The removal of naphthalene from aqueous solutions by filtration using columns filled with sand and natural vermiculite and sand and hydrophobic vermiculite in different proportions of 2%, 5%, and 10% was evaluated. Batch experiments had shown that the removal was higher than 90% when the filled adsorbent was constituted by 10% of hydrophobic vermiculite. When vermiculite was in lower concentration, that is, 2% and 5%, the removal percentage was lower than 74%. The removal of the naphthalene by the column filled with sand and natural vermiculite did not exceed 25%. The capacity of the columns was tested passing four volumes of aqueous solution of 0.01 mol L⁻¹ naphthalene. After the third volume, the capacity dropped but still retained the major part of pollutant. However, the removal can be reached in higher levels (higher than 90%) when it is filled with 10% of modified vermiculite and increasing the length of the column. With 5% of vermiculite, it is possible to remove 94%, increasing the length of column by a factor of 1.1 times, that is, increasing the original length of 25 to 27.5 cm. The results had demonstrated that the columns are efficient in the removal of the naphthalene and bring speculations to remove other possible organic compounds.

In this research, we have investigated the removal efficiency of natural organic matter (NOM) from river and stream water using potassium ferrate(VI). For the study, ferrate was added in 100-ml water sample mixed either with humic acid or with fulvic acid. The removal efficiency at the ferrate dose of 2-46 mg/l (as Fe) was 21-74% for 10 mg/l humic acid and 48-78% for 10 mg/l fulvic acid. NOM was more effectively removed either at lower pH or at higher temperature. The removal performance by ferrate was comparable to that by traditional coagulants (i.e., alum, FeSO₄·7H₂O, and FeO(OH)). In addition, the removal rate of humic acid using traditional coagulants was improved by pretreatment with a very small dose of ferrate. The reaction between ferrate and humic acid was completed within 60 s, while showing first-order kinetic, and then reached a steady state.

The use of vermicompost was expanded as natural adsorbent for cationic dyes retention. The adsorption profiles in batch and flow modes for crystal violet and methylene blue on vermicompost material were evaluated. In batch mode, a retention index higher than 97% was obtained for both compounds, while in flow condition, 40 g of dried adsorbent material were enough to remove 100 mg of crystal violet or methylene blue at column flow rates of 5 and 20 mL min⁻¹. Adsorption isotherms showed adsorptive maximum capacities for vermicompost of 0.78 and 5.47 mg g⁻¹, respectively, which were compatible with the literature. Due to this good efficiency capacity, incineration steps can be considered as acceptable disposal procedures for enriched vermicompost. From these characteristics, economical and environmental advantages of the proposed material for the evaluated cationic dyes retention were evidenced.

The objective of this study was to investigate the changes in the chemical partitioning of Cu, Pb, Cr and Zn within a column of soil incubated with an anaerobic sewage sludge (ANSS) for 2.5 months. The soil was irrigated during the incubation period. A sequential extraction method was used to fractionate these metals into exchangeable, weakly adsorbed, organic, Al oxide, Fe-Mn oxide, and residual, respectively. ANSS was applied at a loading rate of 69 Mg ha⁻¹. The soil is a Dystric Cambisol with low pH (<3.8), low CEC [<10 cmol(+) kg⁻¹ below the first 4 cm depth], and low base saturation (<7%). The addition of the ANSS caused a decrease in concentrations of Cu, Pb, and Cr in the A1 horizon, and an increase in the concentrations with depth. Below the A1 horizon, concentrations of Cu increased uniformly (~1 mg cm⁻¹), and the greatest increases were observed in the residual, Fe-Mn oxides, and weakly adsorbed fractions. Maximum increases in Pb occurred at 4-9 cm of depth (1.6 mg cm⁻¹), and mainly affected the weakly adsorbed fraction. Chromium essentially accumulated at the limit between the A2 and the Bw horizons (1.1-1.5 mg cm⁻¹) as residual and organic bound forms, probably through particulate transport. Zinc mainly accumulated in the A1 horizon (2.9 mg cm⁻¹) as exchangeable Zn. At depth, Zn increments were predominantly observed in the residual fraction. The results of this study thus demonstrate the redistribution of contaminants into different chemical pools and soil layers after sludge amendment.

Variation of mercury (Hg) in sediments and biota from Coatzacoalcos estuary during the dry, rainy and windy seasons was estimated. In sediments, Hg concentrations ranged from 0.07 μg g⁻¹ in site 13 (Ixhuatepec) located upstream, to 1.06 μg g⁻¹ in site 3 (Coatzacoalcos river), located in the industrialized area. Highest enrichment factor (EF) and index of geoaccumulation (I geo) in surficial sediments were 53 and 5.1 respectively. From EF and I geo, it is considered that Coatzacoalcos estuary is from moderately contaminated to contaminated. In most fish species from Coatzacoalcos estuary, the sequence of Hg concentration was liver>muscle>gills. Average Hg concentrations in soft tissue of bivalves ranged from 0.09 μg g⁻¹ in Corbicula fluminea to 0.18 μg g⁻¹ in Polymesoda caroliniana. Biota-sediment accumulation factor (BSAF) ranged from 0.9 in P. caroliniana during the rainy season (site 4) to 3.8 in P. caroliniana from the same site during the windy season.

In this study, the occurrence of toxic heavy metals (As, Cd, Cr, Cu, Pb, and Zn) and relative bioaccumulation in biota samples were investigated in a freshwater ecosystem, the Basento river, one of the main aquatic systems in the south of Italy, which over the last years has been transformed into a sink of urban and industrial wastes. Therefore, the levels of arsenic, cadmium, chromium, copper, lead, and zinc were determined in water, sediments, and tissues of some macroinvertebrate--which are natural assessment endpoints for the evaluation of ecological risk in aquatic systems. Accumulation factors, as a ratio between the concentration of a given contaminant in biota and the one in an abiotic medium, were considered in order to estimate heavy metal contamination loads in biota. Statistical analysis was performed for a comparative evaluation of bioaccumulation among various macroinvertebrates, according to different feeding guilds. The Tukey honestly significantly different test showed significant differences in the bioaccumulation of As, Cd, and Cr among the considered biological receptors (collector-gatherer, predator, and filterer), suggesting that the biological uptake from immediate contact with the sediment or solid substratum (collector-gatherer), instead of the bioconcentration from water (filterer) or biomagnification along the biotic food webs (predators), is the more effective biological sequestering pathway for these metals. Biota-sediment accumulation factors, commonly used for the evaluation of sediment's role in aquatic systems contamination, were determined for the considered metals. A linear correlation between the concentrations of As, Cd, Cr, and Zn in macroinvertebrates and those in the sediments suggested that the metal uptake data in macroinvertebrates can provide useful information for the estimation of heavy metal exposure risk or bioavailability when making assessments of sediment toxicity in freshwater ecosystems.

Municipal solid waste (MSW) source-classified collection represents an advancement in resource recycling and secondary pollution control in China. Comparative experiments were performed to assess the effect of a newly-established MSW source-classified collection system on polycyclic aromatic hydrocarbons (PAHs) in bottom ash from an incinerator (BA), fly ash from a boiler (FAB) and fly ash from a bag filter (FABF) of a full-scale MSW incinerator in China. Compared with FAB or FABF, PAHs were mainly concentrated in BA with a range of 1,961.0-2,420.2 μg/kg. Total amounts of 16 high priority PAHs in BA, FAB and FABF from the classified MSW incineration were significantly reduced by 19.0%, 42.4% and 59.8% respectively in comparison with those from the traditional mixed MSW incineration. Moreover, the toxic equivalent quantity (B[a]Peq) of carcinogenic PAHs in these three kinds of residues from the classified MSW incineration were significantly decreased, with the maximum decrease observed in FABF. As a result of source-classification with effective presorting and dewatering, plastics and metals in the MSW were lower, but combustibles and heat values of the MSW increased. Due to variations of the characteristics of the feed waste, complete combustion conditions including continuous higher incineration temperature, lower CO concentration and higher air excess ratio were observed during the process of classified MSW incineration. Incineration temperature and CO concentration showed a negative and positive correlation, respectively, with total PAHs, indicating that incomplete combustion products such as PAHs could be reduced by controlling combustion conditions directly related to properties of the feed waste. The newly established MSW source-classified collection process could be a feasible method for reducing PAHs formation and emission in residues from MSW incineration.

The unsaturated zone of an aquifer serves as a water reservoir which discharges water and eventual pollution to the saturated zone for a relatively long period after the cessation of surface input. Effective protection of a water resource requires detailed knowledge of transport mechanisms through the unsaturated zone with regard to its protective function. The article presents the application of isotope methods in the study of groundwater transport processes in the unsaturated zone of Selniška Dobrava coarse gravel aquifer. Emphasis is given to the use of environmental isotopes as natural tracers in the study of groundwater dynamics in the unsaturated zone. The estimation of groundwater flow characteristics was based on experimental work in lysimeter. Based on long-time isotope investigations with the use of lumped parameter models, some water flow parameters (mean residence time, mean matrix flow velocity) in the unsaturated zone were calculated. The results were compared with tracing experiment results in the same lysimeter.

Chemical reduction of the hexavalent chromium, Cr(VI), present in contaminated soil and groundwater was carried out in a slurry reactor under dynamic conditions (120 rpm and 25°C) using different reductants [ferrous sulphate (Fe(II))], sodium bisulphite, sucrose, ascorbic acid and zerovalent iron (ZVI)] in order to evaluate the influence of the reductant on the redox process. Chemical analysis of the contaminated soil revealed a Cr(VI) concentration of 528 ± 31 mg kg⁻¹. Batch studies under dynamic conditions (slurry reactor) using different [Cr(VI)]/[reductant] molar ratios revealed that only Fe(II) and ZVI species can promote both reduction of Cr(VI) and immobilisation of Cr(III) (formation of an insoluble hydroxide compound). It was verified that 1.0 g of ZVI is capable of converting 104 ± 5 mg of Cr(VI) in Cr(III). A kinetic redox study was carried out using ZVI in different conditions. In all cases, it was verified that Cr(VI) reduction follows a pseudo-first-order kinetic behaviour. The dependence of the pseudo-first-order kinetic rate constant, k obs, on [ZVI] indicates that the redox process taking place in the slurry reactor is rather complex. A phenomenological kinetic equation for the redox process taking place in the slurry reactor was presented in order to describe the behaviour of k obs under non-ideal conditions.

The debate on sludge recycling and disposal has been recently a target of growing interest due to the expressed concern about the potential risks of its agricultural use on human health and the environment. This fact has led to revisions in government policy and regulations and many novel treatment processes have been proposed in order to make the recycling and reuse of sewage sludge sustainable. In this work, the use of some pretreatments (alkaline, thermal, and ozonation) combined with conventional anaerobic digestion has been assessed on digested sludge quality in terms of pathogens, dewatering properties, heavy metals, and organic pollutants. All pretreatments proved to be efficient to reach the requirements proposed in the Working Document on Sludge prepared by the European Commission (CEC, Council Directive of 27 April 2000 on Working Document on Sludge--third draft. Brussels: European Commission DG Environment. Retrieved from http://ec.europa.eu/environment/waste/sludge/pdf/sludge_en.pdf, 2000a) and also those established by the U.S. Environmental Protection Agency (EPA, Standards for the disposal and utilization of sewage sludge, part 503. Retrieved from http://www.epa.state.il.us/public-notices/2004/lincoln-trails-mhp/draft-permit.pdf, 1993).