Indigenous microorganisms

Biostimulatioo Any process that increases the rates of biological degradation, usually by the addition of nutrients,oxygen, or other electron donors and acceptors so as to increase the number of indigenous microorganisms available for degradation of contaminants. 

Savage, D. C. (1984). Association of indigenous microorganisms with gastrointestinal epithelial surfaces. In "Human Intestinal Microflora in Health and Disease." (D. H. Hentges, ed.), pp. 55-78. Academic Press Inc., New York, NY. 

Contaminated soil from a manufactured coal gas plant that had been exposed to crude oil was spiked with acenaphthene (400 mg/kg soil) to which Fenton s reagent (5 mL 2.8 M hydrogen peroxide 5 mL 0.1 M ferrous sulfate) was added. The treated and nontreated soil samples were incubated at 20 °C for 56 d. Fenton s reagent did not promote the mineralization of acenaphthene by indigenous microorganisms to any appreciable extent. The mineralization of acenaphthene was enhanced only 1.2-fold when compared with the nontreated control sample. The amounts of acenaphthene recovered as carbon dioxide after treatment with and without Fenton s reagent were 20 and 17%, respectively (Martens and Frankenberger, 1995). 

Bradley et al. (1999) studied the degradation of tert-butyl alcohol by indigenous microorganisms in stream-bed sediments from underground gasoline spill sites in Laurens, SC (Laurens) and Charleston, SC (Oasis). Under aerobic conditions, the amount of tert-butyl alcohol mineralizing to carbon dioxide after 27 d was 70% in both Laurens and Oasis sediments. After 80 d, the amount of mineralization reached an asymptiotic level of approximately 84%. No mineralization of /erf-butyl alcohol was observed under strictly anaerobic conditions. 

Indigenous microorganisms obtained from a sandy loam degraded endosulfan to endosulfan diol. This diol was converted to endosulfanhydroxy ether and trace amounts of endosulfan ether and both were degraded to endosulfan lactone (Miles and Moy, 1979). Using settled domestic wastewater inoculum, a-endosulfan (5 and 10 mg/L) did not degrade after 28 d of incubation at 25 °C (Tabak et al, 1981). 

Soil. Metabolites of endosulfan identified in seven soils were endosulfan diol, endosulfanhydroxy ether, endosulfan lactone, and endosulfan sulfate (Martens, 1977 Dreher and Podratzki, 1988). These compounds, including endosulfan ether, were also reported as metabolites identified in aquatic systems (Day, 1991). In soils under aerobic conditions, p-endosulfan is converted to P-endosulfan alcohol and p-endosulfan ether (Perscheid et al., 1973). Endosulfan sulfate was the major biodegradation product in soils under aerobic, anaerobic, and flooded conditions (Martens, 1977). In flooded soils, endolactone was detected only once whereas endodiol and endohydroxy ether were identified in all soils under these conditions. Under anaerobic conditions, endodiol formed in low amounts in two soils (Martens, 1977). Indigenous microorganisms obtained from a sandy loam degraded p-endosulfan to endosulfan diol. This diol was converted to endosulfan a-hydroxy ether and trace amounts of endosulfan ether and both were degraded to endosulfan lactone (Miles and Moy, 1979). 

In a cranberry soil pretreated with 4-nitrophenol, parathion was rapidly mineralized to carbon dioxide by indigenous microorganisms (Ferris and Lichtenstein, 1980). The half-lives of parathion (10 ppm) in a nonsterile sandy loam and a nonsterile organic soil were <1 and 1.5 wk, respectively (Miles et al, 1979). Walker (1976b) reported that 16 to 23% of parathion added to both sterile and nonsterile estuarine water was degraded after incubation in the dark for 40 d. 

A pure culture of Arthrobacter sp. was capable of degrading isofenphos at different soil concentrations (10, 50, and 100 ppm) in less than 6 h. In previously treated soils, isofenphos could be mineralized to carbon dioxide by indigenous microorganisms (Racke and Coats, 1987). Hydrolyzes in soil to salicylic acid (Somasundaram et al., 1991). 

If the rate of bioremediation performed by indigenous microorganisms is not sufficient to achieve the treatment goal within the prescribed duration ... 

Uses indigenous microorganisms, avoiding the introduction of foreign organisms. 

The Earth Tech technology is an ex situ, soil bioremediation process that uses the indigenous microorganisms already present in the soil in a custom-designed approach to enhance microbial activity. The Earth Tech technology is used primarily to treat soil contaminated with petroleum hydrocarbons from fuels (such as gasoline, diesel, kerosene, etc.). In the Earth Tech process. 

EnSafe, Inc., has developed an ex situ bioreactor system for the treatment of perchlorate-contaminated soil and groundwater. The technology involves placing contaminated media into specially designed treatment cells or tanks containing a carbon source, nutrients, and a pH buffer. The carbon source creates an anaerobic environment that promotes the breakdown of perchlorate by indigenous microorganisms. 

The BioTreat system is an in or ex situ treatment that uses specifically selected enzymes and nutrients to encourage biodegradation of hydrocarbons with the indigenous microorganisms. According to the vendor, the system has been used at a number of sites, however, no further information was available. The current availability of this technology is uncertain, however, the vendor has indicated that they plan to offer an improved version of BioTreat in the future. 

Imagine a case in which/>-cresol (PC for structure see Fig. 17.14) is spilled into a pond and dispersed to a initial concentration, [PC]0, of 1 mM (ca. 100 ppm). How long (days) would you think it would be before this contaminant was mostly degraded by the indigenous microorganisms living in the pond water ... 

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