Natural Hexavalent Chromium in the Pollino Massif Groundwater (Southern Apennines, Italy): Occurrence, Geochemistry and Preliminary Remediation Tests by Means of Innovative Adsorbent Nanomaterials.

In this study Cr(tot), Cr(VI), major and trace elements were determined in groundwater of northern sector of the Pollino Massif (southern Italy). The investigated area is characterized by ophiolitic rocks consisting of metabasites, shales and calcschists and fractured serpentinites. Two main hydro-facies were observed, reflecting low temperature water-rock interaction. The Mg-HCO3 hydrofacies is due to the weathering of serpentinites, Ca-HCO3 groundwaters are linked to the interaction with calcschist and metabasites. High Cr(VI) concentrations were detected, exceeding the maximum admissible concentrations by Italian regulation, due to the release of Cr(III) from ophiolitic rocks into water and its oxidation to the hexavalent state. Remediation tests were carried out using two synthetized nanomaterials, Fe(0) and magnetite, characterized by a mean size lower than 50 nm. The experiments were conducted at fixed nanoparticles/Cr(VI) molar ratio and according to previous studies. In addition, the kinetic data were interpreted with a suitable mathematical model.

Hexavalent chromium reduction in contaminated soil: A comparison between ferrous sulphate and nanoscale zero-valent iron.

Iron sulphate (FeSO4) and colloidal nano zero-valent iron (nZVI) as reducing agents were compared, with the aim of assessing their effectiveness in hexavalent chromium [Cr(VI)] removal from a contaminated industrial soil. Experiments were performed on soil samples collected from an industrial site where a nickel contamination, caused by a long-term productive activity, was also verified. The influence of reducing agents amount with respect to chromium content and the effectiveness of deoxygenation of the slurry were discussed. The soil was fully characterized before and after each test, and sequential extractions were performed to assess chemico-physical modifications and evaluate metals mobility induced by washing. Results show that both the reducing agents successfully lowered the amount of Cr(VI) in the soil below the threshold allowed by Italian Environmental Regulation for industrial reuse. Cr(VI) reduction by colloidal nZVI proved to be faster and more effective: the civil reuse of soil [Cr(VI)<2mg/kg] was only achieved using colloidal nZVI within 60min adopting a nZVI/Cr(VI) molar ratio of 30. The reducing treatment resulted in an increase in the amount of chromium in the oxide-hydroxide fraction, thus confirming a mechanism of chromium-iron hydroxides precipitation. In addition, a decrease of nickel (Ni) and lead (Pb) content in soil was also observed when acidic conditions were established.

Target organ damage in hypertensive patients: correlation between retinal arteriovenular ratio and left ventricular geometric patterns.

Early evaluation of cardiovascular (CV) risk in hypertensive patients is of primary importance and studies of retinal vessels can be helpful. The aim of this study is to assess the correlation between retinal vessel changes and target organ damage (TOD), expressed as left ventricular remodelling (LVR) or hypertrophy (LVH). We evaluated 60 treated hypertensive individuals (mean age 60.9±13.3 years). On the basis of echocardiographic results, we divided the subjects showing the presence of TOD and subjects without TOD into Groups A and B, respectively. Both groups underwent a non-mydriatic digital retinography. The obtained vessel images were analysed using dedicated software in order to calculate AVR (arteriovenular ratio), index of the retinal arteriolar narrowing. The data analyses confirmed a mean AVR value of 0.86 in Group B and a mean value of 0.77 in Group A. AVR index was also analysed in a subgroup of A with evidence of LVR, and mean value was 0.76. The same procedure was carried out with subgroup of A with LVH and AVR index resulted 0.77. In all comparisons, P-value was statistically significant (P<0.05). Our findings provide evidence that in hypertensive patients retinal AVR correlates with the presence of TOD, in this study in the context of LVR and LVH. In conclusion, AVR offers a direct vision retinal microcirculation and, also, indirectly, provides information of the left ventricular geometric pattern in hypertensive patients; thus, AVR may have an important role in global CV risk stratification and could possibly be used for optimising the hypertensive patient management.

Batch and column tests of metal mobilization in soil impacted by landfill leachate.

The percolation of landfill leachate, even in the absence of a high concentration of specific pollutant, may induce a strong modification of soil chemical and physical characteristics, due to the alteration of the natural equilibrium between the aqueous phase and the soil matrix. As a result, a huge amount of cations can be solubilized, thus inducing groundwater pollution. In this work batch and column experiments of metal mobilization from a soil sampled down gradient of a municipal waste landfill in Northern Italy are presented. The experiments were initially performed in batch scale on soil slurries at different pH and Eh. Distilled water was used first and then a groundwater sampled down-gradient in the same site. Subsequently, to better simulate the aquifer conditions, 50 d column tests were performed on 15 kg of saturated soil. The concentrations of Fe, Mn, and Ni were evaluated when these selected environmental parameters were altered. Results indicated a greater release when acidic conditions were achieved, a positive effect in this case of the addition of an oxidant and a great Mn mobilization when negative redox potentials were established.

Discrepancy between recalled and recorded bowel habits in irritable bowel syndrome.

BACKGROUND: A discrepancy between recalled and recorded bowel habit subtypes has been reported in irritable bowel syndrome (IBS), but the reasons for it remain unclear. AIM: To assess the agreement between recalled and recorded bowel habit subtypes; to determine whether any discrepancy is related to stool form variability or psychological factors; and to test the correlations of recalled and recorded stool form with colonic transit time. METHODS: Bowel habit subtype was established in 54 IBS patients at the enrolment visit (recalled) and with the aid of diary cards (recorded). Colonic transit time, the variability of stool form and the patients' psychological profiles were also recorded. RESULTS: Recalled and recorded bowel habit subtypes agreed in only 54% of the patients (kappa = 0.28). Stool form variability was greater among the patients whose recalled and recorded bowel habit subtypes were discordant (P = 0.03), whereas the psychological profiles were not different. Colonic transit time significantly correlated with stool form only when it was recorded on diary cards. CONCLUSION: The discrepancy between recalled and recorded bowel habits in IBS patients is related more to stool form variability than an altered psychological profile. Diary cards should be used to ensure that stool form reflects colonic transit time.

The effect of disk rotational speed on oxygen transfer in rotating biological contactors.

Lab-scale experiments using a synthetic wastewater were carried out to assess the influence of disk rotational speed on oxygen transfer rate in a RBC unit in the presence of biomass. The overall oxygen transfer coefficient (K(L)a) was computed. Five different disk rotational speeds were tested, in the typical RBC operating range (3-10 RPM). The soluble organic substrate was monitored through TOC analysis. Influent hydraulic organic loadings were in the range of 5.4-35.2 g TOC/m(2)d. The set of kinetic coefficients calculated fitting the experimental data by the selected model resulted in good agreement with the value reported in literature. A correlation for K(L)a as a function of disk rotational speed and disk diameter was obtained. Accordingly, a new expression of the enhancement factor of oxygen transfer was found, and compared to literature data.

Experimental validation of a model describing the cycle of nitrogen in a step sludge recirculation activated sludge system with denitrification.

In this paper, a model describing the cycle of nitrogen in a Step Sludge Recirculation (SSR) reactor, was developed. The SSR reactor is a multistage, continuous stirred tank reactor where the recycled biomass is distributed over all stages. The SSR system provides a uniform treatment of the wastewater and high purification efficiency for both carbon and nitrogen removal. The objective of this work was to develop a mathematical model of the SSR system, based on the analysis of various parameters that are present in the system. The simplified form of the IWA-ASM model was adapted to include the carbon removal, nitrification and denitrification processes. For model validation, a SSR pilot plant fed with synthetic wastewater was operated for approximately four months. The experimental results show that the SSR system seems to be appropriate to attain maximum TOC and nitrogen removal with minimum sludge production. The proposed model seems to be capable of expressing the behavior of carbon removal, nitrification, denitrification and various microorganism species in a SSR configuration of a nitrogen cycle. When the experimental results were compared with those estimated by the proposed model, the model predictions matched well with the experimental results.

Heavy metals mobilization from harbour sediments using EDTA and citric acid as chelating agents.

In this paper experimental tests of heavy metals mobilization from sediments collected from an Italian harbour are presented and discussed. Batch tests of washing with an aqueous solution of chelating agent were performed at selected liquid/solid (L/S) ratios and chelant concentration (0.01, 0.05 and 0.1M). Two chelating agents were chosen: EDTA and citric acid. The objective of the tests was to investigate metal mobilization and soil mineral dissolution promoted by the washing treatment. The study was focused on the mobilization of Pb, Zn, and Cu: their concentrations in the contact solution, together with Fe and Ca concentration, were monitored along time for 144h. Results of experimental tests performed at different chelant concentration and L/S ratio show EDTA effectiveness in mobilizing metals bond to the sediment. The overall amount of the three selected metals (Cu, Pb and Zn) extracted in the tests with EDTA varied in a quite narrow range (from 2.262 to 2.724mmol), while the higher was the EDTA concentration in the washing solution, the higher the dissolution of other competitive cations, such as Ca and Fe. In addition, a general difficulty in copper extraction from the organic fraction of the sediment was observed, due to the high stability of copper humate. The mechanism of metals extraction was found to involve the initial metals salts dissolution, that was pH-dependant, followed by the development of exchange reactions between the metal-EDTA complexes previously formed. Depending upon the pH of the washing solution an initial high Ca dissolution was observed, followed by dramatic reduction in Ca(2+) content, mainly determined by calcium carbonate precipitation, as a result of the increase of pH during mixing. Metal mobilization was evaluated performing sequential extraction tests: the dissolution of Cu, Pb and Zn from the carbonate fraction of the sediment was almost total, as the mobilization of Pb and Zn from the Fe-Mn oxides and hydroxides fraction. On the contrary, as a consequence of the mobilization induced by washing treatment, about 17% of the remaining Cu and 10% of the remaining Zn resulted in the exchangeable fraction. At the investigated operating conditions, citric acid was unable to extract Pb and Cu from the sediment, while at the strong acidic conditions maintained during the extractions with citric acid, a Zn mobilization up to the 80% of the initial amount was observed, depending upon the operating conditions in the extractions. In addition, because of the great affinity between citric acid and Fe, and the strong acidic conditions maintained during extraction, a high Fe dissolution was observed (up to about the 39% of the total Fe content in the sediment).

Use of EAF dust as heterogeneous catalyst in Fenton oxidation of PCP contaminated wastewaters.

In this study, chemical oxidation tests using H2O2 were performed on a solution contaminated with 100 mg l(-1) of pentachlorophenol (PCP). The effectiveness of electric arc furnace dust and hematite as heterogeneous catalysts was evaluated. Reactions were conducted at pH 2 for 24 h. Either H2O2 stabilized with KH2PO4 or un-stabilized H2O2 was used. Total organic carbon (T.O.C.) removal and chloride release from PCP molecule were monitored. Results showed that the maximum removal yields for electric arc furnace (EAF) dust (49.2% T.O.C., 56.7% Cl) were achieved when H2O2:PCP ratio was 10:1 and Fe:H2O2 = 1:5 for unstabilized H2O2 and when H2O2:PCP = 10:1 and Fe:H2O2 = 1:1 for stabilized H2O2 (48% T.O.C., 60.6% Cl). The maximum yield using hematite (45.2% T.O.C., 55.2% Cl) was obtained when H2O2:PCP ratio was 10:1 and Fe:H2O2 was 1:2. When EAF dust was used and Fe:H2O2 > 1:5, Cl release was higher than the one expected from T.O.C. removal.

Heavy metals extraction from contaminated soil: recovery of the flushing solution.

The optimum conditions for the recovery of copper from a contaminated soil by using the soil flushing technique are evaluated. Tests on a soil artificially contaminated with copper chloride were carried out in order to evaluate the influence of the speed of percolation and of the chelating agent concentration (aqueous solution of an ethylendiaminotetraacetic acid di-sodium salt Na2-EDTA). At pH=7.3 an efficiency up to 93.9% for copper extraction was achieved by flushing 500 ml of Na2-EDTA 0.05 M solution and 100 ml of pure water at 0.792 cm/h. At these operating conditions the formation of EDTA complexes with other competitive cations (calcium and iron) was negligible. The experimental results were in agreement with the ones obtained using a model describing the chemistry of metal extraction. This model assessed that above pH=6 the formation of calcium and iron EDTA complexes was excluded and only the chelation of copper was allowed. The recovery of 91.6% of EDTA was also achieved by evaporating and acidifying the extracted solution: after filtration, solid EDTA was obtained, through the addition of sodium hydroxide Na2-EDTA. About 99.5% of the extracted copper was finally precipitated under alkaline conditions from the liquid phase.

Experimental evaluation of inhibition effects of saline wastewater on activated sludge.

Industrial wastewater often has a high salt content, due to specific factories and to the use of seawater in coastal areas. Once it has reached the activated sludge treatment, saline wastewater may cause biomass inhibition and dramatic loss in purification efficiency. In the present work, the inhibiting effect of saline influent was experimentally evaluated through respirometric tests on samples of the incoming wastewater. Activated sludge was grown in bench-scale continuous flow stirred tank reactor (CFSTR), supplied with synthetic wastewater. Synthetic saline wastewater was prepared using sodium chloride and sodium sulphate at different concentrations. Samples of mixed liquor were drawn from the CFSTR reactor and fed with saline wastewater in shock-load or in continuous mode, then respiration activity and carbon removal yield were evaluated. In batch mode (shock-load), salt/biomass ratios between 0.37 and 30.7 gsalt gvss(-1) gave respiration inhibition between 4% and 84% respectively. The respirometry bioassay required a short response time and the values of respiration inhibition predicted the loss in carbon removal efficiency with a good accuracy. In continuous mode, for salt/biomass ratio of 35.5 gsaltgvss(-1), respiration inhibition of 81% was obtained. This work showed that a relation between inhibition in shock-load and inhibition in continuous mode can be determined, therefore, the procedure herein proposed allows performing offline bioassays on real biological plants, to assess in real time the inhibiting effect of the incoming wastewater before it reaches the activated sludge reactor.

Copper leaching from a sandy soil: mechanism and parameters affecting EDTA extraction.

A series of 24h batch tests of copper extraction from a sandy soil were performed by washing the soil with aqueous solution of ethylenediaminetetraacetic acid, EDTA. EDTA versus copper molar ratio were in the range between 1 (equimolar tests) and 13.3. The tests were performed at three selected liquid/solid ratio, 5, 12.5 and 25. Results show that decreasing the pH of the washing solution an higher copper extraction yield was achieved: an almost complete copper extraction was achieved after 23 h of mixing at a L/S = 5, and after 5 h of mixing at an L/S = 12.5. The mechanism of copper extraction was found to involve two sequential processes: the former dissolution of metal salts, that lead to an initial high concentration of both copper and some competitive cations (essentially Ca(2+)), and the following EDTA exchange reaction between calcium and copper complexes, which corresponded an increase of pH in the washing solution. A negligible extraction of Fe(3+) was also observed at the investigated operative conditions.

EDTA leaching of copper from contaminated soils: experimental study and transport model application for parameters estimation.

EDTA column's extraction were performed on four artificially contaminated soils, followed by the percolation of pure water to ensure the removal of EDTA entrapped in soil. The investigated soils were characterized by a content of organic matter ranging from 1% to 25%. A mathematical model was developed for copper leaching from the soils. The correlation of experimental data shows that while the EDTA transport was not affected by the soil organic fraction, the simulated transport of Cu-EDTA complexes in solution exhibited a delay effect due to the chemical adsorption of such complexes onto the soil organic matter. The distribution coefficient (Kd), between the solid and liquid phases showed a logarithmic increase when the organic content of soil increased. The column's hydrodynamic characteristics (alphaL) and the kinetic coefficients (k) of chelant extraction were estimated independently for each soil. A correlation of kinetic coefficients data versus soil's organic content was also proposed: experimental data showed, in the investigated range, a logarithmic dependence of k on the organic content of soil.

Experimental assessment of the operative conditions of copper extraction from three contaminated soils.

Column experiments of EDTA extraction of copper from a sandy, a calcareous, and a highly organic soil, were performed. The influence of EDTA concentration, pH, and the flow rate of a flushing solution on copper extraction yield was investigated. Extraction yields of 84.8%, 93.0% and 96.9% were achieved respectively for sandy soil, calcareous soil and highly organic soil, after the injection of a volume of flushing solution equal to 15 pore volumes. TOC measurements performed on the extracted solution showed that, after the extraction phase, the percolation of an equal volume of water was necessary to ensure complete EDTA removal from the treated soils. In addition, results showed that the simultaneous dissolution of calcite consumed approximately 93.6% of the chelant agent when EDTA concentration in the flushing solution was 0.05 M.

Effect of ethanol on the oxidation of atrazine in the remediation of contaminated soil.

The oxidation of an atrazine solution obtained from a flushing treatment of a contaminated soil was investigated. Experimental tests were performed on an artificially contaminated standard soil. Atrazine was removed from the soil by flushing with an aqueous solution at 5% volume of ethanol. Oxidative Fenton-type treatment on the extracted solution was then performed in order to transform atrazine into its by-products. The influence of different concentration of ethanol on atrazine oxidation was studied. Results show that the oxidative treatment is strongly affected by the ethanol residual amount. The degradation mechanism of atrazine during oxidation with Fenton's reagent in the presence of ethanol was also investigated.

Recovery of EDTA and metal precipitation from soil flushing solutions.

This work studies the effectiveness of a process proposed for the recovery of ethylenediaminetetraacetic acid (EDTA) and metal precipitation from soil flushing solutions. Two series of experimental tests were carried out on two samples of a soil artificially contaminated with copper or lead. The metals were extracted from the soil by flushing with a 0.05 M aqueous solution of EDTA sodium salt (E-Na(2)). Cu or Pb extraction efficiencies of about 95 and 98% were observed, respectively. The two extracted solutions were then treated to obtain EDTA recovery and metal precipitation from the aqueous solution. EDTA recovery was achieved in two steps. An initial evaporation treatment lead to reduce the solution volume by about 75%. This was followed by the acidification of the residue solution, which precipitated more than 93% of the used EDTA. The precipitated EDTA was removed by filtration, and was suitable for reuse after adding an alkaline agent. Metal precipitation from the filtered solution was performed using two different methods: an almost total (99.5%) Pb precipitation in alkaline conditions was achieved after complex destabilization through the sequential addition of ferric ions and sodium phosphate, while 93.6% copper precipitation was achieved with ferrous sulfate as a destabilization agent.

Experimental study of the remediation of atrazine contaminated soils through soil extraction and subsequent peroxidation.

This paper presents a feasibility study in the field of the remediation of soils contaminated with atrazine. Experimental tests were performed on an artificially contaminated synthetic soil. Atrazine was removed from the soil by flushing with an aqueous solution at 5 vol.% of ethanol. Experimental tests of evaporation and Fenton's oxidation on the extracted solution were then performed in order to transform atrazine into its oxidation products. Tests were performed in the presence of a peroxide excess the ratio between Fe(2+) and H(2)O(2) was 1:10. Peroxide was first added in order to reduce the consumption of hydroxyl radicals by their reaction with the excess of Fe(2+). The degradation mechanism of atrazine during oxidation with Fenton's reagent in the presence of ethanol was investigated. Results showed that due to the non selective nature of Fenton's reagent a high consumption of reagent was needed to achieve a significant atrazine oxidation from solutions at 4.5 vol.% of ethanol. While at a Fe(2+) concentration of 3mM atrazine practically disappeared from pure aqueous solutions within 2h, a degradation yield of only 28.1% was observed in the presence of ethanol even when Fe(2+) concentration was 15 mM.

A steady-state model for the evaluation of disk rotational speed influence on RBC kinetic: model presentation.

The physical and biological mechanisms of attached-biomass growth were analyzed and a steady-state model was proposed to determine the soluble carbonaceous removal in an RBC unit for different organic loading rates in the reactor. The objective of the model was the prediction of the organic loading rate corresponding to the maximum removal capacity in the system. A system of equations was solved where the influent soluble carbonaceous substrate concentration was the main variable. Monod's rate law was used for the growth of microorganism: the soluble carbonaceous substrate was the limiting substrate. Endogenous decay was neglected. The influence of disk rotational speed on the RBC removal capacity was investigated, the disk rotational speed being a parameter acting on oxygen transfer in the biofilm. The criteria for the evaluation of the kinetic parameter in the model were proposed.

Recovery of copper from contaminated soil by flushing.

In this work the development of a process for the recovery of copper from contaminated industrial soils is presented. Experimental tests on a standard soil contaminated with a solution of copper chloride were carried out. The metal was extracted from the contaminated soil by flushing with a 0.1 M aqueous solution of an ethylenediaminetetraacetic acid (EDTA) sodium salt. A maximum copper extraction efficiency of about 60% was observed. Copper was then separated from the extracted solution by precipitation with sodium hydroxide after addition of ferric sulfate.

Assessment of the leaching of metallic elements in the technology of solidification in aqueous solution.

Results are presented of experiments performed to optimize the solidification/stabilization system for metallic elements in aqueous solution. This system involves mixing cement and a solution of metallic elements in a conventional mixer: the paste thus obtained is transferred drop by drop into a recipient filled with an aqueous solution of NaOH at 20% by weight, in which it solidifies immediately. The separate use of chloride solutions of Li+, Cr3+, Pb2+ and Zn2+ makes it possible to obtain granules displaying various levels of compressive strength. Three different inertization matrices were used in the experiments, the first consisting solely of Portland cement, the second of Portland cement and a superplasticizer additive, and the third of Portland cement partially replaced with silica-fume and superplasticizer. The results of the tests performed showed a very low level of leaching into the alkaline solidification solution for Cr3+, the quantity leached being under 2% as against higher levels for the other metallic elements. For all the considered elements, the best results were obtained by using silica-fume in the inertization matrix.