Enrico Veschetti

Pilot-plant comparative study of peracetic acid and sodium hypochlorite wastewater disinfection.

Peracetic acid (PAA) use in wastewater disinfection was assessed by examining its performances in a pilot plant fed by the effluent from a conventional activated-sludge treatment plant. The influence of PAA initial concentrations (0.5-4.0 mg/l) and contact times (8-38 min) on the presence of seven microorganisms (total coliforms, fecal coliforms, fecal streptococci, Escherichia coli, Pseudomonas sp., Salmonella sp., and bacteriophages anti-E. coli) and on residual biocide and halogenated organic compound (AOXs) concentrations were evaluated. The data so obtained were compared to the corresponding results acquired using sodium hypochlorite (HYP) in the same experimental conditions. The biocide effect of PAA against total and fecal coliforms, E. coli, Pseudomonas sp. and Salmonella sp. was similar to that shown by HYP. The former disinfectant was, however, less efficient than the latter in the reduction of fecal streptococci and bacteriophages anti-E. coli. In both cases the biocide quantities initially introduced in the sewage resulted in the presence of significant concentrations at the end of the contact time. No significant variation of AOX content was detected in the effluent treated with PAA, whereas a progressive increment of such compounds was found when increasing quantities of HYP were added to the sewage.

Occurrence of Cryptosporidium oocysts in sewage effluents and correlation with microbial, chemical and physical water variables.

Contaminated water are recognized as a potential source of Cryptosporidium oocysts. In Italy studies on the environmentalspread of the parasite are still scarce even if a high frequencyof serological responses could suggest high rates of endemic Cryptosporidium infections. In this investigation theoccurrence of the parasite in water samples from a municipalwastewater treatment plant was monitored with the aim to evaluatepossible correlation between oocysts and bacterial indicators,pathogens and physico-chemical parameters using a multivariateanalysis. Data collected showed high numbers of oocysts, with ahigh percentage of positive samples and a significant correlationwith pH, redox potential and total organic carbon. No correlationwas found between Cryptosporidium concentration and that of the other microrganisms. The results, through a probing statistical analysis, show that none of the selected microrganisms was a reliable predictor of the presence of theparasite.

MAJOR AND TRACE ELEMENTS GEOCHEMISTRY IN THE GROUND WATERS OF A VOLCANIC AREA: MOUNT ETNA (SICILY, ITALY)

Thirty-five ground-water samples have been collected from wells, springs and drainage galleries on Mt Etna volcano for the determination of major, minor and trace elements in solution. Attention has been focused in particular on dissolved minor and trace elements, for most of which no data were available in the studied area. In general, dissolution of solids into Etnas ground waters follows from strong interaction between water of meteoric origin, CO2 gas of magmatic origin and the volcanic rocks of the aquifers. However, the R-mode analysis allowed to distinguish several sources of solutes: Al, Co, Ni, Fe, Si, As would derive mainly from alteration of the volcanic rocks of Etna; SO4=, K, Na, V, Sr, Mo, Cr and calculated p(CO2) would instead indicate a major contribution of volcanic gases (mostly CO2 and SO2); and TDS, HCO3=, Li Mg, B and Cl− would indicate a derivation from both these sources. Se, Hg, Cu and Mn would derive from hydrothermal fluids, and Ca would derive both from this latter contribution and from rock alteration. The comparison between trace elements abundance in Etnas ground waters and that in the ground waters of other areas of Italy showed that, in general, Etnas waters, like other volcanic ground waters, are enriched in Li, Mn, Si, V, As and Mo. Furthermore, in the areas of Mt Etna where the contribution of volcanic gas to the aquifers is greatest, ground waters are also enriched in B, Se, Co, Hg, Al, Fe and Ni. The obtained results show clearly that, in active volcanic areas, many dissolved elements can attain levels that can be appreciably different from those indicated by WHO for drinking water. Therefore, the local geological factors which can influence the geochemical behavior of these elements in solution should be taken into account when establishing national standards for drinking-water quality. In consideration of the local natural background values, concentrations of dissolved elements that differ from the guideline values should be accepted in areas with peculiar geological characteristics, provided that the elements under consideration do not have a direct influence on health.

Vanadium in Italian waters: monitoring and speciation of V(IV) and V(V)

In this work, a highly sensitive method was developed to separate vanadium (IV) from vanadium (V), which are both contained in water at trace levels. A suitable strong anionic exchange column (SAX) loaded with disodium ethylendiaminetetraacetic acid (Na2EDTA) was used to trap both vanadium species dissolved in 10–100 ml of water at pH 3. The vanadyl ion was selectively eluted by means of 15 ml of an aqueous solution containing Na2EDTA, tetrabutylammonium hydroxide (TBA+OH−), and isopropanol (iPr-OH) and was subsequently determined by atomic absorption spectroscopy with electrothermal atomization. The concentration of vanadate ion was calculated by subtracting the vanadyl concentration from the total concentration of vanadium. The optimal conditions for a selective elution were evaluated. The recovery of vanadium (IV) was 95% or better. The proposed method provides a simple procedure for the speciation of vanadium in aqueous matrices. The collection of the two forms could easily be carried out at the sampling site. Therefore, the risk of changing the concentration ratio between vanadium species was widely reduced. The detection limits were 1 μg/l for both species, when a 10-ml sample was eluted through the column. The method was applied successfully to vanadium speciation on different kinds of Italian volcanic water: Mount Etna (Sicily), Lake Bracciano and Castelli Romani (Latium).

Migration of trace metals in Italian drinking waters from distribution networks

Council Directive 98/83/EC on the quality of water intended for human consumption establishes a high level of protection for the consumer and requires Member States to ensure that substances and materials used in preparation and distribution of drinking water do not reduce that level of protection. The Directives point of compliance is at consumers’ taps. This implies a need for control of all drinking water construction products, including pipes and fittings within consumers’ premises. Most of the metals used in metallic construction products are controlled as parameters by the Drinking Water Directive. The stricter requirements that have been imposed by the 98/83/EC Directive indicate a need for a stricter scrutiny of the leaching characteristics of currently available metallic products. In the light of the above report, a scientific study aiming at the determination of variations in drinking water quality as an effect of interactions with metallic materials in distribution systems was conducted. In Italy, 15 main water suppliers and 13 state laboratories homogeneously distributed over the country, except for Sardinia, were involved in the research. 6000 samples were taken from 3800 sampling sites selected according to specific criteria and following specific sampling procedures. The samples were analyzed for Cr, Cu, Fe, Ni, Pb, and Zn and these experimental data were completed with information on buildings, pipes, etc. The major problems with respect to the metals originated from Fe, Ni, and Pb. High Fe concentrations could be related to corrosion processes, Ni outliers to tap materials and Pb levels to lead pipes in old buildings. With respect to the sampling procedures (random without flushing, migration for 30 min or 240 min, both after 5 min of flushing) the statistical analysis showed that random sampling without flushing gave results similar to those ensuing from 4 h migration time, and this for all types of metals.

Arsenic content in drinking-water supplies of an important volcanic aquifer in central Italy.

In this study, we have investigated arsenic occurrence and distribution in ground waters of a large volcanic area in the central part of Italy. Samples were collected from 100 springs and wells currently supplying drinking water to the province of Viterbo. A complete chemical and physicochemical characterization of the samples was carried out. The concentration of the target element was greater than 10 µg L−1 in 37% of the analyzed samples and greater than three times the legal limit in 12% of the sites (in the south-east area of the Vico lake). A 48% of the concentration values were in the range 0.0–5.0 µg L−1. The presence of arsenic is most likely due to the volcanic origin of the monitored area. Cluster analysis of the whole data set showed the existence of a significant correlation between arsenic and fluoride concentrations.

GC models for separation optimization in pressure-tuneable tandem capillary columns operated isothermally. Part 1: Theoretical aspects

GC column selectivity can be continuously adapted to suit analytical needs using a flow-tuneable tandem system. Its application for the separation of complex mixtures requires a deep understanding of the theory in this area. Although a number of researchers have developed specific models, a general and exhaustive theory is still missing. In this paper, we have made an implementation of pre-existing models on tandem-column assemblies operated isothermally. In particular, we have investigated the effect of column length and diameter, phase thickness, and oven temperature on chromatographic parameters, such as capacity factor, selectivity, and intrinsic resolution. A new approach for the correct choice of the working temperature has been proposed.

Direct determination of halogenated POPs in aqueous samples by in-tube SPME, focalization and GC-ECD analysis

A rapid analytical screening method allowing simultaneous analysis of few halogenated persistent organic pollutants (POPs) in water samples at ultra-trace levels was developed. Two-metre long capillary traps with an inner diameter of 320 μm, internally coated with 1.2 μm thick 5%-diphenyl-95%-dimethylpolysiloxane or 14%-cyanopropylphenyl-86%-dimethyl-polysiloxane stationary phase, were used to extract some chlorinated pesticides (aldrin, heptachlor, heptachlorepoxide, dieldrin, endrin, 4,4′-DDE, α-endosulfan) and polychlorobiphenyls (PCBs 1, 15, 44, 77, and 180) from aqueous media. Water samples were pushed through the traps at constant velocity using nitrogen. Every trap was installed in a GC oven and connected in series to an analytical column (25 m long, 320 μm I.D. of CP-Sil 8 CB with a 1.2 μm film thickness) installed in a second GC equipped with an ECD detector (GC-GC tandem system). The capillary trap in the first GC was quickly heated from 50 to 280 °C to focus the retained analytes into a narrow zone between the trap outlet and the analytical column inlet, temporarily kept at room temperature outside the first GC oven. After moving this zone inside the oven of the second GC, focused solutes were thermally desorbed and separated into the analytical column by programming the temperature of the second GC. Extraction recovery was always greater than 70–80% and nearly quantitative for most of the analytes. The sorptive properties of the two stationary phases were independent of sample volume and velocity but were slightly influenced by their polarity. The latter effect was used to investigate the possibility of fractionating the two classes of compounds. For this purpose, a capillary trap containing 14%-cyanopropylphenyl-86%-dimethylpolysiloxane was connected in series to a second capillary trap containing 5%-diphenyl-95%-dimethyl-polysiloxane immediately before the trapping step. Adsorbed solutes were fractioned between the two traps by eluting 0.5 mL of water–methanol 40 : 60 v/v. Most of the tested compounds were retained exclusively by one of the two stationary phases. Overall, the proposed method proved to be practically insensitive to laboratory contamination, reproducible, and suitable for the determination of halogenated POPs at trace levels (LoD in the range 5–50 pg L−1).

GC models for separation optimization in pressure‐tunable tandem capillary columns operated isothermally

In the previous part of this study, a significant improvement of the fundamental relationships that control GC resolution in a pressure-tunable assembly operating in isothermal conditions inside a single oven was made. A theoretical approach for the correct choice of the working temperature was proposed for the first time. In this second part of our report, a new interfacing device has been proposed for a rapid and reliable alignment of the two columns at the midpoint junction. Moreover, the results of a series of experimental tests have confirmed the validity of the proposed mathematical models.

Threshold flavor and odor concentrations of raw waters treated with peracetic acid or sodium hypochlorite.

Organoleptic properties of aliquots of surface and ground waters collected in Latium (Italy) from lake Bracciano and waterworks Peschiera, respectively, were compared before and after disinfection with sodium hypochlorite (NaClO) or peracetic acid (PAA). Every test was carried out according to the European Standard EN 1622 on the determination of threshold odor and flavor numbers. Assessors were selected by means of preliminary screening tests based on the evaluation of few reference compounds (citric acid, sodium chloride, and sucrose for flavor; n-butanol and NaClO for odor) added to a mineral water with a low content of salts. A series of successive dilutions were prepared and assessed by every candidate applying “paired test” and “forced choice” procedures. Afterwards, selected assessors were asked to perceive odor and flavor of the investigated surface and ground waters added with increasing concentrations of NaClO, PAA, acetic acid or hydrogen peroxide. In this case “paired tests” were evaluated by both “forced” and “unforced choice”. Organoleptic changes induced by the two disinfectants were independent of the aqueous matrix and were perceived when their concentrations became 0.04, 0.23, 6, and 11 mg L−1 for NaClO odor, NaClO flavor, PAA odor, and PAA flavor, respectively.