Treatment of Wastewater Associated With Crude Oil in Reservoirs

The produced water or wastewater resulting from the oil reservoirs in Basrah Petroleum Company / Zubair 1 Warehouse causes very high pollution in the land. The aim of this study is to find possible ways to treat such produced water and to remove turbidity through coagulation, flocculation, sedimentation and adsorption. Experimental tests of the properties for natural produced water such as turbidity, pH, TDS, TSS, and oil content found out that oil content = 137 mg/L and turbidity = 122 NTU. The produced water is treated with two types of coagulant poly aluminum chloride, alum and with two other types of adsorbent (Bentonite , Zeolite (Cation and Anion)). The coagulation, flocculation and sedimentation experiments are performed using a Jar-test device and adsorption experiments , and a magnetic stirrer device are used at different times, speeds, and concentrations. 
    It is found through the practical results that the best dosages of (poly aluminum chloride and alum) are (3, 35, 6.75, and 30) mg/L to obtain R% (96.3, 93, 99, and 98.9), respectively. 
    It is found from the experimental results of adsorption that the best results of weight adsorbent, stirrer time and stirrer speed to obtain maximum removal efficiency are (6 gram anion zeolite ,15 minute and 920 rpm) R% (98 , 97.8 and 99.2), respectively . 
It is found that the best results are poor at different parameters, except when it is used (2) gram of bentonite obtained R% of turbidity weight, stirrer time and stirrer speed by bentonite and zeolite (cation and anion) were (2 gram) . Finally, it was found that removing the oil content by adsorption (97.8) is better than coagulation (96.3). And the results for removing turbidity by coagulation (99) is better than adsorption (97.4)


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Definition  E66

1-Introduction:
The treatment of wastewater associated with crude oil in reservoirs is important processes, where the untreated such water may affect the quality of the oil and its price and properties …. etc. As well as, it affects such produced water on human health, the environment and soil and underground water, so this research is intended to deal with such produced water for the purpose of free of crude oil, water, materials suspended solids and other materials. Produced water is formed by oil and gas extraction with the oil industry. It produces about 14 billion barrels of water per year [1]. The water varies very greatly in quality and quantity, and in some cases water can be useful as secondary product or even a salable commodity. Produced water is one of the major and influential problems in the petroleum industry and generated in increasing volumes from both old and new wells [2]. These effluents represent 98% of the total wastewater from the petroleum industry. It also contains complex organic and inorganic substances Such as metals, salts dispersed oil and dissolved hydrocarbons and high temperature and lack of oxygen [3]. Therefore, produced water is a major and important source of pollutants, and as the environmental laws have become more stringent, the cost of treatment has become increasingly high. This fact has led to many efforts to find more efficient and less costly ways to treat this water [4]. Therefore, the main idea of this work is to use the method treatment (coagulation, flocculation, sedimentation & adsorption) to remove the oil content and the turbidity of the oil reservoirs / Basrah Oil Company. It is also to study the effect of adding (PAC, Alum, Bentonite and Zeolite (Cation &Anion)) individually and collectively, on removal efficiency of oil content and turbidity, as well as, the use of the best dose, best time and speed of the additives (poly aluminum chloride, alum, bentonite, zeolite both types) to remove the oil content and turbidity of the produced water oil in reservoirs.

Methods of Treatment:
There are many treatment processes for removing the solids and impurities from soluble wastewater. These processes can be categorized into chemical, physical or

No.23-(6) 2019 Journal of Petroleum Research & Studies (JPR&S)
E67 biological treatments, such as sedimentation, precipitation, evaporation, extraction, coagulation-flocculation, flotation, electrocoagulation, filtration, adsorption, biodegradation, ion exchange, and electrochemical treatment [5, 6 and 7]. The efficient treatment of wastewater typically requires many steps, and it is often appropriate to combine more than one method [7]. Coagulation and flocculation are among the most widely used technologies for removing solids from industrial and municipal wastewater, while adsorption is the method most frequently used metals in dilute solutions [8,9]. The grease and oil content must be treated before discharge into the city's drainage systems.
The most common treatment methods for wastewater treatment are sedimentation, centrifugal separation, coagulation, flocculation, sorption, flotation, filtration ultrafiltration, and reverse osmosis. These methods can be used separately or in groups [10]. Coagulation and flocculation are simple, inexpensive, efficient and most traditional ways of treating wastewater [11,12].
The coagulation, flocculation, sedimentation and adsorption are used in current work.
Coagulation is a process in which the colloids or particles in a suspension are destabilized, leading to the formation of small groups of molecules [13, 14 and 15].
While in flocculating the resulting destabilized and aggregated particles or other colloidal and particular substances are collected into larger aggregates [13,14].
Flocculation is the process of quiet water movement that promotes the aggregation of small floc particles (microflocs) resulting from coagulation in larger blocks suitable for removal by clarification processes. Flocculation is enhancements sedimentation or filtration treatment system performance by increasing particle size resulting in increased settling rates and filter capture rates.
Sedimentation is a treatment process in which is suspended particles, like flocs, sand and clay which are re-moved from the water. Sedimentation is the process of letting the suspended material settles by the gravity. Adsorption is very efficient, cost effective and most importantly has the ability of meeting the environmental compliance as far as the discharge standard of the oil content of the wastewater is concerned [16].
Adsorption is an increase in the concentration of certain substances in the interface of the two different phases [17].

No.23-(6) 2019 Journal of Petroleum Research & Studies (JPR&S)
E68 Adsorption is used in the industrial field for the separation, purification and recovery of mixtures, chemicals, liquid and gas media [18].

2-1 Methods and materials:
The experimental work to remove the oil content from the produced water is considered in two stages. The first stage includes knowledge of the standard characteristics of the produced water from the Basrah Oil Company tanks. These standard properties include turbidity and oil content. All the experiment procedures are taken from the standard methods in the examination of water and produced water, was developed in 1995 (ASTM) [19]. The second stage includes methods of treatment of  Tables (1 to   4).

2-2 Materials:
There are four types of chemical used in treatment of produced water. Two types are These results are removed from the influence of coagulation, flocculation, which overcomes some of the forces of repulsion between the colloidal particles, and reduces the distances between them, which increases the power of attraction and van der Waals forces and makes them weak Brownian motion and then weaken the value of the existing Zeta [21]. The doses of poly-aluminum chloride and alum increases the efficiency of removing the turbidity until it reaches the best value, and after that the efficiency of deturbidity is reduced because more doses cause the re-stabilization of colloid particles.

Effect of adsorption on the efficiency of removing oil content and turbidity:
Figures (5 to 16) show that the adsorbent at the initial concentration of oil content and turbidity in the produced water are obtained. These figures show that the efficiency of removal of oil content and turbidity increases with increasing adsorption doses until they reach the best dose of removal. The adsorbent materials (bentonite, zeolite (cation and anion)) are used, the removal efficiency of the oil content of the best weight (1, (6 and 6 gram)) is (87.6%, (97% and 98%)), respectively.
Overweight leads bentonite decrease in oil removal efficiency, this is due to the hydration of bentonite which causes organic compounds with average molecular weights are weakly adsorbed or not adsorbed by pure montmorillonites (Bentonite) due to their reliably large solubility in water. Soluble compounds with molecular weights, whether charged or not, are absorbed by montmorillonites because of their low solubility in water [22]. The results of the effect of stirring speed to reduce the oil content is good, where the oil content decreases with increasing stirring speed due to a decrease in the resistance to mass transfer oil from the bulk of the oily waste water to the surface of bentonite. It is scheduled to take the deployment of each particle layer of bentonite in the resistance to mass transfer. For the stirring time, as the increase in the stirring time leads to decrease the efficiency of the removal of the oil content of the inability of the withdrawal of capillary. Water absorption of bentonite occurs through diffusion and capillary suction [23]. The efficiency of removal of oil content increases with increasing (weight, stirring time and stirring speed) for zeolite, until reach the (best weight, best time and best speed) for zeolites. This is due to increase the adsorption sites available by increasing the dose of adsorbents. However, adsorption density is reduced due to unsaturated adsorption sites. Adsorption density is also reduced due to particle interactions resulting from high concentration of adsorption. The removal efficiency of the adsorbent material increases with increasing doses [24].
The comparison between coagulation and adsorption for removal efficiency of the oil

No.23-(6) 2019 Journal of Petroleum Research & Studies (JPR&S)
E73 content, the results show that the adsorbent (bentonite and zeolite both types) better than coagulants (poly aluminum chloride and alum), as shown in Fig. 17. As well as the comparison between coagulation and adsorption of turbidity removal efficiency, the results show that the coagulants (poly aluminum chloride and alum) better than adsorbent (bentonite and zeolite both types), as shown in Fig.18. From the graphical figures it is found the results for removal oil content by adsorption (99.2%) which is showed better than coagulation (96.3%). And the results for removal turbidity by coagulation (99%) were shows better than adsorption (97.4%).

4-Conclusions:
From the pilot study for the treatment of produced water from oil reservoirs in Zubair 1 warehouse / South Oil Company some basic information, extracted from the study as following: 1. The characterization of wastewater in reservoirs is analyzed in laboratory and shows the results: oil content = 137 mg/L, pH = 6.9 and turbidity = 122 NTU.

2.
For coagulation and flocculation treatment of the poly aluminum chloride and alum as coagulant. In the case, it finds a poly aluminum chloride and alum best dose to removal oil content and turbidity by jar test was to be equal to (3, 35 and 6.75, 30 mg/L), respectively. At the best dose, efficiency is the removal of oil content and turbidity (96.3%, 93% and 99%, 98.9%) from (poly aluminum chloride and alum), respectively.

4.
In the case of the adsorbent materials (bentonite, zeolite (cation and anion)), the turbidity removal efficiency of the best weight (2, (4 and 4 gram)) is (99%, (90% and 87.4%)), respectively as well as the best stirring time of adsorbent materials (bentonite,

5.
The results for removal oil content by adsorption (99.2%) show better than coagulation (96.3%) and the results for removal turbidity by coagulation (99%) shows better than adsorption (97.4%).

Fig. (1) Effect of PAC Dose on Oil Removal Efficiency at the best (time and speed)
is (