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The ex situ treatment of N-nitrosodimethylamine (NDMA) and N-nitrodimethylamine (NTDMA) in groundwater was evaluated in a field-scale fluidized bed bioreactor (FBR). Both of these compounds, which originally entered groundwater at the test site from the use of liquid rocket propellant, are suspected human carcinogens. The objective of this research was to examine the application of a novel field-scale propane-fed fluidized bed bioreactor as an alternative to ultraviolet irradiation (UV) for treating NDMA and NTDMA to low part-per-trillion (ng/L) concentrations. Previous laboratory studies have shown that the bacterium Rhodococcus ruber ENV425 can biodegrade NDMA and NTDMA during growth on propane as a primary substrate and that the strain can effectively reduce NDMA concentrations in propane-fed bench-scale bioreactors of different design. R. ruber ENV425 was used as a seed culture for the FBR, which operated at a fluidization flow of ∼19 L-per-min (LPM) and received propane, oxygen, and inorganic nutrients in the feed. The reactor effectively treated ∼1 μg/L of influent NDMA to effluent concentrations of less than 10 ng/L at a hydraulic residence time (HRT) of only 10 min. At a 20 min HRT, the FBR reduced NDMA to 3 of expanded bed/hr of operation and 1.1 mg NTDMA treated/m 3 of expanded bed/hr of operation, respectively. The FBR system was highly resilient to upsets including power outages. Treatment of NDMA, but not NTDMA, was marginally affected when trace co-contaminants including trichloroethene (TCE) and trichlorofluoromethane (Freon 11) were initially added to feed groundwater, but performance recovered over a few weeks in the continued presence of these compounds. Strain ENV425 appeared to be replaced by native propanotrophs over time based on qPCR analysis, but contaminant treatment was not diminished. The results suggest that a FBR can be a viable alternative to UV treatment for removing NDMA from groundwater.

Interactions amongst the degradation rates of toluene, xylenes, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and n-butyl acetate (n-BA) were investigated. Experiments were performed in a biotrickling filter reactor packed with polypropylene Pall rings in a counter-current air-water mode of operation. Under pseudo-steady-state conditions, the removal efficiency (RE) of the individual components in the middle of and at the effluent above the reactor bed was evaluated. By using a mixed microbial culture as the biocatalyst, the results revealed that an increased loading of toluene and xylene had a competitive effect on the RE of MIBK. After reaching a saturation point of the overall catabolic capacity of the biocatalyst, variations of RE were observed for the different components. This was most pronounced under conditions of overloading with the water-soluble components mixture. Despite such variations, the system was able to efficiently degrade this complex pollutant mixture for a period of 1 yr.

The design and the construction of an actual 8.7-m3 pilot/full-scale biotrickling filter for waste air treatment is described and compared with a previous conceptual scale-up of a laboratory reactor. The reactor construction costs are detailed and show that about one-half of the total reactor costs ($97,000 out of $178,000) was for personnel and engineering time, whereas approximately 20% was for monitoring and control equipment. A detailed treatment cost analysis demonstrated that, for an empty bed contact time of 90 sec, the overall treatment costs (including capital charges) were as low as $8.7/1000 m3air in the case where a nonchlorinated volatile organic compound (VOC) was treated, and $14/1000 m3air for chlorinated compounds such as CH2Cl2. Comparison of these costs with conventional air pollution control techniques demonstrates excellent perspectives for more field applications of biotrickling filters. As the specific costs of building and operating biotrickling filter reactors decrease with increasing size of the reactor, the cost benefit of biotrickling filtration is expected to increase for full technical-scale bioreactors.

A pilot/full-scale biotrickling filter reactor experiment was p e rf o rmed at an industrial site to treat styrene laden waste gas. The engineered system consisted of two stainless steel tanks in series, each with filter bed volumes of 4.0 m3 , filled with 3.5inch plastic spheres. The system treated 340 m3 h -1 of air laden with styrene concentrations ranging up to 0.8 g m- 3 . O ver the five-month study, styrene elimination was demons t rated up to 24 g m-3 h -1 (35 g m - 3 h -1 a c ross the first tank in series) with 70 to 85% re m oval. Op e rational and perf o rmance problems we re identified that differ from those deve loped under controlled, labora t o ry set-ups. Op e rational pro blems typically invo l ved equipment malfunctions, with the most prone to failure pieces of equipment being the air sampling system and water level sensors. Pe rf o rmance pro b l e m s we re identified that possibly limited the styrene re m oval. The t ransient operation of the plant, producing discontinuous, unsteady-state concentrations, made it difficult to establish a stable biofilm on the packing material. Experiments we re perf o rmed indicating both biological and mass transfer limitations may have occurred.

N-nitrosodimethylamine (NDMA) is present in groundwater and drinking water from industrial, agricultural, water treatment, and military/aerospace sources. NDMA is a suspected human carcinogen and an emerging groundwater contaminant that has been detected at a number of Department of Defense (DoD) and National Aeronautics and Space Administration (NASA) sites involved in the production, testing, and/or disposal of liquid propellants containing unsymmetrical dimethylhydrazine (UDMH). NDMA was a common contaminant in UDMHcontaining fuels (e.g., Aerozine-50) and is also produced when these fuels enter the environment through natural oxidation processes. Currently, the most effective treatment technology for NDMA in groundwater is pump-and-treat with ultraviolet (UV) irradiation. However, this approach is expensive because it requires high energy input to effectively reduce the levels of NDMA to meet regulatory requirements. The objective of this Environmental Security Technology Certification Program (ESTCP) project was to demonstrate and validate the use of an advanced bioreactor design, a fluidized bed bioreactor (FBR), in the field for the ex situ treatment of NDMA from part-per-billion (micrograms per liter [ g/L]) influent concentrations to low part-per trillion (nanograms per liter [ng/L]) effluent concentrations. The demonstration was conducted at the NASA White Sands Test Facility (WSTF) in Las Cruces, NM. The capital and operational costs of the FBR were subsequently compared to those of an existing UV system for NDMA treatment at the WSTF facility.

Compost and granular activated carbon biofilters operated at a wastewater treatment plant simultaneously removed low concentrations of hydrogen sulfide and volatile organic compounds. Through the use of phospholipid fatty acid analyses, the effects of declining pH caused by sulfide oxidation were established for microbial growth, microorganism stress, and microbial community structure. Microorganisms on both media demonstrated increases in microbial densities, varying degrees of environmental stress, and domination by gram-negative bacteria. However, the declining pH had little effect on compound removal, which was greater than 99% for the hydrogen sulfide and greater than 70% for the oxygenated and aromatic hydrocarbons. The microbial communities adjusted to difficult environmental conditions through acclimation of the species present or by growth of low-pH-tolerant species.

Increasing federal and state regulation has made it necessary to apply air pollution control measures at publicly owned treatment works (POTWs). Traditional control technologies may not be suitable for treating the low and variable contaminant concentrations often found in POTW off-gases. An alternative control technology, biofiltration, was studied. An experiment using bench- and pilot-scale reactors established optimal operating conditions for a full-scale conceptual design. The waste airstream contained ppmv levels of hydrogen sulfide and ppbv levels of specific volatile organic compounds (VOCs). Granular activated carbon (GAC) and yard waste compost (YWG) were tested as possible biofilter media with and without pH control. The 16-month field study bench reactors achieved 99% removal of hydrogen sulfide, 53 to 98% removal of aromatic hydrocarbons, 37 to 95% removal of aldehydes and ketones, and 0 to 85% removal of chlorinated compounds. The GAC and YWC pilot reactors removed more than 80% and 65% of the total VOCs at 17 second and 70 second empty bed retention times, respectively. The YWC reactors performed poorly at empty bed retention times of 30 and 45 seconds, removing less than 40% of total VOCs. Declining pH had little negative effect on contaminant removal, suggesting costly control measures maymore » not be necessary. Biofiltration appears to be a feasible alternative to traditional control technologies in treating off-gases from POTWs. 13 refs., 3 figs., 4 tabs.« less

Most biofilters use compost as the microorganism support medium. This study investigated the use of granular activated carbon (GAC) as a support medium. Its high adsorptive capacity is a feature that makes GAC a potentially good biofilter medium. A bench‐scale column provided the experimental results presented in this paper. Gasoline vapors were the contaminant treated. The GAC was seeded with microorganisms and nutrients, and the system was operated using prehumidification of the incoming gas stream only. The history of treatment efficiency indicated initial adsorption provided high percentages of removal. However, once the adsorption capacity was saturated, the treatment efficiency dropped dramatically. Later, biological activity increased to the point where effective treatment was possible. The main obstacle to effective treatment was the slow growth of biomass in the lower portions of the column. The average and maximum elimination capacities of the biofilter were high compared to published b...

N-nitrosodimethylamine (NDMA) is a suspected human carcinogen that has traditionally been treated in water using ultraviolet irradiation (UV). The objective of this research was to examine the application of a laboratory-scale fluidized bed reactor (FBR) as an alternative technology for treating NDMA to part-per-trillion (ng/L) concentrations in groundwater. Previous studies have shown that the bacterium Rhodococcus ruber ENV425 is capable of cometabolizing NDMA during growth on propane as a primary substrate in batch culture (Fournier et al., 2009) and in a bench-scale membrane bioreactor (Hatzinger et al., 2011) to low ng/L concentrations. R. ruber ENV425 was inoculated into the FBR during this study. With a hydraulic residence time (HRT) of 20 min, the FBR was found to be an effective means to treat 10-20 μg/L of NDMA to effluent concentrations less than 100 ng/L. When the HRT was increased to 30 min and oxygen and propane addition rates were optimized, the FBR system demonstrated treatment of the NDMA to effluent concentrations of less than 10 ng/L. Short-term shutdowns and the presence of trichloroethene (TCE) at 6 μg/L as a co-contaminant had minimal effect on the treatment of NDMA in the FBR. The data suggest that the FBR technology can be a viable alternative to UV for removing NDMA from groundwater.

The goal of this Phase II SBIR effort was to demonstrate the compatibility of a concentrator regenerator coupled with a biofilter air pollution control process for the treatment of intermittent paint booth emissions. A field-pilot system was temporarily installed at Tyndall Air Force Base. The concentrator regenerator was shown to work effectively in the laboratory. In the field, however, a combination of marginal loading from the paint booths and solvent sinks (indicated by a system mass balance) in the pilot unit initially produced too low a delivery rate from the concentrator/regenerator to adequately feed the biofilter on a continuous basis. When supplementary and, later, regenerated vapors became available to the biofilter, it achieved greater than 80% removal of the solvent-laden air. In instances where a constant, synthetic feed stream was supplied to the biofilter over a short time span (within days), the biofilter removed greater than 87% of all the organics within the first 0.5 feet of bed height Air recycling at recycle ratios of 44%, 61%, 73%, and 78% provided increased removal efficiencies of 88%, 94%, 95%, and 98%, respectively. Capital costs for the concentrator regenerator and biofilter were estimated to be $804,500 and $70,700, respectively. Yearly operating costs for the concentrator regenerator and biofilter were estimated to be $68,700 and $5,580, respectively. Robustness, reliability, and minimal intervention are design targets for improvement, but technical feasibility of the design concept was successfully demonstrated.

The objective of this Phase II Option Small Business Innovation Research project was to design, construct, install, and measure the effectiveness of a full-scale biotrickling filter (BTF) to treat volatile organic compounds (VOCs) and odorous (sulfur) air emissions from wastewater load equalization and treatment tanks at Naval Air Station North Island in San Diego, CA. BTFs are similar to chemical scrubbers, but rely on microorganisms on the packing surface to remove and oxidize contaminants rather than chemicals. The full-scale BTF is 3.1 m (10 ft) in diameter and 9.1 m (30 ft) in height. The reactor is an air downflow system and operates in concurrent fashion with a recirculating water phase. Operation began in early December 1999. System performance has demonstrated good removal of the odorous inorganic compounds (nuisance odors have been substantially reduced) and water-soluble organic hazardous air pollutants, while the less water-soluble VOCs have not been removed completely. Adaptation by the system microorganisms to the low aqueous concentrations of these compounds appears to be occurring slowly, and removal of these compounds is improving as additional biomass growth occurs in the lower media layer. Pressure drops across the entire system are very low and the necessary operator attention is at a minimum.

The passage of the Clean Air Act Amendments (CAAA) has justified the need for increased investigation into the treatment of air streams containing volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). In cooperation with Tyndall Air Force Base (Panama City, FL), ENVIROGEN (Lawrenceville, NJ) and CHA Corporation (Laramie, WY) have recently begun the installation and operation of a pilot-scale integrated microwave concentrator/biofilter system for the treatment of solvents discharged from spray paint booth operations.