الفهرس 
Literature reviewOnly 14 pages are availabe for public view
 |  | from | 229 |  |  |
| | | from | 229 | | |
Abstract
Disposal of produced waste water causes an environmental impact which has been reported since the mid-1800s when the first oil and gas wells were drilled and operated. The most commonly reported environmental concerns are as follows: degradation of soils, ground water, surface water, and ecosystems they support.
In recent years, interest in biological treatment, especially to remove the petroleum-derived compounds in produced waste water, has increased due to more stringent environmental standards and the desire/need to reuse the increasing amounts of water rather than pumping the mat high pressure back down the aquifers which is energy intensive and expensive.
Biological treatment is an effective and economical way that can be used in oil de-emulsification and waste water treatment. Crude oil degrading microorganisms, namely bacteria, yeast and fungi, which can grow using crude oil as carbon source, have been reported as oil degraders.
The main objective of this study was concentrated on using bacteria in treatment of produced wastewater from gas reservoir. Also, studying the chemical characteristics and properties of produced waste water.
In this study pH value and water/sludge ratio is very important for enhancing the treatment process of the produced water. An experiment is done to chose the best pH value and water/ sludge ratio, aerobic treatment of produced waste water was done with different sludge/ water ratio (1:3, 1.5:2.5, 2:2 and 3:1) and at different pH value from 3 to 10, it was observed that the treatment reached its best removal values for COD, BOD5, TSS, TDS , oil and grease when pH was between 7 – 9 and water to sludge ratio was 2.5/1.5.
In this study eleven bacterial strains were isolated from sludge to be used in produced water treatment. Enrichment of the eleven isolated strains was done and then each strain was examined separately for its biodegrative ability. Biodegradation of produced water using eleven isolated bacterial (Free cells) strain from sludge in aerobic conditions was done at the optimization conditions (pH range between 7 to 9 and water to sludge ratio 2.5/1.5) shows a great removal percentage for COD, BOD5, total suspended solids (TSS), total dissolved solids (TDS) and also for oil & grease. from the eleven isolates three were selected as the best isolates in the treatment of produced water.
It was found that isolates two, five and eight were the best ones. The identification of the three most biologically active isolates out of the eleven selected isolates using biology system ”Biolog TM microplate” revealed these three isolates as Bacillus licheniformis, Pseudomonas fluorescens and Flavobacterium flevens respectively.
Bacillus licheniformis, Pseudomonas fluorescens and Flavobacterium flevens were immobilized on calcium alginate gel, the formed beds for the three isolates were used separately to detect their efficiency in treatment of produced water at optimization conditions (pH range between 7 to 9 and water to sludge ratio 2.5/1.5). Immobilization of these isolates shows nearly the same removal efficiency as in case of using free cells but it was done in shorter time (one month).
At the end of this study pseudomonas fluorescens was chosen as the best isolate and comparison between three different conditions was done. The three different conditions were:
• First condition was sludge and water without any change in pH value
• Second condition was sludge and water after addition of Pseudomonas fluorescens (free cells) at pH 8 and water to sludge ratio 2.5/1.5
• Third condition was sludge and water after the addition of Pseudomonas fluorescens immobilized on alginate gel at pH 8 and water to sludge ratio 2.5/1.5.
It was found that the second condition gives a better percentage of removal for COD, BOD5, TSS, TDS, oil and grease after eight weeks, where the percentage of removal reaches about (90%, 85%, 75%, 73% and 85% respectively. While in case of immobilization of Pseudomonas fluorescens it gives nearly the same percentage of removal but after four weeks only.
Pseudomonas fluorescens increase the degradtive ability during the treatment of produced water and increase the removal percent of COD, BOD5, TSS, TDS, oil and grease. Also using Pseudomonas fluorescens immobilized on alginate gel reduces the treatment duration.