Master of Science (MS)
Laboratory microcosm experiment and parallel ex situ bioremediation studies were conducted to study the effect of temperature on in situ bioremediation systems installed at Superfund site in southeast Georgia. Laboratory microcosms, inoculated with PAHs/phenols specific microorganisms, at high temperatures (42±2°C; 107±3°F) demonstrated a significant reduction of residual polycyclic aromatic hydrocarbons (PAHs) and selected phenols from 4927±1356ng/g dry weight soil to 1158±530ng/g with a kinetic rate of 76.1±16.8ng/g/day (84% reduction; p≤0.01) in 49days. High temperature non-inoculated microcosms were reduced of residual PAHs and phenols from 1117±436ng/g to 341±116ng/g with a kinetic rate of 15.8±6.5ng/g/day (65% reduction; p≤0.01) in 49days. Low temperature inoculated treatment (21±1°C; 69±2°F), was reduced from 3048±200ng/g to 1,094±240ng/g PAHs/phenols with kinetic rate of 39.8±1ng/g/day (66% reduction, p≤0.01) in 49days; A 50% reduction in low temperature non-inoculated treatment from 813±189ng/g to 367±79ng/g (p≤0.1794) was also observed with kinetic rate of 9.1±2.2ng/g/day. The laboratory study demonstrated that efficiency of bioremediation could be enhanced by maintaining an elevated temperature using amended and/or indigenous microflora. Amended populations were also proved to be more effective at lower temperatures. Field biopile data sets presented somewhat different findings. Minimal reduction at high ambient temperature range of 70-79°F from 9349±1420 to 9300±1017mg/kg (kinetic rate: 0.40±3.3ng/g/day) was seen in the first 120days of the field study. Evaluations of the pile indicated significant desiccation occurred due to black polypropylene cover used to entrain heat. By correcting moisture level using trickling spray under the plastic sheeting, significant reductions of ≥35% (13912±2054 -9021±1660mg/kg PAHs/phenols) with a kinetic rate of 40.7±3.3ng/g/day, despite lower air temperatures of 48-58°F in the last 120days. The results showed the efficacy of correctly using immobilized bed bioreactors (bioplugs) under plastic sheeting coupled with proper soil moisture management during colder winter months. These studies show that optimizing temperature for in situ bioremediation technologies at Superfund sites can reduce time required for treatment of hazardous wastes; hence reduction in operational time and effort to ensure smooth running of the remediation process year round (especially in cold regions and cold weather) can be realized.
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Iqbal, Javed, "Effect of temperature on efficiency of in situ bioremediation technology: a laboratory microcosm and field study" (2003). LSU Master's Theses. 203.
Ralph J. Portier