Exploration and Production Technologies
Use of Wetland Plant Species and Communities for Phytoremediation of Coalbed Natural Gas Produced Water and Waters of Quality Similar to that Associated with Coalbed Natural Gas Deposits of the Powder River Basin

DE-FG26-01BC15166

Project Goal
The project goal is to evaluate coalbed natural gas (CBNG) produced water and determine which plants can best be irrigated with it. The specific focus of the project is to study how produced water with a characteristic saline-sodic fingerprint will interact with soil and water resources in CBNG production areas in the Powder River Basin (PRB) of Montana and Wyoming. This project also encompasses research in development, testing, and evaluation of economically/environmentally acceptable treatment processes for CBNG production water, sealing and infiltration characteristics of CBNG production water impoundment sites, and feasibility for use of CBNG for terrestrial carbon sequestration through enhanced wetland and rangeland biomass.

Performers
Department of Land Resources and Environmental Sciences, Montana State University (MSU), Bozeman, MT
Drake Engineering, Helena, MT
Northern Rockies Soil and Water, Bozeman, MT

Background
Within the past decade America’s resources for natural gas production have dwindled, and exploration and development of new, unconventional reservoirs such as CBNG have increased, and one of the fastest-growing new supplies is CBNG produced in the Powder and Tongue River basins of Wyoming and Montana.

A January 2003 Environmental Impact Statement for CBNG development in Montana’s PRB, prepared by the Bureau of Land Management and Montana’s Department of Environmental Quality (DEQ) and Board of Oil and Gas Conservation, estimated 2.5 trillion cubic feet of recoverable gas within the basin. Estimates from State and Federal agencies and industry are that 15,000-70,000 CBNG wells will be developed in the basin in the next 15-20 years. CBNG extraction requires significant volumes of water to be pumped from coal seams to release water pressure that traps gas within the coals. The quantity, quality, and dispersal of this water needed to be evaluated.

One of the significant environmental production concerns is the amount of water and its mineral constituents associated with CBNG production. It has generated a great deal of interest from the regulatory community, environmental groups, and the agricultural community, as well as a tremendous effort by gas production companies to properly handle, and demonstrate beneficial uses for, produced water. The water associated with much of the basin has the potential to be utilized in irrigation, stock watering, and wildlife enhancement efforts. What to do with the water is an immensely complex problem.

Results
Combinations appropriate management practices, technology-advanced treatment, and bioremediation processes can turn CBNG produced water into a valuable supplement to existing irrigation water supplies. Additionally, efforts have been directed toward implementation of produced water treatment and discharge strategies which will enhance ephemeral and perennial stream corridor function in the Powder River basin. Measurable changes in ephemeral channel biomass production and salt-tolerant species composition are likely to occur in areas of sustained PRB CBNG produced water discharge. Baltic rush, American bulrush, inland salt grass, alkali grass, and prairie and alkaline cord grasses dominated ephemeral channels where PRB CBNG produced water was discharged for extended periods of time. Significant in-channel plant growth (under limited ephemeral and perennial flow) and accumulations of biomass can play a role (although limited) in carbon sequestration, enhanced wildlife habitat, sediment transport abatement, and extreme flow mitigation.

Parametric and non-parametric, flow-weighted time series analyses of quality of the Little Powder River at Weston, WY, a tributary to the Powder River, revealed no significant differences in salinity, sodium, and constituent concentrations between pre-and post-CBNG development. Although trends of elevated salinity and sodicity were determined for low-flow conditions, variability of the data precluded statistical significance of observed differences. More recent results from similarly conducted studies of the Powder River indicate correlation between lowered salinity, elevated sodicity, and increased CBNG produced water discharges into the Powder River.

In many cases, PRB CBNG produced water could be used to augment drought-limited water supplies and complement limited water resources for irrigation within the PRB. Use of CBNG produced water with low concentrations of total salts resulted in 300-400% higher crop yields over non-irrigated crops. Hay barley, native grass, and selected livestock forage crops irrigated with PRB CBNG produced water yields substantially greater than non-irrigated crops. The most functional species identified included Valier, Haybet, and Haxby varieties of hay barley, Altai Basin rye, tall fescue, and intermediate wheatgrass. Sustainable PRB CBNG produced-water irrigation necessitates a dependable, relatively plentiful supply of water and requires detailed site and crop selection and continuous mitigation of sodium-induced soil dispersion with use of surface-applied amendments. Considerations need to be given to shallow alluvial groundwater changes including, elevated salinity and water table.

Use of CBNG produced-water for irrigation of native grasses resulted in uptake of salts, and when harvested or grazed, excess salts were removed from the system. The amount of salt uptake and removal was determined to be a function of both species selectivity and amount of biomass produced. Salt uptake and removal was disproportionately small relative to the amount of salt sourced in PRB CBNG produced water used for irrigation. Phytoremediation for removal of salts and sodic concentrations from the CBNG produced water was determined not to be feasible as a management practice for large volumes of produced water. The agricultural crop and forage species most capable of beneficial use of CBNG produced water were maize, hay, forage barley, Altai Basin rye, tall fescue, intermediate wheatgrass, Atriplex species, Inland saltgrass, and prairie and alkali cord grasses. Irrigation with CBNG water with low total salt yielded crops 300-400% higher in biomass, digestible fiber, and total digestible nutrients than the same crops grown under non-irrigated conditions.

Adaptive wetland halophytes and tolerant glycophytes exhibited various responses to irrigation with CBNG produced-water; from quick establishment to condition-specific propagation and long-term survivability. Prairie cordgrass, Maritime bulrush, Baltic rush and Inland saltgrass appear to be the most likely candidates for long-term use in constructed wetlands, while Canada wildrye, Creeping spikerush and Streambank wheatgrass appear to be better suited for initial site establishment.

As a tool for water management and use, constructed wetlands composed of native halophytic or salt tolerant plant species have potential to utilize saline-sodic water while remaining viable. However, evapoconcentration of salts could lead to adverse soil salinity and sodicity conditions with respect to long-term impoundment, viability and reclamation. High clay content soils are more susceptible than non-clay soils to degradation of physical properties when seasonally irrigated with saline-sodic water. The greatest increase in soil SAR and EC occurred in the top 6 inches of soil with a 20-30 fold increase in SAR and an 8-10 fold increase in EC. Increases in soil SAR could be due to preferential plant uptake of Ca and Mg ions and/or little to no water infiltrating into the soil profile, while increases in soil EC could be due to evapoconcentration of salts (especially sodium) on soil surface. Under circumstances where amendments (gypsum and sulfur) were surface-applied to mitigate sodium-induced dispersion, salinity and sodicity of shallow alluvial groundwater increased subsequent to irrigation and abandoned irrigation sites became both sodic and saline over time. In all circumstances where PRB CBNG produced water was used for irrigation of historically non-irrigated alluvial channel soils, surface soil salinity increased. In some instances, subsurface salinity decreased due to leaching of geologic accumulations below the root zone.

A subset greenhouse study was completed to evaluate the potential for use of CBNG production water to facilitate terrestrial carbon sequestration in the form of increases in sustainable soil organic matter (SOM), or geologic carbon sequestration in the form of calcium carbonate (CaCO3 ) precipitation in the soil. Plant species targeted was American bulrush (Schoenoplectus americanus), which was planted in controlled soil columns and managed under continuous CBNG product water irrigation for approximately 24 months. Soil total carbon (%) and CaCO3 (%) levels increased during the two-year study. Increases were similar in columns irrigated with either CBNG or non-CBNG product water. No correlation to water chemistry could be determined, substantiating that: 1) availability of additional water in water-limited environments such as the Powder River basin can facilitate some short-term carbon accumulation, and 2) species such as American bulrush appear to be generally insensitive to either CBNG product water quality or resulting near-saturated soil conditions under sustained irrigation and/or flooding. Likewise, soil carbon increases could not be correlated to increases in CaCO3. Recent literature suggests sampling to depths below 10 cm may result in a better total carbon budget in irrigated soils (Eshel et al., 2007). Literature also suggests carbon sequestration takes longer than 2 years, some estimates suggest 5-10 years, so continuing the project for more than two irrigation seasons may illustrate some trend in increase in soil carbon and CaCO3 levels.

A significant outcome of a subcontracted research component of this project has been the design, development, testing, and patenting of an onsite, mobile water treatment plant specific to the signature of PRB CBNG produced water (details are available at http://waterquality.montana.edu/docs/methane/cbm-wts.shtml). Drake Engineering’s water-treatment process is an outgrowth of the MSU project evaluating phytoremediation of CBNG produced water. Through a project subcontract, Drake Engineering designed and developed a prototype of a lab-tested fluid-bed resin exchange treatment system for removing sodium from CBNG produced water. The technology has since been patented, and efforts are underway to begin commercializing the process by field-testing it in PRB CBNG operations. Equipment leasing contracts already are being issued.

In association with the Miles City office of the USDI-Bureau of Land Management, Nance Petroleum, Montana State University Department of Film and Television, a 28-minute documentary for public television was developed, highlighting the potential opportunities, land and water resource management issues, and solutions to environmental concerns. This objective, science-based documentary has been aired on local and regional public broadcasting networks and distributed to more than 600 watershed groups, land managers, industry representatives, and policy-makers. Additionally, a comprehensive “outcomes and impacts” assessment tool was developed, tested, implemented, and results summarized.

A multi-year invstigation of effect of sustained CBNG product water discharge into simulated ephermal channels on wetland plant community dynamics was completed in 2007. Plant community dynamics have been the most interesting aspect of this study. Establishment was very good for seven of the nine species, but over the course of the study we have seen a marked change in community composition. The results of this investigation confirmed that changes in ephemeral channel biomass production and salt-tolerant species composition are likely to occur in areas of sustained PRB CBNG produced water discharge. Baltic rush, American bulrush, inland salt grass, alkali grass, and prairie and alkaline cord grasses dominated ephemeral channels where PRB CBNG produced water was discharged for extended periods of time.

Results indicate that constructed wetlands planted with native, salt tolerant species have potential to utilize substantial volumes of CBM product water while remaining robust and viable. However, care must be taken in species selection as some are good colonizers, some make better long-term residents and others will remain dormant until salinity and/or sodicity levels become elevated. Observed increases in soil SAR could be the result of preferential plant uptake of Ca and Mg ions and/or little to no water infiltrating into the soil profile, while increases in soil EC could be due to evapoconcentration of salts (especially sodium) on soil surface. i.e. more water evaporating than infiltrating through. Evapoconcentration of salts could lead to adverse soil salinity and sodicity conditions with respect to long-term impoundment, viability and reclamation with high clay content soils being more susceptible than non-clay soils to degradation of physical properties when seasonally irrigated with saline-sodic water.

Adaptive wetland halophytes and tolerant glycophytes exhibited various responses to irrigation with CBNG produced-water; from quick establishment to condition-specific propagation and long-term survivability. Prairie cordgrass, Maritime bulrush, Baltic rush and Inland saltgrass appear to be the most likely candidates for long-term use in constructed wetlands, while Canada wildrye, Creeping spikerush and Streambank wheatgrass appear to be better suited for initial site establishment.

Field measurements of seepage characteristics of unlined CBNG product water storage impoundments were completed at selected locations in the northern portion of the Powder River basin. Twenty-two measurements of saturated hydraulic conductivity in variable soil and substrate materials and associated infiltration tests were completed to assess how much water will seep out of a specific CBM pond. USDA countywide soil surveys were found to provide good information about general soil properties and how they are spatially distributed over large areas. Thus, use of the soil survey for making interpolations on a small scale, i.e.: large area, basis is an appropriate use of the information available. Soil-landscape units appear to provide the right level of resolution and the proper scale to model spatially distributed functions such as pond seepage potential or infiltration rates across landscapes. That is provided these models are grounded in at least some ground truth data. Results of field measurements of infiltration on selected pond sites revealed that pond seepage in mixed sedimentary landscapes does occur with substantial magnitude. Downward flow of water through mixed sedimentary beds is likely based on the data collected and once water has left the pond, lateral flow is inevitable given the abrupt changes in saturated hydraulic conductivity with depth in mixed sedimentary materials. Temporary storage of CBM product water in fenced, unlined storage ponds is not without environmental costs especially when increasing water volumes mean a continued proliferation of ponds.

The final report summarizes the outcomes and findings of an extensive suite of prospective field, greenhouse, and laboratory studies focused on characterization and management of interactions between CBM-product water and soil, water resources, and vegetation in the Powder River Basin. Initially, the primary focus of research supported by DOE-NETL award DE-FG26-01BC15166 was that of evaluating the potential for phytoremediation of CBM product water and waters of quality similar to that associated with CBM reserves of the Powder River Basin, Montana and Wyoming. Phytoremediation is defined as the process of using plants for treatment (sodium salt removal, in the case of CBM product water) of soil or water. Complimentary undertakings included investigation of feasibility of agronomically beneficial use of CBM product water, i.e., irrigation and enhanced livestock forage production, resin-exchange technologies for economically viable treatment of CBM product water to accomplish sodium reduction, characterization of soil responsiveness to CBM product water spreading, and characterization of the hydraulic properties associated with CBM storage and infiltration impoundments.

Benefits
The evaluation of PRB CBNG produced water resulted in several significant findings. There are agricultural crop species and wetland species which have the capability of beneficially using CBNG produced water as either a sole or blended water source. Additionally, these plant communities offer the opportunity for disposal of CBNG water by means of beneficial use. Native saltbush and maritime barley, both perennial species with good production and forage potential, survived and produced commercially harvestable forage with sustained CBNG water irrigation. Other grass-forage mixes produced favorably under continuous mitigation of soil dispersion due to sodium. Additional studies have assessed the potential utilization of PRB CBNG produced water for shallow alluvial groundwater recharge, low-flow stream augmentation, terrestrial carbon sequestration, biomass production for biofuel synthesis, and low-CO2-emission biofuels for coblending with higher-CO2-emission coals. Essentially all qualities of PRB CBNG produced water present opportunities either for enhanced livestock forage production or enhanced wildlife habitat along ephemeral streams and upland locations or for impoundments.

As a tool for water management and use, constructed wetlands composed of native halophytic or salt tolerant plant species have potential to utilize saline-sodic water while remaining viable. However, evapoconcentration of salts could lead to adverse soil salinity and sodicity conditions with respect to long-term impoundment, viability and reclamation. High clay content soils are more susceptible than non-clay soils to degradation of physical properties when seasonally irrigated with saline-sodic water. The greatest increase in soil SAR and EC occurred in the top 6 inches of soil with a 20-30 fold increase in SAR and an 8-10 fold increase in EC. Increases in soil SAR could be due to preferential plant uptake of Ca and Mg ions and/or little to no water infiltrating into the soil profile, while increases in soil EC could be due to evapoconcentration of salts (especially sodium) on soil surface. Under circumstances where amendments (gypsum and sulfur) were surface-applied to mitigate sodium-induced dispersion, salinity and sodicity of shallow alluvial groundwater increased subsequent to irrigation and abandoned irrigation sites became both sodic and saline over time. In all circumstances where PRB CBNG produced water was used for irrigation of historically non-irrigated alluvial channel soils, surface soil salinity increased. In some instances, subsurface salinity decreased due to leaching of geologic accumulations below the root zone.

Summary
Overall, the project found that when used in combination with existing water resources and/or on selected compatible soils, proper irrigation management with CBNG produced water can be effectively used for irrigation of forage for agricultural use and wildlife enhancement. Sustainability of such irrigation practices mandates considerations of routine surface soil management (amendments), long-term availability of PRB CBNG produced water, alterations to shallow alluvial groundwater and contributory sources to receiving streams, and water conveyance habitat changes. Baseline U.S. Geological Survey, DEQ, local watershed database surveys and a literature search of PRB CBNG produced water found that it is characterized as generally non-saline and ranges from slightly to excessively sodic. Data from the Montana Bureau of Mines and Geology and the Montana and Wyoming boards of oil and gas conservation substantiate these findings. Total dissolved solids concentration ranges from 270 mg per liter to 2,300 mg per liter, with an average of 850 mg per liter. Sodicity ranges from 5 to over 50, with an average sodium adsorption ratio (SAR) of 12 throughout the PRB. Generally, salinity and sodicity are lower in the southeastern portion of the basin. Peak salinity is found just north of the Montana-Wyoming border, and the highest sodicity levels are in the extreme northwestern part of the basin near the Montana-Wyoming border. Once exposed to the atmosphere, CBNG produced water undergoes rapid chemical changes of increasing sodicity or SAR levels and increasing alkalinity (pH level).

In collaboration with Nance Petroleum, the Bureau of Land Management office in Miles City, MT (BLM) and the MSU Film and Television-Theatre Arts Department, a 28-minute documentary detailing CBNG development in the PRB was developed and publicly distributed in 2006-2007. The documentary, titled “Pipelines and Prairies,” has aired on the PBS network, and more than 120 copies of the video have been distributed. Impacts of the documentary on viewers were assessed by distributing the video and a mail survey to 360 individuals in the four major CBM basins in the west. Thirty-seven responses (10% response rate) were collected: Raton (27%), Green River (32%), Powder River (32%), and Atlantic Rim 9%). Significant findings include:

  • Prior to viewing the video, 83% of respondents were “very familiar” to “somewhat familiar” with CBM development.
  • After viewing the video, 87% of respondents indicated their knowledge of social issues associated with CBM development had “changed” or “somewhat changed”.
  • After viewing the video, 86% of respondents indicated their knowledge of soil and water issues associated with CBM development had “changed” or “somewhat changed”.
  • All respondents indicated that the video was a highly (51%) to moderately (49%) effective educational resource. All but two respondents indicated they would recommend the video to others.

Montana State University Extension Service completed publication of a landowner manual “A guide to changing plant communities,” with emphasis on saline and sodic environments. This bulletin, developed cooperatively with the University of Wyoming and South Dakota State University, provides guidance and assistance to land owners seeking information about suitability of various plant communities for irrigation with CBNG-type product water.

As one component of collaborative endeavors with the private sector, new technologies have been developed, patented, and field-tested for treatment of CBNG product water to reduce sodium and salinity. Beta units are scheduled for deployment in the PRB in 2007.

Current Status (February 2009)
Limits for EC and SAR concentrations and appropriate management practices for beneficial use of CBNG produced water have been completed. A native forage biomass and phytoremediation studyhas been completed at MSU. A greenhouse study was completed to evaluate the terrestrial/geologic carbon sequestration potential of American bulrush grown under continuous irrigation with PRB CBNG produced water. A study to evaluate the hydraulic characteristics of PRB CBNG produced water impoundments has been completed. Studies initiated within the PRB to evaluate hydraulic properties of impoundment site locations and remediation of soil sites altered by long-term discharges of PRB CBNG was concluded in fall 2007. Additionally, at the request of landowner groups in the Hanging Woman Drainage, a tributary to the Tongue River, MSU researchers collaborated in the development of a detailed CBNG produced water management plan, complementary to a plan of CBNG development; the completed plan, along with application to Montana DEQ for MPDES permit, has been submitted for large-scale development of CBNG recovery in Hanging Woman Drainage, MT. Additionally, a comprehensive beneficial water use management plan has been submitted to Montana DNRC for review. A collaborative project was initiated with MSU’s Department of Microbiology, wherein CBNG product water samples were collected from diverse PRB sites and subsequently filtered and subjected to DNA analyses to identify uniqueness of methanogenic bacteria contained with CBNG source water. Methanogens of consistent DNA signature were found throughout the sampling area of the northern portion of the Powder River basin, including locations in both Montana and Wyoming. As a related, but independent laboratory studyefforts are underway to assess the potential of enhancing CBNG generation in coal seams from which CBNG has been depleted due to commercial extraction. Additionally, a study will be initiated under separate project in 2008 to assess the feasibility of utilizing CBNG reservoirs as a CO2 storage depot while simultaneously instigating CBNG regeneration. A research proposal which MSUEWQ partnered with MSU’s Institute for biobased products was denied funding and will no be pursued any further at the present time. The final report has been submitted and all project requirements and activities have concluded. The major conclusions of the researchers have been summarized below. Extensive details may be found in other previously submitted reports.

Conclusions:

  • Phytoremediation, i.e., fuctional use of plants, to reduce sodium concentrations in CBM product water is not a sustainable or effective short-term or long-term management option within the Powder River Basin.
  • Phytoremediation, using selected livestock forage species, as a means of reclamation of salt and sodium-affected soils is a viable long-term management consideration in those circumstances where land-application of saline or sodium-rich water has ceased and forage removal by grazing and/or harvesting is adopted as a long-term vegetation management strategy.
  • Industrial-scale water treatment facilities are available and functional for the reduction of salinity and sodicity within CBM product water prior to discharge or land application.
  • Long-term irrigation with CBM product water of the quality commonly occurring in the Powder River Basin poses the potential of elevated salinity levels within shallow alluvial groundwater, alterations in soil physical and chemical properties on selected soils, ultimately requiring remediation intervention.
  • Selected native and introduced livestock forage plants are well-adapted to functional performance (survival, growth, reproduction) in circumstances where CBM product water is either the sole or principal water source. Functional performance might include forage production, wildlife habitat, stream channel stabilization, salineaffected site reclamation/remediation.
  • Currently promoted practices of treating CBM produced water to EC and SAR levels published by Richards et al. (1954) and subsequent use as irrigation water on smectite-dominated soils may lead to soil solution ECe and SAR combinations contributing to sodium-induced dispersion. This is especially the case following rainfall events of sufficient amount on Na-dominated smectitic soils to induce soluble salt leaching from the upper parts of the soil profile.

Funding 
The project was funded through congressional interest in research to investigate PRB CBNG produced water.

Project Start: September 1, 2001
Project End: September 30, 2008

Anticipated DOE Contribution: $1,649,000
Performer Contribution: $432,500 (20 percent of total)

Other Government Agencies Involved: Bureau of Land Management

Contact Information
NETL - Jesse Garcia (jesse.garcia@netl.doe.gov or 918-699-2036
MSU - James Bauder (jbauder@montna.edu or 406-994-5685)

Additional Information

Final Report [PDF-247KB]

Publications:
Bauder, J. W., Kimberly R. Hershberger, and Linzy S. Browning, “Soil solution and exchange complex response to repeated wetting-drying with modestly saline-sodic water,” Journal of Irrigation Science (submitted January 12, 2007).

Kirkpatrick, A., H. Sessoms, J. Bauder, and Q. Skinner, 2006, “A guide to changing plant communities, with emphasis on salinizing sites in the arid and semi-arid Northern Plains and Mountains Region,” Montana State University Extension Bulletin EB 169, Montana State University-Bozeman, MT, 64 pp.

Browning, L. S., J. W. Bauder, and S. D Phelps, 2006, “Effect of irrigation water salinity and sodicity and water table position on water table chemistry beneath Atriplex lentiformis and Hordeum marinum,” Arid Land Research and Management, 20:101-115.

Keith, K., H. Sessoms, M. Neibauer, Q. Skinner, J. Bauder, R. Waskom, and N. Mesner. 2005. Land and water inventory guide for landowners in areas of coal bed methane development. 1st Edition. Montana State University Extension Service, EB166. 77 pp.

Kirkpatrick, A., 2005, “Assessing constructed wetlands as a management option for beneficial use of saline-sodic product water,” M.S. thesis, Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 116 pp.

Sessoms, Holly., 2004, “Water use potential and salt tolerance of riparian species in saline-sodic environments,” M.S. thesis, Land Resources and Environmental Sciences, Montana State University., Bozeman, MT, 73 pp.

Garver, Keri M., 2004, “Assessment of effect of coalbed methane product water intervention on water quality parameters in the Little Powder River at Weston, Wyoming,” M.S. thesis, Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 144 pp.

Robinson (Hershberger), K., 2003, “Effects of Saline-Sodic Water on EC, SAR, and Water Retention.” M.S. thesis, Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 172 pp.

Phelps, Shannon D., 2003, “Effect of Irrigation Water Quality and Water Table Position on Plant Biomass Production, Crude Protein, and Base Cation Removal,” M.S. thesis, Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 188 pp.

“Pipelines and Prairies: Issues in coalbed methane development,” documentary video, Montana State University Extension Publication DVD001, Montana State University, Bozeman, MT, (28:30 minutes).


Wetland site created by surface discharge of CBNG product water.


Plant community transition along an ephemeral stream caused by an increased volume of water and/or water with chemistry different from normal moving into the stream.

Montana State University plant growth center and horticulture research farm.

Lysimeter set up for simulated wetland system.

Additional images available at http://waterquality.montana.edu/docs/photo/research.shtml

 
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