Abstract

This study was carried out to isolate opportunistic hydrocarbons oil-degrading bacteria and develop a consortium or a mixture of bacteria with high biodegradation capabilities which can be used in biological treatment units of the contaminated water before release. The biological processes in general are environmentally friendly and cost effective, as they are easy to design and apply; as such they are more appropriate to the public.
 The location of the study was in Al-Dora refinery sludge holes area. The samples were collected for three seasons (winter, spring and summer) each consisted of three months. The sludge samples were analyzed for various physical and chemical parameters. Temperature values of the sludge were at maximum in summer season, reaching 32˚C, whereas they were at minimum in winter (24 ˚C). The values of sludge pH were at maximum in summer (9.70) and minimum in winter (9.20). Turbidity levels were 382 NTU in spring and 353 NUT in winter. Biological oxygen demand (BOD5) was at maximum in summer (760) and (690 mg/l) in winter. The maximum dissolved oxygen (DO) value of 5.20 mg/l was recorded in winter, while the minimum was 3.80 mg/l recorded in summer. The maximum electrical conductivity (EC) was 17130 μs/cm recorded in summer, while the minimum was 16150 μs/cm recorded in winter. The maximum total dissolved solids (TDS) values were 10335 mg/l recorded in summer, while the minimum (10015 mg/l) was recorded in winter. The maximum total petroleum hydrocarbon (TPH) value (431 mg/l) was recorded in summer, while the minimum (367 mg/l) was recorded in spring. Finally, the maximum salinity value (9.90%) was recorded in spring, while the minimum (9.30%) was recorded in winter. Also, hydrocarbon compounds in sludge samples were measured using Gas Chromatography - Mass Spectrometry (GC-MS), and the result showed that they were composed of 31 hydrocarbon compounds.In the present work, nineteen sludge degrading bacterial strains were isolated from the soil near Al-Dora refinery hole by primary and secondary screenings using a modified mineral salt medium supplemented with 1% (v/v) sludge as a carbon source. The most efficient two sludge degraded isolates identified by VITIK 2 compact were Kocuria rosea and Bacillus amyloliquefaciens. The tow isolates and there mixture showed best growth at 30°C for 12 days, as shown by the measurement of the optical density of the liquid culture and the final oil concentration by spectrophotometer.
 The bacterial isolates in liquid media with 2% (v/v) sludge showed best growth and the maximum biodegradation percentage after 12-day incubation period, as determined by gas chromatographic (GC). The degradation values were 68.9, 93.8 and 95.5% for Bacillus amyloliquefaciens, Kocuria rosea and the mixture of the tow isolates, respectively. In optimum conditions of pH 7, 40°C, 12 days incubation, the mixed bacterial consortium showed maximum sludge degradation.

Highlights

  • Effect of incubation periodOne hundred milliliters of modified mineral salt (MMS) medium were dispensed in Erlenmeyer flasks and the pH was adjusted at 7.0

  • This study was carried out to isolate opportunistic hydrocarbons oil-degrading bacteria and develop a consortium or a mixture of bacteria with high biodegradation capabilities which can be used in biological treatment units of the contaminated water before release

  • The results indicated that the values of some properties were out of acceptable values, pH, temperature were within the limitation. temperature values were 32, 28 and 24 °C The value of wastewater temperature was in the acceptable limit of WHO values [19], which was between 25-30oC. pH values were 9.70, 9.40 and 9.20 All values are in the World Health Organization values (WHO) set limit, 6.5 - 9.6 of wastewater which have to be discharged into the aquatic environment [20]

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Summary

Effect of incubation period

One hundred milliliters of modified mineral salt (MMS) medium were dispensed in Erlenmeyer flasks and the pH was adjusted at 7.0. The mixture was supplemented with 1% sludge as a substrate and 0.5 % of the bacterial isolate and incubated at 30 ̊C for different periods (3 , 7 , 10 , 11 and 12 days ) at 150 rpm [15]

Spring ab
Bute hydrocarbon Tetradecyl iodide
Bacillus amyloliquefaciens
Conclusion
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