M. Ternero Rodríguez

Heavy metal extractable forms in sludge from wastewater treatment plants

The analysis of heavy metals is a very important task to assess the potential environmental and health risk associated with the sludge coming from wastewater treatment plants (WWTPs). However, it is widely accepted that the determination of total elements does not give an accurate estimation of the potential environmental impact. So, it is necessary to apply sequential extraction techniques to obtain a suitable information about their bioavailability or toxicity. In this paper, a sequential extraction scheme according to the BCRs guidelines was applied to sludge samples collected from each sludge treatment step of five municipal activated sludge plants. Al. Cd, Co, Cu, Cr, Fe, Mn, Hg, Mo, Ni, Pb, Ti and Zn were determined in the sludge extracts by inductively coupled plasma atomic emission spectrometry. In relation to current international legislation for the use of sludge for agricultural purposes none of metal concentrations exceeded maximum permitted levels. In most of the metal elements under considerations, results showed a clear rise along the sludge treatment in the proportion of two less-available fractions (oxidizable metal and residual metal).

Assessment of metals in sediments in a tributary of Guadalquivir River (Spain). Heavy metal partitioning and relation between the water and sediment system.

A physical-chemical characterisation of the sedimentsof the Guadaira River in Southwest Spain has beencarried out, determining twenty-three parameters persample. Non-treated urban sewage and industrialwastewaters from olive oil and table olives affectthis river. The factor analysis of the data showshigh organic matter contents with metallicpollution. Consequently, points downstreamstand out because of very high organic and metallicpollution (Zn, Pb, Cr, Cu and Cd, in order ofabundance, showing concentrations in sediments rangingfrom 50–7500 times those of waters). Heavy metals partitioning studies can be a goodapproach to show the real activity of these metals in theaquatic environment. We applied Tessiers analytical sequential extraction scheme to sediments.Sediments would be in general mildly hazardous because wefound low levels of easily interchangeable metals in the first fraction. Nevertheless, that is not thecase in the rivers last stretch, precisely wheresediments are most abundant, the heavy metal levelslargest and dredgings are made periodically. Here,their disposal is of concern; since the actual use ofthese sediments as organic amendment for agriculturalsoils is unacceptable.Interaction between waters and sediments in theriverbed by means of correlation, factor and clusteranalysis on waters and sediments data, wasinvestigated. With this approach we concluded that inthe final stretch there is a problem of contaminationof both, sediments and waters. However, in the middlecourse only sediments are actually polluted. Thiscorresponds to the previous research, when thesituation of waters in this zone was even worse.A physical-chemical characterisation of the sedimentsof the Guadaira River in Southwest Spain has beencarried out, determining twenty-three parameters persample. Non-treated urban sewage and industrialwastewaters from olive oil and table olives affectthis river. The factor analysis of the data showshigh organic matter contents with metallicpollution. Consequently, points downstreamstand out because of very high organic and metallicpollution (Zn, Pb, Cr, Cu and Cd, in order ofabundance, showing concentrations in sediments rangingfrom 50–7500 times those of waters). Heavy metals partitioning studies can be a goodapproach to show the real activity of these metals in theaquatic environment. We applied Tessiers analytical sequential extraction scheme to sediments.Sediments would be in general mildly hazardous because wefound low levels of easily interchangeable metals in the first fraction. Nevertheless, that is not thecase in the rivers last stretch, precisely wheresediments are most abundant, the heavy metal levelslargest and dredgings are made periodically. Here,their disposal is of concern; since the actual use ofthese sediments as organic amendment for agriculturalsoils is unacceptable.Interaction between waters and sediments in theriverbed by means of correlation, factor and clusteranalysis on waters and sediments data, wasinvestigated. With this approach we concluded that inthe final stretch there is a problem of contaminationof both, sediments and waters. However, in the middlecourse only sediments are actually polluted. Thiscorresponds to the previous research, when thesituation of waters in this zone was even worse.

Kinetic-spectrophotometric determination of traces of vanadium(V) by its catalytic effect on the oxidation of 1,4-dihydroxyphthalimide dioxime with bromate

Abstract A kinetic-spectrophotometric method for the determination of trace amounts of vanadium(V) is described. It is based on the catalytic action of this ion on the oxidation of 1,4-dihydroxyphthalimide dioxime by bromate, which yields a red-violet product in acidic medium. The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 500 nm and 30°C. Using several kinetic methods (tangent, fixed-time and fixed-absorbance), vanadium(V) in the range 10–400 ng ml−1 can be determined. The proposed methods are hardly subject to interferences. The tangent method was used for the determination of vanadium in atmospheric particulate matter, human serum and synthetic mixtures. The kinetic parameters of the catalysed and uncatalysed reactions are reported.

Determination of heavy metals in sewage sludge by microwave acid digestion and inductively coupled plasma atomic emission spectrometry

A description is given of a method for the determination of metals in sewage sludge samples using an acid mixture of HNO3, HClO4 and HF and a microwave oven in open vessel. The elements Al, Cd, Co, Cu, Cr, Fe, Mn, Mo, Hg, Ni, Pb, Ti and Zn were measured by inductively coupled plasma atomic emission spectrometry. The results for the analysis of three reference materials (sewage sludge CRM 145R, sewage sludge from domestic origin CRM 144R and sewage sludge from industrial origin CRM 146R) after microwave acid digestion showed close agreement with the state values for all the metals studied (except Hg). The proposed method was applied to the analysis of Al, Cd, Co, Cu, Cr, Fe, Mn, Mo, Ni, Pb, Ti and Zn in a conventional sewage treatment work to the east of Seville.

Hydrochemical study of an aquifer system in an agricultural area in South West Spain

Abstract A hydrochemical study of an aquifer located in a wide agricultural region in the Guadalquivir river basin has been carried out. Samples of 51 points in the aquifer network have been taken, and 30 parameters, indicating its physical-chemical quality, have been determined for each sample. Classifications of the samples according to their hydrochemical facies have been established and the quality of waters for both agricultural and industrial uses has been tested. Its characteristics for processing to make them drinkable have also been assessed. Isocontent maps of some parameters have allowed to show the alarming pollution state of waters caused mainly by nitrates, and to a lesser extent by organic compounds and metals. Statistical Quality Indexes of both global and partial type has also been established.

A Voltammetry Procedure with Medium Exchange for the Speciation of Heavy Metals in Wastewater of a Sewage Treatment Plant

A scheme is proposed for the speciation of heavy metals based on the Nurnberg scheme with two modifications: the application of medium exchange to the anodic stripping voltammetric (ASV) measurement, and the destruction of organic matter and particulate. The protocol is suitable for making operational divisions of four categories for the elements zinc, cadmium, lead and copper in wastewater. Three of these elements can be simultaneously determined by ASV (cadmium is not detected). The parameters of the determination include: electrodeposition potential −1.2 V, time of deaerating 300 s, time of the electrolysis 90 s (with stirring) and the rest time 40 s. Medium exchange is done after the electrodeposition step. We have applied this procedure to the study of metal speciation in effluent from a conventional wastewater treatment plant of the city of Seville (Spain).

Optimization of a Sequential Extraction Scheme for Speciation of Metals in Fine Urban Particles

A sequential extraction procedure fractioned in four steps was optimized with the purpose of improving a previous scheme for determining the chemical forms of metals in fine airborne particles. The optimization was tested on synthetic samples and then confirmed on real samples of fine particles, optimizing the type of reagent, its concentration, pH, temperature and extraction time. Synthetic samples were prepared in the laboratory with compounds of reagent grade. The analytical method applied consisted of extracting the metals from each sample in a rotator with each type of reagent under different conditions of the parameters and then centrifuging before measuring by ICP-AES. The improved and previous scheme was checked on real samples and the differences were significant in the percentages of the soluble chemical forms in the improved scheme (5.2% in front to 22.0% for Pb, 27.0% in front to 50.0% for Cd and 32.4% in front to 9.0% for Ni) from 55.6, 0.23 and 1.48 ng m− 3 of total metal concentrations respectively.

Fluorimetric determination of trace amounts of aluminium and gallium with salicylaldehyde-1-phthalazinohydrazone

Fluorimetric determinations of aluminium and gallium, based on the formation of fluorescence complexes between Al(III) or Ga(III) and salicylaldehyde-1-phthalazinohydrazone, SAPhH, are proposed. The Al(III)-SAPhH complex exhibits fluorescence with maximum emission at 475 nm when excited at 414 nm; the Ga(III)-SAPhH chelate has emission and excitation maxima at 480 and 410 nm, respectively. For both determinations the range of application is 10–100 ng/ml. Aluminium has been determined in waters, and gallium in aluminium and nickel alloys.