scholarly journals The effects of methane seepage at an intertidal/shallow subtidal site on the shore of the Kattegat, Vendsyssel, Denmark

1994 ◽  
Vol 41 ◽  
pp. 65-79
Author(s):  
P. R. Dando ◽  
S. C. M. O'Hara ◽  
S. J. Niven ◽  
U. Schuster ◽  
L. J. Taylor ◽  
...  
Keyword(s):  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Interstitial Water ◽  
Nematode Species ◽  
Water Circulation ◽  
Oxidation Rates ◽  
Methane Seepage ◽  
Sulphide Concentration ◽  
Gas Seepage ◽  
Shallow Subtidal

The effects of methane gas seepage were studied at an intertidal/shallow subtidal site on the Kattegat coast of Denmark. A 30 m wide zone, containing approximately 65 gas seeps, extended over 70 m seawards from the shore. This was characterised by the presence of slabs, pavement and small pillars of carbonate-cemented sandstone which formed a partially buried reef. The escaping gas contained 91-100% methane with some carbon dioxide, 0.6--0.9%, and hydrogen sulphide. The hydrogen sulphide concentration varied over time and between individual seeps. Gas flow rates of individual seeps ranged up to 211 h-1 and the estimated total flow was 110 I h-1• Seeps were often stopped by sand movement, but the overall gas flow from the site appeared to be constant. The escaping gas generated an interstitial water circulation and drew overlying seawater into the sediment. Water pumped out by the seeps was enriched in phosphate and ammonia. Sulphate reduction rates in the seep area were 1.1-17.1 m moles sulphate reduced and aerobic methane oxidation rates were 0.2 - 5.5 m moles methane consumed m-2 day-1• The composition of the flora and fauna surrounding the seeps was affected by the presence of hard substrate (the cemented sandstone). Epifauna was more abundant in the seep zone than else­where, whereas the macrobenthic infauna was reduced in the seep zone, possibly due to the cementation. The sediment was almost devoid of meiobenthic organisms, except nematodes. Nematode species numbers, abundance and biomass were lower at the seeps than 5-20 cm away. The nematode fauna penetrated deeper into the sediment close to the seeps than at the seeps themselves. This is explained by the interstitial water circulation at and close to the seeps. 14C measurements showed that little methane carbon was entering the food web surrounding the seeps.

Gas seep induced interstitial water circulation: observations and environmental implications

1995 ◽  
Vol 15 (8) ◽  
pp. 931-948 ◽  
Author(s):  
S.C.M. O'Hara ◽  
P.R. Dando ◽  
U. Schuster ◽  
A. Bennis ◽  
J.D. Boyle ◽  
...  
Keyword(s):  
Interstitial Water ◽  
Water Circulation ◽  
Environmental Implications

Performance of sanitary sewer collection system odour control devices operating in diverse conditions

2013 ◽  
Vol 68 (12) ◽  
pp. 2527-2533 ◽  
Author(s):  
Mary Kay Camarillo ◽  
William T. Stringfellow ◽  
Jeremy S. Hanlon ◽  
Elizabeth Basha
Keyword(s):  
Service Life ◽  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Pressure Regulation ◽  
Collection System ◽  
Removal Rates ◽  
Flow Rates ◽  
Sanitary Sewer ◽  
Odour Control ◽  
Control Devices

Controlling odours from sanitary sewer systems is challenging as a result of the expansive nature of these systems. Addition of oxidizing chemicals is often practiced as a mitigation strategy. One alternative is to remove odorous compounds in the gases vented from manholes using adsorptive media. In this study, odour control devices located at manholes were observed to determine the ability of these systems to reduce hydrogen sulphide from vented gases. The odour control devices incorporated pressure regulation to control gas flow out of manhole covers and adsorptive media to remove hydrogen sulphide in the vented gases prior to release. Pressure regulation was accomplished using a variable volume bladder and two pressure relief valves that permitted gas flow when pressures exceeded 1.3 to 2.5 cm water column. The reduction in gas flow vented from manholes was intended to extend the service life of the adsorptive media, as compared with odour control devices that do not incorporate pressure modulation. Devices were deployed at four locations and three adsorptive media were tested. Although measured collection system hydrogen sulphide concentrations varied from zero to over 1,000 ppm, the removal rates observed using odour control devices were typically above 90%. The lower removal rates observed at one of the sites (50.5 ± 36.1%) appeared related to high gas flow rates being emitted at this location. Activated carbon was used in most of the tests, although use of iron media resulted in the highest removal observed: 97.8 ± 3.6%. The expected service life of the adsorptive media contained within the odour control devices is a function of site-specific hydrogen sulphide concentrations and gas flow rates. The units used in this study were in service for more than 8 to 12 months prior to requiring media replacement.

scholarly journals Thermos-Solid-Gas Coupling Dynamic Model and Numerical Simulation of Coal Containing Gas

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Xiao Fukun ◽  
Meng Xin ◽  
Li Lianchong ◽  
Liu Jianfeng ◽  
Liu Gang ◽  
...  
Keyword(s):  
Principal Stress ◽  
Dynamic Model ◽  
Gas Flow ◽  
Flow Behavior ◽  
Coupling Model ◽  
Gas Pressure ◽  
Permeability Model ◽  
Gas Seepage ◽  
Coupling Dynamic ◽  
Coupling Dynamic Model

Based on gas seepage characteristics and the basic thermo-solid-gas coupling theory, the porosity model and the dynamic permeability model of coal body containing gas were derived. Based on the relationship between gas pressure, principal stress and temperature, and gas seepage, the thermo-solid-gas coupling dynamic model was established. Initial values and boundary conditions for the model were determined. Numerical simulations using this model were done to predict the gas flow behavior of a gassy coal sample. By using the thermo-solid-gas coupling model, the gas pressure, temperature, and principal stress influence, the change law of the pressure field, displacement field, stress field, temperature field, and permeability were numerically simulated. Research results show the following: (1) Gas pressure and displacement from the top to the end of the model gradually reduce, and stress from the top to the end gradually increases. The average permeability of the Y Z section of the model tends to decrease with the rise of the gas pressure, and the decrease amplitude slows down from the top of the model to the bottom. (2) When the principal stress and temperature are constant, the permeability decreases first and then flattens with the gas pressure. The permeability increases with the decrease of temperature while the gas pressure and principal stress remain unchanged.

scholarly journals Numerical Simulation of Shale Gas Multiscale Seepage Mechanism-Coupled Stress Sensitivity

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Xun Yan ◽  
Jing Sun ◽  
Dehua Liu
Keyword(s):  
Shale Gas ◽  
Gas Flow ◽  
Gas Transport ◽  
Sensitivity Coefficient ◽  
Stress Sensitivity ◽  
Gas Production ◽  
Molecular Flow ◽  
Adsorption Phenomenon ◽  
Gas Seepage ◽  
The Impact

The complexity of the gas transport mechanism in microfractures and nanopores is caused by the feature of multiscale and multiphysics. Figuring out the flow mechanism is of great significance for the efficient development of shale gas. In this paper, an apparent permeability model which covers continue, slip, transition, and molecular flow and geomechanical effect was presented. Additionally, a mathematical model comprising multiscale, geomechanics, and adsorption phenomenon was proposed to characterize gas flow in the shale reservoir. The aim of this paper is to investigate some important impacts in the process of gas transportation, which includes the shale stress sensitivity, adsorption phenomenon, and reservoir porosity. The results reveal that the performance of the multistage fractured horizontal well is strongly influenced by stress sensitivity coefficient. The cumulative gas production will decrease sharply when the shale gas reservoir stress sensitivity coefficient increases. In addition, the adsorption phenomenon has an influence on shale gas seepage and sorption capacity; however, the effect of adsorption is very weak in the early gas transport period, and the impact of later will increase. Moreover, shale porosity also greatly affects the shale gas transportation.

Direct molecular hydrogen sulphide scrubbing with hollow fibre membranes

2001 ◽  
Vol 44 (9) ◽  
pp. 135-142 ◽  
Author(s):  
N. Boucil ◽  
B. Jefferson ◽  
S.A. Parsons ◽  
S.J. Judd ◽  
R.M. Stuetz
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Flow Rate ◽  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Hollow Fibre ◽  
The Other ◽  
Gas Flow Rate

The emission of hydrogen sulphide is a major problem associated with anaerobic treatment of sulphate and sulphite containing wastewaters. Conventional absorbing processes, such as packed towers, spray towers or bubble columns, are all constrained by factors such as flooding and foaming. Membrane systems, on the other hand, enable independent control of the liquid and gas flow rate and a step change order of magnitude increase in the specific surface area of the contact process. The membrane acts as a gas absorber with a design similar to a shell and tube heat exchanger. On the other hand, they are limited by facets of the membrane such as its resistance to mass transfer and permselectivity, as well as its cost. The work presented in this paper refers to an absorption process based on a non-wetted hollow fibre membrane for the scrubbing of hydrogen sulphide from air, with water as the contact solvent. Results presented describe the performance of the unit in terms of overall transfer and outlet liquid concentration as a function of circulation regime, gas flow rate, liquid flow rate and specific surface area. In particular, results are presented using traditional plots of Sherwood number (Sh) against Graetz (Gr) number for the liquid flowing in the lumens, such that experimental and available empirical descriptions of the process performance are directly compared. Results suggest that, as expected, very efficient mass transfer is obtained. However, the mass transfer was found to reach a maximum value against Gr, contrary to available empirical models.

Sewage treatment works odour measurement

2000 ◽  
Vol 41 (6) ◽  
pp. 33-40 ◽  
Author(s):  
P. Gostelow ◽  
S. A. Parsons
Keyword(s):  
Hydrogen Sulphide ◽  
Sewage Treatment ◽  
Dispersion Models ◽  
Single Measure ◽  
Unit Operations ◽  
Sulphide Concentration ◽  
Odour Concentration ◽  
And Control ◽  
The Relationship ◽  
Human Nose

Public concern over odours from sewage treatment works is increasing. More people are being exposed to odours, due to development around existing works or the construction of new works. Raised awareness of both the environment and individual rights has meant people are now more likely to complain. Odourabatement and control is a major issue for sewage works operators. To control odours, they must first be measured. This is no easy task as response to odours is subjective and our understanding of the sense of smell is incomplete. In assessing an odour nuisance, odour formation, emission, dispersion and perception must be considered. There is no single measure that is suitable for this purpose. Odour measurements fall into two classes. Analytical measurements characterise odours in terms of their chemical composition and are more suited to formation, emission and dispersion models. Unfortunately, they tell us little about the perceived effect of the odour. Sensory measurements employ the human nose and characterise odours in terms of their perceived effect. A link between analytical and sensory measurements is clearly needed. In this paper data collected from odour surveys at 17 different wastewater treatment sites are evaluated to explore possibilities for linking analytical and sensory measures. The relationship between hydrogen sulphide concentration and odour concentration as measured by threshold olfactometry is explored. Correlations suggest power-law relationships between hydrogen sulphide and odour concentration, with r2 values as high as 0.69. This paper will assess the use of hydrogen sulphide (H2S) and olfactometry measurements for a range of unit operations and abatement technologies.

Sources of Pollution of the Estuary of the River Nervion, Spain – A Case Study

1984 ◽  
Vol 16 (5-7) ◽  
pp. 95-125 ◽  
Author(s):  
A Azkona ◽  
S H Jenkins ◽  
H M G Roberts
Keyword(s):  
Fresh Water ◽  
Hydrogen Sulphide ◽  
Industrial Wastewater ◽  
Industrial Effluent ◽  
Oxygen Demand ◽  
Industrial Effluents ◽  
Domestic Sewage ◽  
Septic Tank ◽  
Safety Level ◽  
Sulphide Concentration

This paper describes part of a comprehensive multidisciplinary study of the pollution of the estuary of the River Nervion, Bilbao, Spain. The objectives of the study were to determine the sources and loads of pollution from domestic sewage and industrial wastewater; provide information on the extent of pollution; formulate hydrodynamic and predictive models capable of forecasting the effects on the estuary of the anticipated growth of population and industry; determine the amount of polluting matter that would have to be removed in order to reach defined estuary water quality standards; arrive at suitable technical methods able to attain these standards at minimum cost; determine the treatability of wastewater discharges and recommend methods for controlling industrial wastewater. These objectives necessitated a survey of the pollution loads from domestic sources and industry which were discharged to the fresh water and tidal reaches of four major tributaries in addition to the main river Nervion; the results of this part of the survey are described in this paper. The presence of iron in discharges from iron ore mining and metal processing was found to aid flocculation of organic matter and the consequent deposition of sludge in the estuary. This action and the rate of oxygen uptake during the decomposition of such deposits are also described. The domestic sewage of the study area receives treatment in septic tanks before discharging to rivers or the estuary. In spite of free hydrogen sulphide and high concentrations being present in the septic tank effluents, odour nuisance does not occur, because, as is shown in the paper, of the formation of ferrous sulphide. The hydrogen sulphide concentration in the atmosphere at a pumping station was found to be above the safety level. The industrial load of impurity was estimated to be approximately 15% higher than the domestic load, but it is extremly difficult to find a rational basis on which comparisons may be made between domestic sewage and a mixture of industrial effluents containing substances inimical to biological activity. The industrial effluent was contained in a very large volume of water, much of it taken from the estuary for cooling or process water. It is calculated that if the industrial pollutants had been contained only in the fresh water used by industry the COD of the mixture would have been 1317 mg/l; the suspended solids 2143 mg/l; the ammonia nitrogen 191 mg/l; iron 1037 mg/l; other heavy metals 118 mg/l; fluoride as F 14.5 mg/l; cyanide as CN 8.1 mg/l; oil 196 mg/l; phenols 8.1 mg/l; mercury 0.13 mg/l; and the mixture would have had an excess of acidity of 5188 mg/l. An estimate of the load of substances having an oxygen demand indicated that of the total oxygen demand discharged to the system of rivers and estuary approximately 50% entered the estuary from the main tributaries, the remainder being discharged directly to the estuary. An outline is given of the methods that would be used to determine the treatability of industrial effluents which were rendered acceptable for discharge into public sewers.

scholarly journals Technical note: Mobile open dynamic chamber measurement of methane macroseeps in lakes

2020 ◽  
Vol 24 (12) ◽  
pp. 6047-6058
Author(s):  
Frederic Thalasso ◽  
Katey Walter Anthony ◽  
Olya Irzak ◽  
Ethan Chaleff ◽  
Laughlin Barker ◽  
...  
Keyword(s):  
Gas Flow ◽  
Ice Cores ◽  
Technical Note ◽  
Ch4 Emissions ◽  
Methane Seepage ◽  
Radiocarbon Data ◽  
Flux Measurements ◽  
Gaseous Hydrocarbons ◽  
Moderate Cost ◽  
Warming World

Abstract. Methane (CH4) seepage (i.e., steady or episodic flow of gaseous hydrocarbons from subsurface reservoirs) has been identified as a significant source of atmospheric CH4. However, radiocarbon data from polar ice cores have recently brought into question the magnitude of fossil CH4 seepage naturally occurring. In northern high latitudes, seepage of subsurface CH4 is impeded by permafrost and glaciers, which are under an increasing risk of thawing and melting in a globally warming world, implying the potential release of large stores of CH4 in the future. Resolution of these important questions requires a better constraint and monitoring of actual emissions from seepage areas. The measurement of these seeps is challenging, particularly in aquatic environments, because they involve large and irregular gas flow rates, unevenly distributed both spatially and temporally. Large macroseeps are particularly difficult to measure due to a lack of lightweight, inexpensive methods that can be deployed in remote Arctic environments. Here, we report the use of a mobile chamber for measuring emissions at the surface of ice-free lakes subject to intense CH4 macroseepage. Tested in a remote Alaskan lake, the method was validated for the measurement of fossil CH4 emissions of up to 1.08 × 104 g CH4 m−2 d−1 (13.0 L m−2 min−1 of 83.4 % CH4 bubbles), which is within the range of global fossil methane seepage and several orders of magnitude above standard ecological emissions from lakes. In addition, this method allows for low diffusive flux measurements. Thus, the mobile chamber approach presented here covers the entire magnitude range of CH4 emissions currently identified, from those standardly observed in lakes to intense macroseeps, with a single apparatus of moderate cost.

scholarly journals Horizontal Subzone Characteristics and Methane Seepage Properties of the Gas Flowing Fracture Zone above the Gob

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Wei Qin ◽  
Jialin Xu
Keyword(s):  
Fracture Zone ◽  
Gas Flow ◽  
Physical Simulation ◽  
Morphological Development ◽  
Flow State ◽  
Ring Fracture ◽  
Methane Seepage ◽  
Mining Depth ◽  
Seepage Properties ◽  
Mining Height

Gas flowing fracture zone (GFFZ) is an active zone in the gob where pressure-relieved methane can move freely. However, there are very few research findings on the horizontal development characteristics and internal methane seepage properties of GFFZs. In this paper, based on the development height of a GFFZ above the gob, the GFFZ was horizontally divided into the following: a lateral fracture subzone, an O-ring fracture subzone, and a compacted subzone. The identification criteria for all of these horizontal subzones were given by analyzing the influence of the stress in the coal rock mass on the development of mining-induced fractures. A numerical simulation study was conducted to determine the influences of the mining height and mining depth on the morphological development of all horizontal subzones of the GFFZ, and the simulation results showed that the mining height was the main factor influencing the development characteristics of horizontal subzones of the GFFZ. Both the maximum distance of the lateral fracture subzone beyond the mining boundary and the width of the O-ring fracture subzone increased with the increase of mining height. A physical simulation experiment was performed for extraction of gob methane through a surface borehole, and the experimental results showed that the gas flow state was laminar within the range of the lateral fracture subzone and the compacted subzone but that the gas flow state was turbulent, not following Darcy’s law, within the range of the O-ring fracture subzone.

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