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Title: Characterisation and bioremediation of soil impacted by Libyan oilfield produced water
Author: Omar, Salem Abdulla Salem
Awarding Body: Sheffield Hallam University
Current Institution: Sheffield Hallam University
Date of Award: 2013
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A large quantity of produced water (PW) is currently produced during crude oil and natural gas exploration and production. The result and effect of discharging PW on the environment has become a significant issue of environmental concern. PW impacted soil is a common environmental problem associated with oil and gas production. This causes the death of plants and contaminates soil. In addition, impacted soil leads to wide spread contamination of surface waters and shallow aquifers. This work describes an investigation of PW and full characterization of contaminated soils by the disposal of PW at the study site, it includes analysis of both PW and impacted soil using different analytical techniques in order to identify and assay the main constituents that cause the pollution of the soil at the site. The Nasser oilfield, Libya has been chosen as the study site because has a long history of crude oil production since 1956. For this study, six PW samples were collected from the disposal pit bank and through the production stages, eighteen samples of contaminated soil from the disposal pit bank at the study oilfield along with uncontaminated soil samples (taken far from the polluted area) to used as reference. Measurable impacts from PW discharges observed in the soils that have been identified include elevated concentrations of petroleum hydrocarbons and salts in the soil. The total dissolved solids (TDS) concentration in PW and soil can vary between 2540? mg/1 to 126065 mg/1, for PW and 20716 mg/kg to 105240 mg/kg for impacted soil. The most common organic contaminants found in PW are total petroleum hydrocarbon (TPH) and BTEX (benzene, toluene, ethylbenzene and xylenes). The average concentrations of TPH for PW and polluted soil samples ranged from 1.2 mg/1 to 2.9 mg/1 for PW and 10550 mg/kg to 90750 mg/kg for soil samples, BTEX were found in PW at the processes stage and the disposal pit. The average BTEX concentration in PW ranged from 0.11 mg/1 to 1.86 mg/1. The polyaromatic hydrocarbons (PAHs) and oilfield chemicals (OFCs) (i.e. corrosion inhibitors, scale inhibitors, biocides and demulsifiers) were also detected in soil and PW at the study site. Understanding the composition of PW and the impacted soil are necessary for assessing the possibility of beneficial reuse and to selecting suitable treatment process for PW and soil. The results showed that the main constituents that impact the soil are hydrocarbons and salts. In response to a growing need to cleanup environmental contamination, various remediation technologies have been developed to treat soil, wastewater and groundwater contaminated by different pollutants, include in-situ and ex-situ methods, the choice of the remediation method depends on the type, extent, concentration of the pollutant and the figure land use. A combination of method biological, physical, and chemical technologies may be used in combination with one another to decrease the contamination to a harmless and suitable level. Accordingly, to the results an action of soil bioremediation is proposed to remove the hydrocarbons from soil. Bioremediation is one of the most important methods for the remediation of contaminated soil with petroleum hydrocarbons as it is environmentally friendly and a relatively low cost effective alternative to physical and chemical cleanup options. Laboratory pilot studies were carried out on bioremediation of soil contaminated with petroleum hydrocarbon from the Nasser oilfield, Libya. Factors that may influence the rate of TPH removed in a crude oil contaminated soil were investigated. Bioaugmentation and biostimulation (a combined treatment) were applied to three soils polluted with approximately, 1 %, 4 % and 8 % of TPH. The bioaugmentation is performed with addition of isolated microbes from soil contaminated with crude oil which were able to grow in a complex mixture of hydrocarbon via inorganic fertilizer (N:P). Biostimulation is performed with addition of different ratio of inorganic fertilizer (N:P) for a period of 240 days. The rates of degradation of petroleum hydrocarbon by the indigenous soil microbe (biostimulation) and in the addition of microbe (bioaugmentation) show that higher degradation rate in all system occurs within the first 60 days. Between 73% to 99% degradation of crude oils in contaminated soils was achieved after 240 days of incubation, depending on the experimental condition. While, in sterile control soil samples biodegradation ranged from 10.90 % to 17.72 %. However, the most rapid biodegradation occurred in the system with the concentrations of 1 % and 4 % and lower biodegradation occurred in the system with a concentration of 8 % TPH, this due to the high concentration of hydrocarbons which could be toxic to the microbes. The information obtained from the results on small scale bioremediation indicates that biological treatment of contaminated soil is appropriate. Identification of bacteria is of great importance for the best understanding of the biodegradation process. In this study, the isolates microbes from the soil were identified as Bacillus sp., Bacillus simplex strain, Microbacterium sp and Corynebacterium stationis strain by using molecular biology, based on DNA extraction, genomic analysis of 16S rRNA genes and sequencing.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available