Antonio Avalos Ramirez

Control of methanol vapours in a biotrickling filter: performance analysis and experimental determination of partition coefficient.

Methanol vapours were treated in a biotrickling filter (BTF) packed with inert polypropylene spheres. The effects of the nitrogen concentration in the nutrient solution, the empty bed residence time (EBRT) and the methanol inlet concentration, on the BTF performance, were all examined. The elimination capacity (EC), the biomass and the carbon dioxide production rates were all increased with the rising of the nitrogen concentration and the EBRT. The EC also rose with increasing methanol inlet load (IL) when the methanol inlet concentration and the EBRT were varied, from 0.3 to 37.0 g m(-3), and from 20 to 65 s, respectively. The BTF reached its maximum EC level of 2160 g m(-3) h(-1) when it was operated at an IL level of 3700 g m(-3) h(-1). The input methanol was removed through two mechanisms: biodegradation and absorption in the liquid phase. The partition coefficient for the methanol in the BTF was determined at five EBRTs and along the packed bed. It generally followed the Henry model, having an average value of 2.64 x 10(-4)[mol L(-1)](gas)/[mol L(-1)](liquid).

Analysis and comparison of biotreatment of air polluted with ethanol using biofiltration and biotrickling filtration.

This study analyses the performance of ethanol biofiltration with percolation (biotrickling filtration, BTF) comparing to a conventional biofilter (biofiltration, BF). Two biofilters packed with clay balls were operated in a range of inlet concentrations of ethanol in the air varying from 0.47 to 2.36 g m−3. For both the BF and BTF, the specific growth rate (μ) and the elimination capacity (EC) decreased with the ethanol inlet concentration, presenting a kinetic of substrate inhibition. A Haldane-type model was adjusted for both biofilters in order to model both EC and μ as a function of the ethanol inlet concentration in the gas. The maximum EC was similar for both biofilters, at around 46 g m−3 h−1, whereas the maximum μ was 0.0057 h−1 for the BF and 0.0103 h−1 for the BTF. The maximum of ethanol removed, occurned at the lowest inlet concentration of (0.47 g m−3), and reached 86% for the BF and 74% for the BTF.

Biofiltration of air polluted with methane at concentration levels similar to swine slurry emissions: Influence of ammonium concentration

An evaluation of the effect of ammonium on the performance of two up-flow inorganic packed bed biofilters treating methane was conducted. The air flow rate was set to 3.0 L min−1 for an empty bed residence time of 6.0 min. The biofilter was fed with a methane concentration of 0.30% (v/v). The ammonium concentration in the nutrient solution was increased by small increments (from 0.01 to 0.025 gN-NH4 + L−1) for one biofilter and by large increments of 0.05 gN-NH4 + L−1 in the other biofilter. The total concentration of nitrogen was kept constant at 0.5 gN-NH4 + L−1 throughout the experiment by balancing ammonium with nitrate. For both biofilters, the methane elimination capacity, carbon dioxide production, nitrogen bed retention and biomass content decreased with the ammonium concentration in the nutrient solution. The biofilter with smaller ammonium increments featured a higher elimination capacity and carbon dioxide production rate, which varied from 4.9 to 14.3 g m−3 h−1 and from 11.5 to 30 g m−3 h−1, respectively. Denitrification was observed as some values of the nitrate production rate were negative for ammonium concentrations below 0.2 gN-NH4 + L−1. A Michalelis-Menten-type model fitted the ammonium elimination rate and the nitrate production rate.

Solubility of methane in pure non-ionic surfactants and pure and mixtures of linear alcohols at 298 K and 101.3 kPa

The emissions of methane (CH4), a powerful greenhouse gas (GES), contribute to the increase in GES concentration level in the atmosphere. For this reason, the importance of controlling CH4 emissions of anthropogenic origin has increased over the last decades. Physicochemical and biological processes are available for treating CH4. For this reason, such properties as the solubility of CH4 in aqueous solutions and organic solvents are of great relevance in different applications in environmental engineering and biotechnology. In this study, the solubility of CH4 was determined at 298 K and 101.3 kPa in organic solvents, such as polyoxyethylenesorbates (Tween 20, Tween 40, and Tween 60), and linear alcohols (methanol, ethanol, and butan-1-ol) alone and in their admixtures. Admixtures of methanol with butan-1-ol exhibited the highest solubility of CH4, of around 0.49 g m−3 of solvent, whereas the solubility of CH4 in linear alcohols varied from 0.167 g m−3 to 0.41 g m−3 of solvent. In the case of Tweens, CH4 solubility decreased with the hydrophilic-lipophilic balance (HLB) number.

Alternatives to antibiotics in poultry feed: molecular perspectives.

Abstract The discovery of the growth promoting property of antibiotics led to their use as antibiotic feed additives (AFAs) in animal feed at sub-therapeutic doses. Although this has been beneficial for animal health and productivity, it has been, essentially, a double-edged sword. The continued and non-judicious use of AFAs has led to the selection and dissemination of antibiotic-resistant strains of poultry pathogens such as Salmonella, Campylobacter and Escherichia coli. The rapid spread of drug-resistant pathogens as well as emergence of antibiotic-related environmental pollutants is of global concern. Hence, the identification and development of new and effective alternatives to antibiotics that do not hinder productivity is imperative. For this, it is essential to understand not only the molecular basis of development of resistance to AFAs but also the mechanisms of action of AFA alternatives and how they differ from AFAs. This review provides a molecular perspective on the alternatives to antibiotics that have been proposed till date and their current trends, as well as novel approaches such as development of improved delivery systems.

Biovalorization of saccharides derived from industrial wastes such as whey: a review

Whey is a liquid waste issued from the transformation of milk into cheese. Whey is a major environmental problem for the dairy industry due to its high organic load, linked to its high content of lactose. It can be valorized by biological processes based on lactose fermentation into different products such as (1) lactic acid (as food additive), (2) 2,3-butanediol (as feedstock to get products such as methyl-ethyl-ketone or 2-butene for the pharmaceutical and chemical industries), (3) biogas (to obtain energy). The production of 2,3-butanediol from saccharides, such as glucose, has been actively studied over previous decades using several types of microorganisms such as Enterobacter aerogenes, Paenibacillus polymyxa, Klebsiella sp., Serratia marcescens and Escherichia coli. Some of these have even been genetically modified to improve the 2,3-butanediol production. The potential whey fermentation process into 2,3-butanediol depends on several operating conditions such as microorganisms, composition of the culture medium, temperature, pH and aeration. This review first presents a summary of the situation of milk and cheese production in Canada and around the world. It also describes the different kinds of whey and their treatment techniques. Finally, this paper describes the production of 2,3-butanediol from saccharides by various microorganisms under different operating conditions.

Nanotechnology to Remove Contaminants

Emerging contaminants will be a major challenge for human health and environment since their concentrations are increasing. Contaminants occur in air, soil and aquatic media, then finally end up in drinking water. Contaminants cause many health issues to living organisms, by disruption of endocrine systems and feminization of male fish, for instance. Therefore, prevention of contaminant release, and cleaning of contaminated media are needed. Many processes, including physical separation, biological treatment and chemical transformation have been set up to remove contaminants. Here we review methods to remove contaminants using nanomaterials, such as nanoparticles, nanotubes, and nanostructured membranes. New processes based on nanostructured materials such as TiO2 nanowires or nanofiltration membrane can achieve up to 95 % removal of contaminants.

Biofiltration of Air Contaminated by Styrene Vapors on Inorganic Filtering Media: An Experimental Study

Abstract This paper presents a study on the biofiltration of styrene by using two inorganic filtering materials. The effects of styrene inlet load and nitrogen concentration present in the nutrient solution on biofilter performance were studied. The styrene inlet concentration was varied from 65 to 1115 parts per million by volume (ppmv), whereas the contaminated airflow rate was fixed at 1 m3/hr. The nitrogen concentration in nutrient solution was varied from 1 to 4 gN/L. The maximum elimination capacity obtained was 105 g/m3-hr, which corresponded to a removal efficiency of 80% for a styrene inlet load of 130 g/m3-hr. This study shows that the nitrogen content in the nutrient solution affects the removal rate of styrene, with an optimal nitrogen concentration of 3 gN/L. The performance comparison between two different inorganic bed types was undertaken and a comparative study on biofiltration of two aromatic compounds, styrene and toluene, is also presented.

Use of antibiotics in broiler production: Global impacts and alternatives

Antibiotics are used to fight bacterial infections. However, a selective pressure gave rise to bacteria resistant to antibiotics. This leaves scientists worried about the danger to human and animal health. Some strategies can be borrowed to reduce the use of antibiotics in chicken farms. Much research has been carried out to look for natural agents with similar beneficial effects of growth promoters. The aim of these alternatives is to maintain a low mortality rate, a good level of animal yield while preserving environment and consumer health. Among these, the most popular are probiotics, prebiotics, enzymes, organic acids, immunostimulants, bacteriocins, bacteriophages, phytogenic feed additives, phytoncides, nanoparticles and essential oils.

Elimination of nitrogen present in swine manure using a high-efficiency biotrickling filter.

Experiments were performed to remove nitrogen as ammonium in biotrickling filters (BTFs) treating synthetic swine manure. Two BTFs packed with polypropylene spheres and ceramic beads were used. BTFs were continuously fed, and leachate obtained was recirculated at different flow rates in the range from 0 to 1.5 L min−1. When increasing the recirculation flow rate, the carbon dioxide (CO2) production rate increased from 16.5 to 25.6 g CO2 m−3 h−1 and nitrogen elimination decreased from 99% to 86% for the polypropylene spheres, whereas for the ceramic beads the CO2 production rate decreased from 20.3 to 15.0 g CO2 m−3 h−1 and nitrogen removal from 99% to 90%. The increase of recirculation flow rates also promoted the production of nitrite ( ) in the leachate. For both packing types, when increasing nitrogen loads from 60 to 240 g N m−3 day−1 without recirculation of leachate, the BTFs achieved nitrogen removals of more than 99%. For the same nitrogen loads, nitrogen removal increased from 90% to 99% for the BTF packed with ceramic beads at a recirculation flow rate of 0.6 L min−1. Operating the BTFs with continuous purge was optimal for biomass production with a maximum level of 71.3 g m−3 day−1.