Introduction

Constructive Wetlands for the Pre-treatment of Drinking Water Obtained from Abandoned Underground Coalmines

C.J. Varnell, S.A. Thawaba, Thomas McGuire, and J.V. BrahanaUniversity of Arkansas, Fayetteville

Brahana, J. Van, Varnell, Curtis, 2003. Factors Affecting Water Quality and Surface Water/Ground Water Interaction, Greenwood, Arkansas, AWRC Annual Conference, Fayetteville Radisson, April 22 /23, 2003Bastian, Robert, 1993. Constructed Wetlands for Wastewater Treatment and Wildlife Habitat, United States Environmental Protection Agency, EPA832-R-93-005, 174 pp.Campbell, Craig, Ogden, Michael, 1999. Constructed Wetlands in the Sustainable Landscape, John Wiley and Sons, Inc., New York, 271 pp.Cox, John, Garner, Billy, Vodrazka, Frank, 1975. Soil Survey of Sebastian County, Arkansas, United States Department of Agriculture, March, 1975.Hobbs, W., 1987. Underground Coal Mines as Sources of Water for Public Supply in Northern Upshur County, West Virginia, U.S. Geological Survey, Charleston, West Virginia.Moshiri, Gerald, editor, 1993. Constructed Wetlands for Water Quality Improvement, Lewis Publishers, Boca Raton, 614 pp.Nairn, Robert, 2004. Personal communication, University of Oklahoma, Feb. 2004.Robb, Gordon, 1994. “Environmental consequences of Coal Mine Closure,” The Geographic Journal, Vol. 160, No. 1, pp. 33-40Wass, Roland, editor, 1999. Free Water Surface Wetlands for Wastewater Treatment: A Technology Assessment, United States Environmental Protection Agency, EPA 832-S-99-002, 117 pp.Wildeman, Thomas, Bates, Edward, 1993. Handbook for Constructed Wetlands Receiving Acid Mine Drainage, EPA Superfund Innovative Technology Evaluation, EPA/540/SR-93/523.

Fig 4. Anoxic limestone drain, with trail detail.

Fig 9. Bridging the gap between resource usage and preservation through recreation and education.

Greenwood, Arkansas, a city of 7,701 people in west-central Arkansas, has faced a tremendous growth in population during the past ten years. The city has the current capacity to produce 1.2 million gallons of water daily. Demand for city water use is expected to exceed 1.8 million gallons within the next five years. The city water treatment plant has recently been upgraded to process this amount of water, but the current reservoir is not large enough to meet daily demands during periods of drought. An additional 600,000 gallons per day is needed to augment the current supply. Two abandoned, flooded coal mines located near the city have estimated water storage in excess of 500 million gallons of water. The water is currently being considered as an alternative water source for the city. The water has high concentrations of total dissolved solids (TDS), sulfates and iron. If a decision is made to use the water, it will require treatment to lower these constituents to acceptable levels. Constructed wetland treatment systems are engineered systems that are designed and constructed to utilize natural processes involving wetland soils, plants, and associated microbes to treat water. Designing and constructing a viable wetland for pretreatment of mine water would allow Greenwood an inexpensive, passive method to utilize the water from the coal mines. This also provides an excellent opportunity to acquire additional greenspace parks to be used for an educational/recreational nature center. This proposal will allow the city to meet current water demands and to prepare for future expansion in an ecological and sustainable fashion.

Fig 2: Site selection for the proposed Wetlands.

Objectives The primary objective in constructing the wetland is to reduce the constituents that have been identified within the mine waters to acceptable levels for treatment by the current water treatment facility and to do so at a cost that is less than or comparable to currently available technologies. In addition, it is the desire of the city to develop an integrated system that will incorporate the

Methodology

A total of thirty-one water tests have been conducted at the Greenwood site. Information obtained from the water analyses, geological assessment, the USGS Coal Quality Data-base for Greenwood mines, global information system (GIS) database, and from historical analyses conducted at these sites will be referenced to determine the origin of the constituents, the degree to which they are concentrated in the mine waters, and to devise a constructed wetlands which will lower the concentrations of unwanted constituents to a level that they can be treated with current water plant technology.The wetlands will then be integrated into the present Greenwood greenstructure and park system and will function as a model educational/recreational/ecological nature center and hiking trail.

Fig 1: Location of Greenwood, Arkansas

wetlands into an aesthetic, educational, and recreational facility that can be used for the enjoyment of the local populace and for wildlife habitat enhancement.

Fig 3: Hydrologic Flow map “Detention, retention and wetland”.

Fig 5. Proposed wetland and nature trail.

Fig 6. Wetland and trail system

Fig7. Creating a municipal water source and natural habitat through phytoremediation, Typha sp.

Fig8. Comparison of Water Constituents

References

SummaryA model wetland has been devised which will lower the concentrations of iron, heavy metals, sulfates and other undesirable constituents while raising the pH. The water will meet or exceed the water quality found within the Greenwood reservoir and can be used to augment the present water supply.The passive system is extremely efficient, requires low maintenance, and is less expensive than traditional chemical processes used to treat water. In addition, the wetlands will be connected to the Greenwood park system to provide an aesthetically pleasing, environmentally sound, park and wildlife habitat.

Fig 10. Wetland construction