الفهرس 
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Abstract
This study was carried out to investigate the potentiality of some bacteria to treat oil wastewater. Oil wastewater samples were collected from effluent of Oil and Soap Company in Tanta. Tested microorganism: Twenty bacteria were isolated from water of Oil and Soap Company in Tanta. Among to bacterial isolates, only four isolates were able to degrade oil wastewater than the others. These isolates are isolate No (2, 3, 16, and 17). Identification of bacterial isolates: These isolates were identified morphologically under light Microscope and identified biochemically by Vitek 2C. They were identified biochemically as Bacillus cereus1 (isolate No 2), Bacillus cereus2 (isolate No 3), Aeromonas sobria (isolate No 16) and Klebsiella pneumoniae ssp pneumonia (isolate No 17). Bacillus cereus1 (isolate No2) recorded the highest ability to treat oil wastewater so; it was identified genetics by 16S rRNA. It was identified as Bacillus cereus ATCC 14579. Treatment of oil wastewater by: 1- Single bacterial cultures under different incubation periods. 2- Consortium bacterial cultures under different incubation periods. The ability of single bacterial culture in treatment of oil wastewater after (2, 4 and 6) days was investigated. The best incubation period was 6 days as all measured parameters were highly decreased. The treatment efficiency of Bacillus cereus ATCC 14579 showed 53.1% for EC, 52% for TDS, 91.8% for TSS, 89.1% for COD, 93.1% for O&G and the pH value was 7.03 after 6 days of incubation. The treatment efficiency of Bacillus cereus2 was 44.8% for EC, 43.6% for TDS, 90.5% for TSS, 87.8% for COD, 91.8% for O&G and the pH value was 7.47 after 6 days of incubation. The treatment efficiency of Aeromonas sobria was 39.2% for EC, 38.8% for TDS, 78.4% for TSS, 75% for COD, 80.6% for O&G and the pH value was 6.83 after 6 days of incubation. The treatment efficiency of Klebsiella pneumonia was 41.4% for EC, 40.3% for TDS, 84.3% for TSS, 82.3% for COD, 86.1% for O&G, and the pH value was 7.33 after 6 days of incubation. Optimization of biodegradation by selected bacteria The optimization for biodegradation of oil wastewater using Plackett-Burman design was carried out. Bacillus cereus ATCC 14579 was chosen because it has high ability for treatment of industrial oil wastewater than others bacteria. It had the greatest efficiency for treatment of oil wastewater. The obtained results showed that the highest biodegradation of oil wastewater 95% was obtained on using the high level (+1) of all the tested factors except the beef extract and temperature, which must be applied in its low level (-1) Efficiency of selected bacteria on treatment of oil wastewater (pilot scale). It was studied the efficiency of Bacillus cereus ATCC 14579 in treatment of oil wastewater in pilot scale (high load, moderate load and low load) after 8 hours, 10 hours and 12 hours. It was found that the best incubation period for Bacillus cereus ATCC 14579 in pilot scale for treatment of oil wastewater is 10 hours as all parameters were significantly decreased. . The removal efficiency of EC, TDS, TSS, COD and O&G of Bacillus cereus on high load after 10 hours was 33.2, 31.5, 91.8, 89.8 and 93.1% and on moderate load after 10 hours was 40.2, 39.1, 92.1, 90 and 94% and on low load after 10 hours was 51.1, 49.6, 92.3, 90.8 and 95% respectively. Treatment of oil wastewater using bacterial consortium. The ability of consortium bacterial culture in treatment of oil wastewater after (2, 4 and 6) days was investigated. Bacterial consortium gave higher efficiency than single culture. The best incubation period was 6 days as all measured parameters were highly decreased. The treatment efficiency of consortium bacterial culture was 54% for EC, 56% for TDS, % 93.1 for TSS, 90.6% for COD, 94.4% for O&G and the pH value was 7.17 after 6 days of incubation.