Introductıon

Groups of compounds present in the petrochemical industries include Polycyclic Aromatic Hydrocarbons (PAHs), which are listed as US-EPA and EU priority pollutants, and the concentrations of these pollutants therefore need to be controlled in treated wastewater effluents [1]. Due to the associated health concerns, some PAHs are possible or probable human carcinogens, such as benzo(a)pyrene and all PAHs which have four condensed rings pose these risks. Several hydroxy-PAHs such as hydroxylated derivatives of benzo(a)pyrene and chrysene have been shown to possess estrogenic activity and cause damage to DNA (the genetic material of life) leading to cancer and possibly other effects. There is concern that exposure to these PAHs may damage reproductive tissues and affect fertility in exposed organisms [2]. As a consequence of their strongly hydrophobic properties and their resistance to biodegradation, PAHs are not always quantitatively removed from wastewaters by activated sludge treatments, which very efficiently relocate them into treated effluents. Studies in recent literature showed that sonication may be a useful tool in degrading the aqueous pollutants [3]. The irradiation of high power ultrasound can result in acoustic cavitation, namely, the process of the formation, growth and implosive collapse of gas bubbles in liquids, releasing a mass of energies [4]. The literature data concerning the sonodegradation of PAHs is scarce, and, moreover, results are contradictory. Indeed, some works mentioned that PAHs are (i) oxidized by means of H, OH and OOH (hydrogen, hydroxyl and hydroperoxyl radicals) [5,6] whereas other studies argued that (ii) a pyrolytic process can occur [4,7] and finally that (iii) both processes are possible [8,9]. The first process is evidenced by the identification of hydroxylated by-products. These radicals can result in the destruction of solutes containing organic pollutants. In the second pathway the formation of hydroxylated by-products is not observed under ultrasonic irradiation; it is suggested that OH are not important species and PAH removals were performed via high-temperature pyrolysis [3]. The operating costs appear to be less severe than would be required by conventional thermochemical methods (e.g. wet air oxidation), which require high temperatures and pressures [10,11]. Furthermore, the sonication process does not require the use of extra chemicals (e.g. oxidants and catalysts) commonly employed in several advanced oxidation processes (e.g. ozonation, Fenton’s reagent), thus avoiding the respective costs as well as the need to remove the excess of toxic compounds prior to discharge. Among them, ultrasonic treatment has been used widely because of its relatively, low processing cost and high efficiency of reduction. Studies have shown that PAHs in water and wastewaters are degraded with ultrasonic treatment with stronger irradiation intensity and longer irradiation time.

Studies reported in recent literature show that sonication may be a useful tool in removing aqueous pollutants [8,10,12,13]. The sonication process is capable of effectively degrading target compounds including chlorophenols, chloroaromatics and PAHs present in dilute solutions, typically in the micro and nano ranges. Sonochemical destruction of pollutants in the aqueous phase generally occurs as the result of imploding cavitation bubbles and involves several reaction pathways and zones such as pyrolysis inside the bubble and/or at the bubbleliquid interface and hydroxyl radical-induced reactions at the bubble–liquid interface and/or in the liquid [1,12,14-16]. This process is capable of effectively degrading several target compounds including phenol, chlorophenols, nitrophenols, polychlorinated biphenyls, chloroaromatics, pesticides, dyes, polycyclic aromatic hydrocarbons and surfactants [6]. The operating costs appear to be less than those for conventional thermochemical methods (e.g. wet air oxidation), which require high temperatures and pressures [10]. Furthermore, the process does not require the use of extra chemicals (e.g. oxidants and catalysts) commonly employed in several advanced oxidation processes (e.g. ozonation, Fenton’s reagent), thus avoiding the respective costs as well as the need to remove the excess of toxic compounds prior to discharge [11]. In recent years, the technology of ultrasonic degradation has been studied and used extensively to treat some organic pollutants [17]. Irradiation with high power ultrasound can result in acoustic cavitation, namely, the process of the formation, growth and implosive collapse of gas bubbles in liquids, releasing energy [4]. The cleavage of chemical bonds, the oxidation and the pyrolysis and/or combustion of organic compounds are observed when chemistry is involved [18,19]. The literature data concerning sonodegradation of PAHs is scarce, and results are contradictory. Some work states that PAHs are (i) oxidized by means of H^●, OH^● and O₂H^● (hydrogen, hydroxyl and hydroperoxyl radicals) [10,20], whereas other studies argue that (ii) a pyrolytic process can ocur [21,22] and finally that (iii) both processes are possible [23,24]. The first process is evidenced by the identification of hydroxylated byproducts. These radicals can result in the destruction of solutes containing organic pollutants [25]. In the second pathway the formation of hydroxylated byproducts is not observed under ultrasonic irradiation; it is suggested that hydroxyl radicals are not important species and PAH radicals were formed via hightemperature pyrolysis [17].

Agro-industrial wastewaters such as Olive-oil Mill effluent wastewaters (OMI ww) are among the strongest industrial effluents since they cause considerable environmental problems (coloring of natural waters, a serious threat to aquatic life, pollution of surface and ground waters) particularly in the Mediterranean Sea region due to its high organic Chemical Oxygen Demand (COD), polyphenol and aromatic amines concentration [26].

The organic content of the OMI ww consists mainly of phenols, polyphenols, polyalcohols, sugars, tannins and pectins at concentrations as high as 200 g COD/l. [27]. The concentration of phenolic acids in the OMW may vary from as low as 0.05–0.2 g/l to as high as 10 g/l depending on the type and origin of the effluent [27]. The Total Aromatic Amines (TAAs) in the OMI ww are known to be carcinogenic and toxic [28,29].

Recently, significant interest has been shown in the application of ultrasound for the degradation of OMWs [30]. Sonochemical reactions are induced by directing sound waves into liquids, thereby producing cavitation bubbles [31]. Ultrasonicaction produces radicals such as H^●, OH^●, O₂H^●, respectively, and can be classified as an Advanced Oxidation Process (AOP) [32].

Significant numbers of studies were focused on the efficient treatment of the OMI ww including various chemical, physical, physicochemical and biological treatments or combinations of them [31,33]. Usually, the OMI ww is inappropriate for direct biological treatment and the alternative treatment technologies mentioned above did not give sufficient removals for pollution parameters (COD_dis, total phenol, color and aromatic amines). Recently, significant interest has been shown in the application of ultrasound for the degradation of the OMI ww [34]. Hydrophobic compounds with high volatility are easily and directly destroyed inside the cavitation bubbles [35]. Hydrophilic organic compounds are indirectly decomposed mainly through the reaction with OH^● that is produced during cavitation process. The highly reactive OH^● could diffuse from the cavitation bubbles to the interfacial region and bulk solution when large temperature gradient exist [35].

In this study, In Izmir (Turkey) PAHs removal efficiencies are low in petrochemical industry aerobic biological wastewater treatment plants because bacteria are not able to overcome the inhibition of these toxic and refractory organics. In order to increase total PAHs removal, sonication process was chosen among other Advanced Oxidation treatment Processes (AOPs) include sonication processes. The effects of ambient conditions, the effects of increasing sonication time (60 min, 120 and 150 min), increasing temperatures (25^o C, 30^oC and 60^oC), different hydrogen peroxide (H₂O₂) concentrations (100 mg/l, 500 mg/l and 2000 mg/l) on sonication at a Petrochemical Industry wastewater (PCI ww) treatment plant in Izmir (Turkey) and also additionally, Olive Mill Industry wastewater (OMI ww) containing toxic and resistant pollutants was investigated in 500 ml glass reactor, at 640 W sonication power, at 35 kHz sonication frequency. In the final stage of this study, the energy and costs used for the sonication process were compared in detail with other AOPs methods.

 

Materıals and Methods

Raw PCI ww

Raw PCI ww taken from the influent of the aeration unit of a PCI ww treatment plant in Izmir, Turkey were analyzed. The characterization of PCI ww was shown in Table 1.

 

Raw OMI ww

Olive Mill Effluent (OME) arises from the production of olive oil in olive mills. It is produced seasonally by a large number of small olive mills scattered throughout the olive oil-producing countries such as İzmir, Turkey. The characterization of OMI ww was shown in Table 2.

 

Configuration of Sonicator

A Bandelın Electronic RK510 H (Bandelin, Berlin, Germany) sonicator was used for sonication of the PCI ww and OMI ww samples. The sonication frequency and power were 35 kHz and 640 W, respectively. Glass serum bottles in a glass reactor were filled to 500 ml with raw ww and closed with teflon-coated stoppers for the measurement of volatile compounds (evaporation) of the raw ww. The evaporation losses of PAHs were estimated to be 0.01% in the reactor and, therefore, assumed to be negligible. The serum bottles were filled with 0.1 ml of methanol in order to prevent adsorption on the walls of the bottles and to minimize evaporation. Ultrasonic waves for 35 kHz frequency were emitted from the bottom of the reactor through a piezoelectric disc (4 cm diameter) fixed on a pyrex plate (5 cm diameter). The evaporation losses of volatile. Temperatures of 25^oC, 30^oC and 60^oC were adjusted electronically in the sonicator with two thermostatic heaters. The stainless steel sonicator was equipped with a teflon holder to prevent temperature losses. Recent studies showed that high ultrasound frequencies of 80 and 150 kHz did notincrease the yields of the parameters studied [36]. Therefore, they were studied at a sonication frequency of 35 kHz and at a power of 640 W. Increasing the sonication frequency did not increase the number of free radicals, therefore free radicals did not escape from the bubbles and did not produce enough OH ions [36,37].

 

Operational Conditions

Operational Conditions for PCI ww: The effects of ambient conditions (25^oC), increasing sonication time (60 min, 120 min and 150 min), sonication temperature (30^oC and 60^oC) and different H₂O₂ (100 mg/l, 500 mg/l and 2000 mg/l) concentrations on sonication of PCI ww taken from the influent of the aeration tank of a PCI ww treatment plant in Izmir (Turkey) were investigated. Fresh solutions of H₂O₂ were added to the PCI ww before sonication was begun. Sonicated samples were taken at 60 min, 120 min and 150 min and they were kept in a refrigerator at +4^oC until experimental analysis begun. Deionized pure water (H₂O) (conductivity of the system is 18 M/cm while the resistivity is 0.02 µsiemens) was obtained through a SESA, (Izmir-Turkey) Ultrapure water system. Reagent grade H₂O₂ (99% purity, from Sigma Chemicals Co., St. Louis, MO, USA, as analytical grades) were used during PAH analysis. Characterization of raw PCI ww taken from the influent of the aeration unit of a PCI ww treatment plant was given as the mean values of triplicate samplings (Table 1).

Operational Conditions for OMI ww: Fresh solutions of nano-sized metal oxides H₂O₂ (100 mg/l, 500 mg/l and 2000 mg/l) were added to the OMI ww by an peristaltic pump (Watson-Marlow Bredel pumps, USA) with a flow rate of 0.1 ml/min through 5 min before ultrasound (US) was begun at pH=5.4. Sonicated samples were taken at 60^th, 120^th and 150^th min of US time and were kept in refrigerator with a temperature of +4^oC for experimental analysis. Deionized pure H₂O (R ¼ 18 MΏ/ cm) was obtained through a SESA Ultrapure water system. All experiments were in batch mode by using an ultrasonic transducer (horn-type), which has five adjustable active acoustical vibration areas of 12.43, 13.84, 17.34, 26.4 and 40.69 cm² , with diameters 3.98, 4.41, 4.7, 5.8 and 7.2 cm, respectively, and a maximum input power of 640 W. Five ultrasound intensities (15.7, 24.2, 36.9, 46.2 and 51.4 W/cm²) were chosen to identify the optimum intensity for maximum removal of pollutant parameters (COD_dis, color, total phenol and TAAs) in the OMI ww while the sonicator power was 640 W. Samples were taken after 60 min, 120 min and 150 min of US time and they were analyzed immediately as mentioned in the recent studies [37].

 

Analytical Methods

Analytical methods for PCI ww: Sample preparation and PAHs analysis For PAH analyses the water samples were filtered through a glass fiber filter (47 mm-diameter) to collect particle phase in series with a resin column (∼10 g XAD-2) and to collect dissolvedphase polybrominated diphenyl ethers. Resin and water filters were ultrasonically extracted for 60 min with a mixture of 1/1 acetone: hexane. All extracts were analyzed for seventeen (17) PAHs [naphthalene (NAP), acenaphthylene (ACL), acenaphthene (ACT), fluorene (FLN), phenanthrene (PHE), anthracene (ANT), carbazole (CRB), fluoranthene (FL), pyrene (PY), benz[a]anthracene (BaA), chrysene (CHR), benz[b]fluoranthene (BbF), benz[k]fluoranthene (BkF), benz[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (IcdP), dibenzo[a,h]anthracene (DahA), benzo[g,h,i]perylene (BghiP)] with a gas chromatograph (GC) (Agilent Technology model 6890N) equipped with a mass selective detector (Agilent 5973 inert MSD). A capillary column (HP5-MS, 30 m, 0.25 mm, 0.25 µm) was used. The initial oven temperature was kept at 50^oC for 1 min, then raised to 200^oC at 25^oC/min and from 200^oC to 300^oC at 8^oC/min, and was then maintained for 5.5 min. High purity He (g) was used as the carrier gasat constant flow mode (1.5 ml/min, 45 1/cms linear velocity). PAHs were identified on the basis of their retention times, target and qualifier ions and were quantified using the internal standard calibration procedure. Temperature, pH, ORP, COD and TOC concentrations were monitored following Standard Methods 2550, 2580, 5220 D and 5310 [38].

 

Analytical methods for OMI ww: BOD₅ and COD were monitored following standard methods 5210 B and 5220 D, respectively [38]. Total-N, NH₄ -N, NO₃ -N, NO₂ -N, total-P and PO₄ -P were measured with cell test spectroquant kits (Merck) in a spectroquant NOVA 60 (Merck) spectrophotometer (2003). Oil, Na⁺¹ and Cl⁻¹, Total Suspended Solid concentration (TSS), Total Volatile Suspended Solid concentration (TVSS), Dissolved Oxygen (DO), pH, temperature T (°C) and Oxydation Reduction Potential (ORP, mV) were determined following Standard Methods 5520 B, 3550, 2540 C, 2540 E, 2550, 2580, respectively [38]. The measurement of color was carried out following the methods described by Olthof and Eckenfelder (1976) [39]. In order to identify the TAAs, OMI ww (25 ml) was acidified at pH=2.0 with a few drops of 6 N HCl and extracted three times with 25 ml of ethyl acetate. The pooled organic phases were dehydrated on sodium sulphate, filtered and dried under vacuum. The residue was sylilated with bis(trimethylsylil)trifluoroacetamide (BSTFA) in dimethylformamide and analyzed by GC-MS. Mass spectra were recorded using a VGTS 250 spectrometer equipped with a capillary SE 52 column (0.25 mm ID, 25 m) at 220°C with an isothermal program for 10 min. TAAs were measured using retention times and mass spectra analysis. The total phenol was monitored as follows: 40 ml of OMI ww was acidified to pH=2.0 by the addition of concentrated HCl. Phenols were then extracted with ethyl acetate. The organic phase was concentrated at 40°C to about 1 ml and silylized by the addition of N,O-bis(trimethylsilyl) acetamide (BSA). The resulting trimethylsilyl derivatives were analysed by GC-MS (Hewlett-Packard 6980/HP5973MSD). 2-PHE and 3-PHE concentrations were determined with Shimadzu CLASS-VPV6.14SP2 with Phenomenex Hyperclone 125 mm×4.6 mm×5 μm HPLC column using an ultraviolet (UV) method [27]. Aniline, 2,4,6 trimetylaniline and dimethylaniline measurements were carried out using a High Pressure Liquid Chromatograph (HPLC) (Agilent-1100) with a C-18 reverse phase HPLC column (25 cm×4.6 mm, 5 μm (Ace 5C-18)) following the method developed by EPA [28]. Detection was performed at 280, 214 and 216 nm wavelengths using a UV detector for aniline, 2,4,6 trimetylaniline and dimethylaniline, respectively. o-toluidine was determined using a HPLC (Agilent-1100) with a Spectra system model SN4000 pump and Asahipak ODP-506D column (150 mm×6 mm×5 μm). o-anisidine was measured in a HPLC (Agilent-1100) with UV detector at a mobile phase of 35% acetonitrile/65% H₂O at a flow rate of 1.2 ml/min. The column was 50 cm×2 mm ID stainless steel packed with μ-Bondapak C-18. Ethylbenzene and durene (1,2,4,5-tetramethylbenzene) measurements were performed with a GC-MS (GC-MS Agilent Technologies, 7890A (G3440A) GC System, 5975C Inert MSD7683B Series Injector) containing inlet split/splitless ratio of 50/1 with a HP-1 polymethylsiloxane 30 m×0.32 mm×ID 0.25 μm film thickness column (Hewlett-Packard) at 240°C. The carrier was helium (He) with a flowrate of 1.4 ml/min and column 60 m×0.25 m×ID 0.25 μm. The steady-state OH ion concentration [OH•] throughout sonication was calculated following the method proposed by [40], while the second-order reaction kinetics of aromatic amines and phenols were found [27,28].

 

Statistical Analysis

ANOVA analysis of variance between experimental data was performed to detect F and P values, i.e. the ANOVA test was used to test the differences between dependent and independent groups [41]. Comparison between the actual variation of the experimental data averages and standard deviation is expressed in terms of F ratio. F is equal (found variation of the date averages/expected variation of the date averages). P reports the significance level, d.f indicates the number of degrees of freedom. Regression analysis was applied to the experimental data in order to determine the regression coefficient R² [42]. The aforementioned test was performed using Microsoft Excel Program.

All experiments were carried out three times and the results are given as the means of triplicate samplings. The data relevant to the individual pollutant parameters are given as the mean with Standard Deviation (SD) values.

 

Results and Discussions

Effect of H₂O₂ Concentrations on the Removal of PAHs in PCI ww at Increasing Sonication Times and Temperatures

100 mg/l, 500 and 2000 mg/l H₂O₂ were added in PCI ww before the sonication experiments. 89.63%, 93.28% and 96.46% total PAHs removals were observed in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, at pH=7.0 and at 30^oC after 150 min (Figure 1a). An increase of 3.17% and 6.35% in total PAHs removals were measured in 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 30^oC, compared to the control (without H₂O₂ while E=90.11% total PAHs at pH=7.0 and at 30^oC). Although, a correlation between PAHs removals and H₂O₂ concentrations is observed, this relationship is not significant at pH=7.0 and at 30^oC after 60 min and 120 min at 30^oC (R²=0.80, F=2.87, p=0.001) (Figure 1a).

91.33%, 94.19% and 98.04% total PAHs removal efficiencies were obtained in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂ at 60^oC after 150 min, at pH=7.0 (Figure 1b). No significant increase in total PAHs yields was obtained by increasing the H₂O₂ concentrations compared to the control (E=96.90% for total PAHs at pH=7.0) at 60^oC (R²=0.40, F=3.87, p=0.001). The PAH yields in the samples containing H₂O₂ and none containing (control) samples were around 52.61%–57.90% and 77.22%-82.19%, respectively, at 60^oC after 60 min and 120 min, at pH=7.0. The maximum total PAHs removal efficiency was 98.04% after 150 min, in H₂O₂=2000 mg/l at pH=7.0 and at 60^oC (Figure 1b). The maximum COD_dis removal efficiencies were 93.19% COD_dis, at 2000 mg/l H₂O₂, at 60^oC, at pH=7.0 after 150 min in PCI ww, respectively (data not shown).

It was reported that this oxidant elevates the extent of PAHs removal through acoustic cavitation [3]. The similar degradation degree in the control and in the presence of H₂O₂ at 60^oC after 120 min and 150 min may be attributed to the increased level of hydroxyl radicals (OH^l) scavenging by the PAHs and by H₂O₂ itself. During the sonolysis of aqueous solutions, OH^l and H^l are generated by the thermolysis of H₂O in the solution medium and can scavenge OH^l produced. As the concentration of H₂O₂ in the solution is increased, it’s OH^l scavenging effect increases causing decrease in degradation of PAHs. It was reported that at very high H₂O₂ concentrations detrimental effects are observed, since the recombination reaction of OH^l is more predominant and H₂O₂ acts as a scavenger for OH^l [3]. The scavenging of free OH^l becomes the dominant process at high H₂O₂ concentrations in the system, thereby lowering the ability of OH^l to degrade PAHs. A similar trend has been reported in the sonolytic destruction of 5,5–dimethyl–1–pyrroline–N–oxide and oxalic acid using H₂O₂ [43].

H₂O₂ is an oxidizing agent. It was reported that this oxidant increases the extent of PAH removal through acoustic cavitation [3]. During the sonolysis of H₂O, OH^l is produced and recombined into H₂O₂, if no organic compounds such as radical scavengers are present in the H₂O. The formed H₂O₂ and its sonolytic decomposition products would have an effect on the degradation of organic compounds like PAHs during sonication. The H₂O₂ may be mainly present not inside the cavitation bubbles but in the bulk solution due to the high H₂O solubility and low volatility [6]. In our study, no significant total PAHs yields were obtained by the addition of H₂O₂. The scavenging of free OH^l becomes the dominant process at high H₂O₂ concentrations in the system, thereby lowering the ability of OH^l to degrade PAHs [3]. It is also possible that the presence of high H₂O₂ concentrations results in a lower intensity of cavitation, due to the fact that vaporous cavities will be generated in this case, as reported by Rae et al. (2005) [43]. This is not valid for our study since it was performed at high sonication intensity.

Since less hydrophobic PAHs are considerably non-volatile with low Henry’s law constant and solubility [9], sonodegradation inside the cavitation bubble is expected to be insignificant. Therefore, OH^l-induced reactions are likely to be the main degradation mechanism of less hydrophobic ones as follows in Equation 1 and Equation 2:

  (1) Refer in Pdf

 (2) Refer in Pdf

It should be pointed out that OH^l, formed via H₂O sonolysis, can partly recombine yielding H₂O₂ which in turn reacts with H₂ to regenerate OH^l in Equation 3 and Equation 4:

  (3) Refer in Pdf

  (4) Refer in Pdf

The formation of H₂O₂ during ultrasound irradiation was confirmed experimentally during sonication in the absence and presence of less and more hydrophobic PAHs. As the H₂O₂ concentration increased to 176 mg/l after 60 min the less hydrophobic PAHs removals increased to 96%-98% while the removals of more hydrophobic PAHs remained 60.24%-62.32% after 120 min. This process ends with decreasing of H₂O₂ to 5 mg/l. As less hydrophobic PAHs and its degradation metabolites scavenge OH^l (Equation 3 and Equation 4), the yield, defined as H₂O₂ formed in the presence of less hydrophobic PAHs over H₂O₂ formed in deionized H₂O.

 

Effect of H₂O₂ Concentrations on the Removals of COD_dis in OMI ww

Increasing H₂O₂ concentrations (100 mg/l, 500 mg/l mg/l and 2000 mg/l) were added in OMI ww before sonication process. 73.87%, 80.80% and 85.61% COD_dis removals were obtained in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 30^oC (Figure 2a).

89.09%, 91.13% and 93.19% COD_dis yields were measured in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 60^oC (Figure 2b). The contribution of increasing H₂O₂ concentrations were found as 38.34% - 44% and 28.58-32.77% on the COD_dis removals in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 60 min and 120 min, at pH=7.0 and at 60^oC, compared to the control at pH=7.0 and at 60^oC. The contribution of increasing H₂O₂ concentrations on the COD_dis yield were significant (R²=0.79, F=19.98, p=0.01). Sonication alone provided 66.83% COD_dis yield after 150 min, at pH=7.0 and at 60^oC. The maximum COD_dis removal efficiency was 93.19% in H₂O₂=2000 mg/l after 150 min, at pH=7.0 and at 60^oC. A significant linear correlation between COD_dis yields and increasing H₂O₂ concentrations was not observed (R²=0.65, F=3.32, p=0.01) (Figure 2b).

In this study, it was found that the COD_dis removal increased with H₂O₂ concentration and reached the maximum 93.19% by using 2000 mg/l H₂O₂. From this, we can evaluate that 0.02 mg/l of H₂O₂ was needed to the removal of 1 mg/l of COD with a COD_dis yield of 91.37% after 150 min. Sivasankar and Moholkar (2009) [44], estimated that the removal of 1 g of COD needs 2.04 g of H₂O₂. In this optimized condition, the maximum value of COD removal is at the level of 93% with H₂O₂ oxidation [44]. In this study, it is clear that 2000 mg/l of H₂O₂ is the optimum amount to obtain maximum decrease (93.19%) in COD_dis from OMI ww after 150 min, at 60^oC.

Organic compounds may be degraded either at the first two sites upon combined effects of pyrolytic decomposition and hydroxylation or in the solution bulk via oxidative degradation by H₂O₂ in OMI ww [45]. Under ultrasound irradiation, water (H₂O) is pyrolyzed, in which process H^l, OH^l, O^l and O₂H^l are produced and then react with organic pollutants measured as COD in the bulk solution or at the interface between the bubbles and the liquid phase [46]. During aqueous ultrasound irradiation, OH^l forms during the thermolytic reactions of H₂O and self-recombine to form H₂O_2. This showed that the sonodegradation of COD_dis in OMI ww occurred via hydroxylation.

In a study performed by Kallel et al. (2009) [47] a COD removal of 78% was found by sonication at 650 W and at 35 kHz in OMI ww. In this study, it was found that for the sonodegradation of 1 g COD 0.06 M of H₂O₂ is needed. In this study, 93.19% COD_dis removal was observed for 2000 mg/l H₂O₂, at 60^oC after 150 min. In the present study the COD_dis yield is higher than the yield obtained by Kallel et al. (2009) [47] at 60^oC.

 

Effect of H₂O₂ Concentrations on the Color Removal Efficiencies in OMI ww at Increasing Sonication Times and Temperatures

81.96%, 86.07% and 89.88% color removals were observed at 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 30^oC (Table 3). The contribution of 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂ to the color removals were 11.82%-33.56% and 19.73%-30.06% after 60 and 120 min, respectively, at pH=7.0 and at 30^oC, compared to the control at pH=7.0 and at 30^oC. The contribution of increasing H₂O₂ concentrations on the color yields were found to be significant (R²=0.76, F=15.09, p=0.01). Sonication alone provided 74.45% color removal after 150 min, at pH=7.0 and at 30^oC. A significant linear correlation between color yields and increasing H₂O₂ concentrations was observed (R²=0.81, F=14.78, p=0.01) (Table 3).

90.58%, 92.48% and 93.59% color yields were measured in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 60^oC (Table 3). 19.34%-28.76% and 7.51%-16.93% increase in color yields were observed in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 60 min and 120 min, at pH=7.0 and at 60^oC, compared to the control at pH=7.0 and at 60^oC. Control provided 83.77% color removal after 150 min, at pH=7.0 and at 60^oC. The maximum color removal efficiency was 93.59% in H₂O₂=2000 mg/l after 150 min, at pH=7.0 and at 60^oC. A significant linear correlation between color yields and increasing H₂O₂ concentrations was observed (R²=0.83, F=15.98, p=0.01) (Table 3).

A non-volatile organic substance is mainly eliminated by OH^l outside the cavitation bubble: a hydrophobic compound at the bubble-solution interface, while hydrophilic substrates into the bulk solution. Tannins and lignins are non-volatile compounds given color in OMI ww. Therefore, these organics cannot enter inside the bubble. Additionally, the positive charge of the nitrogen (N₂) atoms of the amine groups exhibiting hydrophilic properties to the benzene molecules which are giving the color to the OMI ww. As a consequence, under ultrasonic action, the removal of color must mainly occur through the reaction with OH^l in the bulk solution [48]. Under ultrasonic irradiation water sonodegraded to OH^l and H^l. As a results H₂O₂ is produced according to the Equation 5 and Equation 6:

  (5)  Refer in Pdf

  (6) Refer in Pdf

 If the solution is saturated with O₂ and O₂H, more OH^l are formed in the gas phase of microbubbles (upon the decomposition of molecular O₂), and the recombination of the former at the cooler sites (bubble–solution interface or the solution bulk) produces additional H₂O₂ (Ince et al., 2001) in Equation 7, Equation 8, Equation 9 and Equation 10:

  (7)  Refer in Pdf

  (8) Refer in Pdf

  (9) Referin Pdf

  (10)  Refer in Pdf

 

Effect of H₂O₂ Concentrations on the Total Phenol Removal Efficiencies in OMI ww at Increasing Sonication Times and Temperatures

 

79.20%, 82.30% and 84.74% total phenol removals were observed in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 30^oC (Table 4). 20.56%-21.17% and 21.89%-24.73% increase in total phenol yields were found in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 60 min and 120 min, at pH=7.0 and at 30^oC, compared to the control at pH=7.0 and at 30^oC. Sonication alone provided 59.40% total phenol after 150 min, at pH=7.0 and at 30^oC. The contribution of increasing H₂O₂ concentrations on total phenol removal were significant (R²=0.79, F=19.66, p=0.01) (Table 4).

85.48%, 90.42% and 93.65% total phenol yields were found in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 60^oC (Table 4). The contribution of increasing H₂O₂ concentrations were 19.93% - 45.12% and 20.65% - 28.38% in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 60 min and 120 min, at pH=7.0 and at 60^oC, compared to the control at pH=7.0 and at 60^oC. Control alone provided 61.24% total phenol after 150 min, at 60^oC. The maximum total phenol removal efficiency was 93.65% in H₂O₂=2000 mg/l after 150 min, at pH=7.0 and at 60^oC. A significant linear correlation between total phenol yields and increasing H₂O₂ concentrations was observed (R²=0.79, F=13.95, p=0.01) (Table 4).

Under ultrasound irradiation, water is pyrolyzed, in which process H^l, OH^l, O^l and O₂H^l are produced and H₂O then react with in the bulk solution or at the interface between the bubbles and the liquid phase [49]. During aqueous ultrasound irradiation, OH^l form during the thermolytic reactions of water and self-recombine to form H₂O₂ [50]. Kidak and Ince (2006) [51], determined that the controlling mechanism of sonochemical reactors in degradation of phenol is the production of free radicals and their subsequent attack on the pollutant species. It is accepted that H₂O₂ arises from the reactions of OH^l and O₂H^l in the liquid phase around the cavitational bubble and hence can be used to quantify the efficacy of reactors in generating the desired cavitational intensity. Sivasankar and Moholkar (2009b) [52], found that the generation of H₂O₂ increase linearly with time of ultrasonic irradiation without H₂O₂ addition while 66% total phenol removal was found after 100 min, at pH=4.8.

In a study performed by Mahamuni and Pandit (2006) [53], it was found only 7% phenol degradation after 90 min. The attack of OH^l on phenol was confined through sonication. The formation of the hydrophenols through sonication can be explained by the Equation 11, Equation 12 and Equation 13:

  (11)  Refer in Pdf

  (12)  Refer in Pdf

  (13)  Refer in Pdf

In this study, 93.65% total phenol removal was found in 2000 mg/l H₂O₂ at 60^oC after 150 min. The total phenol yield is higher than the yield obtained by Mahamuni and Pandit (2006) [53], at 60^oC as mentioned above.

 

Effect of H₂O₂ Concentrations on the TAAs Removal Efficiencies in OMI ww at Increasing Sonication Times and Temperatures

68.31%, 72.53% and 75.87% TAAs removals were obtained in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 30^oC (Figure 3a). The contribution of increasing H₂O₂ concentrations on TAAs removals were 19.71-20.54% and 11.19-12.39% in 100 mg/l, 500 and 2000 mg/l H₂O₂, respectively, after 60 min and 120 min, at pH=7.0 and at 30^oC, compared to the control at pH=7.0 and at 30^oC. Sonication alone provided 64.98% TAAs yield after 150 min sonication time at pH=7.0 and at 30^oC. A significant linear correlation between TAAs yields and increasing H₂O₂ concentrations was not observed (R²=0.44, F=3.71, p=0.01) (Figure 3a).

70.21%, 76.93% and 83.68% TAAs yields were observed in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 60^oC (Figure 3b). The contribution of increasing H₂O₂ concentrations on TAAs removals were 20.54%-24.88% and 9.76%-15.29% TAAs yields in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 60 min and 120 min, at pH=7.0 and at 60^oC, compared to the control at pH=7.0 and at 60^oC. Control provided 70.52% TAAs yield after 150 min, at pH=7.0 and at 60^oC. The maximum TAAs removal efficiency was 83.68% in H₂O₂=2000 mg/l after 150 min, at pH=7.0 and at 60^oC. A significant linear correlation between TAAs yields and increasing H₂O₂ concentrations was not observed (R²=0.49, F=4.84, p=0.01) (Figure 3b).

Amir et al. (2004) [54], reported that the H₂O₂ formation in OMI ww cannot be inhibited by TAAs. If it is assumed that the first step of the TAAs degradation results from OH^l reaction in a site close to the surface of the bubble, it should be a competition between reactions. The low TAA yields (48%) throughout sonication could be attributed to the modifications of some sonodegraded aliphatic chains to generate condensed aromatic structures containing large proportions of hydroxyl, methoxyl, carboxyl and carbonyl groups. In this study, 83.68% TAAs removal obtained after 150 min, at 60^oC. This TAAs yield is higher than the yield observed by Amir et al. (2004) [54] at 60^oC.

 

Effect of H₂O₂ Concentrations on the TFAs Removal Efficiencies in OMI ww at Increasing Sonication Times and Temperatures

82.75%, 84.75% and 86.72% TFAs removals were observed in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 30^oC (Figure 4a). The contribution of increasing H₂O₂ concentrations on TFAs removals were 28.38%-30.17% and 52.99%-58.66% in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 60 min and 120 min, at pH=7.0 and at 30^oC, compared to the control reactor at pH=7.0 and at 30^oC. Sonication alone provided 45.66% TFAs yield after 150 min, at pH=7.0 and at 30^oC. A significant linear correlation between TFAs yields and increasing H₂O₂ concentrations was observed (R²=0.74, F=15.61, p=0.01) (Figure 4a).

85.41%, 88.20% and 90.30% TFAs yields were found in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 150 min, at pH=7.0 and at 60^oC (Figure 4b). The contribution of increasing H₂O₂ concentrations on TFAs removals were 29.02%-31.71%, 53.77%-60.96% and 36.57-41.46% in 100 mg/l, 500 mg/l and 2000 mg/l H₂O₂, respectively, after 60 min, 120 mni and 150 min, at pH=7.0 and at 60^oC, compared to the control (E=48.84% TFAs after 150 min, at pH=7.0 and at 60^oC). The maximum TFAs removal efficiency was 90.30% in H₂O₂=2000 mg/l after 150 min, at pH=7.0 and at 60^oC. A significant linear correlation between TFAs yields and increasing H₂O₂ concentrations was observed (R²=0.82, F=16.13, p=0.01) (Figure 4b).

In a study performed by Jahouach-Rabai et al. (2008) [55], 89% TFAs removal was observed at 20 kHz, at 750 W, after 45 min, at 70^oC in an OMI ww. By increasing of H₂O₂ concentrations the TFAs concentrations decreased by oxidation of oleic acid and further degradation to hexanal. In this study, 90.30% TFAs removal was observed in H₂O₂=2000 mg/l at 60^oC after 150 min. The TFAs yield is higher than the yield obtained by Jahouach-Rabai et al. (2008) [55], at 70^oC as mentioned above.

 

Cost and Specific Energy Estimation

Cost Estimation Methodology: A very simple methodology was developed to arrive at the treatment costs of the various AOPs processes studied. First of all, data were collected from the published literature for all the AOPs involving the use of US and some standard commercial AOPs. Table 5 shows the various studies considered for this investigation along with their operating conditions. From this data, the kinetics of pollutant removal was found. If the kinetics is reported then it was taken from the literature as such; otherwise it was calculated from the data given in the literature using standard methods of finding kinetics [56,57]. By kinetics, we mean the order of degradation and the rate constant.

Table 6 depicts the kinetic data collected from these studies. These rate constants were then used to calculate the time required for 90% degradation of the pollutant from its initial concentration. This time was assumed as the residence time for the reactor for ww treatment using the given AOPs. The cost estimation was done for the assumed flow rate of 1000 l/min. The reactor capacity was calculated by multiplying the residence time with the design flow rate (1000 l/min). From the treatability study in the literature, the energy consumption data was then collected as energy dissipated per unit volume (W/ml). The total amount of energy required to treat the ww at the designed flow rate for given residence time was then calculated. From the quotations, which we had invited from manufacturers, we knew the amount of energy supplied by one commercial unit. Hence, the number of such commercial units required for dissipating the required energy was calculated. From the number of commercial units required, the capital cost of the ww treatment unit was calculated (AOP unit cost). This AOP unit cost was used to calculate the total capital cost using certain standard assumptions.

Similarly, total annual operating and maintenance cost was also calculated. The total capital cost was amortized at a rate of 7% over a period of 30 years to arrive at total amortized annual capital cost. Sum of the annual operating and maintenance cost and annual capital cost gave the total annual operating cost. Dividing this cost with the amounts of liters of ww treated in a year gave us the cost of ww treatment per 3.79 liter of H₂O treated. It was assumed that the plant is running throughout the year continuously.

The cost estimation of various ultrasonic AOPs for the elimination of phenol and reactive dyes was performed on the basis of the rate constants. Since the rate of degradation changes significantly with the experimental system, the reactor configuration and the operating conditions such as pH, ultraviolet (UV) intensity or US intensity etc., limited number of sources having similar operating conditions were considered. Kinetic data was collected from a limited number of sources in the literature (Table 6). Five sources were considered for phenol and three sources were considered for reactive dyes. The collected data was then compared with the kinetic data available for a number of other similar treatability studies in the literature to make sure that it is comparable with the reported values.

Adewuyi (2001) [58], has summarized results of a number of studies of ww treatment using ultrasonic processes. They have reported the rates of degradation for phenol, reactive dyes and a number of other hazardous compounds. Kidak and Ince (2006) [51] have recently reviewed the subject of phenol degradation using ultrasonic processes. Beckett and Hua (2001) [59], have described the degradation of phenols and chlorinated compounds and their mixtures using ultrasonic cavitation. Destaillats et al. (2000a) [60], and Destaillats et al. (2000b) [61], have reported the scale up of sonochemical reactors for ww treatment. They have also reported the rates of degradation for reactive dyes. It lies in the range of 0.002–0.045 1/min. Lesko (2006) [62], have reported the rates of degradation of phenol using a pilot station sonochemical reactor. The authors found that the rate of phenol degradation was in the range of 0.0011–0.063 1/min. Zheng et al. (2005) [63], have reported the rates of sonochemical degradation of phenol in the range of 0.014–0.061 1/min. Lesko et al. (2006) [62], have reported the rate of phenol degradation in the presence of ozone (O₃) and US to be in the range of 0.137 1/min. One can observe from Table 6 that the reported rates of degradation of phenol and reactive dyes are in the same range as are considered in this study. Hence, it can safely be said that the results of cost estimation of this study can at least provide an order of magnitude glimpse of the economics involved in the ww treatment using ultrasonic processes.

 

The Calculation of Energy Requirement in Sonication Reactor: From the referred publications or calculations from the data in the publications (energy density, ε), the total energy requirement in the AOP reactor is given by X ε watt [57]. From the manufacturer quotations, the energy supplied by single unit of AOP = E watt. The number of such standard commercial units required is given in Equation 14;

 (14)

where, N: The number of such standard commercial units; X: The total energy requirement in the AOP reactor (W); E: The energy supplied by single unit of AOP. Total cost of N units is given Equation 15:

Total cost of N units = Cost of AOP reactor =  (15)

where, C: Cost of each unit from the manufacturer=1000 $; P: Cost of AOP reactor ($)=1000 $

 

The Calculation of Energy Requirement in Sonication Reactor for PCI ww

 Refer in Pdf

In this study, for PCI ww;

X=640 W=0.64 kW

E=640 W=0.64 kW

N=(640 W) / (640 W)=1 units

P=Total cost of 1 units=Cost of AOP reactor=1000 $

In the present study, rate of electricity=0.165454 TL/kWh=0.11 $/kWh. In the present study for PCI ww; The total hourly electrical cost=0.165454 TL/kWh * 0.64 kWh=0.07 $/h.

 

The Calculation of Energy Requirement in Sonication Reactor for OMI ww

 Refer in Pdf

In this study, for OMI ww;

X=640 W=0.64 kW

E=640 W=0.64 kW

N=(640 W) / (640 W)=1 units

P=Total cost of 1 units=Cost of AOP reactor=1000 $

In the present study, for OMI ww; The total hourly electrical cost=0.165454 TL/kWh * 0.64 kWh=0.07 $/h.

General Calculation of Capital Cost in Sonication Reactor: The general calculation of capital cost for PCI ww and OMI ww during sonication process ARE presented in Table 7. The capital cost is amortized over a span of years at given amortization rate. Amortized capital cost (A) is given by following formula [64], in Equation 16:

 (16)

where, A: Amortized annual capital cost; r: Annual discount rate (assumption = 7%); 1.2S: Total capital cost; n: Life of project (assumption = 30 years) EE/O is kWh/m³/order

In this study; The total capital cost of US system=Cost of US System=1000 $/year. Using Equation 16, Amortized capital cost (A)=[(1500 Tl * 0.07) / {1-(1/(1+0.07))³⁰}]=80 $/year. Total amortized capital cost=A + Cost of US system=1080 $/year

 

General Calculation of Capital Cost in Sonication Reactor for PCI ww

 Refer in Pdf

In this study, for PCI ww;

r=7%=0.07

1.2S=5 N/ C=2.2 P

n=30 year

A=[(2.2 P * 0.07) / {1-(1/(1+0.07))³⁰}]=0.18 P=180 $

 

General Calculation of Capital Cost in Sonication Reactor for OMI ww

 Refer in Pdf

In this study, for OMI ww;

r=7%=0.07

1.2S=5 N/ C=2.2 P

n=30 year

A=[(2.2 P * 0.07) / {1-(1/(1+0.07))³⁰}]=0.18 P=180 $

 

The Compaırison of Cost for AOPs in Different Litearature Studies

Table 8 summarizes the cost estimation of some literature data performed with AOP and sonication including the cost results for PCI ww and OMI ww.

Capital Cost Calculations for US System

Capital cost estimation ($) of various AOPs for degradation given in Table 9. In this study; 1.5 TL=1 $ (was assumed). The total capital cost of US system=Cost of US System=1000 $/year. Using Equation (16), Amortized capital cost (A)=80 $/year. Total amortized capital cost=A + Cost of US system=1080 $/year. Table 9 summarizes the capital cost estimation in different AOPs and in PCI ww and OMI ww throughout sonication.

Operating and Maintenance (O & M) Cost Calculations for Sonication Process: The O&M (operating and maintenance cost) consists of labor costs, analytical costs, chemical costs, energy (electrical) costs and part replacement costs. Total O&M cost=labor cost + analytical cost + chemical cost + energy (electrical) cost + part replacement cost

Labor Cost for Sonication Process: The labor costs consisted of water sampling cost, general and specific system O&M costs. System specific operation and maintenance consisted of inspection, replacement and repair based on hours of service life. General O&M annual labor consists of general system oversight and maintenance such as pressure gauges, control panels, leakages etc.

For ultrasonic systems, it was assumed that sampling frequency (Sf)=2 samples/week; sampling time (St)=2 min/sample=0.033 hours/sample or 1 h/week and time required for O&M=17.16 h/year. Breakdown of labor costs ($) of various AOPs for degradation determined in Table 10.

In this study; US systems, the sampling frequency was taking 2 samples/day. It was assumed to be 52 weeks in 1 year. The sampling period was 2 min/sample=(2 min/sample) * (2 samples/day)=4 min/day=(4 min/day) * (1 h/60 min)=0.067 h/day=(0.067 h/day) * (5 days/week) =0.335 h/week.

In this study; Annual sampling labor=1 h/week * 52 weeks/year=52 h/year. Sampling labor hours=1 h/week: US system O & M=1 h/week * 52 weeks/year=52 h/year. Total annual labor hours=52 h/year + 52 h/year=104 h/year. The sample analysis labor cost is 30 TL/h. Total annual labor cost=104 h/year * 30 TL/h=2080 $/year. Table 10 summarizes the labor cost estimation in different AOPs and in PCI ww and OMI ww throughout sonication.

 

Analytical Costs for Sonication Process: Analytical costs were based upon sampling frequency, the labor required to do the analysis of the samples and the cost of chemicals required for analysis. These costs were considered at a rate of 200 $/h [65]. Analytical costs ($) of various AOPs for degradation shown in Table 11.

In this study; The sample analysis labor cost is 30 TL/h. Annual analysis labor=1 h/week * 52 week/year=52 h/year. Total annual labor hours=52 h/year. Total annual analysis labor hours=Annual analysis labor + Total annual labor hours=52 h/year + 52 h/year=104 h/year. Total annual analysis labor cost=104 h/year * 30 TL/h=2080 $/year. Table 11 summarizes the analitical cost estimation in different AOPs and in PCI ww and OMI ww throughout sonication.

Chemical Costs for Sonication Process: The chemical costs include the costs of consumables such as H₂O₂ (Table 12) These prices were obtained from standard industrial suppliers such as International Construction Information Society (ICIS) Pricing and Inframat Advanced Materials (2011). Chemical costs ($) of various AOPs for degradation indicated in Table 13.

The Annual Chemical Cost for H₂O₂ during Sonication Process: In the present study, 500 ml reactor volume was used during sonication process. For 500 ml sonication reactor=(1.5 TL/100 ml at 1 h) * 5=7.5 TL/500 ml at 1 h. For annual labor cost =52 h/year. The annual chemical cost for H₂O₂ during US system=7.5 TL/h * 52 h/year=260 $/500 ml ww in bottle for 1 year. Table 12 summarizes the annual chemical cost estimation in different AOPs and in PCI ww throughout sonication.

Electrical Cost for US System: Electrical costs were based on the power consumption by a given AOP. The electricity cost was calculated at a rate of 0.11 $/kWh. Power consumption was calculated for each AOP based upon the power consumed in a year multiplied by the electricity rate. Electrical costs ($) of various AOPs is demonstrated in Table 14.

In this study; Power consumption in the US system=The sum of power consumed by US system in 1 h=640 W/h=0.64 kW/h. Power consumption in the US system=The sum of power consumed by US system in 1 day=640 W/h * 5 h/day=3200 W/day= 3.20 kW/day. Power consumption in the US system=The sum of power consumed by US system in 1 week=640 W/h * 5 h/day * 5 days/week=16000 W/week=16 kW/week. Power consumption in the US system=The sum of power consumed by US system in 1 month=640 W/h * 5 h/day * 5 days/week * 4 weeks/month=64000 W/month=64 kW/month. Power consumption in the US system=The sum of power consumed by US system in 1 year=640 W/h * 5 h/day * 5 days/week * 52 weeks/year=832000 W/year =832.00 kW/year.

In this study, 1 kWh=3.60x10⁶ j=3.60x10³ kj. Electrical energy consumed index constant per hour is 1.083 kW/h. Total energy consumed in 1 h=(1.083 kW/h) * 0.64 kW/h=0.69 kW/h. Total energy consumed in 1 day=(1.083 kWh) * 3.20 kW/day * (24 h/day)=83.17 kWh/day. Total energy consumed in a week=(1.083 kWh) * 16 kW/week * (5 days/week) * 5 h/day=433.20 kWh/week. Total energy consumed in a month=(1.083 kWh) * 64 kW/month * (4 weeks/month) * (5 days/week) * (5 h/day)=6931.20 kWh/month. Total energy consumed in a year=(1.083 kWh) * (832 kW/year) * (52 weeks/year) * (5 day/week) * (5 h/day)=1171372.80 kWh/year. Rate of electricity=0.165454 TL/kWh=0.11 $/kWh.

In the present study; The total hourly electrical cost=0.165454 TL/kWh * 0.69 kWh=0.076 $/h. The total daily electrical cost=0.165454 TL/kWh * 83.17 kWh=9.174 $/day. The total weekly electrical cost=0.165454 TL/kWh * 433.20 kWh=47.78 $/week. The total monthly electrical cost=0.165454 TL/kWh * 6931.20 kWh=764.53 $/month. The total annual electrical cost=0.165454 TL/kWh * 1171372.80 kWh=129205.55 $/year. Table 5.207 summarizes the electrical cost estimation in different AOPs and in PCI ww and OMI wws throughout sonication.

 

Part Replacement Cost for Sonication Process: Part replacement cost may include bulb replacements for UV systems, O₃ generator parts for O₃ system, catalyst holder replacements for catalytic systems, tip replacements or electronic circuit replacements or transducer element replacements for ultrasound systems. The part replacement costs were assumed to be 0.5% of the capital cost [65,66]. For UV systems, the part replacement costs were assumed to be 45% of the annual electrical power consumption costs [71]. For O₃ systems, the annual part replacement cost was assumed to be 1.5% of the capital cost [65]. Part replacement cost ($) of various AOPs is shown in Table 15. In this study; Part replacement cost=0.5% of capital cost of US system=0.005 * 1500 TL/year=5 $/year. Table 15 summarizes the part replacement cost estimation in different AOPs and in PCI ww and OMI ww throughout sonication.

In the present study; Total O&M cost= total annual labor cost + total annual analytical cost + total annual chemical cost + total annual electrical cost + total annual part replacement cost. Total O&M cost=3120 TL + 3120 TL + 3380 TL + 193808.32 TL + 7.50 TL=203435.82 TL/year=135623.88 $/year.

In this study; Total annual operating cost for US system=Total amortized annual capital cost + annual O&M cost=1620 TL + 203435.82 TL/year=205055.82 TL/year=136703.88 $/year. Annual operating and maintenance (O&M) cost estimation ($) of various AOPs for degradation of some parameters are shown in Table 16.

In this study; The total annual cost = total annual labor cost + total annual analytical cost + total annual chemical cost + total annual electrical cost + total annual capital cost + total annual part replacement cost. Total annual cost=3120 TL + 3120 TL + 3380 TL + 193808.32 TL + 1500 TL + 7.50 TL=204935.82 TL/year=136623.88 $/year

General Procedure for Calculation of Electric Energy per Order (EE / O) or Electrical Energy per Unit Mass (EE / M)

 

EE/O Calculation for US System: Electric energy per order (EE/O) is the electric energy in kilowatt hours [kWh] required to degrade a contaminant by one order of magnitude in a unit volume (e.g., 1 m³ = 1000 l) of contaminated water or air [70]. This figure-of-merit is best used for situations where final concentration, (C_A, mg/l) is low (i.e., cases that are overall first-order in concentration of pollutant) because the amount of electric energy required to bring about a reduction by one order of magnitude in concentration is independent of (C_A). Thus, it would take the same amount of electric energy to reduce the contaminant concentration from 10 mg/l to 1 mg/l in a given volume as it would to reduce it from 10 μg/l to 1 μg/l. EE/O is, in general, a measure of operating cost. It allows for easy and accurate scale up to a full scales design and costs. EE/O is defined by Bolton et al. (2001) [70], as Equation 17.

  (17)

where, EE/O: Electric energy per order , (kWh/m³/order); P_elec: The input power (kW) to the AOP system; t: The irradiation time (min); V: The volume in liter of water in the reactor (l); C_AO: Initial concentration (mg/l); C_A: Final concentration (mg/l).

 

EE/O Calculation for US System in PCI ww: In this study, for PCI ww at 25^oC; at 640 W; at 150 min; at V=500 ml=0.5 l; COD₀=COD_influent=1027.43 mg/l; COD_effluent=203.835 mg/l.

EE/O=[0.64 kW * 150 min * 1000] / [0.5 l * 60 * log (1027.43/203.835)]=4481.80 kWh/m³/order COD_dis

The electrical cost=0.165454 TL/kWh * 4481.80 kWh/m³/order COD_dis=494.35 $/ m³/order COD_dis

 

EE/O Calculation for US System in OMI ww: In this study, for OMI ww at 25^oC; at 640 W; at 150 min; at V=500 ml=0.5 l; COD₀=COD_influent=109444 mg/l; COD_effluent=42779 mg/l

EE/O=[0.64 kW * 150 min * 1000] / [0.5 l * 60 * log (109444/42779)]=7804.88 kWh/m³/order COD_dis

The electrical cost=0.165454 TL/kWh * 7804.88 kWh/m³/order COD_dis=860.90 $/ m³/order COD_dis

 

EE/M Calculation for US System: For zero order degradations, EE/M (electrical energy per unit mass) is used instead of EE/O. EE/M is defined as Equation 18:

 Refer in Pdf  (18)

where; EE/M: Electrical energy per unit mass (kWh/kg/order); M: Mass (kg); P_elec: The input power (kW) to the AOP system; t: The irradiation time (min); V: The volume in liter of water in the reactor; C_AO: Initial concentration (mg/l); C_A: Final concentration (mg/l)

 

EE/M Calculation for US System in PCI ww: In this study, for PCI ww at 25^oC; at 640 W; at 150 min; at V=500 ml=0.50 l; COD₀=COD_influent=1027.43 mg/l; COD_effluent=203.835 mg/l.

EE/M=[0.64 kW * 150 min * 1000] / [0.5 l * 0.001 kg/g * 60 * (1027.43-203.835)]=3995.41 kWh/kg/order COD_dis

The electrical cost=0.165454 TL/kWh * 3995.41 kWh/kg/order COD_dis=440.70 $/ kg/order COD_dis

 

EE/M Calculation for US System in OMI ww: In this study, for OMI ww at 25^oC; at 640 W; at 150 min; at V=500 ml=0.50 l; COD₀=COD_influent=109444 mg/l; COD_effluent=42779 mg/l.

EE/M=[0.64 kW * 150 min * 1000] / [0.5 l * 0.001 kg/g * 60 * (109444-42779)]=48 kWh/kg/order COD_dis

The electrical cost=0.165454 TL/kWh * 48.00 kWh/kg/order COD_dis=5.30 $/ kg/order COD_dis

 

Specific Energy Calculations for US System

   Refer in Pdf

The specific energy was calculated according to the Equation 19:

 (19)

where, E_s: The specific energy for the maximum COD_dis removal after sonication process (kWh/kg COD₀); Sonicator power: The input power of sonicator during sonication experiments (W); Time: The sonication time during sonication process (h); (1 kj/1000 j): The equation of transformation from 1 kilojoule to 1 joule; V: The sample volume during sonication process (l); COD₀: Initial COD_dis concentration before sonication process (g/l); (1 kg/1000 g): the equation of transformation from 1 kilogram to 1 gram.

 

The Specific Energy (E_s) Calculation for US System in PCI ww: In this study, for PCI ww at 25^oC; at 640 W; at 150 min=2.50 h; at V=500 ml=0.50 l; COD₀=1027.43 mg/l=1.02743 g/l

E_s = {[(640 W * 2.50 h * 1 kj/1000 j)] / [(0.50 l * 1.02743 g/l * 1 kg/1000g)]}=3114.57 Wh / kg COD₀=3.12 kWh / kg COD₀

The electrical cost=0.165454 TL/kWh * 3.12 kWh/ kg COD₀=0.34 $/kg COD₀=0.27 $/kg COD₀

 

The Specific Energy (E_s) Calculation for US System in OMI ww: In this study, for OMI ww at 25^oC; at 640 W, at 150 min=2.50 h, at V=500 ml=0.50 l, COD₀=109444 mg/l=109.444 g/l.

E_s = {[(640 W * 2.50 h * 1 kj/1000 j)] / [(0.50 l * 109.444 g/l * 1 kg/1000g)]=29.24 Wh / kg COD₀ =0.03 kWh / kg COD₀

The electrical cost=0.165454 TL/kWh * 0.03 kWh/ kg COD₀=0.0033 $/ kg COD₀

 

The Cost Comparison of Anaerobic, Aerobic, UV, O₃ and Sonication Treatment: In this study, total enery consumed in a day was calculated to 83.17 kWh/day. The total energy consumed is equal to 83.40 kW/day to obtain 80% PAHs yields after 120 min with 1 l/min flow rate, at 640 W without additives [65,66]. In this study, the total energy consumed in a day is lower than total energy consumed in a day obtained by Melin (1999) [65] and Mahamuni and Adewuyi (2010) [66] as mentioned above.

In this study, the annual chemical cost of TiO₂, H₂O₂ and N₂(g) sparged were calculated as 136.84, 205.26 and 136.84 $/year, respectively. For TiO₂, H₂O₂ and N₂(g) sparged systems the annual chemical cost was calculated as 67, 60 and 40 $/year, respectively [65,66]. In this study, the total annual chemical cost of TiO₂, H₂O₂ and N₂(g) sparged is higher than the total annual chemical cost obtained by Melin (1999) [65] and Mahamuni and Adewuyi (2010) [66], as mentioned above.

In this study, the total annual cost was calculated as 134803.88 $/year with O₂(g) sparging condition including the labor costs, analytical costs, chemical costs, energy (electrical) costs, capital costs and part replacement costs. The removal of PAHs with UV, O₃ and photocatalytic processes the annual total cost increased to 7.35x10⁹, 1x10⁷ and 1.276x10¹⁰ $/year, respectively [65,66]. In this study, the total annual cost of O₂(g) sparged is lower than the total annual cost obtained by Melin (1999) [65] and Mahamuni and Adewuyi (2010) [66] as mentioned above.

Table 17 summarizes the cost comparison of anaerobic, aerobic, UV, O₃ and sonication treatment. The electrical energy requirements of conventional activated sludge process reported by Eckenfelder et al. (2008) [67], between 250 and 1000 kWh/m³ H₂O (=436800–1747200 $/year) with mechanic mixing and recycle pump equipment (1 kWh/m³ electric energy was assumed 0.30 TL m³/h). In this study, 129205.55 $/year total annual electrical cost was observed for sonication process in PCI ww and OMI ww. In this study, the total annual electrical cost is lower than the total annual electrical cost obtained by Eckenfelder et al. (2008) [67], as mentioned above

Tchobanoglous and Burton (1991) [68], determined the electrical energy requirements of CH₄(g) gas production from 60 to 100 kWh/m³ H₂O (=104832–174720 $/year) in an anaerobic digester. In this study, 129205.55 $/year total annual electrical cost was measured for sonication process in PCI ww and OMI ww. In this study, the total annual electrical cost is lower than the total annual electrical cost found by Tchobanoglous and Burton (1991) [68], as mentioned above.

Although, Zhang et al. (2008) [69], found the electrical energy requirement of sonication process only 1–10 kWh/m³ H₂O (=1747.20–17472 $/year) in a sonicator. In this study, 129205.55 $/year total annual electrical cost was measured for sonication process in PCI ww and OMI ww. In this study, the total annual electrical cost is higher than the total annual electrical cost obtained by Zhang et al. (2008) [69], as mentioned above.

Also, the electrical energy consumption of natural gas (biogas, etc) production was higher than 110 kWh/m³ H₂O (=192192 $/year) in an anaerobic digester reported by Tchobanoglous and Burton, (1991) [68]. In this study, 129205.55 $/year total annual electrical cost was calculated for sonication process in PCI ww and OMI ww. In this study, the total annual electrical cost is lower than the total annual electrical cost observed by Tchobanoglous and Burton (1991) [68], as mentioned above.

 

Conclusions and Recommendations

Conclusions

The sonication process does not require the use of extra chemicals (e.g. oxidants and catalysts) commonly employed in several AOPs (for instance, ozonation, Fenton’s reagent), thus avoiding the respective costs as well as the need to remove the excess of toxic compounds prior to discharge [10, 72-75]. The operating and maintenance (O&M) cost in sonication systems consists of labor costs, analytical costs, chemical costs, electrical costs and part replacement costs. For ultrasonic systems, the annual analysis labor time is 52 h/year (sampling frequency is 2 samples/week), sampling time (1 h/week) while the total annual labor cost is 2080 $/year. In the present study, the total annual analytical cost was calculated as 2080 $/year with sonication process in PCI ww and OMI ww at 35 kHz, at 640 W, at 500 ml, after 150 min. The capital cost and the part replacement costs in this study were 1000 $/year and 5 $/year, respectively.

In this study, the total energy consumed in this study was measured as 3.20 kW/day to obtain 79.65% total PAHs removal without additives at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC. The annual total energy utilization was 832 kWh/year while the annual total energy cost was 129205.55 $/year. The electricity cost was calculated at a rate of electricity of 0.11 $/kWh.

4481.80 and 7804.88 kW/m³/order COD electric energy per order (EE/O) values calculated in PCI ww and OMI ww, respectively, at 35 kHz, at 640 W, at 500 ml, without additives, after 150 min, at 25^oC. 741.53 and 1291.35 TL/m³/order COD electrical costs were obtained in PCI ww and OMI ww, respectively, for EE/O values during sonication process.

48 and 3995.41 kWh/kg/order COD electrical energy per unit mass (EE/M) values were measured in OMI ww and PCI ww, respectively, at 35 kHz, at 640 W, at 500 ml, without additives, after 150 min, at 25^oC. 7.94 and 661.06 TL/kg/order COD electrical costs were calculated in OMI ww and PCI ww, respectively, for EE/M values during sonication process.

0.03 and 3.12 kWh / kg COD₀ specific energy (E_s) values were calculated in OMI ww and PCI ww, respectively, at 35 kHz, at 640 W, at 500 ml, without additives, after 150 min, at 25^oC. 0.005 and 0.52 TL/kg COD₀ electrical costs were observed in OMI ww and PCI ww, respectively, for E_s values during sonication process (Table 18).

In this study, the total annual cost for only sonication (without additives) was calculated as follows: Total annual cost= total annual labor cost + total annual analytical cost + total annual electrical cost + total annual capital cost + total annual part replacement cost. 134370.55 $/year total annual cost was calculated for only sonication process without additives in PCI ww (Table 19).

In this study, the total annual cost of sonication with H₂O₂ addition was calculated as follows: Total annual cost with H₂O₂ addition=total annual labor cost + total annual analytical cost + total annual H₂O₂ chemical cost + total annual electrical cost + total annual capital cost + total annual part replacement cost. 134630.55 $/year total annual cost was calculated for sonication with H₂O₂ addition conditions in PCI ww.

Finally, sonication process is cheaper than that the anaerobic, aerobic treatment processes and the other AOPs processes. Sonication process is a cost-effective AOP for the treatment of toxic and recalcitrant compounds in PCI ww and OMI ww, compared to the anaerobic, aerobic, UV and O₃ treatment processes (Table 17).

 

The Evaluation of Specific Energies in COD_dis (E_s ), Electric Energy per Unit Volume in COD_dis (EE/O) and Electrical Energy per Unit Mass in COD_dis (EE/M) Values in PCI ww and OMI ww during Sonication Process with only Sonication.

 

The Evaluation of Specific Energies in COD_dis (E_s ), Electric Energy per Unit Volume in COD_dis (EE/O) and Electrical Energy per Unit Mass in COD_dis (EE/M) Values in PCI ww during Sonication Process with only Sonication

The specific energy in COD_dis (E_s ) parameter was calculated as 3.12 kWh / kg COD_dis in PCI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC with only sonication process. The cost of this specific energy for COD_dis (E_s ) parameter was found as 0.52 TL/kg COD_dis in PCI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC, with only sonication processs.

The electric energy per unit volume in COD_dis (EE/O) parameter was calculated as 4481.80 kW/m³/COD_dis in PCI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC with only sonication process. The cost of this electric energy per unit volume for COD_dis (EE/O) parameter was found as 741.53 TL/m³/COD_dis in PCI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC, with only sonication process.

The electric energy per unit mass in COD_dis (EE/M) parameter was calculated 3995.41 kWh/kg/COD_dis in PCI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC with only sonication process. The cost of this electric energy per unit mass for COD_dis (EE/M) parameter was found 661.06 TL/kg/COD_dis in PCI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC, with only sonication process.

 

The Evaluation of Specific Energies in COD_dis ( E_s ), Electric Energy per Unit Volume in COD_dis (EE/O) and Electrical Energy per Unit Mass in COD_dis (EE/M) Values in OMI ww during Sonication Process with only Sonication

The specific energy in COD_dis (E_s ) parameter was calculated 0.03 kWh / kg COD_dis in OMI ww at 35 kHz sonication frequency, at 640 W, at 500 ml, after 150 min, at 25^oC with only sonication process. The cost of this specific energy for COD_dis (E_s ) parameter was found 0.005 TL/kg COD_dis in OMI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC, with only sonication process.

The electric energy per unit volume in COD_dis (EE/O) parameter was calculated 7804.88 kW/m³/COD_dis in OMI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC with only sonication process. The cost of this electric energy per unit volume for COD_dis (EE/O) parameter was found 1291.35 TL/m³/COD_dis in OMI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC, with only sonication process.

The electric energy per unit mass in COD_dis (EE/M) parameter was calculated 48 kWh/kg/COD_dis in OMI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC with only sonication process. The cost of this electric energy/unit mass for COD_dis (EE/M) parameter was found 7.94 TL/kg/COD_dis in OMI ww at 35 kHz, at 640 W, at 500 ml, after 150 min, at 25^oC, with only sonication process.

 

The Disscussions of Specific Energy and Cost in PCI ww and OMI ww during Sonication Process with only Sonication and with the Addition of Some Chemicals

Less specific energy (3.12 kWh/kg COD_dis) is required to derive a better sonication treatment and cost savings for PCI ww treatment plants with only sonication and with the addition of some chemicals compared to the other AOP processes.

Less specific energy (0.03 kWh/kg COD_dis) is required to derive a better sonication treatment and cost savings for OMI ww treatment plants with only sonication and with the addition of some chemicals compared to the other AOP processes.

 

The Comparison of Anaerobic, Aerobic, Ultraviolet (UV), Ozone (O₃) and Sonication Treatment Processes

Anaerobic pretreatment is most effectively applied to wastewaters with high concentrations of readily degradable organic constituents. The cost-effectiveness of anaerobic pretreatment is specific to each wastewater and associated parameters (for example, ability to use biogas, power costs, sludge disposal costs) (Table 20).

For the operating and maintenance (O&M) cost components, off-site sludge disposal costs and macro-nutrients costs are linear functions of the wastewater strength for both treatment methods; however, absolute costs for the aerobic option are much higher. The energy requirement for aerobic treatment increases rapidly with wastewater strength, since aeration comprises most of the energy needs. For anaerobic systems, the electricity consumption is much lower and virtually constant for the influent strength range, since only pumping costs are incurred. Maintenance costs for both systems are considered aa function of capital costs in this analysis. Alkalinity requirements for anaerobic treatment are higher than for aerobic treatment and increase proportionately with influent strength. This is a consequence of the sensitivity of anaerobic processes to low pH upsets and the necessity to buffer volatile acids generated during the initial reaction step. Labor requirements for both treatment options are not a function of wastewater strength for the plant sizes considered. Heating is specific for anaerobic treatment only. Since heating is mostly a function of the wastewater flow (reactor volume), it does not increase with wastewater strength in the range considered. O&M costs of the anaerobic plant are credited with the biogas generated during the treatment, and the credits are proportional to the mass of organic matter removed (ww strength).

Although high energy requirement and high removal efficiencies observed with UV treatment methods in many industrial ww, however, high capital and high operating area are required for the UV treatment process. Energy requirement, startup time, operation time and capital cost of UV treatment are higher than sonication treatment for many industrial ww.

Although, high removal efficiencies provided with O₃ treatment process in many industrial ww, high capital cost and medium operating area are required for O₃ treatment process. Energy requirement, startup time, operation time and capital cost of O₃ treatment is higher than Sonication treatment for many industrial ww.

The PCI ww and OMI ww have been treated using biological treatment, physical-chemical treatment and their combinations. These processes cannot completely remove the COD_dis, TOC, total PAHs and toxicity in PCI ww. However, sonication process removed the COD_dis, TOC, total PAHs, and the acute toxicity with high yields. Similarly, the sonication process easily removed the COD_dis, TOC, color, total phenol, TAAs, TFAs and toxicity from the OMI ww.

The extent of sonodegradation is a function of sonication time and operating conditions such as US intensity, US frequency, sonication power, sonication temperature and initial concentration, and also depends on the presence of matrix species. These can produce more cavities and free radicals. They may have either a beneficial or detrimental impact on degradation depending on their type and function i.e. whether they act as radical promoters or scavengers. Furthermore, their presence may alter the physicochemical properties of the reaction mixture and consequently affect the cavitation process and associated reaction mechanisms and pathways.

The more hydrophobic PAHs with high benzene rings could be removed just as successfully as the less hydrophobic PAHs with lower benzene rings by sonication. The use of US in PAHs destruction presents unique advantages such as enhancement of mass transfer and removal yields, improvement of surface properties, and lowering of chemical consumption. Sonication is economical for effectively degrading and destroying way fort the all pollutant parameters and some intermediates in PCI ww and OMI ww.

Ultrasonic degradation of all classes of OMI ww is feasible due to free radical reactions, mainly OH^l. Hydroxylation was an important degradation mechanism of OMI ww with only sonication and the addition of some additives. Sonication treatment is economical for effectively degrading and destroying way COD_dis, TOC, color, total phenol, TAAs, TFAs and some intermediates in OMI ww with only sonication and the addition of some additives.

Sonication process works on the principle of generating free radicals and their subsequent attack on the contaminant molecules with the aim of either, completely mineralizing the contaminants or converting it into less harmful or lower chain compounds which cannot be efficiently treated by biological processes.

The sonolysis process can be removed the toxicity and can be increased the biodegradability of pollutant compounds. The chemicals are mineralized or degraded to smaller molecules with improved biodegradability or lower toxicity. The intensification of the organic matter solubilization induced by the ultrasonic action, can lead to an increase of the bioavailability of some micropollutants to the degrader consortium.

The combination of ultrasonic treatment with some additives and biodegradation represents a promising new technique in the field of environmental engineering. Toxic compounds inhibiting the microbial degradation processes can be removed by US.

The sonication process could prove to be less land-intensive, less expensive and require less maintenance and undergo lesser inhibition by the anions than other treatment processes in PCI ww and OMI ww with only sonication and the addition of some additives (Table 20).

 

Recommendations

The recommendations of this study were summarized as follows.

• Sonication process can be easily applied all kind of ww type with only sonication and with the addition of some additives. Sonication removal efficiencies can be increased with the addition of some chemicals (solids or gas bubbles to act as nuclei).
• The optimization of sonication frequency can be required before the sonication process for effectively cavitation reaction. The frequency of irradiation should be selected depending on the desired effects for the specific application, the higher frequency or combination of lower frequencies can be recommended for application dominated by chemical effects and lower frequency can be recommended for applications where the physical effects are controlling.
• The optimization of sonication power can be made before the sonication process for effectively reaction in acoustic cavitation. The optimization of sonication temperature can be done before the sonication process for effectively cavitation reaction.
• The optimization of sonication time can be made before the sonication experiments for effectively acoustic cavitation reaction. The optimization of sonication volume can be fixed before the sonication process for effectively cavitation reaction.
• The sonication process is recommended for the removal of toxic and refractory compounds from ww, compared to the other ww treatment processes.

Sonication process is recommended for the treatment of PCI ww and OMI ww containing toxic and refractory compounds. Sonication process can be applied as a pre-treatment or post-treatment in combination with other water purification processes (such as, AOPs).

 

Acknowledgements

This research study was undertaken in the Environmental Microbiology Laboratories at Dokuz Eylül University Engineering Faculty Environmental Engineering Department, İzmir, Turkey. The authors would like to thank this body for providing financial support.

 

Refer PDF.

Refer PDF

1. Banjoo DR, Nelson PK (2004) Improved ultrasonic extraction procedure for the determination of polycyclic aromatic hydrocarbons in sediments. J Chromatogr A. 1066: 9-18.
2. Gesto M, Tintos A, Rodriguez-Illamola A, Soengas JL, Miquez JM (2009) Effects of naphthalene, beta-naphthoflavone and benzo (a)pyrene on the diurnal and nocturnal indoleamine metabolism and melatonin content in the pineal organ of rainbow trout, Oncorhynchus mykiss. Aquatic toxicology. 92: 1-8.
3. Chakinala AG, Parag RG, Burgess AE, Bremner DH (2008) Treatment of industrial wastewater effluents using hydrodynamic cavitation and the advanced Fenton process. Ultrason Sonochem. 15: 49-54.
4. David B (2009) Sonochemical degradation of PAH in aqueous solution. Part I: monocomponent PAH solution. Ultrason Sonochem. 16: 260-265.
5. Destaillats H, Calussi AJ, Joseph JM, Hoffmann MR (2000) Synergistic effects of sonolysis combined with ozonolysis for the oxidation of azobenzene and methyl orange. J Phys Chem A. 104: 8930-8935.
6. Benabdallah T, El-Hadj S, Dosta T, Marquez-Serrano J, MataAlvaez R (2007) Effect of ultrasound pretreatment in mesophilic and thermophilic anaerobic digestion with emphasis on naphthalene and pyrene removal. Water Res. 41: 87-94.
7. Kojima Y, Fujita T, Ona P, Matsuda H, Koda S, et al. (2005) Effect of dissolved gas species on ultrasonic degradation of (4-chloro-2-methylphenoxy) acetic acid (MCPA) in aqueous solution. Ultrason Sonochem. 12: 359-365.
8. Kim IK, Huang CP, Chiu PC (2001) Sonochemical decomposition of dibenzothiophene in aqueous solution. Water Res. 35: 4370-4378.
9. Lindsey ME, Tarr MA (2000) Inhibiton of hydroxyl radical reaction with aromatics by dissolved natural organic matter. Environ Sci Technol. 34: 444-449.
10. Psillakis E, Goula G, Kalogerakis N, Mantzavinos D (2004) Degradation of polycyclic aromatic hydrocarbons in aqueous solutions by ultrasonic irradiation. J Hazard Mater. 108: 195-102.
11. Papadaki M, Emery RJ, Abu-Hassan MA, Diaz-Bustos A, Metcalfe IS, et al. (2004) Sonocatalytic oxidation processes for the removal of contaminants containing aromatic rings from aqueous effluents. Sep Purif Technol. 34: 35-42.
12. Mason TJ (2007a) Developments in ultrasound, non-medical. Prog Biophys Mol Biol. 108: 166-175.
13. Naddeo V, Belgiorno V, Kassinos D, Mantzavinos D, Meric S (2010) Ultrasonic degradation, mineralization and detoxification of diclofenac in water: optimization of operating parameters. Ultrason Sonochem 17: 179-185.
14. Mason TJ (2007b) Sonochemistry and the environment providing a ‘‘green’’ link between chemistry, physics and engineering. Ultrason Sonochem 14: 476-482.
15. Naddeo V, Belgiorno V, Rodolfo V, Napoli MA (2007) Behaviour of natural organic mater during ultrasonic irradiation. Desal. 210: 175-182.
16. van Iersel MM, Benes SI, Keurentjes JTF (2008) Importance of acoustic shielding in sonochemistry. Ultra Sonochem 15: 294-300.
17. Wang J, Ma T, Zhang Z, Zhang X, Jiang Y, et al. (2006) Investigation on the sonocatalytic degradation of parathion in the presence of nanometer rutile titanium dioxide (TiO2) catalysis. J Hazard Mater 137: 972-1080.
18. Suslick KS, Hammerton DA, Cline Jr RE (1986) The sonochemical hot spot. J Am Chem Soc. 108: 5641-5650.
19. Suslick KS (2000) Sonoluminescence and sonochemistry. Philos Trans Roy Soc London. A: 342-368.
20. Wheat PE, Tumeo MA (1997) Ultrasound induced aqueous polycyclic aromatic hydrocarbon reactivity. Ultrason Sonochem 4: 55-59.
21. Taylor JE, Cook BB, Tarr MA (1999) Dissolved organic matter inhibition of sonochemical degradation of aqueous polycyclic aromatic hydrocarbons. Ultra Sonochem 6: 175-183.
22. David B, Riguier D (2002) Ultrasonication of aqueous and micellar suspensions of anthracene fixed on silica. Ultra Sonochem 9: 45-52.
23. Laughrey Z, Bear E, Jones R and Tarr MA (2001) Aqueous sonolytic decomposition of polycyclic aromatic hydrocarbons in the presence of additional dissolved species. Ultra Sonochem 8: 353-357.
24. Little C, Hepher MJ, El-Sharif M (2002) The sono-degradation of phenanthrene in an aqueous environment. Ultrason 8: 667-674.
25. Taghizadeh MT, Mehrdad A (2009) Calculation of the rate constant for the ultrasonic degradation of aqueous solutions of polyvinyl alcohol by viscometry. Ultrason Sonochem 10: 309-313.
26. Paraskeva P, Diamadopoulos E (2006) Technologies for olive mill wastewater (OMW) treatment: a review. J Chem Technol Biotechnol. 81: 1475-1485.
27. Silva AMT, Nouli E, Carmo-Apolinario AC, Xekoukoulotakis NP, Mantzavinos D (2007) Sonophotocatalytic/H2O2 degradation of phenolic compounds in agro-industrial effluents. Catal Today. 124: 232-239.
28. Bertin L, Majone M, Di Gioia D, Fava F (2001) An aerobic fixed-phase biofilm reactor system for the degradation of the low-molecular weight aromatic compounds occurring in the effluents of anaerobic digestors treating olive mill wastewaters. J Biotechnol. 87: 161-177.
29. Valgimigli L, Sanjust E, Curreli N, Rinaldi A, Pedulli GF, et al. (2001) Photometric assay for polyphenol oxidase activity in olives, olive pastes, and virgin olive oils. J Am Oil Chem Soc. 78: 1245-1248.
30. Atanassova D, Kefalas P, Petrakis C, Mantzavinos D, Kalogerakis N, et al. (2005) Sonochemical reduction of the antioxidant activity of olive mill wastewater. Environ Int 31: 281-287.
31. Lafi WK, Shannak B, Al-Shannag M, Al-Anber Z, Al-Hasan M (2009) Treatment of olive mill wastewater by combined advanced oxidation and biodegradation. Sep Purif Technol. 70: 141-146.
32. Misik V, Miyoshi N, Riesz P (1995) An EPR spin trapping study of the sonolysis of H2O/D2O mixtures probing the temperatures of cavitation regions. J Phys Chem 99: 3605-3611.
33. Uğurlu M, Karaoğlu MH (2011) TiO2 supported on sepiolite: Preparation, structural and thermal characterization and catalytic behaviour in photocatalytic treatment of phenol and lignin from olive mill wastewater. Chem Eng J. 166: 859-867.
34. Khoufi S, Aouissaoui H, Penninckx M, Sayadi S (2004) Application of electrofenton oxidation for the detoxification of olive mill wastewater phenolic compounds. Water Sci Technol. 49: 97-102.
35. Pang YL, Abdullah AZ, Bhatia S (2011) Review on sonochemical methods in the presence of catalysts and chemical additives for treatment of organic pollutants in wastewater. Desalination 277: 1-14.
36. Sponza DT, Oztekin R(2010) Destruction of some more and less hydrophobic PAHs and their toxicities in a petrochemical industry wastewater with sonication in Turkey. Bioresource Technol. 101: 8639-8648.
37. Sponza DT, Oztekin R (2011) Contribution of oxides, salt, and carbonate to the sonication of some hydrophobic polyaromatic hydrocarbons and toxicity in petrochemical industry wastewater in İzmir, Turkey. J Environ Eng. 137: 1012- 1025.
38. Baird RB, Eaton AD, Rice EW (2017) Rice EW (editors), Standard Methods for the Examination of Water and Wastewater. 23rd. Edition, American Public Health Association (APHA), American Water Works Association (AWWA), Water Environment Federation (WEF). American Public Health Association 800 I Street, NW Washington DC: 20001-3770, USA.
39. Olthof M, Eckenfelder JrWW (1976) Coagulation of textile wastewater. Text Chem Color. 8: 18-22.
40. Villeneuve L, Alberti L, Steghens JP, Lancelin JM, Mestas JL (2009) Assay of hydroxyl radicals generated by focused ultrasound. Ultrason Sonochem. 16: 339-344.
41. Zar JH (1984) Biostatistical Analysis. Prentice-Hall, Englewood Cliffs, NJ, USA.
42. Statgraphics Centurion XV, software, (2005). (Statpoint, Inc). StatPoint, Inc. 2005, Statgraphics Centurion XV. Herndon, VA. USA.
43. Rae J, Ashokkumar M, Eulaerts O, Von Sonntag C, Reisse J, et al. (2005) Estimation of ultrasound induced cavitation bubble temperatures in aqueous solutions. Ultrasonics Sonochemistry. 12: 325-329.
44. Sivasankar T, Moholkar VS (2009a) Physical insights into the sonochemical degradation of recalcitrant organic pollutants with cavitation bubble dynamics. Ultrasonics Sonochemistry. 16: 769-781.
45. Entezari MH, Petrier C, Devidal P (2003) Sonochemical degradation of phenol in water: A comparison of classical equipment with a new cylindrical reactor. Ultrasonics Sonochemistry, 10: 103-108.
46. Goel M, Hongqiang H, Mujumdar AS, Ray MB (2004) Sonochemical decomposition of volatile and non-volatile organic compounds. A comparative study. Water Res. 38: 4247-4261.
47. Kallel M, Belaid C, Mechichi T, Ksibi M, Elleuch B (2009) Removal of organic load and phenolic compounds from olive mill wastewater by fenton oxidation with zero-valent iron. Chemical Engineering Journal. 150: 391-395.
48. Guzman-Duque F, Pétrier C, Pulgarin C, Peñuela G, Torres-Palma RA (2011). Effects of sonochemical parameters and inorganic ions during the sonochemical degradation of Crystal Violet in water. Ultrasonics Sonochemistry, 18: 440-446.
49. Suslick KS (1988) in Suslick K. S. (Ed.). In Ultrasound: Its chemical, physical and biological effects (129). VCH Publisher.
50. Petrier C, Francony A (1997) Ultrasonic wastewater treatment: incidence of ultrasonic frequency on the rate of phenol and CCl₄ Ultrasonics Sonochemistry. 4: 295-300.
51. Kidak R, Ince NH (2006) Ultrasonic destruction of phenol and substituted phenols: A review of current research. Ultrasonics Sonochemistry, 13: 195-199.
52. Sivasankar T, Moholkar VS (2009b) Mechanistic approach to intensification of sonochemical degradation of phenol. Chemical Engineering Journal. 149: 57-69.
53. Mahamuni NN, Pandit AB (2006) Effect of additives on ultrasonic degradation of phenol. Ultrasonics Sonochemistry, 13: 165-174.
54. Amir S, Hafidi M, Merlina G, Hamdi H, Revel JC (2004) Elemental analysis, FTIR, 13C-NMR of humic acids from sewage sludge composting. Agronomie, 24: 13-18.
55. Jahouach-Rabai W, Trabelsi M, Van Hoed V, Adams A, Verhe R, et al. (2008) Influence of bleaching by ultrasound on fatty acids and minor compounds of olive oil. Qualitative and quantitative analysis of volatile compounds (by SPME coupled to GC/MS). Ultrasonics Sonochemistry, 15: 590-597.
56. Fogler HS, Barnes D (1968) The shift in the optimal power input in an ultrasonic reaction. Industrial and Engineering Chemistry Fundamentals, 7: 222-229.
57. Fogler HS (2004) Elements of Chemical Reaction Engineering (4th ed.). New Jersey: Prentice Hall Publications, USA.
58. Adewuyi YG (2001) Sonochemistry: Environmental science and engineering applications. Industrial and Engineering Chemistry Research. 40: 4681-4715.
59. Beckett MA, Hua I (2001) Impact of ultrasonic frequency on aqueous sonoluminescence and sonochemistry. Journal of Physical Chemistry A. 105: 3796-3802.
60. Destaillats H, Colussi AJ, Joseph JM, Hoffmann MR (2000a) Synergistic effects of sonolysis combined with ozonolysis for the oxidation of azobenzene and Methyl Orange. Journal of Physical Chemistry A. 104: 8930-8935.
61. Destaillats H, Hung HM, Hoffmann MR (2000b) Degradation of alkylphenol ethoxylate surfactants in water with ultrasonic irradiation. Environental Science and Technology. 34: 311-317.
62. Lesko T, Colussi AJ, Hoffman M (2006) Sonochemical decomposition of phenol: evidence for a synergistic effect of ozone and ultrasound for the elimination of total organic carbon from water. Environmental Science and Technology. 40: 6818-6823.
63. Zheng W, Maurin M, Tarr MA (2005) Enhancement of sonochemical degradation of phenol using hydrogen atom scavengers. Ultrasonics Sonochemistry. 12: 313-317.
64. Zhou Y, Tol RSJ (2004) Implications of desalination for water resources in China-an economic perspective. Desalination. 164: 225-240.
65. Melin G (1999) Treatment technologies for removal of methyl tertiary butyl ether (MTBE) from drinking water: Air stripping, advanced oxidation processes, Granular activated carbon and synthetic resin sorbents, in: G.Melin (Ed.). Center for Groundwater Restoration and Protection, National Water Research Institute, CA.
66. Mahamuni NN, Adewuyi YG (2010) Advanced oxidation processes (AOPs) involving ultrasound for waste water treatment: A review with emphasis on cost estimation. Ultrasonics Sonochemistry. 17: 990-1003.
67. Eckenfelder WWJr, Patozka JB, Pulliam GW (2008) Anaerobic versus aerobic treatment in the USA. (105-114). A ware incorporated 227 French, Landing Nashnele TN 37228, USA.
68. Tchobanoglous G, Burton FL (1991) Anaerobic sludge digestion, Wastewater engineering, treatment, disposal and Reuse, (3rd ed.), (823-826). Singapore: Medcalf & Eddy, Inc., McGraw-Hill, Inc.
69. Zhang G, Zhang P, Gao J, Chen Y (2008) Using acoustic cavitation to improve the bio-activity of activated sludge. Bioresource Technology. 99: 1497-1502.
70. Bolton JR, Bircher KG, Tumas W, Tolman CA (2001) Figures-of-merit for the technical development and application of advanced oxidation technologies for both electric- and solar-driven systems (IUPAC Technical Report). The International Union of Pure and Applied Chemistry. 73: 627-637.
71. Hyman M, Dupont R (2001) Groundwater and soil remediation process design and cost estimating of proven technologies. Reston VA: ASCE Press.
72. Ince NH, Tezcanli G, Belen RK, Apikyan G (2001) Ultrasound as a catalyzer of aqueous reaction systems: The state of the art and environmental applications. Applied Catalysis B-Environmental, 29: 167-176.
73. International Construction Information Society (ICIS) Pricing and Inframat Advanced Materials. (2011).
74. Laughrey Z, Bear E, Jones R, Tarr MA (2001) Aqueous sonolytic decomposition of polycyclic aromatic hydrocarbons in the presence of additional dissolved species. Ultra Sonochem 8: 353-357.
75. United States Environmental Protection Agency (U.S. EPA) & Oregon Department of Environmental Quality [DEQ]. (2006). Portland harbor joint source control strategy. Final Report. Retrieved September 24, 2009.

Citation: Oztekin R, Sponza DT (2022) The Comparison of Energy Consumption and Costs Analysis in the Removal of Operating Parameters by Sonication in Petrochemical Industry Wastewaters and Olive Mill Industry Wastewaters with other Advanced Oxidation Processes. Open J Case Rep 3: 166