathway. The increased photodegradation efficiency of the UV/7.2Fe/TiO₂/H₂O₂ and vis/7.2Fe/TiO₂/H₂O₂ processes was attributed to the surface photoreduction of Fe³⁺ to Fe²⁺, which produces new OH radicals in the reaction with H₂O₂. In the presence of visible light, the efficiency may be partly due to the formation of the H₂O₂–TiO₂ complexes. For the 7.2Fe/TiO₂/H₂O₂ process in the presence of UV or visible radiation, no significant influence on the efficiency of photodegradation was observed in dependence of the structural differences of selected neonicotinoids. These results strongly suggest that highly reactive hydroxyl radicals, generated on the catalyst’s surface in the reaction involving H₂O₂, are responsible for this oxidation. In order to investigate degree of mineralization for all insecticides, TOC measurements were also conducted. Also, it was observed that the removal of pure AIs and their CFs by dark adsorption was almost negligible.

The aim of this study was to investigate the effect of pH 4 and 7 on the cellular toxicity impact of silver nanoparticles (AgNPs) on the green alga Chlamydomonas acidophila. Changes in chlorophyll content, cellular viability, and reactive oxygen species (ROS) formation were determined permitting the characterization of the toxicity of AgNPs. Chemical characterization of AgNPs in suspension showed that nanoparticle size distribution was dependent to the pH of the culture medium, and a higher solubility was observed at pH 4 compared to that at pH 7. After 24 h of exposure, results indicated that the chlorophyll content and cellular viability decreased significantly, while the intracellular ROS production increased significantly, in relation to the increasing concentration of AgNPs (0.1–100 mg/L). Therefore, our results demonstrated that AgNP-induced toxicity was pH dependent as indicated by the cytotoxicity mediated through the induction of oxidative stress. In conclusion, the characterization of the physicochemical properties of AgNPs in aqueous solution having different pH is essential for the understanding of their toxicity impact on algal cells.

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.