1,720,983 research outputs found
GWCarb v1.0: carbonate speciation tool
No full textThis spreadsheet calculates carbonate speciation using carbonate equilibrium equations at standard conditions (T=25°C) with ionic strength corrections. The user will typically be able to calculate the different carbonate species by entering total alkalinity and pH. This spreadsheet contains additional tools to calculate the Langelier Index for calcium and the SAR of the water. Note that in this last calculation the potential for calcium precipitation is not taken into account. The last tool presented here is a carbonate speciation tool in open systems (e.g. open to the atmosphere) which takes into account atmospheric pressure
Coal seam gas development and environmental implications : examples from Australia, USA, and NZ
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Sources of hydrochemical variability and implications associated with CSG water extraction
No full textCoal Seam Gas (CSG) production is achieved by extracting groundwater to depressurize coal seam aquifers in order to promote methane gas desorption from coal micropores. CSG waters are characteristically alkaline, have a neutral pH (~7), are of the Na-HCO3-Cl type, and exhibit brackish salinity. In 2004, a CSG exploration company carried out a gas flow test in an exploration well located in Maramarua (Waikato Region, New Zealand). This resulted in 33 water samples exhibiting noteworthy chemical variations induced by pumping. This research identifies the main causes of hydrochemical variations in CSG water, makes recommendations to manage this effect, and discusses potential environmental implications.\ud
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Hydrochemical variations were studied using Factor Analysis and this was supported with hydrochemical modelling and a laboratory experiment. This reveals carbon dioxide (CO2) degassing as the principal source of hydrochemical variability (about 33%). Factor Analysis also shows that major ion variations could also reflect changes in hydrochemical composition induced by different pumping regimes. Subsequent chloride, calcium, and TDS variations could be a consequence of analytical errors potentially committed during laboratory determinations.\ud
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CSG water chemical variations due to degassing during pumping can be minimized with good completion and production techniques; variations due to sample degassing can be controlled by taking precautions during sampling, transit, storage and analysis. In addition, the degassing effect observed in CSG waters can lead to an underestimation of their potential environmental effect. Calcium precipitation due to exposure to normal atmospheric pressure results in a 23% increase in SAR values from Maramarua CSG water samples.\u
Australia and New Zealand CBNG development and environmental implications
No full textFollowing the success of Coalbed Natural Gas (CBNG) operations in the United \ud
States, companies in Australia and New Zealand have been actively exploring and \ud
developing this technology for the last two decades. In particular, the Bowen and Surat \ud
basins in Queensland, Australia, have undergone extensive CBNG development. \ud
Unfortunately, awareness of potential environmental problems associated with CBNG \ud
abstraction has not been widespread and legislation has at times struggled to keep up with \ud
rapid development. \ud
In Australia, the combined CBNG resource for both the Bowen and Surat basins has \ud
been estimated at approximately 10,500 PJ with gas content as high as 10 m3/tonne of \ud
coal. There are no official estimates for the magnitude of the CBNG resource in New \ud
Zealand but initial estimates suggest this could be up to 1,300 PJ with gas content ranging \ud
from 1 to 5 m3/tonne of coal. \ud
In Queensland, depressurization of the Walloon Coal Measures to recover CBNG \ud
has the potential to induce drawdown in adjacent deep aquifer systems through \ud
intraformational groundwater flow. In addition, CBNG operators have been disposing \ud
their co-produced water by using large unlined ponds, which is not the best practice for \ud
managing co-produced water. CBNG waters in Queensland have the typical geochemical \ud
signature associated with CBNG waters (Van Voast, 2003) and thus have the potential to \ud
impair soils and plant growth where land disposal is considered. Water quality from \ud
exploration wells in New Zealand exhibit the same characteristics although full scale \ud
production has not yet begun. \ud
In general, the environmental impacts that could arise from CBNG water extraction \ud
depend on the aquifer system, the quantity and quality of produced water, and on the \ud
method of treatment and disposal being used. Understanding these impacts is necessary \ud
to adequately manage CBNG waters so that environmental effects are minimized; if properly managed, CBNG waters can be used for beneficial applications and can become \ud
a valuable resource to stakeholders
Coal Seam Gas Water from Maramarua, New Zealand: Characterisation and Comparison to United States Analogues\ud
No full textGroundwater from Maramarua has been identified as coal seam gas (CSG) water by studying its composition, and comparing it against the geochemical signature from other CSG basins. CSG is natural gas that has been produced through thermogenic and biogenic processes in underground coal seams; CSG extraction requires the abstraction of significant amounts of CSG water. To date, no international literature has described coal seam gas water in New Zealand, however recent CSG exploration work has resulted in CSG water quality data from a coal seam in Maramarua, New Zealand. Water quality from this site closely follows the geochemical signature associated with United States CSG waters, and this has helped to characterise the type of water being abstracted. CSG water from this part of Maramarua has low calcium, magnesium, and sulphate concentrations but high sodium (334 mg/l), chloride (146 mg/l) and bicarbonate (435 mg/l) concentrations. In addition, this water has high pH (7.8) and alkalinity (360 mg/l as CaCO3), which is a direct consequence of carbonate dissolution and biogenic processes. Different analyte ratios ('source-rock deduction' method) have helped to identify the different formation processes responsible in shaping Maramarua CSG wate
Sodium removal from Maramarua CSG waters using Ngakuru zeolites
No full textCoal seam gas (CSG) waters are a by-product of natural gas extraction from un derground coal seams. The main\ud
issue with these waters is their elevated sodium content, which in conjunction with their low calcium and\ud
magnesium concentrations can generate soil infiltration problems in the long run , as well as short term toxicity\ud
effects in plants due to the sodium ion itself.\ud
Zeolites are minerals having a porous structure, crystalline characteristics, and an alumino-silicate configuration\ud
resulting in an overall negative charge which is balanced by loosely held cations. In New Zealand, Ngakuru\ud
zeolites have been mined for commercial use in wastewater treatment applications, cosmetics, and pet litter.\ud
This research focuses on assessing the capacity of Ngakuru zeolites to reduce sodium concentrations of CSG\ud
waters from Maramarua. Batch and column test (flow through) experiments revealed that Ngakuru zeolites are\ud
capable of sorbing sodium cations from concentrated solutions of sodium. In b atch tests, the sodium adsorption\ud
capacity ranged from 5.0 to 34.3meq/100g depending on the solution concentration and on the number of times\ud
the zeolite had been regenerated. Regeneration with CaCl2 was foun d to be effective. The calculated sodium\ud
adsorption capacity of Ngakuru zeolites under flow-through conditions ranged from 11 to 42meq/100g\ud
depending on the strength of the solution being treated and on w hether the zeolites had been previously\ud
regenerated. The slow kinetics and low cost of the zeolities, coupled with potentially remote sites for gas\ud
extraction, could make semi-batch operational processes without regeneration more favourable than in more\ud
industrial ion exchange situations
Estimation of WGEN Weather Generation Parameters\ud in Arid Climates
No full textThis research discusses some of the issues encountered while developing a set of WGEN parameters for Chile and advice for others interested in developing WGEN parameters for arid climates. The WGEN program is a commonly used and a valuable research tool; however, it has specific limitations in arid climates that need careful consideration. These limitations are analysed in the context of generating a set of WGEN parameters for Chile. Fourteen to 26 years of precipitation data are used to calculate precipitation parameters for 18 locations in Chile, and 3–8 years of temperature and solar radiation data are analysed to generate parameters for seven of these locations. Results indicate that weather generation parameters in arid regions are sensitive to erroneous or missing precipitation data. Research shows that the WGEN-estimated gamma distribution shape parameter (α) for daily precipitation in arid zones will tend to cluster around discrete values of 0 or 1, masking the high sensitivity of these parameters to additional data. Rather than focus on the length in years when assessing the adequacy of a data record for estimation of precipitation parameters, researchers should focus on the number of wet days in dry months in a data set. Analysis of the WGEN routines for the estimation of temperature and solar radiation parameters indicates that errors can occur when individual ‘months’ have fewer than two wet days in the data set. Recommendations are provided to improve methods for estimation of WGEN parameters in arid climates
Metal Contaminants in Leachate from Sanitary Landfills
No full textThe uncontrolled disposal of solid wastes poses an immediate threat to public\ud
health and a long term threat to the environmental well being of future generations. Solid\ud
waste is waste resulting from human activities that is solid and unwanted (Peavy et al.,\ud
1985). If unmanaged, dumped solid wastes generate liquid and gaseous emissions that are\ud
detrimental to the environment. This can lead to a serious form of contamination known\ud
as metal contamination, which poses a risk to human health and ecosystems. For\ud
example, some heavy metals (cadmium, chromium compounds, and nickel tetracarbonyl)\ud
are known to be highly toxic, and are aggressive at elevated concentrations. Iron, copper,\ud
and manganese can cause staining, and aluminium causes depositions and discolorations.\ud
In addition, calcium and magnesium cause hardness in water causing scale deposition and\ud
scum formation. Though not a metal but a metalloid, arsenic is poisonous at relatively\ud
high concentrations and when diluted at low concentrations causes skin cancer. Normally,\ud
metal contaminants are found in a dissolved form in the liquid percolating through\ud
landfills. Because average metal concentrations from full-scale landfills, test cells, and\ud
laboratory studies have tended to be generally low, metal contamination originating from\ud
landfills is not generally considered a major concern (Kjeldsen et al., 2002; Christensen et\ud
al., 1999). However, a number of factors make it necessary to take a closer look at metal\ud
contaminants from landfills. One of these factors relates to variability. Landfill leachate\ud
can have different qualities depending on the weather and operating conditions.\ud
Therefore, at one moment in time, metal contaminant concentrations may be quite low,\ud
but at a later time these concentrations could be quite high. Also, these conditions relate\ud
to the amount of leachate that is being generated. Another factor is biodiversity. It cannot\ud
be assumed that a particular metal contaminant is harmless to flora and fauna (including\ud
micro organisms) just because it is harmless to human health. This has significant\ud
implications for ecosystems and the environment. Finally, there is the moral factor.\ud
Because uncertainty surrounds the potential effects of metal contamination, it is\ud
appropriate to take precautions to prevent it from taking place. Consequently, it is\ud
necessary to have good scientific knowledge (empirically supported) to adequately\ud
understand the extent of the problem and improve the way waste is being disposed o
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