Extraction of natural gas from a confined coal aquifer requires the pumping of large amounts of groundwater, commonly referred to as produced water. Produced water from the extraction of coalbed natural gas is typically disposed into nearby constructed discharge ponds. The objective of this study was to collect produced water samples at outfalls and corresponding discharge ponds and monitor pH, electrical conductivity (EC), calcium (Ca), magnesium (Mg), sodium (Na), and alkalinity. Outfalls and corresponding discharge ponds were sampled from five different watersheds including Cheyenne River (CHR), Belle Fourche River (BFR), Little Powder River (LPR), Powder River (PR), and Tongue River (TR) within the Powder River Basin (PRB), Wyoming from 2003 to 2005. From Na, Ca, and Mg measurements, sodium adsorption ratios (SAR) were calculated, and used in a regression model. Results suggest that outfalls are chemically different from corresponding discharge ponds. Sodium, alkalinity, and pH all tend to increase, possibly due to environmental factors such as evaporation, while Ca decreased from outfalls to associated discharge ponds due to calcite precipitation. Watersheds examined in this study were chemically different form each other and most discharge ponds with in individual watersheds tended to increase in Na and SAR from 2003 to 2005. Since discharge pond water was chemically changing as a function of watershed chemistry, we predicted SAR of discharge pond water using a regression model. The predicted discharge pond water results suggested a high correlation (R ² = 0.83) to discharge well SAR. Overall, results of this study will be useful for landowners, water quality managers, and industry in properly managing produced water from the natural gas extraction.

This study qualifies and quantifies the effects of pH, hardness, alkalinity, salinity and bone calcination temperature related with the adsorption of As(V) onto biogenic hydroxyapatite (HAPb) obtained from cow-charred bones. Arsenic contamination of surface and subsurface waters is widely extended in Argentina. It is a problem of major concern, particularly in rural and suburban areas where there are not water treatment plants for supplying of drinking water. HAPb is a natural material, whose absorbent properties can be used for the design of low-cost technologies for As(V) abatement in water. In this work HAPb has been characterized by physical and chemical analysis (XRD, SEM, EDAX, BET, and electrophoretic mobility). A Plackett–Burman screening experimental design allowed us to determine the main variables affecting the efficiency of As(V) sorption onto HAPb. Based on these variables and with a design of higher order we developed a model of the system to study its behaviour. Data collection was planned through a Doehlert experimental design and a back propagation artificial neural network was used to work it out. Results showed that salinity is the major variable affecting the efficiency of the As(V) immobilization process but pH and hardness should be taken into account because of associations among them.