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

Irrigation and Hydraulics Department, Faculty of Engineering, Cairo University, Giza, Egypt
Environmental earth sciences (Impact Factor: 1.45). 61(7):1385-1399. DOI:10.1007/s12665-010-0456-z

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.

KeywordsBenzene-Biodegradation-Slow-release oxygen source-Modeling-UAE

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