Nancy J. Pino

Degradation of the antibiotic oxolinic acid by photocatalysis with TiO2 in suspension

In the work presented here, a photocatalytic system using titanium Degussa P-25 in suspension was used to evaluate the degradation of 20mg L(-1) of antibiotic oxolinic acid (OA). The effects of catalyst load (0.2-1.5 g L(-1)) and pH (7.5-11) were evaluated and optimized using the surface response methodology and the Pareto diagram. In the range of variables studied, low pH values and 1.0 g L(-1) of TiO(2) favoured the efficiency of the process. Under optimal conditions the evolution of the substrate, chemical oxygen demand, dissolved organic carbon, toxicity and antimicrobial activity on Escherichia coli cultures were evaluated. The results indicate that, under optimal conditions, after 30 min, the TiO(2) photocatalytic system is able to eliminate both the substrate and the antimicrobial activity, and to reduce the toxicity of the solution by 60%. However, at the same time, ∼53% of both initial DOC and COD remain in solution. Thus, the photocatalytical system is able to transform the target compound into more oxidized by-products without antimicrobial activity and with a low toxicity. The study of OA by-products using liquid chromatography coupled with mass spectrometry, as well as the evaluation of OA degradation in acetonitrile media as solvent or in the presence of isopropanol and iodide suggest that the reaction is initiated by the photo-Kolbe reaction. Adsorption isotherm experiments in the dark indicated that under pH 7.5, adsorption corresponded to the Langmuir adsorption model, indicating the dependence of the reaction on an initial adsorption step.

Monitoring the removal of nitrogen by applying a nitrification-denitrification process in a Sequencing Batch Reactor (SBR).

In this study the evaluation of nitrogen removal in wastewater from a meat products processing company was performed, using a Sequencing Batch Reactor (SBR) at pilot scale. The phases of the SBR operation were: filling, reaction (aeration and intermittent anoxia), sedimentation and discharge. In each of these phases analyses of ammonium (NH(4)(+)), nitrite (NO(2)(-)), nitrate (NO(3)(-)), pH and dissolved oxygen (DO) were carried out to monitor the process of nitrification-denitrification. The results showed that stage IV had the best performance (2.49 g COD(F)/Ld and 1.02 g NH(4)(+)-N/Ld) with a NH(4)(+)-N removal of 71%. The transformation of much of the NH(4)(+)-N to gaseous nitrogen was confirmed, with the concentration of NO(2)(-)-N and NO(3)(-)-N increasing during the reaction phase but decreasing in the effluent due to its transformation to gaseous nitrogen.

Isolation of a selected microbial consortium capable of degrading methyl parathion and p-nitrophenol from a contaminated soil site

A bacterial consortium with the ability to degrade methyl parathion and p-nitrophenol, using these compounds as the only carbon source, was obtained by selective enrichment in a medium with methyl parathion. Samples were taken from Moravia, Medellin; an area that is highly contaminated, owing to the fact that it was used as a garbage dump from 1974 to 1982. Acinetobacter sp, Pseudomonas putida, Bacillus sp, Pseudomonas aeruginosa Citrobacter freundii, Stenotrophomonas sp, Flavobacterium sp, Proteus vulgaris, Pseudomonas sp, Acinetobacter sp, Klebsiella sp and Proteus sp were the microorganisms identified within the consortium. In culture, the consortium was able to degrade 150 mgL−1 of methyl-parathion and p-nitrophenol in 120 h, but after adding glucose or peptone to the culture, the time of degradation decreased to 24 h. In soil, the consortium was also able to degrade 150 mgL−1 of methyl parathion in 120 h at different depths and also managed to decrease the toxicity.

Microbiological quality indicators in waters of dairy farms: Detection of pathogens by PCR in real time

When contaminated water is used to wash the udders of dairy cattle and milking utensils, raw milk may become contaminated with pathogens. Washing with high quality water is essential to reduce the microbial contamination of milk. Furthermore, the wastewater generated in dairy herds also contains high populations of pathogens, antibiotics and nutrients that more often are thrown into the water bodies without any treatment. In this work, both supply water and wastewater from 20 dairy farms from Antioquia, Colombia was monitored for 10months to determine the presence of pathogenic microorganisms. Both Cryptosporidium and Fasciola were determined by the Polymerase Chain Reaction (PCR) technique in real time. The results showed that the supply water used for drinking and activities involving the herd, has high populations of Fasciola hepatica and Cryptosporidium parvum, with percentages of about 53.7% and 64.75% respectively. Additionally high populations of Pseudomonas aeruginosa, Shigella, Salmonella, total coliforms and Escherichia coli were found in both types of water, with values around 9.4×10(7), 2.1×10(7), 1.8×10(7), 1.9×10(10) and 1.5×10(10) UFC/100 ml respectively for the wastewater and 3.1×10(4), 1.9×10(4), 7.3×10(3), 1.2×10(5) and 6.2×10(3) UFC/100 ml for the supply water.

Evaluation of biostimulation and Tween 80 addition for the bioremediation of long-term DDT-contaminated soil

The bioremediation of a long-term contaminated soil through biostimulation and surfactant addition was evaluated. The concentrations of 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) and its metabolites 1,1-dichloro-2,2-bis(4-chlorophenyl) ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene (DDE) were monitored during an 8-week remediation process. Physicochemical characterization of the treated soil was performed before and after the bioremediation process. The isolation and identification of predominant microorganisms during the remediation process were also carried out. The efficiency of detoxification was evaluated after each bioremediation protocol. Humidity and pH and the heterotrophic microorganism count were monitored weekly. The DDT concentration was reduced by 79% after 8 weeks via biostimulation with surfactant addition (B+S) and 94.3% via biostimulation alone (B). Likewise, the concentrations of the metabolites DDE and DDD were reduced to levels below the quantification limits. The microorganisms isolated during bioremediation were identified as Bacillus thuringiensis, Flavobacterium sp., Cuprivadius sp., Variovorax soli, Phenylobacterium sp. and Lysobacter sp., among others. Analysis with scanning electron microscopy (SEM) allowed visualization of the colonization patterns of soil particles. The toxicity of the soil before and after bioremediation was evaluated using Vibrio fischeri as a bioluminescent sensor. A decrease in the toxic potential of the soil was verified by the increase of the concentration/effect relationship EC50 to 26.9% and 27.2% for B+S and B, respectively, compared to 0.4% obtained for the soil before treatment and 2.5% by natural attenuation after 8 weeks of treatment.

Bioaugmentation with Immobilized Microorganisms to Enhance Phytoremediation of PCB-Contaminated Soil

ABSTRACT The aim of this study was evaluate the effect of bioaugmentation by free and immobilized strains of microbial consortium on the phytoremediation of polychlorinated biphenyl (PCB)-contaminated soil using the Avena sativa, Brachiaria decumbens, Brassica juncea, and Medicago sativa plants. Alginate and biochar were used as carrier materials and free cells were used as the control. PCBs 44, 66, 118, 138, 153, 170, and 180 were chosen as indicator PCB congeners. After 60 days of plant growth, the concentration of each congener and the survival of the microbial inoculum were evaluated. The removal of the PCB congener was greater in B. juncea planted treatments and using biochar as a carrier material. PCB 66 was the congener with the highest removal percentage in all using biochar and alginate-immobilized microorganisms and free microorganisms, while PCB 170 had the lowest removal percentage in all treatments. The largest removal percentage for all congeners was obtained using biochar as a carrier material (7.2–30.3%) and the lowest with planted treatments using free microorganisms (2.3–6.8%). Real-time polymerase chain reaction (PCR) showed that the microbial inoculum survived when it was immobilized using both alginate and biochar without any significant differences between treatments; however, PCB removal percentages were obtained with biochar, which demonstrated that this carrier material has a positive effect on microbial activity.

Root exudates and plant secondary metabolites of different plants enhance polychlorinated biphenyl degradation by rhizobacteria

ABSTRACT Polychlorinated biphenyls (PCBs) are toxic and persistent compounds that are difficult to break down and biodegrade. Plant secondary metabolites (PSMs) on root exudates can act as inducers of the biphenyl catabolic pathway, enhancing PCB biodegradation. In this study, the authors evaluated the effect of root exudates and PSMs obtained from Avena sativa, Brachiaria decumbens, Medicago sativa, and Brassica juncea on the biodegradation of PCB 44, PCB 66, PCB 118, PCB 138, PCB 153, PCB 170, and PCB 180 by a microbial consortium isolated from the rhizosphere of plants grown on soil contaminated with Aroclor 1260. Microorganisms were identified as Pseudomonas sp. and Stenotrophomonas sp. based on their 16S rRNA sequence. The plant root exudates increased the degradation percentage of PCB 44, PCB 66, and PCB 118, which were used as carbon source by the microorganisms. Flavanone, flavone, isoflavone, 7-hydroxyflavanone, 7-hydroxyflavone, and 6-hydroxyflavone were the PSMs identified in the root exudates, which increased the degradation percentage of all seven PCB congeners; they were also used as growth substrates by microbial consortium. These results showed the importance of the interaction between plants and microorganisms for achieving the removal of persistent pollutants such as PCBs from soil.