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1.
The presence of high levels of salts because of produced brine water disposal at flare pits and the presence of metals at sufficient concentrations to impact microbial activity are of concern to bioremediation of flare pit waste in the upstream oil and gas industry. Two slurry-phase biotreatment experiments based on three-level factorial statistical experimental design were conducted with a flare pit waste. The experiments separately studied the primary effect of cadmium [Cd(II)] and interaction effect between Cd(II) and salinity and the primary effect of zinc [Zn(II)] and interaction effect between Zn(II) and salinity on hydrocarbon biodegradation. The results showed 42-52.5% hydrocarbon removal in slurries spiked with Cd and 47-62.5% in the slurries spiked with Zn. The analysis of variance showed that the primary effects of Cd and Cd-salinity interaction were statistically significant on hydrocarbon degradation. The primary effects of Zn and the Zn-salinity interaction were statistically insignificant, whereas the quadratic effect of Zn was highly significant on hydrocarbon degradation. The study on effects of metallic chloro-complexes showed that the total aqueous concentration of Cd or Zn does not give a reliable indication of overall toxicity to the microbial activity in the presence of high salinity levels.  相似文献   
2.
The methane oxidation potential of several types of compost methanotrophic biofilter columns were compared in the laboratory over a period of 220 days. The results indicate an increase in methanotrophic activity over a period of about 100 days, up to a maximum of 400 g m(-2) day(-1), and a gradual decline to about 100 g m(-2) day(-1) within the next 120 days. High methane oxidation rates appear to be restricted to a small area of the column, 10-15 cm thick. Based on the laboratory investigations carried out to determine the cause for the decline in methane oxidation rate, it was concluded that the formation of exopolymeric substances (EPS), at the zones of maximum methane oxidation, was responsible for this decline. In monitoring methane oxidation in a column for up to 600 days, it was observed that mixing of the medium after formation of EPS enabled the column to temporarily recover high performance. The results suggest that stable, homogenous compost, with a low C/N and low ammonium content, mixed on a regular basis, could achieve and maintain high methane oxidation efficiencies.  相似文献   
3.
To develop an effective waste management strategy for a given region, it is important to know the amount of waste generated and the composition of the waste stream. Past research has shown that the amount of waste generated is proportional to the population and the average mean living standards or the average income of the people. In addition, other factors may affect the amount and composition of waste. These are climate, living habits, level of education, religious and cultural beliefs, and social and public attitudes. This paper presents the findings of a study carried out in a suburban municipal area in Sri Lanka to determine the solid waste generation rate and waste composition based on field surveys and to determine the related socio-economic factors. A database was developed that included information on the quantity and composition of waste generated in a sample of households in the study area over a time period. The collected data was analysed to relate waste generation and composition data to various socio-economic factors. Over 400 sample households were selected for the study using a stratified random sampling methodology based on municipal wards and property values. A technique that considers both the number of households in a particular income group (property value range) and the standard deviation of property values within a given income group was used to determine the appropriate sample size for each municipal ward. Through category and regression analyses, the quantities of waste and waste composition were related to several socio-economic factors. The paper describes the basis for the sample selection, the methodology adopted for data collection, the socio-economic parameters used for the analysis, and the relationships developed from the analysis.  相似文献   
4.
Methane biofilter (MBF) technology, a cost effective method to control atmospheric emission of CH4, is usually developed as a passively aerated system to control low-volume point-source emissions such as those from landfills with gas collection systems. Actively aerated high-rate methane biofilter (HMBF) systems are designed to overcome the shortcomings of passively aerated systems by ensuring the entire filter bed is utilized for CH4 oxidation. Flow-through column experiments point to the fact that CH4 oxidation rates of actively aerated systems could be several times higher than that of passively aerated systems. However, reports of the performance of field HMBF systems are not available in literature. Furthermore, there are no studies that demonstrate the possibility of using laboratory data in the design and operation of field systems. The current study was conducted to fill this research gap and involve a comparative study of the performance of laboratory columns to field performance of a HMBF system using solution gas produced at an oil battery site as the CH4 source. The actively aerated column studies confirmed past results with high CH4 oxidation rates; one column received air at two injection points and achieved an oxidation rate of 1417 g/m3/d, which is the highest reported value to date for compost-filled columns. Subsequent studies at a specially designed field HMBF filled with compost showed a higher oxidation rate of 1919 g/m3/d, indicating the possibility of exceeding the high CH4 oxidation rates observed in the laboratory. The achievement of observed field oxidation rates being higher than those in the laboratory is attributed to the capability of maintaining higher temperatures in field HMBFs. Furthermore, results show that field HMBFs could operate at lower than stoichiometric air to CH4 ratios, and lower retention times than that of laboratory columns. Results indicated that laboratory columns may not truly represent field behavior, and said results could only be used in the preliminary design of field HMBFs.  相似文献   
5.
Bioreactor landfills are designed to accelerate municipal solid waste biodegradation and stabilization; however, the uncaptured methane gas escapes to the atmosphere during their filling. This research investigates the implementation of a novel methane emission control technique that involves thin biocovers (TBC) placed as intermediate waste covers to oxidize methane without affecting the operation of bioreactor landfills. Batch incubation experiments were conducted for selecting the optimum TBC materials, capable of oxidizing methane to carbon dioxide by methanotrophic bacteria. Column experiments were performed to investigate the TBC performance under varying moisture content, compost-to-sawdust ratio, methane flow rate, and biocover thickness. Overall, the optimum TBC is comprised of a 30-cm thick bed of 0-10mass% sawdust mixed with compost, having a moisture content of 52% ww, which showed 100% CH4 oxidation efficiency over an extended period of time even at a relatively high methane inlet load of 9.4gm(-3)h(-1).  相似文献   
6.
Methane biofiltration (MBF) is a novel low-cost technique for reducing low volume point source emissions of methane (CH4). MBF uses a granular medium, such as soil or compost, to support the growth of methanotrophic bacteria responsible for converting CH4 to carbon dioxide (CO2) and water (H2O). A field research program was undertaken to evaluate the potential to treat low volume point source engineered CH4 emissions using an MBF at a natural gas monitoring station. A new comprehensive three-dimensional numerical model was developed incorporating advection-diffusive flow of gas, biological reactions and heat and moisture flow. The one-dimensional version of this model was used as a guiding tool for designing and operating the MBF. The long-term monitoring results of the field MBF are also presented. The field MBF operated with no control of precipitation, evaporation, and temperature, provided more than 80% of CH4 oxidation throughout spring, summer, and fall seasons. The numerical model was able to predict the CH4 oxidation behavior of the field MBF with high accuracy. The numerical model simulations are presented for estimating CH4 oxidation efficiencies under various operating conditions, including different filter bed depths and CH4 flux rates. The field observations as well as numerical model simulations indicated that the long-term performance of MBFs is strongly dependent on environmental factors, such as ambient temperature and precipitation.  相似文献   
7.
Oxygen concentration plays an important role in the regulation of methane oxidation and the microbial ecology of methanotrophs. However, this effect is still poorly quantified in soil and compost ecosystems. The effect of oxygen on the formation of exopolymeric substances (EPS) is as yet unknown. We studied the effect of oxygen on the evolution of methanotrophic activity. At both high and low oxygen concentrations, peak activity was observed twice within a period of 6 months. Phospholipid fatty acid analysis showed that there was a shift from type I to type II methanotrophs during this period. At high oxygen concentration, EPS production was about 250% of the amount at low oxygen concentration. It is hypothesized that EPS serves as a carbon cycling mechanism for type I methanotrophs when inorganic nitrogen is limiting. Simultaneously, EPS stimulates nitrogenase activity in type II methanotrophs by creating oxygen-depleted zones. The kinetic results were incorporated in a simulation model for gas transport and methane oxidation in a passively aerated biofilter. Comparison between the model and experimental data showed that, besides acting as a micro-scale diffusion barrier, EPS can act as a barrier to macro-scale diffusion, reducing the performance of such biofilters.  相似文献   
8.
Errors associated with the closed flux chamber technique, used to measure surface emissions from landfills, were investigated by using a combination of numerical modeling and laboratory studies. A transient-state, advective–dispersive–reactive model was developed and used in conjunction with its steady-state version to quantify the errors associated with closed flux chambers. In developing the model, all four major gases, CH4, O2, CO2, and N2, and the oxidation of CH4 to CO2 were considered. Laboratory experiments were conducted on a monolayered as well as a two-layered landfill cover system to calibrate and verify the model. The model was used to develop a plot of the percentage errors associated with closed flux chambers of different dimensions and surface flux rates.  相似文献   
9.
10.
Thermal conductivity is an important property that governs the behaviour of leaf compost biofilters used in treating gaseous pollutants. Measurements were carried out for the thermal conductivity (K) of 44 samples of leaf compost, covering wide ranges of the volume fractions of water (xi(w)), solids (xi(s)) and air (xi(a)), at 20 degrees C using an unsteady state thermal probe. The results indicated that the compost thermal conductivity increased with an increase in xi(w), with a decrease in xi(a), and with an increase in the degree of saturation (defined as the volumetric fraction of water in the total void space). The predictions from the Woodside-Messmer quadratic parallel (QP) model for the thermal conductivity of leaf compost were higher than the experimental values. A simple linear relationship was developed between the thermal conductivity and the degree of saturation, which provided a satisfactory correlation for the data measured in this study as well as those reported recently for sandy and clay loams.  相似文献   
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