Environmental Resolutions, Inc

ENVIRONMENTAL RESOLUTIONS, INC.

20372 North Sea Circle, Lake Forest, CA, 92630 949-457-8950

Ex Situ Bioreactor Treatment of Fuel Oxygenates

Bedford, New Hampshire, Gas Station

A remediation system operating in Bedford, New Hampshire, utilizes California microbes to destroy MTBE, TBA, and other gasoline constituents. Environmental Resolutions, Inc. (ERI) has over 20 full-scale bioreactors in operation at gas station sites in California. This case study describes ERI’s first bioreactor on the East Coast.

Background

In late 2003, gasoline was released from an underground storage tank to the shallow bedrock aquifer at the site. Due to the high permeability of the bedrock, product in the bedrock aquifer quickly seeped into surface water in an adjacent small pond. Initial response actions included removing product from the pond and installing product recovery trenches and wells in the shallow bedrock. Product recovery pumps were utilized to recover available product (about 250 to 400 gallons) from site groundwater through October 2004. Product has not been observed since.

A temporary treatment system – consisting of a single extraction well, an air stripper, and two 600-pound GAC vessels – was utilized from May to November 2004. This system was insufficient to effectively capture the dissolved-phase contaminant plume. In addition, MTBE and TBA broke through the carbon vessels in approximately 6 hours, even at a low pumping rate of 0.4 gpm. This required the on-site storage of treated groundwater, followed by transportation and disposal off-site.

An expanded treatment system was implemented in February 2005 that includes 4 bedrock extraction wells, and an air stripper and an ERI bioreactor that are housed in a heated remediation building. A commercial ion exchange system was added in August 2005 for iron pretreatment to reduce O&M costs for solids removal from the treatment equipment.

Until recently, the air stripper was used to remove BTEX, TAME, MTBE, and a portion of the TBA. A high air to water ratio (300 cfm of air for up to 5 gpm of water) was used. The water was then passed through the bioreactor to destroy TBA that the air stripper is unable to remove. Until recently, the water was polished through two 500-pound GAC units in series and then discharged to an on-site dry well. As explained below, the air stripper and GAC units are no longer in use.

Bioreactor Overview

The bioreactor consists of a biomass supported on fine sand. The biomass adheres to the sand while consuming gasoline constituents in water as the water passes upward through the fluidized mass. The biomass is a consortium of naturally occurring bacteria found in many locations. MTBE degraders have been employed to degrade MTBE, TBA, and other fuel oxygenates in bioreactors, BioGAC units, and in situ biobarriers at various locations in the U.S., including the Northeast.

The sand bed is fluidized by a constant 10 gpm recirculation of water that dilutes incoming water from the air stripper. After passing through the fluidized bed, the recirculating stream passes through a re-oxygenation tower. The oxygen from air is augmented with an oxygen booster to increase the capacity of the bioreactor. Nutrients – particularly the macronutrients nitrogen, phosphorus, and potassium (but an array of micronutrients as well) – are metered to the bioreactor via a solution stored in a 55-gallon drum. Heating of the water during winter months was initially provided via a spa heater. The system is equipped with a Sensaphone that automatically calls system operators in the event of an equipment malfunction.

Results

Flow rate, temperature, and VOC data before and after the air stripper and the bioreactor are summarized below. The pump and treat system has operated since February 2005. From startup through October 2005, the bioreactor consistently reduced TBA to levels below the treatment goal of 40 μg/l. In early November 2005, there was a period of intense precipitation; in fact, the Bedford area in 2005 had one of the highest annual rainfall amounts in 150 years. As a result, contamination in the subsurface was mobilized, and an additional extraction well was brought on line to reduce off-site contaminant migration. The flow rate increased by a factor of three and the TBA concentration doubled entering the reactor. These factors coupled with an increase in iron and manganese and a decrease in temperature overwhelmed the biomass for approximately one month. The TBA mass loading to the bioreactor actually increased more than five-fold. The spa heater was not turned on until December 7, and the temperature of the groundwater decreased prior to this. The data in late December 2005 indicate that adequate removal of TBA in the bioreactor has resumed, even though the spa heater has not been used since December 19, 2005. Treatment has been effective even at water temperatures as low as 49 degrees Fahrenheit, which are traditionally viewed as too low for effective treatment.

Until mid-2006, virtually all of the BTEX and most of the MTBE was removed in the air stripper, and as a result, the microorganisms in this particular bioreactor were focused on degrading the TBA but not the MTBE. MTBE that broke through the bioreactor was adsorbed in the GAC units prior to discharge. By mid-2006, VOC concentrations in site groundwater had decreased (see Table 1) to the point that all could be treated by the bioreactor. The air stripper was bypassed in stages, and as of July 21, 2006, is off-line. Also around this time, the GAC units were also taken off-line, and treated water from the bioreactor is now discharged directly to the dry well. Therefore, the subsurface is now being amended with oxygenated water containing bacteria, which is anticipated to promote in situ biodegradation of VOCs at the same time ex situ treatment is taking place.

During the step-wise transition of bypassing the air stripper, from May 19 to July 21, the VOC mass loading to the bioreactor increased just over 100-fold. The bioreactor treated the TBA and BTEX to non-detectable levels. The bioreactor did not quite treat the MTBE to below the treatment goal of 13 μg/l. Based on bioreactor performance at other sites, it is anticipated that the MTBE goal will be achieved after a bit more acclimation time.

Table 1 - Bioreactor Performance Data

Date	Approx. Flow (gpm)	% of Flow Bypassing Stripper	Approximate Temperature (Degrees F)	MTBE (µg/l)			TBA (µg/l)			Total BTEX (µg/l)
Date	Approx. Flow (gpm)	% of Flow Bypassing Stripper	Approximate Temperature (Degrees F)	Stripper Influent	Bioreactor Influent	Bioreactor Effluent	Stripper Influent	Bioreactor Influent	Bioreactor Effluent	Stripper Influent	Bioreactor Influent	Bioreactor Effluent
2/15/05	1.4	0	65	157,000	390	109	<8,000	6,440	<20	41,390	22	ND
2/22/05	1.5	0	63	84,400	8	42	<8,000	4,930	27	32,750	ND	ND
2/28/05	1.4	0	65	80,900	26	97	13,700	5,820	<20	24,160	ND	ND
3/7/05	1.4	0	80	73,400	9	4	<8,000	6,320	<20	24,520	ND	ND
3/14/05	0.5	0	77	87,300	3	<10	<8,000	3,570	<20	23,120	ND	ND
4/5/05	0.9	0	72	41,900	<10	35	<8,000	2,770	<20	25,580	ND	ND
5/2/05	0.8	0	67	52,900	<10	<2	2,780	4,230	<20	33,321	ND	ND
6/28/05	1.5	0	81	39,100	<10	<2	<3,000	1,230	<20	16,093	ND	ND
7/19/05	2.0	0	86	38,900	<10	<2	<1,600	608	<20	3,700	ND	ND
7/20/05	1.0	0	79	28,800	267	210	4,060	574	<20	5,182	ND	ND
8/12/05	2.0	0	76	31,600	<10	64	5,720	<20	<20	5,311	ND	ND
8/22/05	1.8	0	73	29,000	<10	<10	3,300	890	<20	4,431	ND	ND
9/20/05	0.9	0	75	21,200	<10	<10	<3,200	374	<20	379	ND	ND
10/22/05	1.7	0	60	23,600	<10	<10	<3,000	3,930	<20	16,963	ND	ND
11/4/05	4.9	0	54	22,600	10	9	4,530	7,210	4,030	15,822	ND	ND
11/5/05	4.9	0	54	21,800	7	5	7,770	4,590	1,820	15,003	ND	ND
11/28/05	4.9	0	56	5,400	<2	5	3,020	1,940	540	7,340	ND	ND
12/31/05	2.7	0	57	7,890	<2	<2	<1,600	490	<20	2,204	ND	ND
1/20/06	3.9	0	56	4,360	<2	<2	2,280	1,600	34	9,109	ND	ND
2/13/06	3.3	0	51	4,260	<2	<2	2,970	1,480	<20	7,509	ND	ND
3/13/06	4.4	0	55	NA	<2	<2	NA	245	<20	NA	ND	ND
4/14/06	4.6	0	57	NA	<2	<2	NA	276	<20	NA	ND	ND
5/19/06	2.2	0	65	7,200	<2	<2	1,430	70	<20	3,686	ND	ND
6/5/06	4.6	0	59	NA	51	19	NA	185	<20	NA	ND	ND
6/26/06	5.8	25	64	2,200	530	46	684	912	<20	3,305	663	ND
7/10/06	5.1	50	64	3,700	>1,900	16	<500	417	<20	1,021	707	ND
7/21/06	4.5	75	65	3,550	2,990	29	277	258	<20	1,148	579	ND

Note: Only temperature and flow data for the sampling dates are shown – other flow and temperature data are not included. NA = not analyzed. ND = not detected.

Site groundwater has elevated iron and manganese concentrations of up to 13 and 30 mg/l, respectively. Before installation of the ion exchange system, iron primarily precipitated out in the air stripper, and manganese was removed in the bioreactor. Most of the manganese formed a distinct layer of nodules in the bioreactor that was easily siphoned out, but manganese precipitation did lead to increased O&M requirements for the bioreactor. The oxygen booster has effectively

delivered oxygen to the system. Dissolved oxygen concentrations as high as 38 mg/l have been achieved.

Costs

Costs for the bioreactor are summarized in Table 2. Bioreactor treatment was chosen for this site largely due to its low cost relative to other technologies.

Table 2 - Bioreactor Costs
Capital	Cost	Monthly On-Site O&M to Date	Cost
Bioreactor, including sand and bacteria	$35,000	Labor*	$450
Auxiliary tanks and equipment	$8,500	Electricity	$300
Shipment and assembly on site	$6,000	Misc. chemicals, materials, parts	$25
Startup and shakedown	$4,000
Total Capital	$53,500	Total Monthly O&M*	$775

*Assumes iron pretreatment equipment is functioning properly.

Conclusion

The bioreactor successfully and consistently treated TBA to low levels until the TBA mass loading was suddenly increased and the groundwater temperature decreased. The bioreactor subsequently adjusted to the reduced temperatures and changes in mass loading, and is once again reducing TBA to concentrations below the standard. In mid-2006, the air stripper was taken off-line, and the bioreactor is being used to treat all of the groundwater VOCs. Possible changes for the future include: similarly bypassing the ion exchange system to allow the bioreactor to remove the iron in addition to the manganese, and allowing the bioreactor to gradually acclimate to even lower water temperatures during the fall and winter months (to reduce energy costs). When remediation is complete, the bioreactor may be used at another site.

Contacts West Coast: East Coast:

Joseph O’Connell, Sc.D., P.E. Ellen Moyer, Ph.D., P.E.

President Principal

Environmental Resolutions, Inc. Greenvironment, LLC

20372 North Sea Circle 258 Main Road

Lake Forest, CA 92630 Montgomery, MA 01085

949-457-8950 413-862-3452

Joconnell@eri-us.com Ellenmoyer@em-green.com

Special thanks to Armand A. Juneau, Jr., P.G. of Juneau Geoservices, LLC, of Goffstown, New Hampshire, the consultant handling the site and ERI’s client. He also worked with ERI to install and start up the bioreactor, and is operating and maintaining the remediation system.