Detection of hotspots and rapid determination of methane emissions from landfills via a ground-surface method.

We present a method for the rapid determination of methane emissions from landfills based on atmospheric dispersion theory, which suggests that the methane concentration, at a small distance from the soil/atmosphere interface, is proportional to its flux. Thus, after suitable calibration, the determination of methane concentrations close to the ground allows for flux determination in a shorter time than with standard enclosure techniques. This concept was tested using a surface probe in direct contact with the ground. The probe extracts a continuous sample of the air at the probe/ground interface and transports it to a portable methane analyzer. It was observed that stable methane concentrations were measured 30 s after the probe was positioned at the measurement point. These concentrations correlated well with the fluxes measured by standard static chambers. The method was used to determine the fluxes at 217 points within a 90,000 m(2) landfill. These measurements facilitated mapping of the CH4 emissions and the localization of hotspots. We conclude that the method is simple, effective, and relatively quick, compared to existing standard methods.

Greenhouse gas emissions from stabilization ponds in subtropical climate.

Waste stabilization ponds (WSPs) are a cost-efficient method to treat municipal and non-toxic industrial effluents. Numerous studies have shown that WSPs are a source of greenhouse gas (GHG). However, most reports concerned anaerobic ponds (AP) and few have addressed GHG emissions from facultative (FP) and aerobic/maturation ponds (MPs). In this paper, GHG emissions from three WSP in series are presented. These WSPs were designed as anaerobic, facultative and aerobic/maturation and were treating agricultural wastewater. CH4 fluxes from 0.6 +/- 0.4 g CH4 m(-2) d(-1) in the MP, to 7.0 +/- 1.0 g CH4 m(-2) d(-1) in the (AP), were measured. A linear correlation was found between the loading rates of the ponds and CH4 emissions. Relatively low CO2 fluxes (0.2 +/- 0.1 to 1.0 +/- 0.8 g CO2 m(-2) d(-1)) were found, which suggest that carbonate/bicarbonate formation is caused by alkaline pH. A mass balance performed showed that 30% of the total chemical oxygen demand removed was converted to CH4. It has been concluded that the WSP system studied emits at least three times more GHG than aerobic activated sludge systems and that the surface loading rate is the most important design parameter for CH4 emissions.

Comparison of static and dynamic respirometry for the determination of stoichiometric and kinetic parameters of a nitrifying process.

Respirometry consists in the measurement of the biological oxygen consumption rate under well-defined conditions and has been used for the characterization of countless biological processes. In the field of biotechnology and applied microbiology, several respirometry methods are commonly used for the determination of process parameters. Dynamic and static respirometry, which are based on oxygen measurements with or without continuous aeration, respectively, are the methods most commonly used. Additionally to several respirometry methods, different methods have also been developed to retrieve process parameters from respirometric data. Among them, methods based on model fitting and methods based on the injection of substrate pulse at increasing concentration are commonly used. An important question is then; what respirometry and data interpretation methods should be preferably used? So far, and despite a growing interest for respirometry, relatively little attention has been paid on the comparison between the different methods available. In this work, both static and dynamic respirometry methods and both interpretation methods; model fitting and pulses of increasing concentration, were compared to characterize an autotrophic nitrification process. A total of 60 respirometry experiments were done and exhaustively analysed, including sensitivity and error analyses. According to the results obtained, the substrate affinity constant (K S ) was better determined by static respirometry with pulses of increasing concentration and the maximum oxygen uptake rate (OUR ex.max ) was better determined by dynamic respirometry coupled to fitting procedure. The best method for combined K S and OUR ex.max determination was static respirometry with pulses of increasing concentration.

Biofiltration of methanol in an organic biofilter using peanut shells as medium.

Biofiltration consists of a filter-bed of organic matter serving both as carrier for the active biomass and as nutrient supply, through which the polluted gas passes. The selection of a suitable medium material is of major importance to ensure optimum biofilter efficiency. Peanut shells are an agricultural byproduct locally available in large quantities at a low price in most tropical and sub-tropical countries. A previous study showed that peanut shells are physically and chemically suitable for biofiltration. This paper presents the results obtained during a six month biofiltration experiment using peanut shells as medium and methanol as air pollutant. It is shown that peanut shells are potentially suitable as biofiltration medium, since degradation rates of up to 30 kg MeOH/m(3)d with an empty bed residence time of 19s was obtained. The biofilter showed a good resistance to shock load and no operational problems were observed.

Flocculant in wastewater affects dynamics of inorganic N and accelerates removal of phenanthrene and anthracene in soil.

Recycling of municipal wastewater requires treatment with flocculants, such as polyacrylamide. It is unknown how polyacrylamide in sludge affects removal of polycyclic aromatic hydrocarbons (PAH) from soil. An alkaline-saline soil and an agricultural soil were contaminated with phenanthrene and anthracene. Sludge with or without polyacrylamide was added while emission of CO(2) and concentrations of NH(4)(+), NO(3)(-), NO(2)(-), phenanthrene and anthracene were monitored in an aerobic incubation experiment. Polyacrylamide in the sludge had no effect on the production of CO(2), but it reduced the concentration of NH(4)(+), increased the concentration of NO(3)(-) in the Acolman soil and NO(2)(-) in the Texcoco soil, and increased N mineralization compared to the soil amended with sludge without polyacrylamide. After 112d, polyacrylamide accelerated the removal of anthracene from both soils and that of phenanthrene in the Acolman soil. It was found that polyacrylamide accelerated removal of phenanthrene and anthracene from soil.

Remediation of PAHs in a saline-alkaline soil amended with wastewater sludge and the effect on dynamics of C and N.

Contamination of soil with hydrocarbons occurs frequently and organic material, such as sludge, is often applied to accelerate their dissipation. Little is known, however, how sludge characteristics affect removal of polycyclic aromatic hydrocarbons (PAHs) from alkaline-saline soil. Soil of the former lake Texcoco with pH 9 and electrolytic conductivity 7 dS m(-1) was contaminated with phenanthrene and anthracene and amended with sludge, sterilized sludge, sludge adjusted to maintain pH in contaminated soil or glucose plus an inorganic N and P source while emission of CO2 and concentrations of NH4+, NO3-, NO2-, extractable P, phenanthrene and anthracene were monitored in an aerobic incubation experiment of 112 days. An agricultural soil from Acolman treated in the same way served as control. Contaminating the Texcoco soil increased emission of CO2 significantly, but not in the Acolman soil. After 112 days, the largest concentration of anthracene and phenanthrene was found in the Acolman soil added with glucose and the lowest in the sludge-amended soil. The largest concentration of anthracene in the Texcoco soil was found in soil added with sterile sludge and the lowest in the sludge-amended soil. The largest concentration of phenanthrene in the Texcoco soil was found in the glucose-amended soil and the lowest in the sludge-amended soil. It was found that addition of sludge removed more phenanthrene, but not anthracene from soil compared to the unamended contaminated soil, glucose inhibited dissipation of PAHs while microorganisms in the sludge contributed to their removal, and adjustment of soil pH had no effect. Organic material can be used to accelerate removal of hydrocarbons from soil, but the effect is controlled by soil type, contaminant and organic material characteristics.

Labscale anoxic stabilization ponds operated under high organic loads: long term effect of enrichment with activated sludge.

The addition of acclimatized activated sludge has been suggested as an effective enrichment procedure to increase the biological activity of waste stabilization ponds. This enrichment results in higher degradation rates compared to non enriched stabilization ponds. However, the comparison between enriched and non enriched ponds has been observed during short term experiments and it is unknown if this enrichment has long-term effect. This paper compares enriched and non enriched experimental ponds over two years of continuous operation. The enriched pond showed a degradation activity constantly twice higher. The biological indicators such as the heterotrophic and facultative plate count numbers, the chlorophyll "a" concentration and the oxygen consumption rate were also constantly higher in the enriched pond. These results suggest that an initial enrichment has a long term enhancement effect on stabilization ponds treating complex wastewaters.

Treatment of wastewater containing high phenol concentrations using stabilisation ponds enriched with activated sludge.

Treatment of wastewater containing high phenol concentrations (up to 4,000 mg/l, 1,600 kg/ha.d) in laboratory-scale stabilisation ponds enriched with activated sludge was studied. Phenol was biodegraded efficiently, even when fed as the sole carbon source. At influent concentrations of 1,000, 1,300, 1,600, 1,900, 2,500, 3,000 and 4,000 mg/l of phenol (loading rates of 400, 520, 640, 760, 1,000, 1,200 and 1,600 kg phenol/ha.d), the phenol removal efficiencies were 92, 89, 81, 81, 76, 65 and 22%, respectively. At 4,000 mg/l of phenol, the enriched ponds were significantly inhibited. The maximum phenol removal rate observed was 780 kg/ha.d, which is 7.7 times higher than the maximum value reported for attached-growth waste stabilisation ponds. All along the experiments, the enriched ponds showed removal rates 1.8-20.5 times higher than the values observed in control pond (not enriched). The results suggest that enrichment is an effective method to increase xenobiotic removal rates of stabilisation ponds.

Microbial characterization of organic carrier colonization during a model biofiltration experiment.

AIMS: Dynamic microbial characterization of the colonization of organic carrier during a model biofiltration experiment using methanol as air pollutant. METHODS AND RESULTS: A model biofilter was used in order to characterize the micro-organisms involved in the colonization of a model organic carrier. The model system consisted of closed vial as biofilter, peanut shells as lignocellulosic carrier and methanol as air pollutant. The micro-organisms involved in biofiltration were identified and characterized for their lignocellulolytic and methylotrophic activities. Fungi presented a higher lignocellulolytic activity than bacteria. A steady-state was reached after 15 to 20 days. CONCLUSIONS: The consortium naturally associated to peanut shells is limited to few aerobic bacteria and lignocellulolytic fungi. This consortium was able to degrade methanol without external nutrient supply. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first paper that focuses on carrier degradation processes and the micro-organisms involved during the start-up period of a biofiltration process.

Evidence of anoxic methane oxidation coupled to denitrification.

Denitrification using methane as sole electron donor under anoxic condition was investigated. Sludge produced by a denitrifying reactor using acetate as electron donor was put in contact with methane at partial pressures from 1.8 to 35.7kPa. Nitrate depletion and gaseous nitrogen production were measured. The denitrification rate was independent of the methane partial pressure when superior or equal to 8.8kPa. The nitrate depletion was asymptotic. A denitrification rate of 0.25g NO(3)(-)-Ng(-1) VSSd(-1) was observed at the onset of culturing, followed by a slower and lineal denitrification rate of 4.9x10(-3)g NO(3)(-)-Ng(-1) VSSd(-1). Abiotic nitrate removal or the availability of another carbon source were discarded from control experiments made in the absence of methane or using sterilized inoculum.

Phenol removal in upgraded facultative waste stabilisation ponds.

Treatment of wastewater containing phenol using laboratory scale waste stabilisation ponds enriched with activated sludge was studied. After enrichment, the efficiency of these ponds under high phenol loading rates (i.e. up to 408 kg phenol ha(-1) day(-1)) was studied. At phenol loading rates of 6, 52, 312, 636 and 972 COD ha(-1) day(-1), the phenol removal efficiencies were 77, 69, 76, 59 and 52%, respectively. The results suggest that enrichment is an effective potential method to increase the removal capability of facultative ponds, not only or easily biodegradable compounds but also for xenobiotics.

Respiration rate measurement in a submerged fixed bed reactor.

A novel method is presented to measure the overall biofilm respiration rate in a submerged fixed bed reactor. The method, named "double gassing-out" is based on the measurement of the oxygen uptake rate under two different conditions: (i) replacing the air flow rate by nitrogen in the biological reactor, ensuring the conservation of the same hydraulic conditions and (ii) measuring the oxygen displacement rate by nitrogen in an identical reactor design with no microorganisms. The difference between these measurements gives the overall biofilm respiration rate. Results obtained in a nitrifying fixed bed reactor are presented, compared to classical techniques and discussed.

Characterization of five agricultural by-products as potential biofilter carriers.

Biofiltration is the most commonly used biological gas treatment technology and is extensively used for the treatment of polluted air with gas flow rates of up to 2 x 10(5) m(3)/h. It involves a filter bed of organic matter serving both as carrier for microorganisms and as nutrient supplier. Polluted gas passes through the filter bed and is cleaned by biological activity. Biofiltration is not being developed in Latin America as in the USA, Canada or Europe; the main reason probably being the absence of specific technology and of potential organic carriers locally available. Five different agriculture by-products available in Latin America: peanut shells, rice husk, coconut shells, cane bagasse and maize stubble, were chemically, physically and structurally characterized for their potential use as biofilter carrier. It was found that peanut shells could be used as biofilter carrier and therefore would have potential biological application.

Pressure-drops control strategy in a fixed-bed reactor.

This paper presents a strategy to control pressure-drops (head loss) in a biofilter designed according to the "Mist-Foam" concept. This concept is based on the mixing of the gaseous substrate and a liquid nutrient solution with an atomization nozzle to generate a mist passing subsequently through a synthetic polyurethane foam. In this type of bioreactor, the microbial growth reduces progressively the empty bed volume of the biofilter and causes an increase in the pressure-drops. This phenomenon can result in a complete clogging of the biofilter. The strategy of pressure-drops control presented here consists of successive interruption of the liquid flow, automatically controlled, resulting in a drying effect of the biomass. Tested during a 160 days experiment, this system has permitted to reduce and stabilize the pressure-drops in a biofilter in which the carrier exhibited a high likelihood of clogging.

Biotransformation of n-hexadecane by cell suspension cultures of Cinchona robusta and Dioscorea composita.

This manuscript evaluates the phytotoxicity and biotransformation of n-hexadecane as well as peroxidase activity and cytochrome P450 concentration in microsomes for cell suspension cultures of Cinchona robusta and Dioscorea composita. Phytotoxicity was evaluated based on viability and growth. Cell cultures were exposed to a 2 and 4% (v/v) dose of n-hexadecane. The biotransformation of n-hexadecane was determined based on labeled recovery in polar, nonpolar, and cell residue fractions after cell culture extraction during exponential cell growth phase and stationary phase. Differences were observed in accumulation of label during cell growth phase and stationary phase for the cells of the two plants. Differences also were observed between phases for label in polar and nonpolar fractions. Thin-layer chromatography determined labeled intermediates and some were identified. The activity of peroxidase and concentration of cytochrome P450 was lower in C. robusta than in controls and greater in D. composita than in controls. In vitro biotransformation was not successful.

Biological and biochemical comparison of bovid herpesvirus-4 strains.

Bovid herpesvirus-4 (BHV-4) isolates V.Test and LVR140, isolated from genital disease, respectively, in bull and in cow, and the reference strains Movar 33/63 and DN599 were compared by several methods: cross-serological relationship studied by indirect immunofluorescence; kinetics of intracellular and extracellular viral production; comparison of the mean plaque size; restriction analysis of viral DNA with restriction enzymes EcoRI, BamHI and HindIII. BHV-4 strains were serologically identical and the kinetics of viral production were very similar. Comparison of the mean plaque size allowed classification into 3 classes (Class I, Movar33/63; Class II, LVR140; Class III, V.Test and DN599) and restriction analysis of viral DNA revealed clear differences between the electrophoretic patterns of the four BHV-4 strains. The differentiation between BHV-4 strains can therefore be achieved by a biological method (mean plaque size) and by restriction analysis. The two genital isolates are easily differentiated by the two methods.

Effect of prostaglandins PGE2 and PGF alpha 2 on the mean plaque size of bovine herpesvirus 1.

The effect of prostaglandins PGE2 and PGF alpha 2 on infectious bovine rhinotracheitis (IBR) virus (bovine herpesvirus 1; BHV-1) was studied by using the measurement of the mean size of plaques produced in cell culture by IBR/Cu5 strain. Three concentrations (0.1, 1 and 10 micrograms/ml) of prostaglandins, PGE2 and PGF alpha 2 were used. Each prostaglandin provoked an increase in the mean plaque size when compared to control plaques, at the concentrations 1 and 10 micrograms/ml for PGE2 and 10 micrograms/ml for PGF alpha 2.