Immobilization of nitrifying bacteria on composite based on polymers and eggshells for nitrate production.

Nitrification is a key step in biological nitrogen transformation which depends on the performance of specialized microorganisms. Generally, nitrifying bacteria present a low growth rate and performance which can be improved when immobilized as a biofilm. The development of new materials suitable for the immobilization of nitrifying microorganisms is very important in nitrification and wastewater treatment. In this study, the effect of eggshell powder on biofilm formation by Nitrosomonas europaea an ammonium-oxidizing bacteria and Nitrobacter vulgaris a nitrite-oxidizing bacteria, on new polymeric supports were analyzed. Polylactic acid, polyvinyl chloride and polystyrene were tested to produce polymer-eggshells powder composites and used as biofilm supports for nitrifying bacteria. The support material was characterized to identify the most suitable polymer-eggshells powder combination for the cell adhesion and biofilm formation. The nitrification results showed a highest nitrate production of 42 mg NO3--N/L with polylactic acid-eggshell composite, with the best surface properties for cellular adhesion. Finally, scanning electron microscopy micrographs confirmed the best biofilm formed on polylactic acid-eggshell.

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.

Methane biofiltration in the presence of ethanol vapor under steady and transient state conditions: an experimental study.

Methane (CH4) removal in the presence of ethanol vapors was performed by a stone-based bed and a hybrid packing biofilter in parallel. In the absence of ethanol, a methane removal efficiency of 55 ± 1% was obtained for both biofilters under similar CH4 inlet load (IL) of 13 ± 0.5 gCH4 m-3 h-1 and an empty bed residence time (EBRT) of 6 min. The results proved the key role of the bottom section in both biofilters for simultaneous removal of CH4 and ethanol. Ethanol vapor was completely eliminated in the bottom sections for an ethanol IL variation between 1 and 11 gethanol m-3 h-1. Ethanol absorption and accumulation in the biofilm phase as well as ethanol conversion to CO2 contributed to ethanol removal efficiency of 100%. In the presence of ethanol vapor, CO2 productions in the bottom section increased almost fourfold in both biofilters. The ethanol concentration in the leachate of the biofilter exceeding 2200 gethanol m-3leachate in both biofilters demonstrated the excess accumulation of ethanol in the biofilm phase. The biofilters responded quickly to an ethanol shock load followed by a starvation with 20% decrease of their performance. The return to normal operations in both biofilters after the transient conditions took less than 5 days. Unlike the hybrid packing biofilter, excess pressure drop (up to 1.9 cmH2O m-1) was an important concern for the stone bed biofilter. The biomass accumulation in the bottom section of the stone bed biofilter contributed to 80% of the total pressure drop. However, the 14-day starvation reduced the pressure drop to 0.25 cmH2O m-1.

Parameters determining the use of zeolite 5A as collector medium in passive flux samplers to estimate N2O emissions from livestock sources.

The present study analyzes the effect of parameters that determine the use of the zeolite 5A as collector medium in passive flux samplers (PFS) developed to estimate N2O emissions from livestock buildings. The study analyzes the mass of N2O collected on the zeolite 5A as a function of gas flow rate (40 and 130 ml/min), inlet mass of N2O to the PFS (from 7 to 84 µg), adsorbent mass (4 and 13.6 g), length of the adsorbent bed (1.9 and 10.9 cm), and inlet N2O concentration (0.6 and 2 ppmv). The mass of N2O collected on the zeolite 5A ranged from 1.24 to 6.19 µg of N2O/g of adsorbent, which was mainly affected by inlet N2O concentration and mass of adsorbent contained in the PFS. The mass of N2O collected presented a significant relationship with the inlet N2O concentration and the adsorbent bed. Tests were performed using PFS in a laboratory farm under semi-real conditions. It was found that at sampling time of 1.5 h, the accuracy and precision of PFS was appropriate. Under evaluated conditions, a maximum variation between PFS and direct detection of around 12% was estimated.

Adsorption of methylene blue on biochar microparticles derived from different waste materials.

Biochar microparticles were prepared from three different types of biochar, derived from waste materials, such as pine wood (BC-PW), pig manure (BC-PM) and cardboard (BC-PD) under various pyrolysis conditions. The microparticles were prepared by dry grinding and sequential sieving through various ASTM sieves. Particle size and specific surface area were analyzed using laser particle size analyzer. The particles were further characterized using scanning electron microscope (SEM). The adsorption capacity of each class of adsorbent was determined by methylene blue adsorption tests in comparison with commercially available activated carbon. Experimental results showed that dye adsorption increased with initial concentration of the adsorbate and biochar dosage. Biochar microparticles prepared from different sources exhibited improvement in adsorption capacity (7.8±0.5 mg g(-1) to 25±1.3 mg g(-1)) in comparison with raw biochar and commercially available activated carbon. The adsorption capacity varied with source material and method of production of biochar. The maximum adsorption capacity was 25 mg g(-1) for BC-PM microparticles at 25°C for an adsorbate concentration of 500 mg L(-1) in comparison with 48.30±3.6 mg g(-1) for activated carbon. The equilibrium adsorption data were best described by Langmuir model for BC-PM and BC-PD and Freundlich model for BC-PW.

Enrichment of Secondary Wastewater Sludge for Production of Hydrogen from Crude Glycerol and Comparative Evaluation of Mono-, Co- and Mixed-Culture Systems.

Anaerobic digestion using mixed-culture with broader choice of pretreatments for hydrogen (H2) production was investigated. Pretreatment of wastewater sludge by five methods, such as heat, acid, base, microwave and chloroform was conducted using crude glycerol (CG) as substrate. Results for heat treatment (100 °C for 15 min) showed the highest H2 production across the pretreatment methods with 15.18 ± 0.26 mmol/L of medium at 30 °C in absence of complex media and nutrient solution. The heat-pretreated inoculum eliminated H2 consuming bacteria and produced twice as much as H2 as compared to other pretreatment methods. The fermentation conditions, such as CG concentration (1.23 to 24 g/L), percentage of inoculum size (InS) (1.23% to 24% v/v) along with initial pH (2.98 to 8.02) was tested using central composite design (CCD) with H2 production as response parameter. The maximum H2 production of 29.43 ± 0.71 mmol/L obtained at optimum conditions of 20 g/L CG, 20% InS and pH 7. Symbiotic correlation of pH over CG and InS had a significant (p-value: 0.0011) contribution to H2 production. The mixed-culture possessed better natural acclimatization activity for degrading CG, at substrate inhibition concentration and provided efficient inoculum conditions in comparison to mono- and co-culture systems. The heat pretreatment step used across mixed-culture system is simple, cheap and industrially applicable in comparison to mono-/co-culture systems for H2 production.

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 (NO2(-)) 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 71.0 g m(-3) day(-1).

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 (mu) 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 mu 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 mu was 0.0057 h(-1) for the BF and 0.0103 h(-1) for the BTF. The maximum of ethanol removed, occurred at the lowest inlet concentration of (0.47 gm(-3)), and reached 86% for the BF and 74% for the BTF.