Technology:
- Demonstration of prepump separation technologies to enhance bioslurper systems; prepump separation of LNAPL prevents the formation of emulsions and floating solids in the bioslurper process effluent, thereby minimizing/eliminating the need for downstream waste treatment and decreases the concentrations of contaminants in the process off-gases
- Evaluated in-well and above-ground prepump (knockout tank) separation technologies in short-term single-well and long term multiple well demonstrations; compared to conventional bioslurper
- Various configurations tested including use of dual drop tubes for in-well prepump system to extract the LNAPL and water/soil gas in two separate streams and use of a knockout tank to separate LNAPL from the liquid stream prior to entry into the liquid pump ring; report included detailed information about configurations tested and testing sequence
- Primary components of the bioslurper system (liquid ring pump, oil/water separator and piping) were the same for all tests; operating conditions of the system were held constant
- Baseline data included depth to groundwater, LNAPL thickness, lateral extent of the plume, TPH concentrations and subsurface vacuum
- System performance parameters included petroleum hydrocarbon concentrations in effluents, emulsions and floating solids formed, LNAPL recovery rates, groundwater recovery rates, and stackgas flow rates
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Cleanup Authority:
State
Contacts:
Navy
Commanding Officer (specific name not provided)
Naval Facilities Engineering Service Center
1100 23rd Avenue
Port Hueneme, CA 93043 |
Contaminants:
Petroleum Hydrocarbons, LNAPL
- Demonstration site was selected because it appeared to contain sufficient LNAPL to support a four month demonstration |
Waste Source:
Leaks from JP-5 fuel storage tanks |
Type/Quantity of Media Treated:
Groundwater
- Soils - fine sand and clay loam, underlain by alternating layers of clay, silty/clayey sand, and sand
- Vadose zone - primarily clay loam
- Depth to groundwater - 7 to 15 ft bgs
- Demonstration site selected based on soils being sufficiently permeable to allow LNAPL flow while still being “tight” enough to allow the bioslurper to create a vacuum-induced pressure gradient (no specific data were provided) |
Purpose/Significance of Application:
Field demonstration of prepump technologies to enhance the cost-effectiveness of bioslurping to treat LNAPL-contaminated groundwater |
Regulatory Requirements/Cleanup Goals:
- The objectives of the demonstration included quantifying the cost effectiveness of prepump LNAPL separation methods in controlling effluent emulsion formation and reducing the concentrations of petroleum hydrocarbons in the aqueous and off-gas streams from the bioslurper |
Results:
- Assessment of performance was based primarily on aqueous and vapor TPH concentrations; production of floating solids and emulsions formed by the different configurations was also assessed, along with information of LNAPL and groundwater recovery
- Average TPH concentration reduction in the seal tank water compared to conventional bioslurper - 98% for in-well and 82% for the knockout tank (report includes data for each configuration)
- LNAPL recovery and groundwater recovery rates generally remained constant
- Dual drop and knockout tank configurations reduced the formation of milky emulsions; site did not produce floating solids during the demonstration
- While TPH concentrations in the off-gas were not affected during the long term demonstration, average TPH concentrations were observed in other demonstrations by both prepump configurations |
Cost Factors:
- Total cost of the long term demonstration was about $70,000 with a unit cost of $10 per gallon of fuel removed; total cost for the demonstration program (seven demonstrations) was $480,000
- Estimated cost for full-scale implementation at a 2-acre site - in-well separation bioslurping - about $309,000; more cost-effective than conventional systems ( bioslurping with a DAF unit for postpump treatment - about $519,000; bioslurping with manual removal of floating solids - about $554,000)
- Costs for prepump separation systems at a site are affected primarily by the potential for emulsion formation, free product recovery rates, and groundwater recovery rates |
Description:
The NAS in Fallon Nevada was selected by the Navy for a demonstration of prepump separation technologies to enhance the cost-effectiveness of bioslurping to treat LNAPL in groundwater. The New Fuel Farm, located in the northwestern portion of the NAS Fallon, is used for the storage of jet propulsion (JP) jet fuel in underground and aboveground storage tanks, and historically has been used for the storage of jet fuel, aviation gasoline, diesel, and motor gasoline. An LNAPL plume is located beneath the site. According to the Navy, this site was selected for the demonstration based on soils being sufficiently permeable to allow LNAPL flow while still being “tight” enough to allow the bioslurper to create a vacuum-induced pressure gradient, and because it appeared to contain sufficient LNAPL to support a four month demonstration (long term demonstration). The prepump separation technologies were evaluated in both short-term, single well configurations and in long-term, multiple well configurations. This report focuses on the long-term demonstration.
Two prepump separation technologies were evaluated - in-well and knockout tanks. These technologies were compared to conventional bioslurper systems. The results of the demonstrations showed that the in-well and knockout systems were effective in reducing TPH concentrations in the seal tank water and in the off-gas, and are more cost effective than conventional bioslurper systems (including manual separation and DAF). Costs for prepump separation systems at a site are affected primarily by the potential for emulsion formation, free product recovery rates, and groundwater recovery rates. According to the Navy, the results of the short-term and long-term demonstrations show that the dual drop configuration worked well at a variety of sites that include tidal influence, varied geologic conditions, and varied LNAPL type and thickness. Scale-up considerations include proper sizing of components for full-scale operations; pilot-scale testing is recommended to determine the feasibility of bioslurping and the scale-up engineering evaluation for a specific site. |
