Journal Issue: Proceedings of the Annual International Conference on Soils: Volume 15, Issue 1
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Limited-Access Bioremediation in a Factory Setting
Farnsworth, Deborah R.; Murray, Willard A; Bronson, Daniel L.
A factory in New Hampshire had a volatile organic compound (VOC) release detected in a storm-water outfall pipe. Hydrogen Release Compound (HRC) injection was determined to be the best remedial solution. Tight soils, shallow water table, access limitations, and pending property sale complicated remediation. Groundwater was directly below the floor slab. The plume was centered on the storm-water drain which carries runoff from the upgradient parking lot under the building. The VOCs are believed to have entered the subsurface in the central area of the building through spillage; the storm drain system was a preferential pathway. The groundwater contamination was addressed through bioremediation using HRC. Application required many injection points and applications, due to the low permeability of the soil. Due to interference with operations and property sale, repeated openings of the floor for injections using a drill rig were not feasible. Permanent injection points were installed, but would not be accessible for direct injection. Therefore, a trench was cut into the concrete floor slab between each point and the wall. Piping ran from the injection point to the wall, terminating at a standpipe with a quick-connect fitting. Each trench was then fillled with concrete to restore the floor slab. Since starting HRC treatment, VOC levels at the outfall have dropped to below the state regulatory standard. One well had levels of 1800 ug/L and 1200 ug/L of Cis-1,2 Dichloroethene and Vinyl Chloride in April, 2008. By January, 2009, both were below MCLs. Site closure is expected to be completed in a reasonable timeframe. The treatment has not interfered with Site activities or with sale of the Site.
Perchlorate Reduction Using Fine Media Fluidized Bed Bioreactor with Oxidation-Reduction Potential-Based Feed Control
Nozawa-Inoue, Mamie; Weaver, Dallas E; O’Connell, Joseph E
Certain bacteria, prevalent in the environment, use perchlorate as an electron acceptor and reduce it to chloride under anaerobic conditions. To develop an ex-situ treatment system for perchlorate-contaminated groundwater, we performed bench-scale test using a fine media fluidized bed reactor (FMFBR; 0.5-ft diameter, 8-ft high) inoculated with a perchlorate-reducing culture. The system was operated under anaerobic conditions. A perchlorate-water solution was introduced into a recirculating stream in the FMFBR at an upward velocity of 16 cm/min. Acetate (acetic acid) was fed as an electron donor. The objective of this study was to establish a minimal acetate feed ratio for sufficient perchlorate reduction by monitoring oxidation-reduction potential (ORP) and, consequently, to prevent ORP from falling to a range of sulfate reduction, and to limit the biomass growth from excess acetate. The FMFBR was able to degrade 3000 - 5000 μg/l perchlorate to less than 4 μg/l in a single pass (16 min empty bed contact time) without excessive hydrogen sulfide production, when effluent ORP (vs. Ag/AgCl) was -290 - -410 mV. Accurate feed control is essential since an imbalance in acetate feed ratio results in unreacted perchlorate or sulfide production. A base feed pump was used to provide 80 % of the acetate required and an ORP controller was used to trim and balance the feed rate using a second pump. The second feed pump was activated when effluent ORP rose to or above -315 mV and deactivated when it fell to or below -320 mV. Some oscillation of effluent ORP was observed, but perchlorate was not detected in the effluent when the oscillation was kept relatively small. Average acetate feed ratio was approximately 1.1-times stoichiometry. For more stable perchlorate degradation, we will examine an earlier ORP detection in the bioreactor column and a more flexible control method for acetate feed.
Application of Microemulsion to remediate Organochlorine Pesticides Contaminated Soils
Zheng, Guanyu; Wong, Jonathan W.C.
Microemulsion, a system containing water, surfactant, cosurfactant and oil phase, has the potential to enhance the solubility and bioavailability of hydrophobic organic compounds (HOCs). The aim of this study is to develop microemulsion which could enhance the bioremediation of organochlorine pesticides (OCPs) contaminated soils. After screening four surfactants and two plant oils, Triton X-100 and linseed oil were selected for microemulsion formation because of their respective instinctive higher solubilizing capacity over other candidates. Microemulsions formed with Triton X-100 and linseed oil could effectively enhance the aqueous solubility of 1,1,1,-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT), and the enhancement was much higher than that achieved by Triton X-100 solution alone. Besides, the solubilization capacity of Triton X-100-linseed oil system was positively influenced by both cosurfactant (C/S ratios) and oil (O/S ratios) contents of the microemulsions. Desorption tests reveal that this microemulsion system is more effective than its counterpart Triton X-100 solution to desorb DDT from contaminated soil.
Biosurfactants from Acinetobacter calcoaceticus BU03 Enhance the Bioavailability and Biodegradation of Polycyclic Aromatic Hydrocarbons
Wong, Jonathan W.C.; Zhao, Zhenyong; Zheng, Guanyu
Biosurfactants produced by an isolated thermophilic strain Acinetobacter calcoaceticus BU03 were demonstrated to be effective in enhancing the solubility of polycyclic aromatic hydrocarbons (PAHs) and the present study aimed at investigating its effectiveness in increasing bioavailability of PAHs in soil for biodegradation under thermophilic composting condition. At 25 times of its critical micelle concentration (CMC), biosurfactants by BU03 significantly increased the apparent aqueous solubility of phenanthrene (PHE) and benzo[a]pyrene (B[a]P) to 54.3 and 2.08 mg L-1, respectively. After confirmation of its ability in enhancing the solubility of PAHs, the isolated biosurfactants were applied to a thermophilic soil composting system. Within 42 days of composting period, the degradation of PHE and B[a]P in the absence of the biosurfactants was 71.2 and 16.4%, respectively. Inoculation of A. calcoaceticus BU03 or biosurfactants produced by this strain significantly increased the emulsifying capacity of soil, and therefore enhanced the desorption of PAHs from soil to aqueous phase in which they can be degraded by an inoculated degradative strain Bacillus subtilis B-UM. Therefore inoculation of A. calcoaceticus BU03 or biosurfactants from BU03 together with inoculation of B. subtilis B-UM increased the degradation of B[a]P to 83.8 and 65.1%, respectively, while PHE was almost completely removed with these two treatments. The results indicate that the application of biosurfactants produced by A. calcoaceticus is an effective means to enhance the biodegradation of PAHs in thermophilic composting, while inoculation of biosurfactants producing strains in PAHs contaminated soil is a more practical and cost-effective approach than direct addition of biosurfactants.