Removal of oxyfluorfen from polluted effluents by combined bio-electro processes.

In this work, the combination of biological and electrochemical processes to mineralize oxyfluorfen has been studied. First, an acclimatized mixed-culture biological treatment was used to degrade the biodegradable fraction of the pesticide, reaching up to 90% removal. After that, the non-biodegraded fraction was oxidised by electrolysis using boron-doped diamond as the anode. The results showed that the electrochemical technique was able to completely mineralize the residual pollutants. The study of the influence of the supporting electrolyte on the electrochemical process showed that the trace mineral solution used in the biological treatment was enough to completely mineralize the oxyfluorfen, resulting in total organic carbon removal rates that were well-fitted by a first-order model with a kinetic constant of 0.91 h-1. However, the first-order degradation rate increased approximately 20% when Na2SO4 was added as supporting electrolyte, reaching a degradation rate of 1.16 h-1 with a power consumption that was approximately 70% lower.

Influence of hydraulic retention time and carbon loading rate on the production of algae.

This paper is focused on the assessment of the production of algae in batch bioreactors. Hydraulic retention time, carbon loading rate and light color were the inputs of the study and algae production the main output. Bioreactors were operated in semi-continuous mode and tests lasted two months, more than two times the period required to meet a steady-state response. This steady-state was verified with plateau responses in both, soluble parameters and suspended solids. Results points out the great relevance of temperature. Likewise, they show that green light improves the production of algae, as well as long HRT and high CLR. Maximum production rates attained were in the range 4-14 mg d-1 L-1. The ratio COD /TSS for this biofuel was almost constant (3.13 mg COD mg-1 TSS) but the quality of the product obtained in terms of the Mean Oxidation State of Carbon is completely different. Longer HRT leads to lower MOSC and hence to potentially more valuable fuels.

Effect of electric field on the performance of soil electro-bioremediation with a periodic polarity reversal strategy.

In this work, it is studied the effect of the electric fields (within the range 0.0-1.5 V cm(-1)) on the performance of electrobioremediation with polarity reversal, using a bench scale plant with diesel-spiked kaolinite with 14-d long tests. Results obtained show that the periodic changes in the polarity of the electric field results in a more efficient treatment as compared with the single electro-bioremediation process, and it does not require the addition of a buffer to keep the pH within a suitable range. The soil heating was not very important and it did not cause a change in the temperature of the soil up to values incompatible with the life of microorganisms. Low values of water transported by the electro-osmosis process were attained with this strategy. After only 14 d of treatment, by using the highest electric field studied in this work (1.5 V cm(-1)), up to 35.40% of the diesel added at the beginning of the test was removed, value much higher than the 10.5% obtained by the single bioremediation technology in the same period.

Operation of a horizontal subsurface flow constructed wetland--microbial fuel cell treating wastewater under different organic loading rates.

The aim of the present work is to determine whether a horizontal subsurface flow constructed wetland treating wastewater could act simultaneously as a microbial fuel cell (MFC). Specifically, and as the main variable under study, different organic loading rates were used, and the response of the system was monitored. The installation consisted of a synthetic domestic wastewater-feeding system and a pilot-scale constructed wetland for wastewater treatment, which also included coupled devices necessary to function as an MFC. The wetland worked under continuous operation for 180 d, treating three types of synthetic wastewater with increasing organic loading rates: 13.9 g COD m(-2) d(-1), 31.1 g COD m(-2) d(-1), and 61.1 g COD m(-2) d(-1). The COD removal efficiencies and the cell voltage generation were continuously monitored. The wetland worked simultaneously as an MFC generating electric power. Under low organic loading rates, the wastewater organic matter was completely oxidised in the lower anaerobic compartment, and there were slight aerobic conditions in the upper cathodic compartment, thus causing an electrical current. Under high organic loading rates, the organic matter could not be completely oxidised in the anodic compartment and flowed to the cathodic one, which entered into anaerobic conditions and caused the MFC to stop working. The system developed in this work offered similar cell voltage, power density, and current density values compared with the ones obtained in previous studies using photosynthetic MFCs, sediment-type MFCs, and plant-type MFCs. The light/darkness changes caused voltage fluctuations due to the photosynthetic activity of the macrophytes used (Phragmites australis), which affected the conditions in the cathodic compartment.

Simulation of carbon degradation in a rotary drum pilot scale composting process.

This paper studies the simulation of carbon degradation in pilot scale solid waste composting processes using first-order kinetic models previously calibrated by laboratory experiments at different temperatures. Different solid biowastes (olive mill waste, winery waste, sewage sludge and reed biomass) were used. Three mixtures were prepared from combinations of the materials listed above, and they were used in both the laboratory kinetic experiments and the pilot scale composting experiments. Lab experiments were conducted in small reactors with temperature (T) control and forced aeration of the solid mixture. Each biowaste mixture was treated at four different temperatures, 25, 40, 50 and 60 °C, with controlled moisture; the carbon (C) concentration of the samples was measured weekly. Two different kinetic models were used to fit the carbon mineralisation curves: the 2C model, which considers two organic fractions (biodegradable and non-biodegradable), and the 3C model, which considers three fractions (easily biodegradable, slowly biodegradable and non-biodegradable). In both cases, the kinetic rate constants were calculated by mathematical fitting. The influence of temperature on the rate constants was also studied for both models using a T-dependent equation. The theoretical k(T) curves showed classical shapes, and the temperatures for optimum k values and thermal inactivation were obtained. Once the C degradation rate constants and their T dependence equations were available, it was possible to simulate the evolution of C degradation in an actual pilot scale rotary drum composting process under varying temperatures and using the same biowaste mixtures. The comparison between the theoretical profiles and the experimental data showed that the thermophilic stage could be accurately simulated; however, errors and lower levels of model accuracy occurred when the maturation stage was simulated. The simulation was valid for all of the viewed biowaste mixtures. The 2C and 3C simulation profiles were quite similar in all cases for much of the process duration; the differences between the profiles only occurred after the end of the thermophilic stage. It was concluded that the 2C model would be only valid for shorter experimental periods, until the readily biodegradable carbon fraction was removed, while the 3C model reproduced the subsequent degradation in the maturation stage more closely.

Thermogravimetric-mass spectrometric analysis of lignocellulosic and marine biomass pyrolysis.

The pyrolysis characteristics of three lignocellulosic biomasses (fir wood, eucalyptus and pine bark) and a marine biomass (Nannochloropsis gaditana microalgae) were investigated by thermogravimetric analysis coupled with mass spectrometry (TGA-MS). Thermal degradation of lignocellulosic biomass was divided into four zones, corresponding to the decomposition of their main components (cellulose, hemicellulose and lignin) and a first step associated to water removal. Differences in volatile matter and cellulose content of lignocellulosic species resulted in different degradation rates. Microalgae pyrolysis occurred in three stages due to the main components of them (proteins), which are greatly different from lignocellulosic biomass. Heating rate effect was also studied. The main gaseous products formed were CO(2), light hydrocarbons and H(2)O. H(2) was detected at high temperatures, being associated to secondary reactions (char self-gasification). Pyrolysis kinetics were studied using a multiple-step model. The proposed model successfully predicted the pyrolytic behaviour of these samples resulting to be statistically meaningful.

Respiration indices and stability measurements of compost through electrolytic respirometry.

An experimental technique for compost stability measurements based on Sapromat electrolytic respirometry was optimised and subsequently applied to a sludge composting process. Anaerobically digested sewage sludge mixed with reed was composted during 90 days in a pilot-scale rotary drum with forced aeration. Periodic solid samples were taken, and a previously optimised respirometric procedure was applied in order to measure the oxygen consumption. The respirometric experiments were made directly with a few grams of solid samples, optimum moisture and 37 °C over a period of 96 h. The results obtained showed how the respiration activity of the sludge decreased during the composting experiment under the specific operating conditions. The specific oxygen uptake rate (SOUR) instant values from the oxygen consumption curves were obtained, and two commonly used respirometric indexes (RI(24) and AT(4)) were calculated for all samples. Both RI(24) (a mean of the SOUR values during the 24 h maximum activity period) and AT(4) (total oxygen consumption after 4 days) were the recommended parameters for the estimation of compost stability by the European Union in the second draft of the Working Document on the Biological Treatment of Biowaste in 2001. Both indexes exponentially decreased with the composting time, and a good linear correlation between them was observed. Final values of RI(24) and AT(4) after 90 days were 600 mg O(2) kg VS(-1) h(-1) and 26 mg O(2) gTS(-1), respectively. We also considered if this technique could be classified as a Dynamic or Static method, the two primary respirometric techniques for measuring compost stability. Supposing that the proposed procedure is considered a dynamic method (no limitations on the amount of oxygen supply), the final RI(24) obtained was compared with the dynamic respiration index (DRI) proposed by the EU (1000 mg O(2) kg VS(-1) h(-1)). Our result indicated that stable compost was obtained after 90 d. However, if a static limit was considered (AT(4) lower than 10 mg O(2) gTS(-1) as proposed by the EU), our result would indicate that more residence composting time would be needed. Taking into account these results, the advantages and disadvantages and the validity of the proposed method are discussed.

Kinetics of forced aerated biodegradation of digested sewage sludge-reed mixtures at different temperatures.

This work presents a kinetic analysis of the aerobic biodegradation of anaerobically digested sewage sludge and dried reed mixtures at different temperatures. Batch experiments were conducted in laboratory-scale reactors with temperature (T) control and forced aeration of the solid mixture. The biowaste mixture was treated at four different temperatures: 25, 40, 50 and 60 °C, with moisture controlled and samples taken weekly for carbon (C) and volatile solids (VS) measurements. The duration of experiments was either 90 d (at 25 °C) or 60 d (at 40, 50 and 60 °C). Two different kinetic models were used to fit the carbon mineralisation curves: the 2C model, which considers two organic fractions (biodegradable and non-biodegradable) and the 3C model, which considers three fractions (easily biodegradable, slowly biodegradable and non-biodegradable). In both cases, the kinetic rate constants were calculated by mathematical fitting and were compared with previously reported values. The temperature influence on the rate constants was studied for both models using a T-dependent equation. The calculated kinetic rate constants were in agreement with previously published values, and good fitting of the experimental data was obtained with both models. Similar rate constant values were obtained for mineralisation of the biodegradable fraction (2C model) and the easily biodegradable fraction (3C model). The rate constants for the slowly biodegradable fraction (3C model) were much lower. A good correlation between rate constants and T was observed. Different optimum temperature values were obtained for each rate constant depending on which carbon fraction was degraded. The T-dependent rate constant values obtained could be used for modelling the C mineralisation of real variable-temperature composting processes.

Composting domestic sewage sludge with natural zeolites in a rotary drum reactor.

This work aimed the influence of zeolites addition on a sludge-straw composting process using a pilot-scale rotary drum reactor. The type and concentration of three commercial natural zeolites were considered: a mordenite and two clinoptilolites (Klinolith and Zeocat). Mordenite caused the greatest carbon removal (58%), while the clinoptilolites halved losses of ammonium. All zeolites removed 100% of Ni, Cr, Pb, and significant amounts (more than 60%) of Cu, Zn and Hg. Zeocat displayed the greatest retention of ammonium and metals, and retention efficiencies increased as Zeocat concentration increased. The addition of 10% Zeocat produced compost compliant with Spanish regulations. Zeolites were separated from the final compost, and leaching studies suggested that zeolites leachates contained very low metals concentrations (<1 mg/kg). Thus, the final compost could be applied directly to soil, or metal-polluted zeolites could be separated from the compost prior to application. The different options have been discussed.

[Spain, New Spain and the autopsy of an anatomic malformation]. / La España peninsular, la Nueva España y la autopsia de una malformación anatómica.

Almost 250 years ago the autopsy of Agustin de Ahumada y Villalon was performed by Domingo Russi, Chief Surgeon at the Royal Hospital for Natives in Mexico City. This situation will be unimportant if the former wasn't the 42nd Viceroy of New Spain; his autopsy showed a situs inversus totalis, and probably this is the first scientific report of such malformation. For many years the report by Mathew Baillie (1761-1823) of an autopsy with the same findings as the first of its kind was believed, but actually the former almost three decades earlier was performed. In 1688 Jean M. Mery (1645-1722) at the Paris Academy of Medicine gave a talk reporting autopsy findings of the same malformations. Some aspects of the life of both personages are described, the autopsy report is showed and a short history about postmortem studies are mentioned mainly those made in Spain and New Spain. Through many centuries a very close relationship has been kept and medicine has not been the exception, in the field of human pathology in the middle third of the 20th century a distinguished pathologist, Dr. Isaac Costero-Tudanca, migrated to Mexico and gave flowering to pathology and a great generation of Mexican pathologists was generated headed by Dr. Ruy Perez-Tamayo.

Evaluation of carbon degradation during co-composting of exhausted grape marc with different biowastes.

In this work the carbon biodegradation of exhausted grape marc (EGM) combined with other organic wastes using the turned pile composting system was studied. Four different piles were made of EGM in Pile 1, EGM mixed with cow manure and straw (CMS) in Pile 2, EGM mixed with municipal solid waste (MSW) in Pile 3 and EGM mixed with grape stalks (GS) in Pile 4. The results obtained were modelled to determine the main kinetic and stoichiometric parameters. Regarding to the rate constants of the composting processes they were increased from 0.033d(-1), the value obtained when EGM was composted alone, to 0.040 and 0.044d(-1) when MSW and GS were added, respectively as co-substrates. However, the addition of CMS reduced the rate constant. About the biodegradable carbon fractions, it was observed that the co-composting reduced significantly the remanent carbon concentration after composting in all the piles whilst increased the readily biodegradable carbon fractions from 35, the value obtained when EGM was composted alone, to 50 and 60%, respectively when MSW or GS were added. As regards the temperature profiles, only Piles 1 and 4 achieved thermal hygienization values and about the nitrogen losses, the lowest percentage of nitrogen loss took place when GS were added, because of its optimum pH and C/N initial ratio. Thus, though any of these wastes could be used for co-composting with EGM, the use of GS as co-substrate and bulking agent for the co-composting process of EGM was recommended.

Biodegradability of meat industry wastes under anaerobic and aerobic conditions.

In this study the biodegradation kinetics and the different biologically degradable fractions (readily, slowly and inert fractions) of the organic wastes generated in a meat industry have been estimated under both anaerobic and aerobic conditions. Three of these could be degraded under both conditions, whereas one (pig/cow waste slurries) could only be aerobically degraded since the high ammonia concentration caused inhibition in anaerobic experiments. Mathematical models for anaerobic and aerobic degradations were used to estimate the readily (S(S)) and slowly (X) biodegradable fractions of the meat industry wastes. Using these models, a good agreement was observed between the calculated S(S) fractions for each waste under anaerobic and aerobic conditions, while the calculated X fractions in the aerobic tests were lower than in the anaerobic tests. The experiments, in combination with the modelling, showed that aerobic respirometric test may be used for predicting readily biodegradable fractions under both anaerobic and aerobic conditions provided that ammonia concentration is not significantly high. Thus, for complex organic wastes the length of experiments for estimating biodegradable fractions may be considerably reduced (in this case by 10-12 days).

Comparación entre lidocaína tópica, intravenosa y en el interior del globo del tubo endotraqueal para disminuir la tos tras la extubación en la educción anestésica / Comparison of topical, intravenous, and intracuff lidocaine for reducing coughing after extubation during emergence from general anesthesia

OBJETIVOS: Comparar el efecto del uso tópico, intravenoso, así como en el interior del globo del tubo endotraqueal de la lidocaína para disminuir la tos en la educción anestésica.PACIENTES Y MÉTODOS: Se incluyeron pacientes deestado físico ASA I y II, mayores de 18 años de edad,programados para cirugía electiva bajo anestesia generalbalanceada con intubación orotraqueal, con unaduración de entre 60 y 120 minutos. Se distribuyeron alazar entre lidocaína intravenosa, tópica, en el interiordel globo del tubo endotraqueal o en el grupo control.Las variables numéricas se describieron utilizandomedia M y desviación estándar (M±DE) o mediana eintervalo intercuartilar [MD(25-75)] en dependencia dela distribución que mostrase. Las variables categóricasse describen con frecuencias (n) y porcentajes (%). Lascomparaciones entre múltiples grupos se realizaron conANOVA, prueba de Kruskal-Wallis o χ2 según correspondiera. Se consideró significancia estadística cuando P fue menor a 0,05.RESULTADOS: Se incluyeron 80 pacientes y se pudieronanalizar 78. La tos se presentó en 13 pacientes (65%) enel grupo control, en 5 (26,3%) en el grupo tópico, en 3(15,8%) en el grupo del globo y en 3 (16%) en el grupointravenoso (p < 0,05).CONCLUSIONES: La lidocaína intravenosa y en el interiordel globo del tubo endotraqueal disminuyen de unaforma estadísticamente significativa la incidencia de tosen la educción anestésica

OBJETIVOS: To compare the effect of topical, intravenous, and intracuff lidocaine on reducingcoughing during emergence from general anesthesia.PATIENTS AND METHODS: Patients with an ASA physicalstatus of I or II were enrolled if they were over 18 years of age and scheduled for elective surgery lasting between 60 and 120 minutes under balanced anesthesia withorotracheal intubation. Enrolled patients were randomlyassigned to one of 3 treatment groups (intravenouslidocaine, topical lidocaine, or intracuff lidocaine) or to the control group. Numerical variables were describedas mean (SD) or median and interquartile range,depending on distribution. Categorical variables weredescribed using frequencies (number) and percentages.Multiple-group comparisons were performed usinganalysis of variance, the Kruskal-Wallis test, or the χ2test, as appropriate. A level of P<.05 was considered tobe statistically significant.RESULTS: We enrolled 80 patients; data for 78 wereentered into analysis. Thirteen patients (65%) presentedcoughing in the control group, 5 (26.3%) in the topicallidocaine group, 3 (15.8%) in the intracuff group, and 3(16%) in the intravenous group (P<.05).CONCLUSIONS: Intravenous lidocaine and intracufflidocaine significantly reduce the incidence of coughing during emergence from anesthesia (AU)

Anaerobic co-digestion of winery wastewater.

The operational performance of anaerobic batch reactors treating winery wastewater (WW) combined with waste activated sludge (WAS) in different proportions was investigated under mesophilic conditions. In these experiments it was shown that for anaerobic digestion of WW alone, methane production rate was lower than the rates achieved when WW and WAS were treated together. When WW was mixed with WAS at a concentration of 50% WW resulted in the highest methane production rates. A simplified anaerobic model was used to determine the main kinetic parameters; maximum COD reduction rate (q(DA)) and maximum methane generation rate (k(max)). The maximum values of q(DA) and k(max) were 16.50 kgCOD COD(-1) d(-1) and 14.34 kgCOD kgCOD(-1) d(-1), respectively.

Re-use of winery wastewaters for biological nutrient removal.

The aim of this study was to evaluate the feasibility of the re-use of the winery wastewater to enhance the biological nutrient removal (BNR) process. In batch experiments it was observed that the addition of winery wastewater mainly enhanced the nitrogen removal process because of the high denitrification potential (DNP), of about 130 mg N/g COD, of the contained substrates. This value is very similar to that obtained by using pure organic substrates such as acetate. The addition of winery wastewater did not significantly affect either phosphorus or COD removal processes. Based on the experimental results obtained, the optimum dosage to remove each mg of N-NO3 was determined, being a value of 6.7 mg COD/mg N-NO3. Because of the good properties of the winery wastewater to enhance the nitrogen removal, the viability of its continuous addition in an activated sludge pilot-scale plant for BNR was studied. Dosing the winery wastewater to the pilot plant a significant increase in the nitrogen removal was detected, from 58 to 75%. The COD removal was slightly increased, from 89 to 95%, and the phosphorus removal remained constant.

Use of agro-food wastewaters for the optimisation of the denitrification process.

The aim of this work was to study the feasibility of the denitrification process enhancement, in the Ciudad Real (Spain) WWTP, by dosing agro-food wastewaters generated nearby the city. The studied agro-food wastewaters were characterised by a high COD and low nutrients concentration. The denitrification rates with these wastewaters were lower than those obtained either with acetate or urban sewage, however the dose of agro-food wastewaters raised significantly the denitrification capacity in the WWTP because of the significant increase of easily biodegradable substrates in the wastewater. From the laboratory NUR batch test it was observed that the best agro-food wastewater to enhance the denitrification process was that coming from tomato processing, which presented an average denitrification rate of 1.9 mg NOx-N/(g VSS.h) and an average denitrification yield of 0.2 mg NOx-N/mg COD. The viability of the use of tomato processing wastewater was checked in a pilot plant optimised for urban sewage treatment with biological nutrient removal. The optimum dose, 5.9 mg COD/mg NOx-N, was applied and 99% of the nitrate was removed from the wastewater without influencing negatively either the COD or P effluent concentrations.

Fermentation of agro-food wastewaters by activated sludge.

This study investigates the potential of agro-food wastewater fermentation by activated sludge. Experimental results shown that all of the agro-food wastewaters studied initially had considerable concentrations of fermentable substrates, ranging from 19% to 68% of the total COD, but not all of the substrates contained in this COD fraction were fermented after an anaerobic stage of 10h. The percentage of fermentable substrates fermented by the activated sludge during the anaerobic stage ranged from 14% to 68%, presenting the potato processing wastewater the highest concentration of fermented substrates. A mathematical model was proposed to describe the fermentation process. By using this model, the maximum fermentation rates were obtained, ranging their values from 0.6 to 3.4 (gCODgCOD(-1)d(-1)). The fermentation potentials of the agro-food wastewaters were also determined, their values ranged from 0.17 to 0.20 (gCODgCOD(-1)) except for the cheese and the winery wastewater which presented fermentation potentials of 0.12 and 0.14 (gCODgCOD(-1)), respectively.

[Comparison of topical, intravenous, and intracuff lidocaine for reducing coughing after extubation during emergence from general anesthesia]. / Comparación entre lidocaína tópica, intravenosa y en el interior del globo del tubo endotraqueal para disminuir la tos tras la extubación en la educción anestésica.

OBJECTIVE: To compare the effect of topical, intravenous, and intracuff lidocaine on reducing coughing during emergence from general anesthesia. PATIENTS AND METHODS: Patients with an ASA physical status of I or II were enrolled if they were over 18 years of age and scheduled for elective surgery lasting between 60 and 120 minutes under balanced anesthesia with orotracheal intubation. Enrolled patients were randomly assigned to one of 3 treatment groups (intravenous lidocaine, topical lidocaine, or intracuff lidocaine) or to the control group. Numerical variables were described as mean (SD) or median and interquartile range, depending on distribution. Categorical variables were described using frequencies (number) and percentages. Multiple-group comparisons were performed using analysis of variance, the Kruskal-Wallis test, or the chi2 test, as appropriate. A level of P < .05 was considered to be statistically significant. RESULTS: We enrolled 80 patients; data for 78 were entered into analysis. Thirteen patients (65%) presented coughing in the control group, 5 (263%) in the topical lidocaine group, 3 (15.8%) in the intracuff group, and 3 (16%) in the intravenous group (P < .05). CONCLUSIONS: Intravenous lidocaine and intracuff lidocaine significantly reduce the incidence of coughing during emergence from anesthesia.

Discovery of the short gamma-ray burst GRB 050709.

Gamma-ray bursts (GRBs) fall into two classes: short-hard and long-soft bursts. The latter are now known to have X-ray and optical afterglows, to occur at cosmological distances in star-forming galaxies, and to be associated with the explosion of massive stars. In contrast, the distance scale, the energy scale and the progenitors of the short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow and (for the first time) the optical afterglow of a short-hard burst; this in turn led to the identification of the host galaxy of the burst as a late-type galaxy at z = 0.16 (ref. 10). These results show that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be caused by the merging of compact binaries.

Denitrification potential of industrial wastewaters.

Nitrate utilisation batch experiments have been carried out with different agro-food industrial wastewaters. The results obtained were modelled using a modification of the ASM2d to determine the main kinetic and stoichiometric parameters: denitrification rate with fermentation products (q(N-SA)) and with fermentable substrates (q(N-SF)); fermentation products and fermentable substrates consumption rates, (qSA) and (qSF), respectively; yield coefficient with fermentation products (Y(H-SA)) and with fermentable substrates (Y(H-SF)) and saturation coefficient for growth on fermentation products (K(H-SA)). It was found that fermentation products (SA) and fermentable substrates (SF) consumption rates can be assumed to be both constant and independent of the agro-food industrial wastewater used, with values of 14.6 and 5.4 (mg S(COD) g COD-X(-1)OHO h(-1)), respectively. The mean denitrification rates obtained with each agro-food industrial wastewater ranged from 1.5 to 2.5 (mg S(N) g COD-X(-1)OHO h(-1)), values slightly lower to the obtained with domestic wastewater (2.7 mg S(N) g COD-X(-1)OHO h(-1)). Given the substrate consumption rate and the denitrification rate, the yields with fermentation products and fermentable substrates for each wastewater were determined. The values obtained for the yields ranged from 0.50 to 0.69 on using SA and from 0.50 to 0.70 on using SF. Having determined these parameters, the denitrification potential (DNP) was evaluated for each agro-food wastewater. Wastewater from slaughterhouses gave the lowest DNP (22.6 mg S(N) g S(-1)COD), whereas wastewater from potato and tomato processing plants gave the highest values (126.5 and 128.2 mg S(N) g S(-1)COD), respectively), which are very similar to that obtained with domestic wastewater (130.3 and 128.2 mg S(N) g S(-1)COD). Taking into account the low N/COD ratio presented in the agro-food wastewaters, the last wastewaters are the most indicated to enhance the nitrogen removal in the WWTP. Finally, a relationship between the denitrification rates of several agro-food industrial wastewaters and their respective S(A)/(S(A) + S(F)) ratio was obtained. This relationship can be used to estimate the mean denitrification rate of an agro-food industrial wastewater.