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Evaluation of a three-step process for the treatment of petroleum refinery wastewater
Journal of Environmental Chemical Engineering 2 (2014) 56–62
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Evaluation of a three-step process for the treatment of petroleum refinery wastewater Muftah H. El-Naas *, Manal Abu Alhaija, Sulaiman Al-Zuhair Chemical and Petroleum Engineering Department, UAE University, P.O. Box 15551, Al-Ain, United Arab Emirates
A R T I C L E I N F O
A B S T R A C T
Article history: Received 29 July 2013 Accepted 25 November 2013
In this study, a novel three-step process was developed and evaluated for the treatment of highly contaminated refinery wastewater. The process consisted of an electrocoagulation cell (EC), a spouted bed bioreactor (SBBR) with Pseudonymous putida immobilized in polyvinyl alcohol gel, and an adsorption column packed with granular activated carbon produced from agricultural waste, specifically date pits. The units were evaluated individually and as combinations with different arrangements at different operating conditions to treat refinery wastewater with varying levels of contaminants. The EC unit was found to be effective as a pretreatment step to reduce the large concentrations of COD and suspended solid and reduce the load on the bioreactor and the adsorption column. At optimum conditions and unit arrangement, the process was able to reduce the concentration of COD, phenol and cresols by 97%, 100% and 100%, respectively. The process was found to be highly competitive in comparison with other combined systems used in the treatment of industrial wastewater and can handle highly contaminated refinery or industrial wastewater with relatively wide range of operating conditions. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Petroleum refinery wastewater Electrocoagulation SBBR Adsorption COD Phenol
Introduction With the remarkable economic growth envisaged in the world nowadays, concerns are raised about many environmental challenges. In petroleum and petrochemical industry, more than 2500 useful petroleum products are produced from crude oil [1] and the annual worldwide consumption of petroleum hydrocarbons is estimated to be approximately 1012 US gallons [2]. Depending on the size, type of crude oil, products and complexity of operation, a petroleum refinery can be a large consumer of water and can generate significant volumes of wastewater. The estimated average water consumption in processing a barrel of crude oil is 65–90 gallon (246–341 L) [3]. Approximately 0.4–1.6 times the volume of the processed crude oil is discharged as petroleum refinery wastewater [4]. Thus, based on the current yield of 84 million barrels per day (mbpd) of crude oil, a total of 33.6 mbpd of effluent is generated globally [5]. World oil demand is expected to rise to about 107 mbpd over the next two decades, and oil will account for 32% of the world’s energy supply by 2030 [5]. These data clearly indicate that effluents from the oil industry will continually be produced and discharged into the world’s main water bodies.
* Corresponding author. Tel.: +971 3 713 5188; fax: +971 3 713 5188. E-mail address: [email protected] (M.H. El-Naas). 2213-3437/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jece.2013.11.024
In petroleum and petrochemical industries, there is strong interest in improving wastewater management by optimizing water use and introducing recycling technologies in production units. In general, refinery wastewater contains many and diverse contaminants, several inorganic substances, such as Mg2+, Ca2+, S2 , Cl , and SO42 that upgrade the mineralization of water; emulsified oil and grease, phenols, cresols, sulfides, ammonia and cyanides contribute to the chemical oxygen demand (COD). As a result, an effective approach should be developed to face stringent environmental regulations on the quality of effluent discharged for recycling purposes [6]. Table 1 summarizes the main pollutants in different petroleum refining units. The traditional treatment of refinery wastewater is based on physicochemical, mechanical methods and further biological treatment in the integrated activated-sludge treatment unit. Several solutions are proposed including electrocoagulation [1,7,8], photocatalytic oxidation [9], wet oxidation [10], photodegradation [11], catalytic vacuum distillation [6], coagulation– flocculation [12,13], fenton oxidation [14], adsorption [15,16], biodegradation [17], membrane [18] and membrane bioreactor [19–21], ultrasound [22] and chemical precipitation [23]. However, because of the variability of refinery wastewater composition, the traditional methods become inadequate and could not be used individually in full scale. So, there is still a need for advanced techniques to remove non-biodegradable, high concentration organic substance of petroleum refinery wastewater [10]. In other words, researchers are attempting to design a combination of
M.H. El-Naas et al. / Journal of Environmental Chemical Engineering 2 (2014) 56–62 Table 1 Major water sources in petroleum refining process [3].
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Table 2 Characteristics of refinery wastewater samples as ranges of values.
Unit
Wastewater main pollutants
Parameter
Value
Crude desalting Crude oil distillation Thermal cracking Catalytic cracking Hydrocracking Polymerization Alkylation Isomerization Reforming Hydrotreating
Free oil, ammonia, sulfides and suspended solids Sulfides, ammonia, phenols, oil, chloride, mercaptans H2S, ammonia, phenols Oil, sulfides, phenol, cyanide, ammonia High in sulfides Sulfides, mercaptans, ammonia Spent caustic, oil, sulfides Low level of phenols Sulfide Ammonia, sulfides, phenol
pH Conductivity (mS/cm) Total suspended solid (g/l) Total dissolved solid (g/l) SO4 (mg/l) COD (mg/l) Total phenol (mg/l) Phenol (mg/l) o-Cresol (mg/l) m,p-Cresol (mg/l) N-hexane (mg/l)
8.3–8.9 5.2–6.8 0.03–0.04 3.8–6.2 14.5–16 3600–5300 160–185 11–14 14–16.5 72–75 1.8–1.85
treatment methods for a complete and successful removal of such pollutants. Although biological treatment and bioremediation techniques are well established for the clean-up of petroleum contaminated land and wastewater [11], there is a need for enhancement of enzymatic capacity of the employed microbial communities. An improvement can also be achieved by pretreatment technologies, to decrease the priority pollutants concentration as much as possible before the biodegradation step. Several solutions are proposed including the use of coagulants and electrochemical oxidation [13,24], fenton oxidation [25], electron-beam [26], ozonation [27]. In recent years, there has been increased interest in the application of electrocoagulation in the treatment and purification of industrial wastewater [28]. Electrocoagulation is efficient in removing suspended solids as well as oil and greases. It removes metals, colloidal solids and particles, and soluble inorganic pollutants from aqueous media by introducing highly charged polymeric metal hydroxide species. These species neutralize the electrostatic charges on suspended solids and oil droplets to facilitate agglomeration or coagulation. Because of the many advantages for this technique, electrocoagulation has been suggested widely as one of those advanced alternatives used as a pretreatment step for industrial wastewater treatment. A combination between EC and TiO2 photocatalysis was applied for the reduction of COD from pharmaceutical and cosmetic industries wastewater [29]. 90% of COD reduction was achieved after the EC process. Linares-Herna´ndez et al. found a complete elimination of COD by combining EC with electrooxidation [30]; whereas, 84% COD reduction efficiency was achieved using EC– biosorption process [31]. EC was also combined with a biological treatment used for winery wastewater [32]. Combinations of different treatment techniques were recommended for the treatment of highly contaminated industrial wastewater. Ultrafiltration with electrocoagulation [33] and advanced oxidation with biodegradation [34] were suggested for the treatment of olive mill wastewater with COD reduction efficiency of about 96% and 91%, respectively. EC–irradiation treatment was another combination used in the treatment of highly colored and polluted industrial wastewater with COD reduction of about 95% [35]. Chemical coagulation, electrochemical oxidation and biological treatment were used as a combination for the treatment of bactericide [24] and textile wastewaters [36]. Leather industry [37] and integrated dyeing [25] wastewaters were also treated using biological and fenton oxidation process. Jung et al. [38] suggested the combination between adsorption and microfiltration membrane bioreactor for advanced tertiary wastewater treatment. Pre-oxidation, co-precipitation, adsorption and coagulation were used as a combined process for the treatment of high arsenic content industrial wastewater [39]. A combination of PAC’s and coagulant with ultrafiltration [40] and microwaveassisted catalytic wet air oxidation [10] were investigated for refinery wastewater treatment.
In this study, a combination of an electrochemical process, a biological treatment with a spouted bed bioreactor (SBBR) and an adsorption fixed bed column packed with granular activated carbon was evaluated for the treatment of refinery wastewater. The integrated three-step system was tested under different operating conditions and the experimental results obtained for the optimized system were compared with those reported in the literature for similar processes.
Experimental methods Wastewater characterization Refinery wastewater samples were obtained from a petroleum refinery and were preserved in dark, plastic containers. Analyses of the samples are given as ranges of values in Table 2. Bacterial suspension A special strain of the bacterium Pseudonymous putida was obtained in a cereal form (AMNITE P 300) from Cleveland Biotech Ltd., UK. A 100 g of the cereal was mixed in a 1 L of 0.22% sodium hexametaphosphate buffered with Na2CO3 to a pH of 8.5. The mixture was homogenized in a blender for about one hour, decanted and kept in the refrigerator at 4 8C for 24 h. Bacteria slurry was prepared by first low speed centrifugation at 6000 rpm (4508 g) for 15 min. Then, the supernatant was collected and centrifuged again at 10,000 rpm (12,522 g) for 20 min. The centrifugation was carried out using IEC CL31R Multispeed Centrifuge, Thermo Electron Cooperation, USA. Harvested bacteria cells were collected and kept in the refrigerator for immobilization. Nutrients mineral media was prepared according to Table 3. Immobilization of bacteria in PVA gel Polyvinyl alcohol (PVA) gel was used for immobilizing the bacteria cells as reported in a previous study [41]. A homogenous 10 wt% PVA viscous solution was prepared by mixing 100 g of PVA Table 3 Composition of nutrient mineral media. Component
Concentration (g m
MgSO47H2O K2HPO4 CaCl22H2O (NH4)2CO3 FeSO47H2O ZnSO47H2O MnCl24H2O CuSO45H2O CoCl26H2O Na2MoO42H2O
300 250 150 120 3.5 1.3 0.13 0.018 0.015 0.013
3
)
[(Fig._1)TD$IG]
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After cooling to room temperature, the material is considered carbonized, but still inactive. After weighing the inactive carbon, it was activated in the same tube furnace at a temperature of 900 8C using a flow of carbon dioxide instead of nitrogen. The resulting AC was then degassed under vacuum (Shel Lab, USA) for about 2 h before use [15]. Experimental setup
Fig. 1. SEM photo for immobilized bacteria in PVA.
powder with 900 ml of distilled water at about 70–80 8C. PVA is a synthetic polymer that has better mechanical properties, and it is more durable than Ca-alginate which is biodegradable and can be subject to abrasion [42]. The formed mixture was allowed to cool to room temperature before adding 10 ml of the bacterial suspension prepared as in Bacterial suspension section, then well stirred for 10–15 min to ensure homogeneity of the solution. The solution was then poured into special molds and kept in a freezer at 20 8C for 24 h, then transferred to the refrigerator and allowed to thaw at about 4 8C. The freezing–thawing process was repeated 3– 4 times, with 5 h for each cycle. The frozen molds were cut into 1 cm3 cubes, washed with distilled water to remove any uncrosslinked chains, and sent for acclimatization as per the procedure described in [41]. Fig. 1 shows the distribution of immobilized bacteria in PVA. Date pits activated carbon Date pits activated carbon (DP-AC) was prepared from raw date pits granules. The granules were washed, dried, grinded and screened. The collected granules were carbonated and activated to produce DP-AC. The carbonization was performed in a tube furnace (Thermolyene, USA) which was initially purged with a flow of nitrogen for 10 min. After that, the furnace was heated at a rate of 10 8C/min up to 600 8C and then kept at this temperature for 4 h.
Refinery wastewater samples were treated using the integrated system shown in Fig. 2. The wastewater was pumped to the 1500 ml cylindrical electrocoagulation reactor (14 cm in diameter and 6 cm height) using peristaltic pump (GILSON Mini plus 3) with a flow rate of 10 ml/min. The aluminum plate electrodes (4 cm 6 cm 1 mm) were dipped into the wastewater and connected to a DC power source (POPULAR PE-23005) to provide a current of 0.1 A (current density of 3 mA/cm2) and a voltage of about 17 V; the voltage depends on the conductivity of the wastewater. The distance between the anode and the cathode was kept constant at 7.5 cm. The effluent from the electrocoagulation unit was sent to a settling tank, where the overflow was pumped to the spouted bed bioreactor (SBBR). The spouted bed bioreactor was made of Plexiglas with a total volume of 1.1 L and was equipped with a surrounding jacket for temperature control. Detailed description of the SBBR can be found elsewhere [43,44]. The temperature of the reactor system was controlled by circulating water into the reactor jacket from a water bath set at the desired temperature. Air was continuously introduced through the bottom of the reactor at a flow rate of 3 L/min to enhance mixing and at the same time provide excess oxygen to sustain aerobic conditions. The reactor was initially filled with standard nutrient media containing 30 vol% PVA gel cubes with immobilized bacteria. The temperature of the water bath, and hence the reactor system, was set at 30 8C. This temperature was found to be the optimum in a preliminary runs which also agrees with previous studies in the literature [45]. The product from the bioreactor was then fed to the adsorption column, which was made of a Plexiglas column (50 cm in length and 3 cm inside diameter). The column was packed with 130 g of granular activated carbon. More details about the adsorption kinetics and equilibrium data as well as the regeneration of the saturated activated carbon can be found elsewhere [15,16]. At regular intervals, samples were collected from the effluent of each treatment unit and analyzed for COD and phenol concentrations. All experiments were carried out at room temperature.
[(Fig._2)TD$IG]
Fig. 2. A schematic diagram of the integrated system. (1) Feed tank, (2) feed pump, (3) electrocoagulation reactor, (4) magnetic stirrer, (5) DC power supply, (6) settling tank, (7) pump, (8) biological reactor, (9) adsorption column and (10) product tank.
[(Fig._4)TD$IG]
M.H. El-Naas et al. / Journal of Environmental Chemical Engineering 2 (2014) 56–62 Table 4 Operation conditions for the three unit system.
12
SBBR
Adsorption system
Electrodes type: aluminum PVA amount: 300 ml Adsorbent: AC Temperature: 30 8C Adsorbent mass: 130 g Current density: 3 mA/cm2 Current: 100 mA pH: 7.5 Room temperature 2 Area of the electrodes: 36 cm Air flow rate: 3 L/min Liquid flow rate: 10 ml/min Liquid flow rate: 10 ml/min Liquid flow rate: 10 ml/min
Phenol Concentration (mg/l)
Electrocoagulation
59
Results and discussion
10 8 6 4 2 0 Feed
The electrocoagulation unit, spouted bed bioreactor and adsorption column were connected in series with different configurations and operated continuously for the treatment of real refinery wastewater, which had a dark greenish color and a strong, pungent odor, with initial concentrations ranging from 3600 to 5300 mg/l and 11 to 14 mg/l for COD and phenol, respectively. The samples withdrawn after each treatment unit were analyzed for their COD content and phenol concentrations as a function of time. Table 4 summarizes conditions used in the experiment for each treatment unit.
EC
Adsorption
SBBR
Treatment Step Fig. 4. Phenol concentration after each treatment step for the refinery wastewater in electrocoagulation–adsorption–biodegradation system.
adsorption column then the concentration increases with time as the activated carbon gets saturated. Electrocoagulation–biodegradation–adsorption arrangement
Electrocoagulation–adsorption–biodegradation arrangement In this section, results for the arrangement of electrocoagulation–adsorption–SBBR are shown for the reduction of COD and phenol for about 3 h. Fig. 3 shows the COD reduction after each treatment unit, with the electrocoagulation pretreatment step contributing 46% to the overall reduction of COD. However, the reduction percentage increased to about 83% by passing the effluent through the adsorption column. The effluent from the adsorption is sent to the bioreactor, where the COD reduction is very low compared to the electrocoagulation and adsorption stages. The cumulative COD reduction after the biodegradation increased to only 85%. It is worth noting here that the adsorption column reached the saturation after the third hour which increased the load on the SBBR and consequently decreased the efficiency of the overall treatment process. Fig. 4 shows the reduction of phenol concentration for this system. There is no significant reduction in phenol concentration in the electrocoagulation unit, but a very high reduction occurs in the adsorption column which initially reduces the phenol concentration to zero in the first 3 h after the feed enters the
Figs. 5 and 6 show the effluent concentrations of COD and phenol at steady state conditions for electrocoagulation and after 24 h of operation for both biodegradation and adsorption systems. The results show that the electrocoagulation unit reduced the COD concentration by about 46%. The bioreactor further reduced the feed contaminants, which came from the electrocoagulation step, by about 73% for COD, 61% for the phenol. Nevertheless, most of the reduction in COD and other phenols has taken place in the adsorption unit, where the final cumulative reduction reached 97% and 100% for COD and phenol, respectively. The final effluent after the adsorption column had COD and phenol concentrations within the acceptable discharge limits. A summary of the complete system results is shown in Table 5, where after the last treatment step the effluent showed almost complete reduction for phenols and 97% reduction for COD content. To demonstrate the effectiveness using a combination of electrochemical process, biological treatment using SBBR and
[(Fig._5)TD$IG]
[(Fig._3)TD$IG] COD Concentration (mg/l)
4000
COD Concentration (mg/l)
4000
3000
2000
1000
3000
2000
1000
0
0 Feed
EC
Adsorption
SBBR
Treatment Step Fig. 3. The COD concentration after each treatment step for the refinery wastewater in electrocoagulation–adsorption–biodegradation system.
Feed
EC
SBBR
Adsorption
Treatment Step Fig. 5. The COD concentration after each treatment step for the refinery wastewater in electrocoagulation–biodegradation–adsorption system.
[(Fig._6)TD$IG]
[(Fig._7)TD$IG]
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60
100
Percentage Reduction %
Phenol Concentration (mg/l)
12 10 8 6 4
COD Phenol
80
60
40
20
2 0 EC
0 Feed
EC
SBBR
Table 5 Summary of the results of EC–SBBR–AD treatment system. SBBR
In
In
Out
Adsorption Out
EC-SBBR-AD
Fig. 7. Comparison for the percentage reduction of COD and phenol after individual unit treatment and the three units in series.
Fig. 6. Phenol concentration after each treatment step for the refinery wastewater in electrocoagulation–biodegradation–adsorption system.
Electrocoagulation
AD (8h)
Treatment Setup
Adsorption
Treatment Step
Test
SBBR
In
Out
pH 7.2 9.1 7.8 8.2 8.2 8.2 Conductivity (mS) 5.4 6.2 6.2 6.73 6.73 8.24 TSS (g/l) 0.072 0.244 0.11 0.17 0.05 0.01 TDS (g/l) 3.38 3.6 3.6 4.03 4.03 4.95 COD (mg/l) 4190 2267 2267 1116 1116 110 Phenol (mg/l) 12.2 8.1 8.1 4.8 4.8 0 m,p-Cresol (mg/l) 75 64 64 33 33 0
adsorption for treating refinery wastewater, results were compared to the percentage reduction for both COD and phenol after the treatment of such wastewater using the same continuous treatment units individually. Fig. 7 shows that biological method
could not be used as an individual treatment unit for the refinery wastewater treatment as a pretreatment step is needed in conjunction with this sensitive technology. Electrocoagulation reduced the contamination of the refinery wastewater by 46% and 34% for COD and phenol, respectively. Meanwhile, passing refinery wastewater through the packed bed of activated carbon showed a reduction of 65% and 85% for COD and phenol. However, the activated carbon was saturated after only 8 h of operation. On the other hand, 97% reduction for COD and a complete reduction of phenol were achieved when using the three units in series for a longer operating time of 24 h, giving a clear indication that this combination can be considered to be the most efficient unit arrangement and as one of the most effective alternatives for the treatment of refinery wastewater. A comparison of the percentage reduction in COD in this study with those reported in the literature using different combined processes for the treatment of several types of industrial wastewaters in batch and continuous studies is presented in Table 6. It shows that this combined process of electrocoagulation, spouted
Table 6 Comparison in the COD reduction using different combined treatment methods for the treatment of different industrial wastewater. Wastewater source
Combined treatment method
COD (mg/l)
COD % reduction
Ref.
1100–1300 2400 3500–4000 675 20 3279 312,000–588,800 28,000 117,100 3400 25 1700–2500 800–1200 1596–2598 1753
Winery Ammunition Leather Semiconductor Printed circuit board Paper industry Petroleum refinery
Fenton oxidation–membrane bioreactor (B) Electro-fenton + chemical precipitation Ozonation–sequencing batch biofilm reactor Fenton–sequencing batch reactor (SBR) Polyferric sulfate coagulation–fenton–sedimentation Chemical recovery + electrochemical Ultrafiltration + electrochemical Advanced oxidation (O3)–biodegradation Electrochemical–irradiation Electrocoagulation–sorption Electrocoagulation–electrooxidation Fenton’s peroxidation–coagulation Electrocoagulation–TiO2 photo-assisted Fenton–sequencing batch reactor (SBR) Electrocoagulation–optional dilution–aquatic plants Ultrasound–fenton Aerobic biological–fenton oxidation Fenton–sequencing batch reactor (SBR) Ferrite process–fenton method Ozonation-activated sludge process Microwave-assisted catalytic wet air oxidation
5500
77–80 88 97 89 96.9 100 93 91 95 84 >99 90 97 98 98.2 92 77 99.8 80 75.5 90
[25] [46] [47] [48] [49] [50] [33] [34] [35] [31] [30] [51] [29] [52] [32] [53] [37] [54] [55] [56] [10]
Continuous study Dyeing Textile Petroleum refinery
Electron beam + biological Fluidized biofilm + chemical coagulation–electrochemical oxidation This work
3220 870 4190
60 95.4 97
[26] [36]
Batch study Dyeing Rayon industry Tannery Antibiotic Biodiesel Olive mill Industrial wastewater
Pharmaceutical and cosmetic
10,168 1580 20 2533 80,000 406
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bed bioreactor (SBBR) and adsorption is highly competitive in comparison to other combination systems used for the reduction of COD in different industrial wastewaters. Conclusions Samples of heavily contaminated refinery wastewater with high concentrations of COD and phenols have been treated by a novel three-step process involving an electrocoagulation cell, a spouted bed bioreactor (SBBR) and adsorption column packed with activated carbon. The overall COD and phenol reduction reached 97% and 100%, respectively, indicating that the combined process was effective for the treatment of petroleum refinery wastewater and might offer a potential application for reusing the treated water and will significantly contribute to reducing freshwater consumption. The process was found to be highly competitive in comparison with other combined systems used in the treatment of industrial wastewater and can handle refinery or industrial wastewater with varying concentrations of contaminants. Work is currently underway at the pilot scale to further assess the technical and economic feasibility of the process. Acknowledgements The authors would like to acknowledge the financial support provided by the Japan Cooperation Center, Petroleum (JCCP) and the technical support of the JX Nippon Research Institute Co., Ltd. (JX-NRI). References ¨ gu¨tveren, Treatment of petroleum refinery waste¨ .B. O [1] Y. Yavuz, A.S. Koparal, U water by electrochemical methods, Desalination 258 (1–3) (2010) 201–205. [2] S.O. Rastegar, S.M. Mousavi, S.A. Shojaosadati, S. Sheibani, Optimization of petroleum refinery effluent treatment in a UASB reactor using response surface methodology, Journal of Hazardous Materials 197 (2011) 26–32. [3] A. Alva-Arga´ez, A.C. Kokossis, R. Smith, The design of water-using systems in petroleum refining using a water-pinch decomposition, Chemical Engineering Journal 128 (1) (2007) 33–46. [4] A. Coelho, A.V. Castro, M. Dezotti, G.L. Sant’Anna Jr., Treatment of petroleum refinery sourwater by advanced oxidation processes, Journal of Hazardous Materials 137 (1) (2006) 178–184. [5] B.H. Diya’uddeen, W.M.A.W. Daud, A.R. Abdul Aziz, Treatment technologies for petroleum refinery effluents: a review, Process Safety and Environmental Protection 89 (2) (2011) 95–105. [6] L. Yan, H. Ma, B. Wang, W. Mao, Y. Chen, Advanced purification of petroleum refinery wastewater by catalytic vacuum distillation, Journal of Hazardous Materials 178 (1–3) (2010) 1120–1124. [7] M.H. El-Naas, S. Al-Zuhair, A. Al-Lobaney, S. Makhlouf, Assessment of electrocoagulation for the treatment of petroleum refinery wastewater, Journal of Environmental Management 91 (1) (2009) 180–185. [8] L. Yan, H. Ma, B. Wang, Y. Wang, Y. Chen, Electrochemical treatment of petroleum refinery wastewater with three-dimensional multi-phase electrode, Desalination 276 (1–3) (2011) 397–402. [9] F. Shahrezaei, Y. Mansouri, A.A.L. Zinatizadeh, A. Akhbari, Process modeling and kinetic evaluation of petroleum refinery wastewater treatment in a photocatalytic reactor using TiO2 nanoparticles, Powder Technology 221 (2012) 203–212. [10] Y. Sun, Y. Zhang, X. Quan, Treatment of petroleum refinery wastewater by microwave-assisted catalytic wet air oxidation under low temperature and low pressure, Separation and Purification Technology 62 (3) (2008) 565–570. [11] P. Stepnowski, E.M. Siedlecka, P. Behrend, B. Jastorff, Enhanced photo-degradation of contaminants in petroleum refinery wastewater, Water Research 36 (9) (2002) 2167–2172. [12] C.E. Santo, V.J.P. Vilar, C.M.S. Botelho, A. Bhatnagar, E. Kumar, R.A.R. Boaventura, Optimization of coagulation–flocculation and flotation parameters for the treatment of a petroleum refinery effluent from a Portuguese plant, Chemical Engineering Journal 183 (2012) 117–123. ˘ an, R. O ¨ zcımder, Wastewater treatment at the petroleum [13] S¸. Demırcı, B. ErdoG refinery, Kirikkale, Turkey using some coagulants and Turkish clays as coagulant aids, Water Research 32 (11) (1998) 3495–3499. [14] D.U.B. Hasan, A.R. Abdul Aziz, W.M.A.W. Daud, Oxidative mineralisation of petroleum refinery effluent using Fenton-like process, Chemical Engineering Research and Design 90 (2) (2012) 298–307. [15] M.H. El-Naas, S. Al-Zuhair, M.A. Alhaija, Reduction of COD in refinery wastewater through adsorption on date-pit activated carbon, Journal of Hazardous Materials 173 (1–3) (2010) 750–757.
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Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece
Evaluation of a three-step process for the treatment of petroleum refinery wastewater Muftah H. El-Naas *, Manal Abu Alhaija, Sulaiman Al-Zuhair Chemical and Petroleum Engineering Department, UAE University, P.O. Box 15551, Al-Ain, United Arab Emirates
A R T I C L E I N F O
A B S T R A C T
Article history: Received 29 July 2013 Accepted 25 November 2013
In this study, a novel three-step process was developed and evaluated for the treatment of highly contaminated refinery wastewater. The process consisted of an electrocoagulation cell (EC), a spouted bed bioreactor (SBBR) with Pseudonymous putida immobilized in polyvinyl alcohol gel, and an adsorption column packed with granular activated carbon produced from agricultural waste, specifically date pits. The units were evaluated individually and as combinations with different arrangements at different operating conditions to treat refinery wastewater with varying levels of contaminants. The EC unit was found to be effective as a pretreatment step to reduce the large concentrations of COD and suspended solid and reduce the load on the bioreactor and the adsorption column. At optimum conditions and unit arrangement, the process was able to reduce the concentration of COD, phenol and cresols by 97%, 100% and 100%, respectively. The process was found to be highly competitive in comparison with other combined systems used in the treatment of industrial wastewater and can handle highly contaminated refinery or industrial wastewater with relatively wide range of operating conditions. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Petroleum refinery wastewater Electrocoagulation SBBR Adsorption COD Phenol
Introduction With the remarkable economic growth envisaged in the world nowadays, concerns are raised about many environmental challenges. In petroleum and petrochemical industry, more than 2500 useful petroleum products are produced from crude oil [1] and the annual worldwide consumption of petroleum hydrocarbons is estimated to be approximately 1012 US gallons [2]. Depending on the size, type of crude oil, products and complexity of operation, a petroleum refinery can be a large consumer of water and can generate significant volumes of wastewater. The estimated average water consumption in processing a barrel of crude oil is 65–90 gallon (246–341 L) [3]. Approximately 0.4–1.6 times the volume of the processed crude oil is discharged as petroleum refinery wastewater [4]. Thus, based on the current yield of 84 million barrels per day (mbpd) of crude oil, a total of 33.6 mbpd of effluent is generated globally [5]. World oil demand is expected to rise to about 107 mbpd over the next two decades, and oil will account for 32% of the world’s energy supply by 2030 [5]. These data clearly indicate that effluents from the oil industry will continually be produced and discharged into the world’s main water bodies.
* Corresponding author. Tel.: +971 3 713 5188; fax: +971 3 713 5188. E-mail address: [email protected] (M.H. El-Naas). 2213-3437/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jece.2013.11.024
In petroleum and petrochemical industries, there is strong interest in improving wastewater management by optimizing water use and introducing recycling technologies in production units. In general, refinery wastewater contains many and diverse contaminants, several inorganic substances, such as Mg2+, Ca2+, S2 , Cl , and SO42 that upgrade the mineralization of water; emulsified oil and grease, phenols, cresols, sulfides, ammonia and cyanides contribute to the chemical oxygen demand (COD). As a result, an effective approach should be developed to face stringent environmental regulations on the quality of effluent discharged for recycling purposes [6]. Table 1 summarizes the main pollutants in different petroleum refining units. The traditional treatment of refinery wastewater is based on physicochemical, mechanical methods and further biological treatment in the integrated activated-sludge treatment unit. Several solutions are proposed including electrocoagulation [1,7,8], photocatalytic oxidation [9], wet oxidation [10], photodegradation [11], catalytic vacuum distillation [6], coagulation– flocculation [12,13], fenton oxidation [14], adsorption [15,16], biodegradation [17], membrane [18] and membrane bioreactor [19–21], ultrasound [22] and chemical precipitation [23]. However, because of the variability of refinery wastewater composition, the traditional methods become inadequate and could not be used individually in full scale. So, there is still a need for advanced techniques to remove non-biodegradable, high concentration organic substance of petroleum refinery wastewater [10]. In other words, researchers are attempting to design a combination of
M.H. El-Naas et al. / Journal of Environmental Chemical Engineering 2 (2014) 56–62 Table 1 Major water sources in petroleum refining process [3].
57
Table 2 Characteristics of refinery wastewater samples as ranges of values.
Unit
Wastewater main pollutants
Parameter
Value
Crude desalting Crude oil distillation Thermal cracking Catalytic cracking Hydrocracking Polymerization Alkylation Isomerization Reforming Hydrotreating
Free oil, ammonia, sulfides and suspended solids Sulfides, ammonia, phenols, oil, chloride, mercaptans H2S, ammonia, phenols Oil, sulfides, phenol, cyanide, ammonia High in sulfides Sulfides, mercaptans, ammonia Spent caustic, oil, sulfides Low level of phenols Sulfide Ammonia, sulfides, phenol
pH Conductivity (mS/cm) Total suspended solid (g/l) Total dissolved solid (g/l) SO4 (mg/l) COD (mg/l) Total phenol (mg/l) Phenol (mg/l) o-Cresol (mg/l) m,p-Cresol (mg/l) N-hexane (mg/l)
8.3–8.9 5.2–6.8 0.03–0.04 3.8–6.2 14.5–16 3600–5300 160–185 11–14 14–16.5 72–75 1.8–1.85
treatment methods for a complete and successful removal of such pollutants. Although biological treatment and bioremediation techniques are well established for the clean-up of petroleum contaminated land and wastewater [11], there is a need for enhancement of enzymatic capacity of the employed microbial communities. An improvement can also be achieved by pretreatment technologies, to decrease the priority pollutants concentration as much as possible before the biodegradation step. Several solutions are proposed including the use of coagulants and electrochemical oxidation [13,24], fenton oxidation [25], electron-beam [26], ozonation [27]. In recent years, there has been increased interest in the application of electrocoagulation in the treatment and purification of industrial wastewater [28]. Electrocoagulation is efficient in removing suspended solids as well as oil and greases. It removes metals, colloidal solids and particles, and soluble inorganic pollutants from aqueous media by introducing highly charged polymeric metal hydroxide species. These species neutralize the electrostatic charges on suspended solids and oil droplets to facilitate agglomeration or coagulation. Because of the many advantages for this technique, electrocoagulation has been suggested widely as one of those advanced alternatives used as a pretreatment step for industrial wastewater treatment. A combination between EC and TiO2 photocatalysis was applied for the reduction of COD from pharmaceutical and cosmetic industries wastewater [29]. 90% of COD reduction was achieved after the EC process. Linares-Herna´ndez et al. found a complete elimination of COD by combining EC with electrooxidation [30]; whereas, 84% COD reduction efficiency was achieved using EC– biosorption process [31]. EC was also combined with a biological treatment used for winery wastewater [32]. Combinations of different treatment techniques were recommended for the treatment of highly contaminated industrial wastewater. Ultrafiltration with electrocoagulation [33] and advanced oxidation with biodegradation [34] were suggested for the treatment of olive mill wastewater with COD reduction efficiency of about 96% and 91%, respectively. EC–irradiation treatment was another combination used in the treatment of highly colored and polluted industrial wastewater with COD reduction of about 95% [35]. Chemical coagulation, electrochemical oxidation and biological treatment were used as a combination for the treatment of bactericide [24] and textile wastewaters [36]. Leather industry [37] and integrated dyeing [25] wastewaters were also treated using biological and fenton oxidation process. Jung et al. [38] suggested the combination between adsorption and microfiltration membrane bioreactor for advanced tertiary wastewater treatment. Pre-oxidation, co-precipitation, adsorption and coagulation were used as a combined process for the treatment of high arsenic content industrial wastewater [39]. A combination of PAC’s and coagulant with ultrafiltration [40] and microwaveassisted catalytic wet air oxidation [10] were investigated for refinery wastewater treatment.
In this study, a combination of an electrochemical process, a biological treatment with a spouted bed bioreactor (SBBR) and an adsorption fixed bed column packed with granular activated carbon was evaluated for the treatment of refinery wastewater. The integrated three-step system was tested under different operating conditions and the experimental results obtained for the optimized system were compared with those reported in the literature for similar processes.
Experimental methods Wastewater characterization Refinery wastewater samples were obtained from a petroleum refinery and were preserved in dark, plastic containers. Analyses of the samples are given as ranges of values in Table 2. Bacterial suspension A special strain of the bacterium Pseudonymous putida was obtained in a cereal form (AMNITE P 300) from Cleveland Biotech Ltd., UK. A 100 g of the cereal was mixed in a 1 L of 0.22% sodium hexametaphosphate buffered with Na2CO3 to a pH of 8.5. The mixture was homogenized in a blender for about one hour, decanted and kept in the refrigerator at 4 8C for 24 h. Bacteria slurry was prepared by first low speed centrifugation at 6000 rpm (4508 g) for 15 min. Then, the supernatant was collected and centrifuged again at 10,000 rpm (12,522 g) for 20 min. The centrifugation was carried out using IEC CL31R Multispeed Centrifuge, Thermo Electron Cooperation, USA. Harvested bacteria cells were collected and kept in the refrigerator for immobilization. Nutrients mineral media was prepared according to Table 3. Immobilization of bacteria in PVA gel Polyvinyl alcohol (PVA) gel was used for immobilizing the bacteria cells as reported in a previous study [41]. A homogenous 10 wt% PVA viscous solution was prepared by mixing 100 g of PVA Table 3 Composition of nutrient mineral media. Component
Concentration (g m
MgSO47H2O K2HPO4 CaCl22H2O (NH4)2CO3 FeSO47H2O ZnSO47H2O MnCl24H2O CuSO45H2O CoCl26H2O Na2MoO42H2O
300 250 150 120 3.5 1.3 0.13 0.018 0.015 0.013
3
)
[(Fig._1)TD$IG]
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58
After cooling to room temperature, the material is considered carbonized, but still inactive. After weighing the inactive carbon, it was activated in the same tube furnace at a temperature of 900 8C using a flow of carbon dioxide instead of nitrogen. The resulting AC was then degassed under vacuum (Shel Lab, USA) for about 2 h before use [15]. Experimental setup
Fig. 1. SEM photo for immobilized bacteria in PVA.
powder with 900 ml of distilled water at about 70–80 8C. PVA is a synthetic polymer that has better mechanical properties, and it is more durable than Ca-alginate which is biodegradable and can be subject to abrasion [42]. The formed mixture was allowed to cool to room temperature before adding 10 ml of the bacterial suspension prepared as in Bacterial suspension section, then well stirred for 10–15 min to ensure homogeneity of the solution. The solution was then poured into special molds and kept in a freezer at 20 8C for 24 h, then transferred to the refrigerator and allowed to thaw at about 4 8C. The freezing–thawing process was repeated 3– 4 times, with 5 h for each cycle. The frozen molds were cut into 1 cm3 cubes, washed with distilled water to remove any uncrosslinked chains, and sent for acclimatization as per the procedure described in [41]. Fig. 1 shows the distribution of immobilized bacteria in PVA. Date pits activated carbon Date pits activated carbon (DP-AC) was prepared from raw date pits granules. The granules were washed, dried, grinded and screened. The collected granules were carbonated and activated to produce DP-AC. The carbonization was performed in a tube furnace (Thermolyene, USA) which was initially purged with a flow of nitrogen for 10 min. After that, the furnace was heated at a rate of 10 8C/min up to 600 8C and then kept at this temperature for 4 h.
Refinery wastewater samples were treated using the integrated system shown in Fig. 2. The wastewater was pumped to the 1500 ml cylindrical electrocoagulation reactor (14 cm in diameter and 6 cm height) using peristaltic pump (GILSON Mini plus 3) with a flow rate of 10 ml/min. The aluminum plate electrodes (4 cm 6 cm 1 mm) were dipped into the wastewater and connected to a DC power source (POPULAR PE-23005) to provide a current of 0.1 A (current density of 3 mA/cm2) and a voltage of about 17 V; the voltage depends on the conductivity of the wastewater. The distance between the anode and the cathode was kept constant at 7.5 cm. The effluent from the electrocoagulation unit was sent to a settling tank, where the overflow was pumped to the spouted bed bioreactor (SBBR). The spouted bed bioreactor was made of Plexiglas with a total volume of 1.1 L and was equipped with a surrounding jacket for temperature control. Detailed description of the SBBR can be found elsewhere [43,44]. The temperature of the reactor system was controlled by circulating water into the reactor jacket from a water bath set at the desired temperature. Air was continuously introduced through the bottom of the reactor at a flow rate of 3 L/min to enhance mixing and at the same time provide excess oxygen to sustain aerobic conditions. The reactor was initially filled with standard nutrient media containing 30 vol% PVA gel cubes with immobilized bacteria. The temperature of the water bath, and hence the reactor system, was set at 30 8C. This temperature was found to be the optimum in a preliminary runs which also agrees with previous studies in the literature [45]. The product from the bioreactor was then fed to the adsorption column, which was made of a Plexiglas column (50 cm in length and 3 cm inside diameter). The column was packed with 130 g of granular activated carbon. More details about the adsorption kinetics and equilibrium data as well as the regeneration of the saturated activated carbon can be found elsewhere [15,16]. At regular intervals, samples were collected from the effluent of each treatment unit and analyzed for COD and phenol concentrations. All experiments were carried out at room temperature.
[(Fig._2)TD$IG]
Fig. 2. A schematic diagram of the integrated system. (1) Feed tank, (2) feed pump, (3) electrocoagulation reactor, (4) magnetic stirrer, (5) DC power supply, (6) settling tank, (7) pump, (8) biological reactor, (9) adsorption column and (10) product tank.
[(Fig._4)TD$IG]
M.H. El-Naas et al. / Journal of Environmental Chemical Engineering 2 (2014) 56–62 Table 4 Operation conditions for the three unit system.
12
SBBR
Adsorption system
Electrodes type: aluminum PVA amount: 300 ml Adsorbent: AC Temperature: 30 8C Adsorbent mass: 130 g Current density: 3 mA/cm2 Current: 100 mA pH: 7.5 Room temperature 2 Area of the electrodes: 36 cm Air flow rate: 3 L/min Liquid flow rate: 10 ml/min Liquid flow rate: 10 ml/min Liquid flow rate: 10 ml/min
Phenol Concentration (mg/l)
Electrocoagulation
59
Results and discussion
10 8 6 4 2 0 Feed
The electrocoagulation unit, spouted bed bioreactor and adsorption column were connected in series with different configurations and operated continuously for the treatment of real refinery wastewater, which had a dark greenish color and a strong, pungent odor, with initial concentrations ranging from 3600 to 5300 mg/l and 11 to 14 mg/l for COD and phenol, respectively. The samples withdrawn after each treatment unit were analyzed for their COD content and phenol concentrations as a function of time. Table 4 summarizes conditions used in the experiment for each treatment unit.
EC
Adsorption
SBBR
Treatment Step Fig. 4. Phenol concentration after each treatment step for the refinery wastewater in electrocoagulation–adsorption–biodegradation system.
adsorption column then the concentration increases with time as the activated carbon gets saturated. Electrocoagulation–biodegradation–adsorption arrangement
Electrocoagulation–adsorption–biodegradation arrangement In this section, results for the arrangement of electrocoagulation–adsorption–SBBR are shown for the reduction of COD and phenol for about 3 h. Fig. 3 shows the COD reduction after each treatment unit, with the electrocoagulation pretreatment step contributing 46% to the overall reduction of COD. However, the reduction percentage increased to about 83% by passing the effluent through the adsorption column. The effluent from the adsorption is sent to the bioreactor, where the COD reduction is very low compared to the electrocoagulation and adsorption stages. The cumulative COD reduction after the biodegradation increased to only 85%. It is worth noting here that the adsorption column reached the saturation after the third hour which increased the load on the SBBR and consequently decreased the efficiency of the overall treatment process. Fig. 4 shows the reduction of phenol concentration for this system. There is no significant reduction in phenol concentration in the electrocoagulation unit, but a very high reduction occurs in the adsorption column which initially reduces the phenol concentration to zero in the first 3 h after the feed enters the
Figs. 5 and 6 show the effluent concentrations of COD and phenol at steady state conditions for electrocoagulation and after 24 h of operation for both biodegradation and adsorption systems. The results show that the electrocoagulation unit reduced the COD concentration by about 46%. The bioreactor further reduced the feed contaminants, which came from the electrocoagulation step, by about 73% for COD, 61% for the phenol. Nevertheless, most of the reduction in COD and other phenols has taken place in the adsorption unit, where the final cumulative reduction reached 97% and 100% for COD and phenol, respectively. The final effluent after the adsorption column had COD and phenol concentrations within the acceptable discharge limits. A summary of the complete system results is shown in Table 5, where after the last treatment step the effluent showed almost complete reduction for phenols and 97% reduction for COD content. To demonstrate the effectiveness using a combination of electrochemical process, biological treatment using SBBR and
[(Fig._5)TD$IG]
[(Fig._3)TD$IG] COD Concentration (mg/l)
4000
COD Concentration (mg/l)
4000
3000
2000
1000
3000
2000
1000
0
0 Feed
EC
Adsorption
SBBR
Treatment Step Fig. 3. The COD concentration after each treatment step for the refinery wastewater in electrocoagulation–adsorption–biodegradation system.
Feed
EC
SBBR
Adsorption
Treatment Step Fig. 5. The COD concentration after each treatment step for the refinery wastewater in electrocoagulation–biodegradation–adsorption system.
[(Fig._6)TD$IG]
[(Fig._7)TD$IG]
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60
100
Percentage Reduction %
Phenol Concentration (mg/l)
12 10 8 6 4
COD Phenol
80
60
40
20
2 0 EC
0 Feed
EC
SBBR
Table 5 Summary of the results of EC–SBBR–AD treatment system. SBBR
In
In
Out
Adsorption Out
EC-SBBR-AD
Fig. 7. Comparison for the percentage reduction of COD and phenol after individual unit treatment and the three units in series.
Fig. 6. Phenol concentration after each treatment step for the refinery wastewater in electrocoagulation–biodegradation–adsorption system.
Electrocoagulation
AD (8h)
Treatment Setup
Adsorption
Treatment Step
Test
SBBR
In
Out
pH 7.2 9.1 7.8 8.2 8.2 8.2 Conductivity (mS) 5.4 6.2 6.2 6.73 6.73 8.24 TSS (g/l) 0.072 0.244 0.11 0.17 0.05 0.01 TDS (g/l) 3.38 3.6 3.6 4.03 4.03 4.95 COD (mg/l) 4190 2267 2267 1116 1116 110 Phenol (mg/l) 12.2 8.1 8.1 4.8 4.8 0 m,p-Cresol (mg/l) 75 64 64 33 33 0
adsorption for treating refinery wastewater, results were compared to the percentage reduction for both COD and phenol after the treatment of such wastewater using the same continuous treatment units individually. Fig. 7 shows that biological method
could not be used as an individual treatment unit for the refinery wastewater treatment as a pretreatment step is needed in conjunction with this sensitive technology. Electrocoagulation reduced the contamination of the refinery wastewater by 46% and 34% for COD and phenol, respectively. Meanwhile, passing refinery wastewater through the packed bed of activated carbon showed a reduction of 65% and 85% for COD and phenol. However, the activated carbon was saturated after only 8 h of operation. On the other hand, 97% reduction for COD and a complete reduction of phenol were achieved when using the three units in series for a longer operating time of 24 h, giving a clear indication that this combination can be considered to be the most efficient unit arrangement and as one of the most effective alternatives for the treatment of refinery wastewater. A comparison of the percentage reduction in COD in this study with those reported in the literature using different combined processes for the treatment of several types of industrial wastewaters in batch and continuous studies is presented in Table 6. It shows that this combined process of electrocoagulation, spouted
Table 6 Comparison in the COD reduction using different combined treatment methods for the treatment of different industrial wastewater. Wastewater source
Combined treatment method
COD (mg/l)
COD % reduction
Ref.
1100–1300 2400 3500–4000 675 20 3279 312,000–588,800 28,000 117,100 3400 25 1700–2500 800–1200 1596–2598 1753
Winery Ammunition Leather Semiconductor Printed circuit board Paper industry Petroleum refinery
Fenton oxidation–membrane bioreactor (B) Electro-fenton + chemical precipitation Ozonation–sequencing batch biofilm reactor Fenton–sequencing batch reactor (SBR) Polyferric sulfate coagulation–fenton–sedimentation Chemical recovery + electrochemical Ultrafiltration + electrochemical Advanced oxidation (O3)–biodegradation Electrochemical–irradiation Electrocoagulation–sorption Electrocoagulation–electrooxidation Fenton’s peroxidation–coagulation Electrocoagulation–TiO2 photo-assisted Fenton–sequencing batch reactor (SBR) Electrocoagulation–optional dilution–aquatic plants Ultrasound–fenton Aerobic biological–fenton oxidation Fenton–sequencing batch reactor (SBR) Ferrite process–fenton method Ozonation-activated sludge process Microwave-assisted catalytic wet air oxidation
5500
77–80 88 97 89 96.9 100 93 91 95 84 >99 90 97 98 98.2 92 77 99.8 80 75.5 90
[25] [46] [47] [48] [49] [50] [33] [34] [35] [31] [30] [51] [29] [52] [32] [53] [37] [54] [55] [56] [10]
Continuous study Dyeing Textile Petroleum refinery
Electron beam + biological Fluidized biofilm + chemical coagulation–electrochemical oxidation This work
3220 870 4190
60 95.4 97
[26] [36]
Batch study Dyeing Rayon industry Tannery Antibiotic Biodiesel Olive mill Industrial wastewater
Pharmaceutical and cosmetic
10,168 1580 20 2533 80,000 406
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bed bioreactor (SBBR) and adsorption is highly competitive in comparison to other combination systems used for the reduction of COD in different industrial wastewaters. Conclusions Samples of heavily contaminated refinery wastewater with high concentrations of COD and phenols have been treated by a novel three-step process involving an electrocoagulation cell, a spouted bed bioreactor (SBBR) and adsorption column packed with activated carbon. The overall COD and phenol reduction reached 97% and 100%, respectively, indicating that the combined process was effective for the treatment of petroleum refinery wastewater and might offer a potential application for reusing the treated water and will significantly contribute to reducing freshwater consumption. The process was found to be highly competitive in comparison with other combined systems used in the treatment of industrial wastewater and can handle refinery or industrial wastewater with varying concentrations of contaminants. Work is currently underway at the pilot scale to further assess the technical and economic feasibility of the process. Acknowledgements The authors would like to acknowledge the financial support provided by the Japan Cooperation Center, Petroleum (JCCP) and the technical support of the JX Nippon Research Institute Co., Ltd. (JX-NRI). References ¨ gu¨tveren, Treatment of petroleum refinery waste¨ .B. O [1] Y. Yavuz, A.S. Koparal, U water by electrochemical methods, Desalination 258 (1–3) (2010) 201–205. [2] S.O. Rastegar, S.M. Mousavi, S.A. Shojaosadati, S. Sheibani, Optimization of petroleum refinery effluent treatment in a UASB reactor using response surface methodology, Journal of Hazardous Materials 197 (2011) 26–32. [3] A. Alva-Arga´ez, A.C. Kokossis, R. Smith, The design of water-using systems in petroleum refining using a water-pinch decomposition, Chemical Engineering Journal 128 (1) (2007) 33–46. [4] A. Coelho, A.V. Castro, M. Dezotti, G.L. Sant’Anna Jr., Treatment of petroleum refinery sourwater by advanced oxidation processes, Journal of Hazardous Materials 137 (1) (2006) 178–184. [5] B.H. Diya’uddeen, W.M.A.W. Daud, A.R. Abdul Aziz, Treatment technologies for petroleum refinery effluents: a review, Process Safety and Environmental Protection 89 (2) (2011) 95–105. [6] L. Yan, H. Ma, B. Wang, W. Mao, Y. Chen, Advanced purification of petroleum refinery wastewater by catalytic vacuum distillation, Journal of Hazardous Materials 178 (1–3) (2010) 1120–1124. [7] M.H. El-Naas, S. Al-Zuhair, A. Al-Lobaney, S. Makhlouf, Assessment of electrocoagulation for the treatment of petroleum refinery wastewater, Journal of Environmental Management 91 (1) (2009) 180–185. [8] L. Yan, H. Ma, B. Wang, Y. Wang, Y. Chen, Electrochemical treatment of petroleum refinery wastewater with three-dimensional multi-phase electrode, Desalination 276 (1–3) (2011) 397–402. [9] F. Shahrezaei, Y. Mansouri, A.A.L. Zinatizadeh, A. Akhbari, Process modeling and kinetic evaluation of petroleum refinery wastewater treatment in a photocatalytic reactor using TiO2 nanoparticles, Powder Technology 221 (2012) 203–212. [10] Y. Sun, Y. Zhang, X. Quan, Treatment of petroleum refinery wastewater by microwave-assisted catalytic wet air oxidation under low temperature and low pressure, Separation and Purification Technology 62 (3) (2008) 565–570. [11] P. Stepnowski, E.M. Siedlecka, P. Behrend, B. Jastorff, Enhanced photo-degradation of contaminants in petroleum refinery wastewater, Water Research 36 (9) (2002) 2167–2172. [12] C.E. Santo, V.J.P. Vilar, C.M.S. Botelho, A. Bhatnagar, E. Kumar, R.A.R. Boaventura, Optimization of coagulation–flocculation and flotation parameters for the treatment of a petroleum refinery effluent from a Portuguese plant, Chemical Engineering Journal 183 (2012) 117–123. ˘ an, R. O ¨ zcımder, Wastewater treatment at the petroleum [13] S¸. Demırcı, B. ErdoG refinery, Kirikkale, Turkey using some coagulants and Turkish clays as coagulant aids, Water Research 32 (11) (1998) 3495–3499. [14] D.U.B. Hasan, A.R. Abdul Aziz, W.M.A.W. Daud, Oxidative mineralisation of petroleum refinery effluent using Fenton-like process, Chemical Engineering Research and Design 90 (2) (2012) 298–307. [15] M.H. El-Naas, S. Al-Zuhair, M.A. Alhaija, Reduction of COD in refinery wastewater through adsorption on date-pit activated carbon, Journal of Hazardous Materials 173 (1–3) (2010) 750–757.
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