Grantee Research Project Results
Final Report: Ground Water Remediation Powered with Renewable Energy
EPA Grant Number: SU831829Title: Ground Water Remediation Powered with Renewable Energy
Investigators: Elmore, Curt , Cable, John W. , Dilly, Rachel , Gallagher, Ron , Seabaugh, Ryan
Institution: University of Missouri - Rolla
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 30, 2004 through May 30, 2005
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2004) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Safe and Sustainable Water Resources , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities
Objective:
Ground water is a very small fraction of the earth’s available water but it is a critically important resource because it represents 98 percent of the fresh water available for human use (Zaporozec & Miller, 2000). In many locations across the U.S. and the world, man’s activities have resulted in contamination of the ground water supplies. Currently the predominant ground water remediation focus is the use of in-situ technologies such as permeable reactive barriers (PRBs) which are effective at treating contamination without removing the water from the ground. These technologies are often cost effective to operate lnnual costs. However, there are some major challenges associated with in-snologies such as PRBs. In some locations, it may be a problem to emplace the treatment material at the required depths, and/or it may be prohibitively expensive to construct the PRB. Instead, a system design has been proposed which uses wind energy to power a ground water circulation well (GCW) at the former Nebraska Ordnance Plant site under a U.S. Environmental Protection Agency limovative Work Group grant. This work has encouraged us to propose the use of renewable energy to pump contaminated ground water to a quasi-in situ treatment vessel. The treatment vessel would contain zero valent iron (ZVI) which is the material which is typically placed in permeable reactive barriers. The ZVI produces a strong reducing environment in the saturated zone, and chlorinated volatile organic compounds such as trichloroethylene have been successfully remediated in ground water due to abiotic reductive dechlorination (ESTCP, 1999).
Summary/Accomplishments (Outputs/Outcomes):
The horizontal gradient for the water table aquifer is approximately 0.001 with flow to the ESE direction. Therefore the general layout of the extraction well will be up gradient from the treatment vessel (to the WNW). A capture zone analysis was performed and it was determined that the aquifer will yield a minimum of 10 gallons per minute. The static water level of the previously existing bedrock wells is approximately equal to that measured in the surficial aquifer material. Hence there must be very little vertical movement of the groundwater at this site. There has been strong development of irrigation since much of the hydrogeologic data has been published, therefore it is suggested that field measurements (via piezometer nests or static water levels) be conducted to assess current conditions. With strong irrigation draws from the bedrock wells, the gradient of the aquifer should be downward and vertical.
The treatment vessel will be eight feet deep and contain one foot of pea gravel filling the lower end of the container. The pea gravel will then be overlain with a geosynthetic fiber to inhibit the infiltration of its overlying two feet deep zero valent iron (ZVI) and sand mixture. The ZVI/sand reaction filter media will then be overlain by a one half foot sacrificial layer of 100 percent ZVI. The sacrificial reactor layer prolongs the life of the iron in the primary reactor. The primary purpose of the sacrificial reactor is to remove any dissolved oxygen present in the influent water. Dissolved oxygen has resulted in a significant loss in hydraulic conductivity in bench-scale column tests and field-scale above-ground and in-situ fixed-bed reactors. Dissolved oxygen corrodes the iron and results in the precipitation of amorphous iron hydroxide, which can result in significant flow reduction through a reactor containing 100 percent granular iron (Envirometal 2005). A geosynthetic filter will overly the sacrificial reactor layer and be capped by a four and one-half foot layer of pea gravel.
The extraction well supplying the water to the treatment vessel will extend approximately 125 feet into the subsurface and transcend three formation layers. Its borehole will measure eight inches in diameter and contains a six inch PVC casing extending to the pitless adaptor. This pitless adaptor is used as “a sanitary underground discharge assembly... [which] provides the most practical solution to the sanitary completion of the upper part of the well when offset-pump installations are specified. This device [...] attaches directly to the well casing and extends the casing above the ground surface. It provides a watertight subsurface connection for buried pump discharge or suction lines.” (Driscoll, 1995) A one and a half inch PVC pipe extends from the submersible pump to the pitless adaptor. The pitless adaptor then transfers the water to a one inch PVC pipe leading to the treatment vessels.
Wind speed data from 1995 through 2005 for Grand Island, a weather station located near Hastings, NE was retrieved from the High Plains Regional Climate Center (HPRCC). The average daily wind speed over this ten year period was calculated at 8.8 mph at an elevation of 9.8 feet (3 meters). Review of the National Wind Map published by the Department of Energy revealed that the majority of the state of Nebraska lies within the Class 3 wind zone at an average of 1 5 mph, with measurements obtained from a 50 foot (15.2 meter) elevation. The wind turbine for this project will be at an elevation of 64 feet, and thus past wind speeds were analyzed and extrapolated to predict the expected wind speeds. An anemometer will be placed at the site of the wind turbine to generate more precise data. A computer model available from Bergey WindPower has been used to extrapolate the wind speed data and performance of the desired wind turbine system. Data extrapolated from the High Plains network results in low estimates of the wind energy. Expected wind speeds will generate 4.4lkWh per day using the HPRCC data. This number is adjusted for the power required for the pump, 19.2kWh, to determine the percentage of the day for expected operation of the pump. The High Plains data results in 5.52 hours of extraction per day. (Appendix J) Using wind speeds from the National Wind Map, the turbine will provide an actual 6.3 kWh per day. This amount of power will generate 7.68 hours per day of operation. The difference in gallons per day extracted from the subsurface aquifer is approximately 2,000 gallons. Actual flow averages cannot be accurately determined until the extraction well has been operational for some time. Intemittent operation of the extraction well system is expected using a 1kW wind turbine. Three to four 1kW turbines would be required to operate nearly 24 hours per day, depending on which dataset is used. A more cost effective design for 24 hour operation would be a 7.5kW turbine. However, this design will use one I kW wind turbine due to the nature of the project and uncertainty of the water bearing capacity of the affected aquifer.
The wind turbine package is produced by Bergey WindPower is a 1 kW model number XL. 1 developed specifically for pumping applications. This package includes a 1kW wind turbine with PowerCenter, 64 ft. tilt up tower, 5.3 kWh Battery Bank, 1500 W inverter system, 120/240 VAC Transformer, and a Grundfos submersible pump. The batteries are used as a buffer between the power input and the power output and are not designed for mass storage. In this design, power will be used as quickly as it will be generated. However, the load on the batteries is 33.3 A, therefore at full capacity the batteries would be able to deliver 4.4 hours of operation. The submersible pump is manufactured by Grundfos. Its features include overvoltage and undervoltage protection, as well as dry run protection to ensure the pump will not run under hazardous conditions.
Supplemental Keywords:
Scientific Discipline, Waste, Geographic Area, Water, POLLUTANTS/TOXICS, Remediation, Contaminated Sediments, Environmental Chemistry, Water Pollutants, Groundwater remediation, Environmental Engineering, EPA Region, energy conservation, predictive understanding, contaminated sediment, reductive treatment, remediation technologies, zero valent iron, chlorinated organic compounds, Region 7, permeable reactive barriers, contaminated groundwater, contaminated aquifers, wind energyThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.