Bioreactors soil remediation

In particular, techniqnes based on conpUng membrane processes and appropriate complexing agents, snpported Uqnid membranes (SLMs), pervaporation (PV) and membrane bioreactors (MBRs) are reviewed and discussed for their capacity to remove undesired componnds. Case studies referring to the treatment of ammoniacal etching solntion by SLM, complexation-nltrafiltration conpled with soil washing for soil remediation, volatile organic componnds removal by PV and treatment of tannery wastewaters by MBRs are also presented and discnssed. 

Koran, K.M., Suidan, M.T., Khodadoust, A.R, Sorial, G.A., and Brenner, R.C. Effectiveness of an anaerobic granular activated carbon fluidized-bed bioreactor to treat soil wash fluids a proposed strategy for remediating PCP/PAH contaminated soils, Water Res., 35, 2363-2370, 2001. 

Environmental Remediation Consultants, Inc. (ERC) offers the BIO-INTEGRATION method for in sitn and ex situ destruction of organic compounds in soil, sediment, sludge, groundwater, snrface water, and wastewater. The BIO-INTEGRATION approach combines biotic and abiotic treatment methods to remediate subsurface contamination. On-site bioreactors are used to grow substrate- and contaminant-specific microbes. The microbes are combined with abiotic amendments and injected into the subsurface. 

Compeau et al. (1990) reported a full-scale slurry-phase PCP remediation. The system consisted of soil washing and screening and resulted in clean soil and wash solution. The wash solution was a slurry containing PCP and < 60-mesh-size soil particles at approximately 20% solids concentration. Slurry was treated subsequently in on-site slurry-phase bioreactors. A 50 m3 slurry reactor was operated in batch mode and inoculated by an uncharacterized PCP-mineralizing culture (107 cells/ml of slurry). After 14 days, 370mg PCP/kg slurry had been degraded to below 0.5 mg/kg. For effective biogradation to occur, inoculation was required. 

Table 4.12 Bioreactor remediation of creosote (PAH) contaminated soil, adapted from US Environmental Protection Agency technology demonstration sheet EPA/540/S5-91/009.

Bioreactors containing an undefined anaerobic consortium reduced TNT to 2,4,6-triaminotoluene (TAT) in the presence of glucose (Daun et al. 1998). The sorption of TAT to montmorillonite clay was irreversible, and the substrate could not be released by solvent extraction or by add or alkaline treatment. Similar results were obtained with humic acids in which covalent reaction with carbonyl or activated C=C bonds bonding presumably occurs (Chapter 3, Section 3.2.4). Results from laboratory experiments using 14C-labeled TNT in reactors to which molasses was added as carbon source showed that after 9 weeks, 83% of the radioactivity was recovered in soil components (humin, humic adds, and fulvic acids) (Drzyzga et al. 1998). These results illustrate the important issue of the association of metabolic products from TNT with soil components which in turn may reduce the effectiveness of remediation. 

The aim of many of the described anaerobic bioreactors was only to test the potential use of this technology to remediate soil, water or air streams contaminated with organochlorines. In this regard, most of them were successful, even without reaching 100% removal. However, partial reductive dechlorination in other systems led to low removal rates (<30%) and to the formation of other, equally or more, toxic compounds like VC, biphenyl or monochlorobenzene, making the efficiency of these processes questionable, especially for extremely recalcitrant compounds like HCB, Polychlorinated Biphenyls or CF. Finally, it is important to note that all these reactors were designed and operated on lab-scale, where processes can be more easily... 

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