Characterisation and bioremediation of soil impacted by Libyan oilfield produced water.

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 25407 mg/l 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/l 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/l to 1.86 mg/l. 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. (Abstract shortened by ProQuest.).