Modeling in situ benzene bioremediation in the contaminated Liwa aquifer (UAE) using the slow-release oxygen source technique

Abstract

Dissolved benzene was detected in the shallow unconfined Liwa aquifer, UAE, which represents the main freshwater source for the nearby residence Bu Hasa camp area. The main source of this contamination is believed to be the rejected water released from Bu Hasa liquid recovery plant. In this paper, a finite element model (METABIOTRANS) is used to simulate the fate and transport of the dissolved benzene plume in Liwa aquifer. Different remediation scenarios were simulated in which the slow-release oxygen source (SOS) technique is utilized to minimize benzene concentrations at the nearest camp supply wells downstream of the contamination zone. Results of the remediation scenarios show that the highest biodegradation rates occur when the oxygen source is placed near the plume center; where higher benzene concentrations exist. The nearest oxygen release source to the contamination zone caused higher stimulation to bacterial growth than further down-gradient oxygen sources. It also exhibited longer resident time of oxygen in the aquifer; and therefore, yielded higher reductions in benzene concentrations. However, using one central SOS proved to be insufficient as contaminant escaped laterally. Additional four transverse oxygen sources were necessary to capture benzene that laterally spread away from the contamination zone. These lateral SOSs were essential to reduce benzene concentrations at the supply wells that are located at the plume fringes. Finally, it was found that increasing oxygen release from one source did not always improve remediation; and that using several SOSs with lower release rates could be a more practical approach to enhance benzene biodegradation in the aquifer.

Dimensionless parameters to summarize the influence of microbial growth and inhibition on the bioremediation of groundwater contaminants

“…Therefore, this parameter provides a unique description of the actual bioremediation status of an aquifer. Other parameters use traditional mass loss ratios to indicate bioremediation efficiency (such as Phanikumar and Hyndman 2003;Mohamed et al 2006Mohamed et al , 2010a. This method uses the ratio of biodegraded contaminant mass to the total contaminate mass; whereas g* (in the same sense) reflects the biodegraded contaminant mass to the total biodegradable contaminant mass.…”

Identification of parameter importance for benzene transport in the unsaturated zone using global sensitivity analysis

“…Few studies have also assessed the movement of benzene in unsaturated porous media (Berlin et al, 2016;Berlin and Suresh, 2019;Troldborg et al, 2009;Ciriello et al, 2017). Benzene transport models typically combine Darcy-type water flow; advectivedispersive transport; and a source/sink term considering various physical, chemical, and biological processes including sorption, dissolution, and biodegradation (Mohamed and Sherif, 2010). Yet, the typical heterogeneity of the subsurface environment and the difficulty in obtaining sufficient relevant physical and bio-geochemical characterizations of the site lead to high uncertainty of these parameters (Ciriello et al, 2017;Tartakovsky, 2007).…”

Sensitivity of Benzene Biodegradation to Variations in Kinetic Parameters in a Brazilian Residual Soil

“…In Brazil, groundwater contamination with benzene is mainly associated with spills and leaks from fuel tanks. As a toxic substance with relatively high solubility in water, benzene can cause serious health risks (Alvarez and Illman 2006;Alvarez et al 2006;Mohamed et al 2010a). A noteworthy remediation technique for benzene remediation is natural attenuation: more efficient and cost-effective when compared to active conventional techniques, this method has become an attractive alternative for the remediation of contaminated sites when conducted in optimal conditions.…”

“…To that end, a high level of certainty is necessary when choosing the conceptual model and estimating the kinetic parameters. Benzene biodegradation is usually simulated using the multiplicative Monod Kinetic Model (Chen et al 1992;Godeke et al 2008;Mohamed et al 2010aMohamed et al , 2010bXu et al, 2015;Romero Velásquez 2015). An important advantage of Monod kinetics is that the function itself contains regions of zero order, first-order, and mixed order (Mohamed et al 2010a).…”

“…Benzene biodegradation is usually simulated using the multiplicative Monod Kinetic Model (Chen et al 1992;Godeke et al 2008;Mohamed et al 2010aMohamed et al , 2010bXu et al, 2015;Romero Velásquez 2015). An important advantage of Monod kinetics is that the function itself contains regions of zero order, first-order, and mixed order (Mohamed et al 2010a). Due to the wide utilization of this model, several kinetic parameters can be found in the literature, but there are very few studies on soils of tropical regions.…”