J.C. Tapias

Analysis of inlet and outlet industrial wastewater effluents by means of benchtop total reflection X-ray fluorescence spectrometry

The monitoring of heavy metals in industrial waste water effluents is an important activity in many laboratories. Of special interest is the screening of elemental composition of inlet effluents and quantitative analysis of outlet effluents to study the efficiency of chemical treatment process to eliminate metals and to comply with current established concentration limits, respectively. In this sense, fast analytical methodologies which entail simple sample preparation are desired. In the present work, the possibilities and drawbacks of a benchtop total reflection X-ray fluorescence spectrometer (TXRF) for the rapid and simple determination of some inorganic impurities (As, Ba, Cd, Cu, Cr, Sn, Fe, Mn, Ni, Pb, Se and Zn) in inlet and outlet industrial waste water effluents from metallurgical and tanning leather factories have been tested. An evaluation of different simple sample treatments is presented and it is followed by a discussion of spectral and chemical matrix effects when dealing with this type of samples. Analytical figures of merit such as accuracy, precision and limits of detection have also been carefully studied. Finally, the data obtained by direct TXRF analysis has been compared to that obtained by ICP-OES/ICP-MS after a microwave digestion.

Analytical approaches for Hg determination in wastewater samples by means of total reflection X-ray fluorescence spectrometry

At present, there is a considerable interest in Hg monitoring in wastewater samples due to its widespread occurrence and the high toxicity of most of its compounds. Hg determination in water samples by means of total reflection X-ray fluorescence spectrometry (TXRF) entails some difficulties due to the high vapor pressure and low boiling point of this element that produce evaporation and loss of Hg from the surface of the reflector during the drying process, commonly used for sample preparation in TXRF analysis. The main goal of the present research was to develop a fast and simple chemical strategy to avoid Hg volatilization during the analysis of wastewater samples by TXRF spectrometry. Three different analytical procedures were tested for this purpose: (i) increasing the viscosity of the wastewater sample by adding a non-ionic surfactant (Triton X-114), (ii) Hg immobilization on the quartz reflectors using the extractant tri-isobutylphosphine (Cyanex 471X) and (iii) formation of a stable and non-volatile Hg complex into the wastewater sample. The best analytical strategy was found to be the formation of a Hg complex with thiourea (pH=10) before the deposition of 10 microL of sample on the reflector for following TXRF analysis. Analytical figures of merit such as linearity, limits of detection, accuracy and precision were carefully evaluated. Finally, the developed methodology was applied for the determination of Hg in different types of wastewater samples (industrial effluents, municipal effluents from conventional systems and municipal effluents from constructed wetlands).

Assessing the agricultural reuse of the digestate from microalgae anaerobic digestion and co-digestion with sewage sludge

Microalgae anaerobic digestion produces biogas along with a digestate that may be reused in agriculture. However, the properties of this digestate for agricultural reuse have yet to be determined. The aim of this study was to characterise digestates from different microalgae anaerobic digestion processes (i.e. digestion of untreated microalgae, thermally pretreated microalgae and thermally pretreated microalgae in co-digestion with primary sludge). The main parameters evaluated were organic matter, macronutrients and heavy metals content, hygenisation, potential phytotoxicity and organic matter stabilisation. According to the results, all microalgae digestates presented suitable organic matter and macronutrients, especially organic and ammonium nitrogen, for agricultural soils amendment. However, the thermally pretreated microalgae digestate was the least stabilised digestate in comparison with untreated microalgae and co-digestion digestates. In vivo bioassays demonstrated that the digestates did not show residual phytotoxicity when properly diluted, being the co-digestion digestate the one which presented less phytotoxicity. Heavy metals contents resulted far below the threshold established by the European legislation on sludge spreading. Moreover, low presence of E. coli was observed in all digestates. Therefore, agricultural reuse of thermally pretreated microalgae and primary sludge co-digestate through irrigation emerges a suitable strategy to recycle nutrients from wastewater.

Bromine and bromide content in soils: Analytical approach from total reflection X-ray fluorescence spectrometry.

Monitoring total bromine and bromide concentrations in soils is significant in many environmental studies. Thus fast analytical methodologies that entail simple sample preparation and low-cost analyses are desired. In the present work, the possibilities and drawbacks of low-power total reflection X-ray fluorescence spectrometry (TXRF) for the determination of total bromine and bromide contents in soils were evaluated. The direct analysis of a solid suspension using 20xa0mg of fine ground soil (<63xa0μm) gave a 3.7xa0mgxa0kg(-1) limit of detection for bromine which, in most cases, was suitable for monitoring total bromine content in soils (Br content range in soilsxa0=xa05-40xa0mgxa0kg(-1)). Information about bromide determination in soils is also possible by analyzing the Br content in water soil extracts. In this case, the TXRF analysis can be directly performed by depositing 10xa0μL of the internal standardized soil extract sample on a quartz glass reflector in a measuring time of 1500xa0s. The bromide limit of detection by this approach was 10xa0μgxa0L(-1). Good agreement was obtained between the TXRF results for the total bromine and bromide determinations in soils and those obtained by other popular analytical techniques, e.g. energy dispersive X-ray fluorescence spectrometry (total bromine) and ionic chromatography (bromide). As a study case, the TXRF method was applied to study bromine accumulation in two agricultural soils fumigated with a methyl bromide pesticide and irrigated with regenerated waste water.

Using 3-D structures and their virtual representation as a tool for restoring opencast mines and quarries

An important factor in the restoration studies of quarries and open-cast mines is the ability of generating final restored models of visualisation. These 3-D models are particularly useful for presenting projects, as they can greatly enhance the analysis of different alternatives. A method involving several subroutines for simulation purposes is presented in this paper. The system allows for the simulation of a variety of geological structures, both real and restored. The subroutines facilitate: (1) the automatic integration between the restoration structure and its geotechnical and morphological parameters, (2) the achievement of a uniform slope, and (3) the adjustment of the talus of the restoration structure to the relief. Graphic output in DXF and VRML formats allows for both static and dynamic optimal visualisation. Readers interested in subroutines written in Visual Basic can contact the first author: victor@geo.ub.es.

Non-conventional water resources in coastal areas: a review on the use of reclaimed water

In an era of increasing contest for limited water resources a wise joint management of conventional and non-conventional water resources must be considered. Water scarcity aggravates in coastal zones which are often characterised by high population density, intense economic activity and tourism meaning heavy seasonal water demands. The relationships between sea and land water can also compromise the quality of available freshwater. In this context, the use of non-conventional water increases the availability of water supplies. Non-conventional water resources of lower quality could be directed to meet several needs (like watering lawns, washing cars, flushing toilets and cooling systems, among others). Therefore, significantly more potable water would be available to meet human demand for safe water.

Removal and relationships of microbial indicators in a water treatment and reclamation facility

A wastewater treatment and reclamation facility in north-east Spain was monitored over 1 year to determine the occurrence and concentrations of different microbial indicators (Escherichia coli, fecal enterococci, somatic bacteriophages and spores of sulfite-reducing clostridia). The removal of the indicators and its relationships through the wastewater treatment and reclamation trains were evaluated. The results obtained show that the reclamation treatments evaluated present a different efficiency in indicator microorganisms removal depending on the type of microorganism. The E. coli and enterococci present an average reduction slightly higher than the other indicators, followed by somatic bacteriophages and spores of sulfite-reducing clostridia. The Spearmans correlations indicate that it is not suitable to use any of the bacterial indicators evaluated to predict the content of virus or spores of sulfite-reducing clostridia. Therefore, in order to evaluate the microbiological risk of the reclaimed effluent use, it is necessary to monitor the three types of indicator microorganisms (bacteria, virus and protozoa).

Secondary effluent reclamation: combination of pre-treatment and disinfection technologies

A study was carried out to evaluate the efficiency of secondary effluent additional treatment, using a combination of pre-treatments (ring filter, physico-chemical and infiltration-percolation) followed by disinfection methods (chlorine dioxide, peracetic acid and ultraviolet light). Three different indicator microorganisms were determined: E. coli, total coliforms and somatic bacteriophages. The results show better efficiency of physico-chemical and infiltration-percolation processes. Bacteriophages were eliminated to a lesser extent than bacterial indicators in all the treatment systems. Chlorine dioxide and peracetic acid seems to be more efficient in disinfection than ultraviolet light when a ring filter is the pre-treatment used. For the same doses and contact times, the efficiency of the disinfection methods is higher when the pre-treatment used is the physico-chemical or the infiltration-percolation system. The final effluent quality from the physico-chemical treatment train and the infiltration-percolation treatment train, followed by the disinfectants, achieves an E. coli content that allows the reuse in most of the uses described in the Spanish legislation for wastewater reuse.

An evaluation of aquifer vulnerability in two nitrate sensitive areas of Catalonia (NE Spain) based on electrical resistivity methods

The protection of groundwater has become one of the most important European environmental policies as evidenced by the Orders relating to the protection of water from contamination, Directive 2000/60/CE of the European Parliament and the European Union Council, and more concretely Directive 2006/118/118/CE, related to the protection of groundwater from pollution and degradation. Traditional methods for assessing vulnerability include soil surveys, drilling and analysis of lithology logs from wells with the objective of characterising the thickness, hydraulic properties and lateral extend of the protective layers. However, such studies can be labour-intensive and expensive. In addition, the parameters measured may have high spatial variability, which makes accurate characterization over large areas difficult. Fortunately, a numerical index of protection can be assigned from the longitudinal electrical conductance parameter derived from electrical resistivity surveys (VES, ERT or any other electrical or EM method). This can be more accurate and reliable than any other vulnerability index derived only from visual inspection or interpolated from sparse borehole data.

Assessing the Vulnerability of Groundwater Pollution at Sensitive Areas by Geophysical Methods

The protection of groundwater has became one of the foremost environmental European policies according the Orders on the Protection of Water Against Contamination Directive 2000/60/CE of the European Parliament and the European Union Council, and more concretely with the Directive 2006/118/118/CE, related to groundwater protection against the pollution and degradation. Traditional methods for assessing vulnerability include soil surveys, drilling and analyses of logs from wells with the objective to characterize the thickness, hydraulic properties and lateral extent of the protective layers. Disadvantages of such investigations are that they can be labour-intensive and expensive. In addition, the measured parameters may have high spatial variability making accurate characterization over large areas difficult. As a result, a numerical index of protection can be assessed from the longitudinal electrical conductance parameter derived from electrical resistivity surveys (VES, ERT or any other electrical or EM method), that can be more accurate and reliable than any other vulnerability index assumed only by visual inspection or interpolated from sparse borehole data.