Bioaugmentation Treatment of a PAH-Polluted Soil in a Slurry Bioreactor

[EN] A bioslurry reactor was designed and used to treat loamy clay soil polluted with polycyclic aromatic hydrocarbons (PAHs). To this end, biostimulation alone, or combined with bioaugmentation with two bacterial strains (Rhodocccus erythropolis and Pseudomonas stuzeri) previously isolated from the polluted site, was applied. The PAH concentrations decreased notably after 15 days in all of the treatments. The concentrations of the two- and three-ring compounds fell by >80%, and, remarkably, the four- to six-ring PAHs also showed a marked decrease (>70%). These results thus indicate the capacity of bioslurry treatments to improve, notably, the degradation yields obtained in a previous real-scale remediation carried out using biopiles. In this sense, the remarkable results for recalcitrant PAHs can be attributed to the increase pollutants’ bioavailability achieves in the slurry bioreactors. Regarding bioaugmentation, although treatment with R. erythropolis led to a somewhat greater reduction of lighter PAHs at 15 days, the most time-effective treatment was achieved using P. stutzeri, which led to an 84% depletion of total PAHs in only three days. The effects of microbial degradation of other organic compounds were also monitored by means of combined qualitative and quantitative gas chromatography mass spectrometry (GC–MS) tools, as was the evolution of microbial populations, which was analyzed by culture and molecular fingerprinting experiments. On the basis of our findings, bioslurry technology emerges as a rapid and operative option for the remediation of polluted sites, especially for fine soil fractions with a high load of recalcitrant pollutants

Influence of pyrolysis temperature and feedstock biomass on Cu2+, Pb2+, and Zn2+ sorption capacity of biochar

Biochar has attracted significantly growing attention due to its effectiveness in terms of both cost and environmental safety in removing trace metals from soil and water. Its metal sorption capacity depends on its properties, which are in turn governed by pyrolysis temperature and type of biomass. Therefore, this study examines the role of pyrolysis temperature and biomass in biochars sorption capacity of Pb2+, Cu2+ and Zn2+. Biochars produced by pyrolysis of maize (Zea mays L.) cobs at different temperatures were used to assess the effect of temperature, whereas evergreen oak (Quercus ilex L.) pyrolyzed at 500 °C was used to assess the effect of biomass. Sorption isotherms were constructed by batch method and compared with Langmuir and Freundlich models. Most of the sorption isotherms displayed irregular curves and not all of the isotherms fitted the models. Therefore, sorption distribution coefficients and metal removal percentages were used to determine sorption capacities biochars for studied metals. Accordingly, Quercus ilex L. was most effective in sorbing all studied metals, which indicates the role of biomass. The maize biochar pyrolyzed at 500 °C was most effective among maize cob biochars, which revealed the influence pyrolysis temperature. The concentrations of added sorption solutions also played significant role in sorption, and consequently biochar pyrolyzed 350 °C was least effective. The targeted metals also affected the sorption as they compete for sorption sites. Thus, their selective sequence was in the order of Pb2+ ˃ Cu2+ ˃ Zn2+.Universidade de VigoFinanciado para publicación en acceso aberto: Universidade de Vigo/CISU

Cianoalerta: a strategy to predict the development of toxic cyanobacterial blooms in water reservoirs

La eutrofización de los pantanos destinados al abastecimiento de agua de consumo humano supone un deterioro de la calidad de la misma, e incluso puede afectar a la salud de los consumidores. Éste es el caso de la presencia de la hepatotoxina microcistina, producida fundamentalmente por la cianobacteria Microcystis aeruginosa. A través de los proyectos Cianoalerta hemos desarrollado métodos para la pronta detección de blooms específicos de cianobacterias, necesarios para llevar a cabo un adecuado tratamiento del agua, evitando el suministro de un producto de baja calidad a los consumidores. El análisis de la evolución estacional de cianopigmentos, y su correlación con la abundancia y dinámica de las poblaciones de microorganismos fotosintéticos ha permitido concluir que la evolución estacional de zeaxantina y beta-caroteno presenta una dinámica muy similar a la evolución observada de las poblaciones de las cianobacterias Oscillatoria spp, Anabaena spp. y formas cocoides de cianobacterias, y diferente a la evolución de Microcystis spp. De acuerdo con nuestros resultados, estos fotopigmentos podrían emplearse como indicadores de la proliferación de estas poblaciones.Eutrofization of reservoirs supplying drinking water deteriorates water quality, and may affect consumer’s health. This is the case of the hepatotoxin microcystin, which is produced by the cyanobacteria Microcystis aeruginosa. Within the framework of Cianoalerta projects we have developed methods for the prompt detection of specific cyanobacteria blooms, a crucial step towards efficient water treatment, thus improving the quality of the product supplied. Seasonal changes in zeaxanthin and beta-carotene paralleled those shown by the cyanobacteria Oscillatoria spp, Anabaena and cocoid forms of cyanobacteria, but were different from those shown by Microcystis. According to our results, these photopigments can be used as indicators of the dynamics of these cyanobacterial populations

Bioaugmentation Treatment of a PAH-Polluted Soil in a Slurry Bioreactor

A bioslurry reactor was designed and used to treat loamy clay soil polluted with polycyclic aromatic hydrocarbons (PAHs). To this end, biostimulation alone, or combined with bioaugmentation with two bacterial strains (Rhodocccus erythropolis and Pseudomonas stuzeri) previously isolated from the polluted site, was applied. The PAH concentrations decreased notably after 15 days in all of the treatments. The concentrations of the two- and three-ring compounds fell by >80%, and, remarkably, the four- to six-ring PAHs also showed a marked decrease (>70%). These results thus indicate the capacity of bioslurry treatments to improve, notably, the degradation yields obtained in a previous real-scale remediation carried out using biopiles. In this sense, the remarkable results for recalcitrant PAHs can be attributed to the increase pollutants’ bioavailability achieves in the slurry bioreactors. Regarding bioaugmentation, although treatment with R. erythropolis led to a somewhat greater reduction of lighter PAHs at 15 days, the most time-effective treatment was achieved using P. stutzeri, which led to an 84% depletion of total PAHs in only three days. The effects of microbial degradation of other organic compounds were also monitored by means of combined qualitative and quantitative gas chromatography mass spectrometry (GC–MS) tools, as was the evolution of microbial populations, which was analyzed by culture and molecular fingerprinting experiments. On the basis of our findings, bioslurry technology emerges as a rapid and operative option for the remediation of polluted sites, especially for fine soil fractions with a high load of recalcitrant pollutants

Reuse of Dunite Mining Waste and Subproducts for the Stabilization of Metal(oid)s in Polluted Soils

The circular economy seeks to minimize the use of raw materials and waste generation. In this context, here we addressed the use of dunite mining tailings and subproducts to stabilize metal(oid)s in polluted soils. We first characterized the dunite mining tailings and subproducts, and a paradigmatic polluted soil in depth to determine their chemical and mineralogical properties. Experimental trials using Brassica juncea L. were performed to evaluate the impact of the two materials on vegetation growth, edaphic properties and pollutant stabilization yields. To this end, the plants were grown over 75 days in 1 kg pots containing the polluted soil amended with the dunite materials. Notably, both amendments caused a dramatic decrease in the available Zn and a moderate reduction in available Cu, Cd and Pb. In contrast, the concentration of available As was not modified. The cation exchange capacity (CEC) was improved by treatment with the amendments, allowing an increase in the biomass harvested. The immobilization mechanism achieved was probably due to an increase in pH and CEC. In conclusion, the dunite tailings and subproducts could be effective amendments for stabilizing polluted soil. This work paves the way for additional studies with distinct types of soils and conditions