Part 1: Vadose-Zone Column Studies of Toluene (Enhanced Bioremediation) in a Shallow Unconfined Aquifer

Abstract

The objectives of the laboratory study described in this paper were (1) to determine the effectiveness of four nutrient solutions and a control in stimulating the microbial degradation of toluene in the unsaturated zone as an alternative to bioremediation methodologies such as air sparging, in situ vitrification, or others (Part I), and (2) to compare the effectiveness of the addition of the most effective nutrient solution from Part I (modified Hoagland type, nitrate-rich) and hydrogen peroxide (H 2 O 2 ) on microbial degradation of toluene for repeated, simulated spills in the unsaturated zone (Part II).For Part 1, fifteen columns (30-cm diameter by 150-cm height), packed with air-dried, 0.25-mm, medium-fine sand, were prepared to simulate shallow unconfined aquifer conditions. Toluene (10 mL) was added to the surface of each column, and soil solution and soil gas samples were collected from the columns every third day for 21 days. On day 21, a second application of toluene (10 mL) was made, and the experiment was run for another 21 days. Solution 4 was the most effective for microbial degradation in Part I. For Part II, three columns were designated nutrient-rich 3-day toluene columns and received toluene injections every 3 days; three columns were designated as nutrient-rich 7-day columns and received toluene injections every 7 days; and two columns were used as controls to which no nutrient was added.As measured by CO 2 respiration, the initial benefits for aerobic organisms from the O 2 enhancement were sustained by the bacteria for only a short period of time (about 8 days). Degradation benefits from the nutrient solution were sustained throughout the experiment.The O 2 and nutrient-enhanced columns degraded significantly more toluene than the control columns when simulating repeated spills onto the unsaturated zone, and demonstrated a potentially effective in situ bioremediation technology when used immediately or within days after a spill. The combined usage of H 2 O 2 and nitrate-rich nutrients served to effectively maximize natural aerobic and anaerobic metabolic processes that biodegrade hydrocarbons in petroleum-contaminated media. Applications of this technology in the field may offer economical advantages to other, more intrusive abatement technologies.

Bioremediation of Organic Pollutants in Soil–Water System: A Review

“…In order to examine the efficacy of this technique, a wetland-assisted integrated soil colums was designed for in-situ bioremediation was carried out following numerical modelling and experimental setup using a vertical soil column and wetland ( Figure 3 ). Tindall et al [ 43 ] and Ranier et al [ 44 ] have jointly assessed the performance of pollutant removal either by sand columns or in wetlands. To simulate the actual field scenario of the contaminated vadose zone, a laboratory experiment was carried out using a large vertical column setup of 120 cm high plexiglass with an inner diameter of 15 cm, with 23 sampling ports fixed at an equal spacing of 5 cm along the column depth.…”

“…In order to examine the efficacy of this technique, a wetland-assisted integrated soil colums was designed for in-situ bioremediation was carried out following numerical modelling and experimental setup using a vertical soil column and wetland (Figure 3). Tindall et al [43] and Ranier et al [44]…”

In Situ Bioremediation of Toluene‐Polluted Vadose Zone: Integrated Column and Wetland Study

“…[ 14 ] Tindall et al. [ 15 ] and Ranieri et al. [ 16 ] evaluated performance of pollutant removal either by sand column or in wetlands.…”

Remediation of Artificially Hydrocarbon Polluted Vadose Zone Soil in Glass Column through Percolation with Solution of Nutrient, Nutrient-Surfactant or Surfactant

“…Use of conventional soil surface based remediation strategies such as tilling or application of solid compendium of nutrients (Chorom et al 2010;Ezeonu et al, 2012) is not feasible in remediating petroleum contaminated soil layers in deeper part of the vadose zone. Liquid formulations of nutrientsor surfactants,and water-based, surfactant-based, and foam-based oxidative formulations have been investigated for use in the remediation of simulated petroleum-hydrocarbon contaminated vadose zone through continuous flooding or forced flushing (Boopathy, 2004;Bouzid et al, 2019;Widrig and Manning, 1995;Tindall et al, 2005;Zhu et al, 2005). These investigations were however targeted at single fractions of petroleum, and one or two soil layers.…”