Characterization of the bacterial community structure and physicochemical properties of produced water from A4 well, north Hamada oilfield in Libya

Abstract

Produced water is contaminated water that is withdrawn from underground formations to the surface during oil and gas production. Samples from A4 Well - North Hamada Oilfield were collected and analysed to evaluate the quality of the produced water. Physico chemical analysis such as pH, salinity, electrical conductivity, total dissolved solids (TDS), sulphate, carbonate, bicarbonate, hardness, heavy metals, total petroleum hydrocarbons (TPHs) and Benzene, Toluene, Ethylbenzene and Xylene (BTEX) were analysed. The radioactive survey was conducted to measure the activity of alpha (α) and beta (β) particles and gamma (ɣ) rays. Culture-independent approach was carried out to investigate the bacterial diversity of produced water. 16S rRNA gene amplification technique using a universal bacterial oligonucleotide primer set was conducted. The results show wide variations in the different properties measured. The key contaminants of concern in the produced water that is more likely to affect the environment negatively are high concentrations of the following: salts content (109980 ± 129.12 m g/L of TDS), EC (169200 ± 105.36 μS/cm), salinity (84158 ± 50.48 mg/L), TPHs (58.5 ± 1.55 mg/L), BTEX (57.87 ± 2.65 mg/L) and some heavy metals (Ba 11.9 ± 1.1ppm, Fe 311 ppm ± 12.8 ppm, Se 3.61± 0.42 ppm and Sr 122.± 3.6 ppm). Two oil-degrading bacterial strains were isolated. The isolates are closely related to Kocuria rosea strain DSM 20447 with 99.81% gene sequence similarity and Nocardia coubleae strain OFN N12 with 98.57% gene sequence similarity. This study emphasises the importance of studying the microbial communities’ structure that inhabit such oil by-products using genetic techniques.