Javier Martín-Villacorta

Dye adsorption by sewage sludge-based activated carbons in batch and fixed-bed systems.

The present research work deals with the production of activated carbons by chemical activation and pyrolysis of sewage sludges. The adsorbent properties of these sewage sludges based activated carbons were studied by liquid-phase adsorption tests. Dyes removal from colored wastewater being a possible application for sludge based adsorbents, methylene blue and saphranine removing from solution was studied. Pure and binary adsorption assays were performed in batch and fixed bed systems. In all cases studied, the adsorbents produced from sewage sludges were able to adsorb both the compounds considered here. Nevertheless, time required for reaching equilibrium, adsorptive capacity and fixed bed characteristic parameters were different for these two compounds. Methylene blue adsorption occurred faster than that of saphranine, and it was preferably adsorbed when treating binary solutions. It could be concluded that the sewage sludge-based activated carbons may be promising for dyes removal from aqueous streams.

Comprehensive assessment of the design configuration of constructed wetlands for the removal of pharmaceuticals and personal care products from urban wastewaters

Seven mesocosm-scale constructed wetlands (CWs) of different configurations were operated outdoors for nine months to assess their ability to remove pharmaceuticals and personal care products (PPCPs) from urban wastewaters. CWs differed in some design parameters, namely the presence of plants, the species chosen (i.e., Typha angustifolia vs Phragmites australis), flow configuration (i.e., surface flow vs subsurface flow) and the presence of a gravel bed. A nearby conventional activated-sludge wastewater treatment plant (WWTP) fed with the same sewage was simultaneously monitored for comparison. The PPCPs ketoprofen, naproxen, ibuprofen, diclofenac, salicylic acid, carbamazepine, caffeine, galaxolide, tonalide and methyl dihydrojasmonate were monitored. The presence of plants favoured the removal of some PPCPs. The performance of the mesocosm studied was compound-dependant, soilless CWs showing the highest removal efficiency for ketoprofen, ibuprofen and carbamazepine, while free-water CWs with effluent leaving through the bottom of the tank performed well for the degradation of ketoprofen, salicylic acid, galaxolide and tonalide. Finally, subsurface horizontal flow CWs were efficient for the removal of caffeine. Significant linear correlations were observed between the removal of some PPCPs and temperature or redox potential. Hence, microbiological pathways appear to be the most probable degradation route for PPCPs in the CWs studied.

Assessment of full-scale natural systems for the removal of PPCPs from wastewater in small communities.

This study assessed the ability to remove pharmaceuticals and personal care products (PPCPs) of three different full-scale hybrid pond-constructed wetlands and a conventional wastewater treatment plant (WWTP). The four systems were fed with primary-treated urban wastewaters. The three hybrid systems consisted of several different subsystems (ponds, surface flow constructed wetlands and horizontal subsurface flow constructed wetlands) connected in series, and their PPCP degradation efficiency was monitored. In addition, the enantiomeric behaviour of ibuprofen was studied in all the subsystems. The hybrid systems were at least as efficient in PPCP removal as the WWTP, removal efficiencies mainly exceeding 70%. Moreover, enantiomeric analysis indicates that ibuprofen removal followed a predominantly aerobic and microbiological pathway. Constructed wetlands and ponds are therefore successful technologies for removing PPCPs from wastewater and the most significant removal process in these systems is biologically mediated.

Removal of antibiotics from urban wastewater by constructed wetland optimization

Seven mesocosm-scale constructed wetlands (CWs), differing in their design characteristics, were set up in the open air to assess their efficiency to remove antibiotics from urban raw wastewater. A conventional wastewater treatment plant (WWTP) was simultaneously monitored. The experiment took place in autumn. An analytical methodology including HPLC-MS/MS was developed to measure antibiotic concentrations in the soluble water fraction, in the suspended solids fraction and in the WWTP sludge. Considering the soluble water fraction, the only easily eliminated antibiotics in the WWTP were doxycycline (61±38%) and sulfamethoxazole (60±26%). All the studied types of CWs were efficient for the removal of sulfamethoxazole (59±30-87±41%), as found in the WWTP, and, in addition, they removed trimethoprim (65±21-96±29%). The elimination of other antibiotics in CWs was limited by the specific system-configuration: amoxicillin (45±15%) was only eliminated by a free-water (FW) subsurface flow (SSF) CW planted with Typha angustifolia; doxycycline was removed in FW systems planted with T. angustifolia (65±34-75±40%), in a Phragmites australis-floating macrophytes system (62±31%) and in conventional horizontal SSF-systems (71±39%); clarithromycin was partially eliminated by an unplanted FW-SSF system (50±18%); erythromycin could only be removed by a P. australis-horizontal SSF system (64±30%); and ampicillin was eliminated by a T. angustifolia-floating macrophytes system (29±4%). Lincomycin was not removed by any of the systems (WWTP or CWs). The presence or absence of plants, the vegetal species (T. angustifolia or P. australis), the flow type and the CW design characteristics regulated the specific removal mechanisms. Therefore, CWs are not an overall solution to remove antibiotics from urban wastewater during cold seasons. However, more studies are needed to assess their ability in warmer periods and to determine the behaviour of full-scale systems.

Statistical modelling of organic matter and emerging pollutants removal in constructed wetlands

Multiple regression models, clustering tree diagrams, regression trees (CHAID) and redundancy analysis (RDA) were applied to the study of the removal of organic matter and pharmaceuticals and personal care products (PPCPs) from urban wastewater by means of constructed wetlands (CWs). These four statistical analyses pointed out the importance of physico-chemical parameters, plant presence and chemical structure in the elimination of most pollutants. Temperature, pH values, dissolved oxygen concentration, redox potential and conductivity were related to the removal of the studied substances. Plant presence (Typha angustifolia and Phragmites australis) enhanced the removal of organic matter and some PPCPs. Multiple regression equations and CHAID trees provided numerical estimations of pollutant removal efficiencies in CWs. These models were validated and they could be a useful and interesting tool for the quick estimation of removal efficiencies in already working CWs and for the design of new systems which must fulfil certain quality requirements.

Evaluation of primary treatment and loading regimes in the removal of pharmaceuticals and personal care products from urban wastewaters by subsurface-flow constructed wetlands

The ability of several mesocosm-scale horizontal subsurface flow (SSF) constructed wetlands (CW) to remove pharmaceuticals and personal care products (PPCPs) from urban wastewater was assessed in the winter and summer of 2008. As CWs are generally used as secondary or tertiary wastewater treatment systems, their efficacy was compared when fed from two different primary treatment systems, a sedimentation tank and an anaerobic hydrolysis upflow sludge bed reactor (HUSB). The influence of plants (Phragmites australis) in the CWs and their feeding regime (continuous flow or batch flow) on PPCP removal were also monitored. One of the CWs was replicated and operated simultaneously in Barcelona and León, Spain, in order to study the effect of environmental conditions on PPCP removal. All systems operated in the open air. The sedimentation tank offered slightly better removal values throughout the experimental period than the HUSB. The presence of P. australis enhanced the removal of salicylic acid, galaxolide, tonalide and methyl dihydrojasmonate, but only in summer (when plants were more active). The use of a batch flow or a continuous flow made very little difference to PPCP removal efficiency. When the two mesocosm replicates were compared, temperature proved to be one of the most determining parameters affecting PPCP elimination, with naproxen, ibuprofen, diclofenac, caffeine, galaxolide, tonalide and methyl dihydrojasmonate being removed in SSF-CWs more efficiently at higher temperatures. In general, the most easily removed PPCPs in planted CWs were caffeine (14 ± 74%–84 ± 7% in winter, 98 ± 1%–99 ± 1% in summer), methyl dihydrojasmonate (28 ± 21%–63 ± 17% in winter, 93 ± 2%–98 ± 1% in summer) and salicylic acid (0%–97 ± 4% in winter, 41 ± 40%–89 ± 9% in summer), followed by naproxen (0%–41 ± 16% in winter, 60 ± 18%–95 ± 4% in summer) and ibuprofen (0%–47 ± 26% in winter, 35 ± 12%–99 ± 1% in summer). Other substances experimented lower removal efficiencies, like ketoprofen (4 ± 27%–27 ± 14% in winter, 0%–37 ± 32% in summer), diclofenac (0%–22 ± 22% in winter, 0%–71 ± 8% in summer), carbamazepine (0%–9 ± 100% in winter, 0%–58 ± 21% in summer), galaxolide (0% in winter, 25 ± 14%–87 ± 5% in summer) and tonalide (0% in winter, 32 ± 12%–76 ± 12% in summer).

Optimization of performance assessment and design characteristics in constructed wetlands for the removal of organic matter

Some of the most used constructed wetland (CW) configurations [conventional and modified free-water (FW) flow, surface flow, conventional horizontal subsurface flow (SSF) and soilless systems with floating macrophytes (FM)] were assessed in order to compare their efficiencies for the removal of organic pollutants [COD, filtered COD (FCOD), BOD and total suspended solids (TSS)] from urban sewage under the same climatic and wastewater conditions. The removal performance was calculated using three approaches: effluent concentrations, areal removed loads and mass removal. Results were very different depending on the approach, which indicates that the way to present CW efficiency should be considered carefully. All CW-configurations obtained BOD effluent concentrations below 25 mg L(-1) in summer, with a FW-CW with effluent leaving through the bottom of the tank being the only one maintaining low BOD effluent concentrations even in winter and under high organic loading conditions. In this kind of CW, the presence of plants favoured pollutant removal. SSF-CWs were the most efficient for the removal of COD. FM systems can be as efficient as some gravel bed CWs. Typhaangustifolia worked better than Phragmitesaustralis, at least when the systems were at the beginning of their operation period.

Determination of Diazinon and Fenitrothion in Environmental Water and Soil Samples by HPLC

Abstract High performance liquid chromatography (HPLC) methods have been developed for the determination of the organophosphorus pesticides, diazinon, and fenitrothion in environmental water and soil samples; a simple and rapid sample preparation procedure using solid‐phase extraction being developed in the case of water samples. In soil samples, the analytical procedure proposed consisted of a 10‐min ultrasonic extraction of the target compounds from a 20 g soil sample with 20 mL of acetonitrile and, after centrifugation, the filtering and concentration of the supernatant in an SC110H Speed Vac Plus concentrator to evaporate solvents. The quantification of diazinon and fenitrothion was performed using UV photodiode detection at 245 and 267 nm, respectively. The average recoveries from spiked water and soil samples at various concentration levels exceeded 86% with relative standard deviations of 1.8–5.1%. It was possible to determine concentrations of these pesticides in the range 0.1–2 ng/g in water and soil samples with a good level of reproducibility and accuracy.

Zn2+ catalysed hydrolysis of β-lactams: experimental and theoretical studies on the influence of the β-lactam structure

We present both experimental and theoretical results on simple model systems of zinc-β-lactamases. Kinetic studies show that the rate of degradation of β-lactam antibiotics in the presence of zinc ions and tris(hydroxymethyl)aminomethane buffers depends markedly on the structure of the β-lactam. Carbapenems are highly reactive whereas monobactam antibiotics like aztreonam, which are known to be non-susceptible to the catalytic action of the metallo-β-lactamases, are less reactive by three orders of magnitude. To complement the experimental studies, density functional calculations were carried out on model systems. These calculations allowed us to characterise the reactive mode of binding between the β-lactam nucleus and Zn2+ ions as well as to rationalise the kinetic trends observed experimentally. Docking analyses are reported for the complex formed between aztreonam and the mononuclear metallo-β-lactamase from Bacillus cereus. On the basis of all the results, we hypothesise that the aztreonam–metallo-β-lactamase complex might be poorly reactive due to a potential interaction of the N-sulfonate group of aztreonam with the essential Zn ion at the active site.

Solid‐Phase Extraction for the Determination of Dimethoate in Environmental Water and Soil Samples by Micellar Electrokinetic Capillary Chromatography (MEKC)

Abstract A micellar electrokinetic chromatography (MEKC) procedure has been developed for the analysis of dimethoate (DM) in environmental water and soil samples, using solid phase extraction (SPE) as a clean‐up and pre‐concentration technique to improve selectivity and DM detection limits. The limit of quantification (LOQ) was 1 µg/mL for direct injection and 3 ng/mL after the SPE pre‐concentration procedure. Within‐run and between‐day reproducibility studies performed at 0.02, 0.05, and 0.2 µg/mL indicated that the procedure was indeed reproducible. Quantification was by UV detection at 200 nm. The capillary electrophoresis (CE) method proposed uses sodium borate 100 mM with sodium dodecyl sulfate 50 mM, pH 8.4 as a buffer. The method was simple and fast, with good recoveries, which on average ranged from 82 to 92% with a relative standard deviation of 7% or less for water and soil samples fortified at 10, 20, 30, and 300 ng/mL. Our results show CE to be a powerful analytical tool for the determination of DM in environmental water and soil samples.