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Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF
G Model JIEC 3122 No. of Pages 9
Journal of Industrial and Engineering Chemistry xxx (2016) xxx–xxx
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Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF Mohammad Mehdi Amina,b , Mohammad Mehdi Golbini Mofradb,c,* , Hamidreza Pourzamania,b , Seyed Mohammad Sebaradara , Karim Ebrahima,b a Environment Research Center, Research Institute for Primordial Prevention of Non-communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran b Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran c Student Research Center, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran
A R T I C L E I N F O
Article history: Received 3 July 2016 Received in revised form 29 August 2016 Accepted 1 October 2016 Available online xxx Keywords: Industrial wastewater Metal working fluids (MWFs) Photo-Fenton DAF
A B S T R A C T
Post-treatment of the industrial wastewater polluted by metalworking fluids (MWFs) was performed using the photo-Fenton process in following of the chemical addition-dissolved air flotation (CA-DAF) unit. Prior to this study, the CA-DAF was operated as full-scale by trial and error. For the photo-Fenton process as a pilot-scale batch reactor, initial pH value, FeSO4, and H2O2 concentrations were considered to study the effect of different operating conditions on chemical oxygen demand (COD) and total petroleum hydrocarbon (TPH) removals. This hybrid approach revealed removal efficiencies of 99.85% and 98.9% for COD and TPH in the optimized photo-Fenton process as pH 3, FeSO4: 100 mg/l, and H2O2: 17.8 g/l. The COD degradation results for the photo-Fenton system indicated that it could be well fit using a pseudo firstorder kinetic model. By the GC–MS analysis of DAF and applied photo-Fenton effluents, a 73% removal rate of mono(2-ethylhexyl) phthalate was detected. It is likely favorable to increase the biodegradability. The cost analysis of this process for the consumed energy (6 kWh) and chemicals (0.01818 kg FeSO4 and 17.15 kg H2O2) was estimated at approximately 26 $ per 1 m3 of DAF effluent. Generally, these results imply that the CA-DAF unit followed by photo-Fenton is an effective and practical method for treating MWFs wastewater. ã 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Introduction Metalworking fluids (MWFs) are generally used in manufacturing industries (e.g., tooling industry). These fluids are deliberately added to applied water in metal machining operations to cool and lubricate or inhibit rusting of contact place between machining tools and working fragment. It also has other benefits, such as the removal of small metal scraps by washing, tool protection against corrosion, tool life improvement, friction diminution in fragment and tool interface, and altogether the final quality development of products [1–3]. Despite these advantages, MWFs is known as the main source of oily wastewater in the metal industries sector with
* Corresponding author at: Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran. E-mail address: [email protected] (M.M. Golbini Mofrad).
high chemical oxygen demand (COD), approximately 10,000– 100,000 mg/l [4,5]. MWF formulations are chemically complex and composed of base mineral oil, emulsifiers and surfactants, extreme pressure and anti-weld agents, corrosion inhibitors, biocides (phenolic and aliphatic derivatives), foam inhibitors, friction reduction agents, and alkaline reserve compounds [6–8]. Owing to the presence of all these compounds and microbial agents (bacteria and fungi), which have proven toxic effects, MWFs are non-biodegradable and hazardous and are associated with diseases such as cancer, skin disease, respiratory disease, and other diseases [5,7,9]. It is estimated that more than 2,000,000 m3 MWF are annually used worldwide and that wastewater volume by dilution of MWFs prior to use could be ten times higher [1,6,10,11]. Because of the complicated chemical contents as trade secrets for MWFs producers, the disposal of related wastewater is progressively difficult [7]. Further, since the MWFs are categorized as
http://dx.doi.org/10.1016/j.jiec.2016.10.010 1226-086X/ã 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010
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hazardous wastes along with relative toxicity to aquatic organisms, disposal options for this oily waste is expensive [12]. For the disposal of used MWFs, conventional physical and chemical techniques or minimization approaches are typically used, and generally have single or multiple stages, depending on the stage of treatment needed. In the multiple stage systems, solids and oil phase during the elementary phase is removed, and then the volume and COD loading are reduced by the secondary stage. Finally, for compliance with severe discharge limits, posttreatment is usually appropriate to develop the effluent quality [1]. The toxicity of these fluids is an obstacle because all biological treatment processes need high concentrations of organic compounds with low molecular weight and BOD/COD ratio higher than 0.4 (a desirable value) [4,5,13]. Considering the stable nature of these fluids in high pressures and temperatures, MWF wastewater treatment can be chemically and biologically laborious. Applying the existing approaches or processes requires further refining costs [5]. Evaporation, thermal splitting, and incineration are the most predominant disposal methods, while the latest technique releases a lot of air pollutants (e.g., NOx, SO2, HCl) [6–8]. Therefore, we have the risk of untreated wastewater discharge to soil and water resources, such as rivers, lakes, and so on, at any time and any place [5]. Other used treatment options for these recalcitrant wastewaters are chemical stabilization, electrocoagulation, and coagulation along with dissolved air flotation (DAF) [14], microfiltration [15], flow equalization, gravity separation of free oil, chemical emulsion breaking, flocculation (DAF), and clarification/filtration for oil removal [10], coagulation–flocculation [4], advanced oxidation processes, photo-Fenton oxidation system, and Fenton oxidation [16–19]. MWFs treatment problem will not likely be solved with all mentioned approaches (apart from incineration), because of emulsion splits to water and oil phases and thus require additional utilization; further, the defects of these procedures are their inability to completely remove inorganic/organic, volatile/ semi volatile compounds, and COD [17,20]. Hence, post-treatment is necessitated for the effluent of each process [17]. Furthermore, applying two or more techniques in combination is more efficient than one [7]. The hybrid technologies were studied by a series of researchers incorporating biodegradation and advanced oxidation process [1], coagulation process combined with mechanically induced air floatation [21], and coupling coagulation and DAF [14], as well as other coupled approaches [5,6,8,22]. In general, the
integrated approach is considered as the best option for complex wastewaters [23]. Air flotation, in all its varieties, is an efficient technique to separate light particles and oils from wastewater. DAF not only is more efficient and faster than sedimentation techniques, but also produces minor sludge volumes [24,25]. The organic matter removal by this technique can be higher than 98%, depending on the main operating parameters (e.g., saturation time and separation time and pressure, size and diameter of the gas bubbles, and chemical additive dosage) [14,25,26]. The photo-Fenton can be divided into two phases with regard to hydroxyl radical (OH) formation. First, in Fenton reaction, ferrous iron oxides are oxidized into ferric iron oxides in the presence of hydrogen peroxide (Eq. (1)) [27]. In the next step, ferric oxides generated in the Fenton reaction are photo-catalytically transformed to ferrous ions (Eq. (2)) [16].
Fe2þ þ H2 O2 ! Fe3þ þ HO þ OH
k ¼ ð63 76Þ M1 S1
hv
½FeðOHÞ2þ ! Fe2þ þ HO þ Hþ
ð1Þ
ð2Þ
In the presence of organic matter, hydroxyl radical reacts with this, increasing the oxidized products (Eq. (3)) [16,28].
chain propagation
HO þ RH
!
R þ H2 O
ð3Þ
The aim of this research was the evaluation of COD, total petroleum hydrocarbon (TPH), and oil removal efficiencies by the photo-Fenton reaction as post-treatment coupled with a full-scale DAF unit. The specific goals of this work, considering COD and TPH as indicators, were to determine: (1) the effect of the reagent concentrations (FeSO4, H2O2) and initial pH value in COD and TPH removal, (3) the synergistic effect of FeSO4, H2O2, and ultraviolet (UV) radiation in the optimized condition, (4) the organic matters analysis, (5) the removal kinetics of COD, and (6) cost analysis for running of process in optimized condition. Materials and methods Reagents and chemicals Hydroxyl radicals were provided by hydrogen peroxide (H2O2; 30%, Catalog Number 1085979025) as oxidant and ferrous sulfate
Fig. 1. The pilot-scale photo-Fenton unit coupled with a full-scale Chemical Addition-Dissolved Air Floatation (CA-DAF) system.
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010
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heptahydrate (CAS Number 7782-63-0) as a catalyst. The pH adjustment of wastewater solution into the pilot also was performed by injection of concentrated sulfuric acid (H2SO4; 98%, CAS Number 7664-93-9) and sodium hydroxide (CAS Number 1310-73-2). The COD over measuring problem affected by H2O2 solved with adding MnO2 (CAS Number 1313-13-9) to samples [29,30]. N-pentane 99% (CAS Number 109-66-0) was applied for sample extractions. Raw wastewater characteristics In this study, the water contaminated by semi-synthetic MWF, density: 1.0186 g/cm3 and viscosity: 138 centipoises, from the machining industries in the center of Iran, was used as influent wastewater. Semi-synthetic MWFs are the type of water based MWFs which typically contain 2–50% of mineral oil and also compounds used in synthetic MWFs [31]. The wastewater was collected in the storage tank before injection to a full-scale DAF unit in downstream of the cutting hall (Fig. 1). Table 1 indicates the physicochemical parameters of MWF wastewater.
3
and sampling throughout the pilot and preventing the liquid return from the pump to the tank. Photo-Fenton process procedures The recirculation tank was filled with 5.5 l DAF effluent. Then, the operation condition for a pre-test run was considered as (1) the recirculation pump was turned on (at the recirculation flow rate was mentioned in wastewater volume) and the initial pH of the solution was regulated in 3, simultaneously, (2) the UV lamp and the mechanical stirrer were turned on, and the solution of 40 mg/l (100 ml) FeSO47H2O was injected, (3) the timing (100 min total) of the first run was started along with the beginning of slow injection H2O2 (60 ml total, at a rate of 0.85 ml/min) during the first 70 min of reaction, (4) at the end of reaction, duplicate samples (each 20 ml) was taken for the sampling time [32,33], and (5) for the next runs, with fixing all variables (pH, FeSO4, H2O2) except for one, the study progressed step-by-step, obtaining optimal conditions of treatment to optimal variables. All the experiments have been conducted with the same wastewater, and because of the lack of biological and chemical interactions in the DAF effluent storage tank, data variations were negligible for quality characteristics.
DAF unit in treatment step Analytical determinations The first stage of physicochemical treatment of the wastewater was performed using a full-scale Chemical Addition-Dissolved Air Floatation (CA-DAF) system placed in a chemical treatment plant as batch mode operation and periodical treatment. In each treatment period, wastewater volume and loading rate in DAF inlet were 7 m3 and 35–40 l/min. Current and optimized operating conditions were found by trial and error: aeration rate 15–20 l/min, and pressure was set at 3 bar and the saturation time of 30 min, injected to its wastewater volume after filling floatation cells. The dosage of chemical additives used per 7 m3 of wastewater is shown in Table 2. Then, DAF effluent was discharged to a storage tank. Photo-Fenton process of pre-treated wastewater Apparatus and experimental set-up The photo-Fenton process performed in the pilot-scale unit (operated batch mode) as shown in Fig. 1. This unit consisted in a one-liter capacity photochemical reactor, as a packed plexiglas chamber with a 20 W and low-pressure mercury vapor UV lamp with a quartz glass sleeve and steel shield. It was connected to a five-liter capacity pyrex-glass recirculation tank surrounded by a water jacket chamber for adjusting to the desired temperature (26 2 C). The recirculation tank was equipped with a mechanical stirrer (490 10 rpm) for mixing the tank content (3.5 l). Therefore, the pilot content of wastewater under treatment by considering the recirculation pump and fittings volume (1 l) reached 5.5 l. The recirculation flow rate (Qr) between the photochemical reactor and recirculation tank was controlled to 12 l/min by means of a centrifugal pump. A set of valves was applied for flow rate control
Measurement of BOD5, TP, TOC, and oil to samples was performed in accordance with the standard methods [34]. In the oil analysis, samples extracted by Freon solvent (1,1,2-trichlorotrifluoroethane; 99%, CAS Number 76-13-1) and standards (from 0 ppm to 100 ppm) for quantification were finally analyzed by Shimadzu IR-470 instrument [35]. For the COD analysis, raw and treated wastewater samples were spectrophotometrically tested by applying Hack Lange cuvette test (Hack Lang, Dusseldropf) and measured with a Hach Lange DR 5000 Model spectrophotometer (Hach Lange, Dusseldropf). The dissolved oxygen (DO) concentration and temperature were monitored by Waterproof DO 300 Dissolved Oxygen Meter. The pH adjustment and ORP checking were measured by WTW pH 330i pH & Redox messgerät im Koffer. The total dissolved solids (TDS) and electrical conductivity (EC) were obtained by WTW Cond 330i Conductivity Meter. The total organic carbon (TOC) was measured by a Shimadzu TOC-5000A TOC analyzer [18]. In addition, TPH analysis of samples from sampling and preservation to gas chromatography (GC) analysis performed in pursuant to Texas Natural Resource Conservation Commission (TNRCC-1005) with some modifications [36]. For this goal, the extracted samples were finally injected to A7890/C5975 GC–MS system (Agilent, USA) equipped with a CP-Sil 5 CB capillary column (30 m long, 0.25 mm ID, and 0.25 mm film). TPH standardization was performed with unleaded gasoline, and correlation for the achieved calibration curves is 0.99 as Eq. (4): y ¼ 9:8307x þ 1615:6
TPH concentration of the aqueous samples was obtained by using Eq. (5) [36]: C s ¼ ðC c V t DÞ=W s
Table 1 MWF wastewater characteristics. Parameter
Value
TPH (mg/l) COD (mg/l) TOC (mg/l) Oil & grease (mg/l) BOD5 (mg/l) BOD5/COD pH Suspended solids (mg/l) Turbidity (NTU)
3200 20 35000 500 5800 25 15500 500 280 17 0.008 4 9 0.2 5700 32 710 6
ð4Þ
ð5Þ
Cost analysis Power consumption was calculated using Eq. (6), developed by Bolton et al. [37]: EEO kWh m3 ¼
P t 1000 C V 60 log Cefinff
ð6Þ
where EEO: modified electrical energy per order that is the energy in kWh required for achieving 90% destruction of pollutants in 103 l
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010
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Table 2 Chemical dosage used in DAF unit per 7 m3 of MWF wastewater under treatment. Chemical
FeCl3 (as coagulant)
Micronized CaCO3
NaOH
Poly-aluminum chloride (flocculant)
Hydrogen peroxide
80 kg
15 kg
18.5 kg
0.05 kg
2.75 kg
of wastewater, P: lamp power in kW, t: irradiation time in min, V: volume of the treated wastewater in liters, Cinf: influent COD concentration in mg/l, and Ceff: effluent COD concentration in mg/l. Chemical costs were estimated based on the trading price unit for H2O2 (30%) and FeSO47H2O to 103 l of the treated wastewater at the optimized condition (90% efficiency) of the photo-Fenton process. Results and discussion CA-DAF unit was operated with the condition mentioned above. Under this circumstance, treatment parameters in the effluent are presented in Table 3. Knowing the effluent quality at this treatment step, the study was progressing toward photo-Fenton experiments that were performed as a pilot-scale batch reactor. The purpose of these experiments was to obtain the suitable operational condition for the photo-Fenton process at the post-treatment of DAF in order to reduce the impact of final MWF effluent discharge into natural water streams (e.g., rivers) and resources (e.g., pools), or even the biological and membrane approaches to industrial wastewater treatment with higher goals (e.g., reuse). Effect of the initial pH value and reagents The pilot-scale unit was charged seven times, with DAF effluent for evaluation of the pH role in the process, particularly. Among the operated runs for each pH value (1.5, 2.5, 3, 4, 5.5, 7, 8.5, and 10) it was found that the optimum pH could be 2.5–3, since the removal rate reached to 70% and 74% to COD, respectively, and 73% and 78% to TPH, consistent with other studies based on Fenton reaction [6,28]. When the experiments were conducted in an acidic medium, the pH rapidly increased, whereas in an alkaline medium, it rapidly decreased. The first trend is likely to follow from Eq. (1), and hydrogen peroxide decomposes into OH and HO. The second trend was caused by H+ production through Eq. (7) [8,28,38]. Therefore, the components will be partially created to the right side of the equation, and as a final step, Fe3+ will be reacted with HO2 (Eq. (8)). Fe2+ production through Eqs. (2),(7), and (8) will help produce hydroxyl radicals and HO2 in pH value higher than 7, poorly so. However, these proceedings will have a minor role in increasing removal efficiency in extremely alkaline conditions.
Fe3þ þ H2 O2 þ hv ! Fe2þ þ HO2 þ Hþ k ¼ ð0:001 0:01 m1 s1 Þ
Fe3þ þ HO2 ! Fe2þ þ O2 þ Hþ
ð7Þ
1 1
k < 2 103 l mol
ð8Þ
s
Fig. 2. The effect of the initial pH value on the removal % of COD and TPH and DO concentration. Experimental condition for each run was: initial COD concentration = 506 mg/l, initial TPH concentration = 958 mg/l, retention time = 100 min, temperature = 26 2 C, [Fe2+] = 40 mg/l (or 0.273 mmol/l), H2O2 = 60 ml (1.9588 mol or 66.572 g), molar ratio weight ratio
H2 O2 TPH
H2 O2 = 7175, ½Fe2þ
weight ratio
H2 O2 COD
= 23.968,
= 69.5.
Fig. 2 illustrates that COD and TPH removal efficiencies have a general downward trend with increasing the pH from 2.5 to 10, while this trend was upward for pH 1.5–2.5. Despite these, the produced sludge (as Fe(OH)3) was partially increased with pH increasing, so that the highest sludge value was at pH 5–10, which could be due to the increase of available hydroxyl ions and greater precipitation of Fe3+ [39,40]. The sludge XRF is given in Fig. 3. Consistent with the results of previous studies of Fenton and photo-Fenton processes, various species of iron as a function of pH in the heterogeneous reaction can be considered as Table 4 [41,42]. Therefore, the maximum produced hydroxyl radicals was at a pH value close to 3, because FeOH2+(H2O)5 (or Fe2+) concentration as a semi-conductor with a higher light absorption coefficient than other species reached the maximum, which is crucial to the photoFenton reaction, resulting in photo-catalytic decomposition of hydrogen peroxide into H2O and O2 [16,38,41]. Moreover, the sludge formation was not observed at this pH range. By contrast, in the alkaline condition (pH 5) in the absence of Fe2+ and abundant Fe(OH)3 as a precipitation, chemical coagulation mechanism will be dominant to advanced oxidation mechanism with generation of OH, and under irradiating with ultraviolet light H2O2 is directly decomposed to H2O and O2 [16,40,43]. Under these conditions of the UV/H2O2 system, it was observed the DO concentration curve slowly increased. Overall, the H2O2 decomposition and DO concentration will be likely lower rather than photo-catalytic decomposition in acidic pH (as can be seen in Fig. 2), and as a result,
Table 3 The physico-chemical treatment parameters measured in DAF and photo-Fenton effluents, and removal efficiency to a–c (overall reduction). Parameter Unit
pH –
COD mg/l
BOD5 mg/l
BOD5/COD –
Oil mg/l
TPH mg/l
TOC mg/l
T-P mg/l
Turbidity NTU
ORP mV
TDS mg/l
506 49.5
110 36
0.217 0.726
35 5.6
958 35.4
143 37
0.09 <0.01
29.5 1.26
26 303
2060 2470
61 67.2 87.2
– – –
99.77 84 99.96
70 96.3 98.9
– >88.8 –
95.8 95.7 99.8
– – –
– – –
Value
a b
7.8 3
Removal efficiency %
a b c
– – –
98.5 90.2 99.85
97.5 74.1 99.3
a: by the current operation of DAF, b: by the optimized photo-Fenton.
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010
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Fig. 3. The ferric iron sludge XRF reveals the high weight percentage of Fe3+ to other ions. The pH value was 8.5 and other experimental conditions were same with Fig. 2.
Table 4 The likely iron species as a function of the initial pH value in the photo-Fenton reaction (a heterogeneous reaction). pH
2
2–3 (or 2.7–3.2)
5
5
Species
[Fe(H2O)6]3+ or Fe3+
[Fe(OH)(H2O)5]2+ or Fe2+
[Fe(OH)2(H2O)4]+ or Fe+
Fe(OH)3 or Fe
catalyst amounts and OH production are reduced in solution at this pH range [1,41]. In the highly acidic condition (pH < 2), decrease of degradation rate was found owing to two possible reasons: (1) greater stability of hydrogen peroxide at this pH ranges and reduced reactivity with ferrous ion, that is influenced by the oxonium ions (H3O+) from to make electrophobic H2O2 [6,44], and (2) the scavenging of hydroxyl radical by H+ and inhibits the reaction of Fe3+ with H2O2 [8,16,39]. Then, OH and O2 generations are limited for these reasons. Owing to the small difference in removal rates between the two pH values, 2.5 and 3, and prevention of apparatus corrosions and lower acid consumption was considered pH 3 as the optimal value to following of this study. The effect of the reaction catalyst concentration (as Fe2+) on COD and TPH removal was investigated by adding FeSO4 solution in doses of 0–140 mg/l, while other reaction variables were fixed, including pH, H2O2 concentration, temperature, retention time, initial COD and TPH concentration as 3, 12.1 g/l, 26 2 C, 100 min,
506 mg/l, and 958 mg/l. The results of removal efficiency and residual concentration as a function of FeSO4 dose are illustrated in Fig. 4. According to this, an increase of 70 and 73.35% removals were respectively obtained to COD and TPH only by eking of FeSO4 40 mg/l, then, this rate in ferrous sulfate 100 mg/l with a minor increase reached to 80.8% and 88.5%. Hence, it can be deducted that OH generation and subsequently oxidation rate significantly rises simultaneously with enhancing of Fe2+ ion concentration in the reaction solution in lower FeSO4 doses according to Eq. (1). The Fe2 + usage in high concentrations as 40–100 mg/l FeSO4 leads to HO2 generation with a lower oxidation potential than hydroxyl radical through H2O2 decomposition [39]. In the very high ferrous sulfate or Fe2+ concentrations, organic matter degradation will be low for two possible reasons: (1) a negative reaction of the excess Fe2+ with hydroxyl radical, which is influenced by the scavenger features as Eq. (9), thus hindering COD and TPH oxidation by reducing OH [16], and (2) the brownish yellow turbidity formed in solution during the photo-Fenton process inhibits the ultraviolet radiation influence on H2O2 decomposition and some reactions such as Eq. (2), and assists lack of UV light absorption and excess Fe2+ in the solution [29]. As seen from Fig. 4, these factors are more important in concentrations greater than 100 mg/l (especially FeSO4 140 mg/l where removal is respectively diminished to 76.2 and 83.4% for COD and TPH).
Fe2þ þ OH ! Fe3þ þ OH
Fig. 4. The effect of FeSO4 doses on the degradation efficiency and residual effluent concentration of COD and TPH. Experimental condition for each run: initial COD concentration = 506 mg/l, initial TPH concentration = 958 mg/l, retention time = 100 min, pH = 3, temperature = 26 2 C, H2O2 = 60 ml (1.9588 mol or 66.572 g), weight ratio
H2 O2 COD
= 23.968, weight ratio
H2 O2 TPH
= 69.5.
k ¼ ð3:0 4:3Þ 108 M1 S1
ð9Þ
By contrast, post-treatment with UV light and hydrogen peroxide did not provide greater removal efficiency of 18 and 23.85% for COD and TPH. Under this condition, auto H2O2 decomposition affected by UV radiation along with minimum hydroxyl radical generation will be occurred. Accordingly, retention time 100 min, pH 3, and FeSO4 100 mg/l were selected optimal for analyzing of H2O2 effect. In order to complete the effect of process variables used for final purification of MWF wastewater hydrogen peroxide, doses of 0, 5.04, 9.03, 13.11, 17.15, and 20.17 g/l were examined with other fixed variables. The results of the removal and residual concentration are
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010
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(AOP) based on H2O2. 1 H2 O2 ! O2 þ H2 O 2
H2 O2 þ OH ! H2 O þ HO2
Fig. 5. The effect of hydrogen peroxide doses on the degradation efficiency and residual concentration of COD and TPH. Experimental condition for each run: initial COD concentration = 506 mg/l, initial TPH concentration = 958 mg/l, retention time = 100 min, pH = 3, temperature = 26 2 C, [Fe2+] = 100 mg/l (or 0.6825 mmol/l).
ð10Þ
k ¼ ð1:2 4:5Þ 107 M1 S1
ð11Þ
After achieving the optimal condition as pH 3, FeSO4: 100 mg/l, and H2O2: 17.15 g/l to photo-Fenton system, it was appeared COD, TPH, oil, TOC, and turbidity could be reduced to 99% by combining the DAF unit and photo-Fenton. Therefore, this yield is superior to some hybrid approaches accomplished in MWF wastewater treatment, such as harmonisation of chemical and biological process with 92% COD and 86% TOC removals, a novel hybrid nano zarovalent iron initiated oxidation-biological degradation approach with 95.5% COD removal that studied by Jagadevan et al. [6,8]. Further, conventional separation processes (coagulation/ filtration) combined with sono-Fenton process with 90% removal efficiency was investigated by Painmanakul et al. [22].
illustrated in Fig. 5. The best COD and TPH reductions were achieved at an H2O2 dose of 17.15 g/l (85 ml in volume) with 90.2 and 96.3%, respectively. As seen in Fig. 5, oxidation reaction in H2O2 dose lower than 17.15 g/l is strongly dependent on the hydrogen peroxide concentration into solution and increasing the hydroxyl radical generation rate as a result thereof, so that, the COD and TPH degradation rates from 0 g/l H2O2 with 17.8 and 21.4% rose to 90.2 and 96.3% at this H2O2 concentration. In the concentration of 20.17 g/l H2O2, COD, and TPH degradation efficiencies decreased to 85.8 and 92.5%, likely as a result of the auto-decomposition hydrogen peroxide to O2 and H2O as Eq. (10), and the scavenging of hydroxyl radical by H2O2 from Eq. (11). This was consistent with the results of other studies [29,44,45]. Consequently, the optimal
The synergistic effect of FeSO4, H2O2, and UV The optimized photo-Fenton condition was separately assessed by the synergistic effect of FeSO4, H2O2, and UV in the COD and TPH removal. The removal efficiency only with UV/H2O2 and 17.15 g/l hydrogen peroxide was obtained 36.5% and 31.1% for COD and TPH, respectively. Under the H2O2/Fe2+ system or Fenton reaction, these values were as 45.3% and 44% to COD and TPH. Eventually, the reduction 20% was found in the context of these parameters by using UV/Fe2+. These results reveal that the Fenton reaction is the main reaction in the optimal condition only.
O2 2 O2 H2 O2 , TPH , and ½HFe2 2þ were favorable as 33.89, 17.9, and weight ratio for HCOD
The suitable biodegradability to industrial wastewater in BOD5/ COD (B/C) ratio higher than 0.4 will usually happen [4,29]. The raw MWF wastewater with a B/C ratio of 0.00781–0.00833 was highly non-biodegradable, increasing to 0.217 by the CA-DAF system, and increasing further to 0.726 after achieving optimal condition to
171.5, respectively. The weight ratio obtained for
H2 O2 ½Fe2þ
is same with
investigation carried out by Gunes [29] on removal of COD from oil recovery industry wastewater by the advanced oxidation process
Organic matters analysis
Fig. 6. GC–MS chromatograms of: (a) CA-DAF effluent and (b) final treated MWF wastewater by photo-Fenton process.
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010
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Table 5 The significant organic pollutants identified in the effluent of CA-DAF unit by GC–MS analysis. Area (105)
Retention time (min)
Boiling point ( C)
Formula
Chemicals
Similarity (%)
1 2 3 4 5 6
5.739 10.286 10.754 11.281 11.838 12.480
174 272 243 254 302
C10H16 C16H26O C11H24O C16H34 C17H36 C21H14FeN2O3
86 98 65 83 73 79
0.78345 1.759 0.05663 0.50204 0.23485 0.66645
ND >99.9 0.34787 81 ND >99.9 0.25181 49.84 0.08899 62.1 0.01287 98
7 8 9 10 11 12 13 14 15
13.535 14.590 15.689 18.102 19.401 20.734 22.172 22.714 24.774
317 330 343 369 391 432 400 409 474
C18H38 C19H40 C20H42 C22H46 C24H50 C27H56 C24H38O4 C16H22O4 C33H68
Alpha-terpinene Phenol, 2,6-bis(1,1-dimethylethyl)-4-ethyl 1-Undecanol Hexadecane Heptadecane Iron, tricarbonyl (N-(phenyl-2-pyridyl methylene) benzenamine-N,N) Octadecane Nonadecane Eicosane Docosane Tetracosane Octacosane 1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester 1,2-Benzenedicarboxylic acid, mono(2-ethylhexyl) ester Tritriacontane
93 73 87 83 70 82 91 91 65
0.21103 0.52329 0.58189 0.62866 0.26959 0.69644 1.72665 549.18425 0.64618
0.05883 72.12 0.03483 93.34 0.02668 95.41 ND >99.9 0.01032 96.17 0.01018 98.54 ND >99.9 150.763 73 0.00427 97.82
Untreated
Removal (%) Treated
ND: non detected.
photo-Fenton process. Under this condition, the final effluent quality for COD, TPH, TOC, BOD5, and other parameters was obtained as Table 3. Development of biodegradability after post-treatment can be illustrated as the removal of bio-refractory organic compounds by gas chromatography–mass spectrophotometry (GC–MS) chromatogram and IR spectrum analysis of DAF and AOP effluents. In accordance with Fig. 6a, by GC–MS analysis more than ten organic compounds were detected in DAF effluent (see Table 5). These matters consisted in straight-chain paraffin (45%), aromatic organics (25%), alcohol (5%), and other hazardous organic pollutants (15%) that were compared with GC–MS data collected in the NIST library and from similar sources. The dominant organic matter detected included alpha-terpinene (0.14%), 2,6-bis(1,1dimethylethyl)-4-ethyl phenol (0.32%), bis(2-ethylhexyl) phthalate (0.31%), and mon (2-ethylhexyl) phthalate (99.12%), which are toxic and non-biodegradable, and can disrupt the biological processes of wastewater treatment. However, the low biodegradability of the MWF wastewater could be due to the presence of these compounds. By comparing the chromatograms (a) and (b) in Fig. 6, the sum of the organic compounds decreased significantly and removal efficiency for the named compound is 88.5%, on average, indicating that the performance of the photo-Fenton process in the optimal condition was acceptable, in accordance with studies based on the Fenton process [46]. Among these compounds, mono(2-ethylhexyl) phthalate was the most prominent detected matter with a chemical structure as illustrated in Fig. 6a, which was reduced 73%. This compound and other compounds detected in DAF effluent were consistent with the MWF patent formulations presented by Dihora et al. [47]. For the oil analysis, the CA-DAF effluent and optimized photoFenton was assessed by IR spectra in wavelength 2930 cm1 (as shown by dotted line) and based on transmittance percentage, as seen in Fig. 7. For comparison, Freon solvent was used as a blank solution with 0 mg/l oil and 73.3% transmittance to IR. The findings indicated that the applied AOP through 84% yield (Y ¼ cb c ) decreased oil concentration from 35 mg/l to 5.6 mg/l in the solution. Kinetic study Despite the heterogeneous composition of MWF wastewater, as well as the complexity of chemical compounds formed as intermediates during photo-Fenton oxidation, which render
impractical a detailed kinetic investigation of different singular reactions occurring during chemical oxidation, the disappearance of simple and complex organic compounds during the 100 min of oxidation in varied pH values could be described as pseudo firstorder reaction kinetics with regard to COD concentration, consistent with the data in Fig. 8. The reaction kinetics fitted well with R2 = 0.988. The applied kinetic model shows that the rate of reaction will be limited only by the concentration of OH in solution as a function of the initial pH value. The rate constants for reactions 0.01204, 0.00755, 0.003, and 0.001744 were obtained at pH values of 3, 5.5, 8.5, and 7, respectively, by Eq. (13). In the present study, a kinetic model will be used, following the assumption that COD degradation follows pseudo first-order kinetics Eq. (12) [43]. dCOD ¼ kt dt
ð12Þ
where k and t are the reaction rate constant, and reaction time, respectively. This equation can be integrated between t = 0 and t = t, yielding: ln
COD ¼ kt COD0
ð13Þ
where COD and COD0 are the final COD concentration after t min of reaction and the initial COD concentration of MWF wastewater or DAF effluent. Consequently, based on Fig. 8, and obtained rate constants, it was found that the decrease of pH value increases the pseudo firstorder rate constant. Also, in reaction times higher than 100 min, degradation is slow, which would be impractical from an economic perspective. Cost analysis Currently, the DAF effluent is discharged into the evaporation lagoon without any additional treatment. The economic cost of this disposal method with regard to operating and maintenance costs is almost $36/m3. Also, before applying the CA-DAF unit, the disposal cost by this procedure and incineration of the produced sludge was about $105/m3. For the cost analysis of a full-scale treatment system, various aspects should be considered, including capital, operating, and maintenance cost, and, depending on some factors, such as an applied treatment system, reactor configuration, operating
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Fig. 7. IR spectra of: (a) blank solution (0 mg/l), (b) photo-Fenton effluent (5.6 mg/l), and (c) CA-DAF effluent (35 mg/l).
biological reactor (with 92% efficiency) will respectively costs $86 and $139 per 1 m3 [1]. The sum of the costs shown in Table 6 was $26 per 1 m3 that nearly all of it is devoted to hydrogen peroxide, while at this compared investigation the electricity cost was dominant. Conclusion
Fig. 8. Pseudo first-order plot for the COD removal. Experimental condition was: initial COD = 506 mg/l, initial TPH = 958 mg/l, t (reaction time) = 100 min, tempera ture = 26 2 C, [FeSO4] = 40 ppm, [Fe2+] = 0.273 mmol/l, H2O2 = 60 ml (1.9588 mol or 66.572 g), molar ratio H 2 O2 TPH
H2 O2 = 7175, ½Fe2þ
weight ratio
H2 O2 COD
= 23.968, weight ratio
= 69.5.
Table 6 The operating costs for the studied UV/H2O2/Fe2+ system in optimal condition. Process components
Consumed
Costs ($ m3)
UV (kWh) FeSO4 (kg) H2O2 (kg)
6 0.01818 17.15
0.27 0.023 25.72
conditions, and the type of effluent to be treated [48]. In this case, cost analysis was performed for the optimized photo-Fenton process to estimate electrical energy by Eq. (6), and the amount of required chemicals by trade price. Therefore, EEO for UV lamp was achieved 6 kWh m3. The unit cost of chemicals added to the pilot and used electricity was as following: H2O2 (30%) $1.5 kg1, FeSO47H2O $1.3 kg1, $0.045 kWh1. The post-treatment costs per each cubic meter of MWF wastewater is presented in Table 6. Few studies have been done on the economic analysis of the MWF wastewater post-treatment with advanced oxidation processes. However, in the study conducted by MacAdam et al. it was found the use of the optimized UV/Fe2+/H2O2 system (as 0.165 g l1 Fe, 4 g l1 H2O2, pH 3) either as the main treatment process (with 85% efficiency) or as a polishing process post-pretreatment in a
In this study, post-treatment of MWF wastewater was assessed as a pilot-scale with the photo-Fenton process in following of the full-scale CA-DAF unit. Under optimized conditions by the initial pH value and Fenton reagents yielded a removal efficiency of 90% for COD and TPH, and favorable reduction to mono(2-ethylhexyl) phthalate and other non-biodegradable compounds. These findings were proven through the significantly low sludge production and maximum DO generation in the acidic medium. Also, the synergistic effect analysis in the optimal condition of photo-Fenton system constituents was obtained as H2O2/Fe2+ > UV/H2O2 > UV/Fe2 + . The kinetic study conducted through the COD degradation results showed it could well be fit using a pseudo first-order kinetic model. The post-treatment cost was estimated as approximately $26 per 1 m3 of DAF effluent. The findings indicate that the CA-DAF unit followed by photo-Fenton is an effective and practical method for treating MWF wastewater, owing to its high reduction efficiencies to organic parameters, so that the final effluent after photo-Fenton was highly biodegradable to non-biodegradable raw wastewater. Further investigations to complete this study can be done by (1) the bioassay study on the final effluent [49], (2) the effect of other catalysts instead of Fe2+, and (3) the aeration effect on photo-Fenton. References [1] J. MacAdam, H. Ozgencil, O. Autin, M. Pidou, C. Temple, S. Parsons, B. Jefferson, Environ. Technol. 33 (2012) 2741. [2] N. Hilal, G. Busca, F. Talens-Alesson, B.P. Atkin, Chem. Eng. Process.: Process Intensif. 43 (2004) 811. [3] C.C. Lee, Environmental Engineering Dictionary, Government Institutes, 2005. [4] A. Vahid, F. Mojtaba, S. Abbas, K. Reza, Casp. J. Appl. Sci. Res. 2 (2013). [5] D. Seo, H. Lee, H. Hwang, M. Park, N. Kwak, I. Cho, J. Cho, J. Seo, W. Joo, K. Park, Water Sci. Technol. 55 (2007) 251. [6] S. Jagadevan, M. Jayamurthy, P. Dobson, I.P. Thompson, Water Res. 46 (2012) 2395. ski, M. Załe˛ska-Radziwiłł, M. Łebkowska, D. Nowak, Arch. Environ. [7] A. Muszyn Contam. Toxicol. 52 (2007) 483. [8] S. Jagadevan, P. Dobson, I.P. Thompson, Bioresour. Technol. 102 (2011) 8783. [9] J.P. Byers, Metalworking Fluids, CRC Press, 2006. [10] C. Cheng, D. Phipps, R.M. Alkhaddar, Water Res. 39 (2005) 4051. [11] A. Teli, I. Vyrides, D.C. Stuckey, J. Chem. Technol. Biotechnol. 90 (2015) 507.
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M.M. Amin et al. / Journal of Industrial and Engineering Chemistry xxx (2016) xxx–xxx [12] J. Benito, A. Cambiella, A. Lobo, G. Gutiérrez, J. Coca, C. Pazos, Clean Technol. Environ. Policy 12 (2010) 31. [13] C. Remino, A. Attanasio, M. Gelfi, M. La Vecchia, R. Pedrazzani, Minimum quantity lubrication in turning: tool life tests, Technische Akademie Esslingen International Tribology Colloquium Proceedings 14 III (2004) 1497. [14] K. Bensadok, M. Belkacem, G. Nezzal, Desalination 206 (2007) 440. [15] K. Rajagopalan, T. Rusk, M. Dianovsky, Tribol. Lubr. Technol. 60 (2004) 38. [16] S.R. Pouran, A.A. Aziz, W.M.A.W. Daud, J. Ind. Eng. Chem. 21 (2015) 53. [17] E.B. Estrada-Arriaga, J.A. Zepeda-Aviles, L. García-Sánchez, Chem. Eng. J. 285 (2016) 508. [18] H. Hansson, F. Kaczala, M. Marques, W. Hogland, Int. J. Photoenergy 2012 (2012). [19] C. Feng, H. Sun, S. Li, M.K. Camarillo, W.T. Stringfellow, Y. Liang, Water Sci. Technol. 71 (2015) 1884. ski, M. Łebkowska, Pol. J. Environ. Stud. 14 (2005) 73. [20] A. Muszyn [21] S.M. Hoseini, M.M. Salarirad, M.R. Alavi Moghaddam, Desalin. Water Treat. 53 (2015) 300. [22] P. Painmanakul, T. Chintateerachai, S. Lertlapwasin, N. Rojvilavan, T. Chalermsinsuwan, N. Chawaloesphonsiya, O.-a. Larpparisudthi, Int. J. Environ. Earth Sci. 84 (2013) 128. [23] G. Bertanza, M. Collivignarelli, B. Crotti, R. Pedrazzani, Water Sci. Technol. 61 (2010) 227. [24] L.K. Wang, N.K. Shammas, W.A. Selke, D.B. Aulenbach, Flotation Technology, Springer, 2010. [25] R.F. De Sena, J.L. Tambosi, A.K. Genena, R. de F.P.M. Moreira, H.F. Schröder, H.J. José, Chem. Eng. J. 152 (2009) 151. [26] J. Rubio, M. Souza, R. Smith, Miner. Eng. 15 (2002) 139. [27] A.R., Dincer, V.-M., Sarria Muñoz, Coupled Advanced oxidation and biological processes for wastewater treatment (2003). [28] P. Bautista, A. Mohedano, J. Casas, J. Zazo, J. Rodriguez, J. Chem. Technol. Biotechnol. 83 (2008) 1323.
9
[29] N. Karakaya, E. Gunes, E. Gunes, Removal of COD from oil recovery industry wastewater by the advanced oxidation process (AOP) based on H2O2, Glob. Nest. J. 10 (2008) 31–38. [30] Y.H. Choi, S.U. Son, S.S. Lee, Sens. Actuators A: Phys. 111 (2004) 8. [31] A. Chindris, Degradation of refractory organic compounds in aqueous wastes employing a combination of biological and chemical treatments (2011). [32] J.E.F. Moraes, F.H. Quina, C.A.O. Nascimento, D.N. Silva, O. Chiavone-Filho, Environ. Sci. Technol. 38 (2004) 1183. [33] S.A.O. Galvão, A.L. Mota, D.N. Silva, J.E.F. Moraes, C.A. Nascimento, O. ChiavoneFilho, Sci. Total Environ. 367 (2006) 42. [34] L.S. Clesceri (Ed.), Standard Methods for the Examination of Water and Wastewater, 22nd ed., American Public Health Association, American Water Works Association & Water Environment Federation, Washington, 2012. [35] V. Roanoke, Evaluation of Oils and Grease and Total Petroleum Hydrocarbons in Industrial Laundry Effluents and Detergents, ETS Analytical Services, Inc., 1994 June 25. [36] Texas Natural Resource Conservation Commission Revision 03, 2001, June 1. [37] J.R. Bolton, K.G. Bircher, W. Tumas, C.A. Tolman, Pure Appl. Chem. 73 (2001) 627. [38] J.J. Pignatello, E. Oliveros, A. MacKay, Crit. Rev. Environ. Sci. Technol. 36 (2006) 1. [39] S. Karthikeyan, A. Titus, A. Gnanamani, A. Mandal, G. Sekaran, Desalination 281 (2011) 438. [40] M. Umar, H.A. Aziz, M.S. Yusoff, Waste Manag. 30 (2010) 2113. [41] J.L. Wang, L.J. Xu, Crit. Rev. Environ. Sci. Technol. 42 (2012) 251. [42] A.D. Bokare, W. Choi, J. Hazard. Mater. 275 (2014) 121. [43] M. Muruganandham, M. Swaminathan, Dyes Pigments 62 (2004) 269. [44] E. Elmolla, M. Chaudhuri, J. Hazard. Mater. 170 (2009) 666. [45] A. Rubio-Clemente, E. Chica, G.A. Peñuela, Water Air Soil Pollut. 226 (2015) 1. [46] J. Wei, Y. Song, X. Tu, L. Zhao, E. Zhi, Chem. Eng. J. 218 (2013) 319. [47] J.O. Dihora, J. Smets, T.A. Schwantes, P.D. Sands, Delivery particles, Google Patents, 2014. [48] R. Andreozzi, V. Caprio, A. Insola, R. Marotta, Catal. Today 53 (1999) 51. [49] M. Papa, R. Pedrazzani, G. Bertanza, Water Res. 47 (2013) 3679.
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Journal of Industrial and Engineering Chemistry xxx (2016) xxx–xxx
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Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF Mohammad Mehdi Amina,b , Mohammad Mehdi Golbini Mofradb,c,* , Hamidreza Pourzamania,b , Seyed Mohammad Sebaradara , Karim Ebrahima,b a Environment Research Center, Research Institute for Primordial Prevention of Non-communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran b Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran c Student Research Center, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran
A R T I C L E I N F O
Article history: Received 3 July 2016 Received in revised form 29 August 2016 Accepted 1 October 2016 Available online xxx Keywords: Industrial wastewater Metal working fluids (MWFs) Photo-Fenton DAF
A B S T R A C T
Post-treatment of the industrial wastewater polluted by metalworking fluids (MWFs) was performed using the photo-Fenton process in following of the chemical addition-dissolved air flotation (CA-DAF) unit. Prior to this study, the CA-DAF was operated as full-scale by trial and error. For the photo-Fenton process as a pilot-scale batch reactor, initial pH value, FeSO4, and H2O2 concentrations were considered to study the effect of different operating conditions on chemical oxygen demand (COD) and total petroleum hydrocarbon (TPH) removals. This hybrid approach revealed removal efficiencies of 99.85% and 98.9% for COD and TPH in the optimized photo-Fenton process as pH 3, FeSO4: 100 mg/l, and H2O2: 17.8 g/l. The COD degradation results for the photo-Fenton system indicated that it could be well fit using a pseudo firstorder kinetic model. By the GC–MS analysis of DAF and applied photo-Fenton effluents, a 73% removal rate of mono(2-ethylhexyl) phthalate was detected. It is likely favorable to increase the biodegradability. The cost analysis of this process for the consumed energy (6 kWh) and chemicals (0.01818 kg FeSO4 and 17.15 kg H2O2) was estimated at approximately 26 $ per 1 m3 of DAF effluent. Generally, these results imply that the CA-DAF unit followed by photo-Fenton is an effective and practical method for treating MWFs wastewater. ã 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Introduction Metalworking fluids (MWFs) are generally used in manufacturing industries (e.g., tooling industry). These fluids are deliberately added to applied water in metal machining operations to cool and lubricate or inhibit rusting of contact place between machining tools and working fragment. It also has other benefits, such as the removal of small metal scraps by washing, tool protection against corrosion, tool life improvement, friction diminution in fragment and tool interface, and altogether the final quality development of products [1–3]. Despite these advantages, MWFs is known as the main source of oily wastewater in the metal industries sector with
* Corresponding author at: Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran. E-mail address: [email protected] (M.M. Golbini Mofrad).
high chemical oxygen demand (COD), approximately 10,000– 100,000 mg/l [4,5]. MWF formulations are chemically complex and composed of base mineral oil, emulsifiers and surfactants, extreme pressure and anti-weld agents, corrosion inhibitors, biocides (phenolic and aliphatic derivatives), foam inhibitors, friction reduction agents, and alkaline reserve compounds [6–8]. Owing to the presence of all these compounds and microbial agents (bacteria and fungi), which have proven toxic effects, MWFs are non-biodegradable and hazardous and are associated with diseases such as cancer, skin disease, respiratory disease, and other diseases [5,7,9]. It is estimated that more than 2,000,000 m3 MWF are annually used worldwide and that wastewater volume by dilution of MWFs prior to use could be ten times higher [1,6,10,11]. Because of the complicated chemical contents as trade secrets for MWFs producers, the disposal of related wastewater is progressively difficult [7]. Further, since the MWFs are categorized as
http://dx.doi.org/10.1016/j.jiec.2016.10.010 1226-086X/ã 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
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hazardous wastes along with relative toxicity to aquatic organisms, disposal options for this oily waste is expensive [12]. For the disposal of used MWFs, conventional physical and chemical techniques or minimization approaches are typically used, and generally have single or multiple stages, depending on the stage of treatment needed. In the multiple stage systems, solids and oil phase during the elementary phase is removed, and then the volume and COD loading are reduced by the secondary stage. Finally, for compliance with severe discharge limits, posttreatment is usually appropriate to develop the effluent quality [1]. The toxicity of these fluids is an obstacle because all biological treatment processes need high concentrations of organic compounds with low molecular weight and BOD/COD ratio higher than 0.4 (a desirable value) [4,5,13]. Considering the stable nature of these fluids in high pressures and temperatures, MWF wastewater treatment can be chemically and biologically laborious. Applying the existing approaches or processes requires further refining costs [5]. Evaporation, thermal splitting, and incineration are the most predominant disposal methods, while the latest technique releases a lot of air pollutants (e.g., NOx, SO2, HCl) [6–8]. Therefore, we have the risk of untreated wastewater discharge to soil and water resources, such as rivers, lakes, and so on, at any time and any place [5]. Other used treatment options for these recalcitrant wastewaters are chemical stabilization, electrocoagulation, and coagulation along with dissolved air flotation (DAF) [14], microfiltration [15], flow equalization, gravity separation of free oil, chemical emulsion breaking, flocculation (DAF), and clarification/filtration for oil removal [10], coagulation–flocculation [4], advanced oxidation processes, photo-Fenton oxidation system, and Fenton oxidation [16–19]. MWFs treatment problem will not likely be solved with all mentioned approaches (apart from incineration), because of emulsion splits to water and oil phases and thus require additional utilization; further, the defects of these procedures are their inability to completely remove inorganic/organic, volatile/ semi volatile compounds, and COD [17,20]. Hence, post-treatment is necessitated for the effluent of each process [17]. Furthermore, applying two or more techniques in combination is more efficient than one [7]. The hybrid technologies were studied by a series of researchers incorporating biodegradation and advanced oxidation process [1], coagulation process combined with mechanically induced air floatation [21], and coupling coagulation and DAF [14], as well as other coupled approaches [5,6,8,22]. In general, the
integrated approach is considered as the best option for complex wastewaters [23]. Air flotation, in all its varieties, is an efficient technique to separate light particles and oils from wastewater. DAF not only is more efficient and faster than sedimentation techniques, but also produces minor sludge volumes [24,25]. The organic matter removal by this technique can be higher than 98%, depending on the main operating parameters (e.g., saturation time and separation time and pressure, size and diameter of the gas bubbles, and chemical additive dosage) [14,25,26]. The photo-Fenton can be divided into two phases with regard to hydroxyl radical (OH) formation. First, in Fenton reaction, ferrous iron oxides are oxidized into ferric iron oxides in the presence of hydrogen peroxide (Eq. (1)) [27]. In the next step, ferric oxides generated in the Fenton reaction are photo-catalytically transformed to ferrous ions (Eq. (2)) [16].
Fe2þ þ H2 O2 ! Fe3þ þ HO þ OH
k ¼ ð63 76Þ M1 S1
hv
½FeðOHÞ2þ ! Fe2þ þ HO þ Hþ
ð1Þ
ð2Þ
In the presence of organic matter, hydroxyl radical reacts with this, increasing the oxidized products (Eq. (3)) [16,28].
chain propagation
HO þ RH
!
R þ H2 O
ð3Þ
The aim of this research was the evaluation of COD, total petroleum hydrocarbon (TPH), and oil removal efficiencies by the photo-Fenton reaction as post-treatment coupled with a full-scale DAF unit. The specific goals of this work, considering COD and TPH as indicators, were to determine: (1) the effect of the reagent concentrations (FeSO4, H2O2) and initial pH value in COD and TPH removal, (3) the synergistic effect of FeSO4, H2O2, and ultraviolet (UV) radiation in the optimized condition, (4) the organic matters analysis, (5) the removal kinetics of COD, and (6) cost analysis for running of process in optimized condition. Materials and methods Reagents and chemicals Hydroxyl radicals were provided by hydrogen peroxide (H2O2; 30%, Catalog Number 1085979025) as oxidant and ferrous sulfate
Fig. 1. The pilot-scale photo-Fenton unit coupled with a full-scale Chemical Addition-Dissolved Air Floatation (CA-DAF) system.
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heptahydrate (CAS Number 7782-63-0) as a catalyst. The pH adjustment of wastewater solution into the pilot also was performed by injection of concentrated sulfuric acid (H2SO4; 98%, CAS Number 7664-93-9) and sodium hydroxide (CAS Number 1310-73-2). The COD over measuring problem affected by H2O2 solved with adding MnO2 (CAS Number 1313-13-9) to samples [29,30]. N-pentane 99% (CAS Number 109-66-0) was applied for sample extractions. Raw wastewater characteristics In this study, the water contaminated by semi-synthetic MWF, density: 1.0186 g/cm3 and viscosity: 138 centipoises, from the machining industries in the center of Iran, was used as influent wastewater. Semi-synthetic MWFs are the type of water based MWFs which typically contain 2–50% of mineral oil and also compounds used in synthetic MWFs [31]. The wastewater was collected in the storage tank before injection to a full-scale DAF unit in downstream of the cutting hall (Fig. 1). Table 1 indicates the physicochemical parameters of MWF wastewater.
3
and sampling throughout the pilot and preventing the liquid return from the pump to the tank. Photo-Fenton process procedures The recirculation tank was filled with 5.5 l DAF effluent. Then, the operation condition for a pre-test run was considered as (1) the recirculation pump was turned on (at the recirculation flow rate was mentioned in wastewater volume) and the initial pH of the solution was regulated in 3, simultaneously, (2) the UV lamp and the mechanical stirrer were turned on, and the solution of 40 mg/l (100 ml) FeSO47H2O was injected, (3) the timing (100 min total) of the first run was started along with the beginning of slow injection H2O2 (60 ml total, at a rate of 0.85 ml/min) during the first 70 min of reaction, (4) at the end of reaction, duplicate samples (each 20 ml) was taken for the sampling time [32,33], and (5) for the next runs, with fixing all variables (pH, FeSO4, H2O2) except for one, the study progressed step-by-step, obtaining optimal conditions of treatment to optimal variables. All the experiments have been conducted with the same wastewater, and because of the lack of biological and chemical interactions in the DAF effluent storage tank, data variations were negligible for quality characteristics.
DAF unit in treatment step Analytical determinations The first stage of physicochemical treatment of the wastewater was performed using a full-scale Chemical Addition-Dissolved Air Floatation (CA-DAF) system placed in a chemical treatment plant as batch mode operation and periodical treatment. In each treatment period, wastewater volume and loading rate in DAF inlet were 7 m3 and 35–40 l/min. Current and optimized operating conditions were found by trial and error: aeration rate 15–20 l/min, and pressure was set at 3 bar and the saturation time of 30 min, injected to its wastewater volume after filling floatation cells. The dosage of chemical additives used per 7 m3 of wastewater is shown in Table 2. Then, DAF effluent was discharged to a storage tank. Photo-Fenton process of pre-treated wastewater Apparatus and experimental set-up The photo-Fenton process performed in the pilot-scale unit (operated batch mode) as shown in Fig. 1. This unit consisted in a one-liter capacity photochemical reactor, as a packed plexiglas chamber with a 20 W and low-pressure mercury vapor UV lamp with a quartz glass sleeve and steel shield. It was connected to a five-liter capacity pyrex-glass recirculation tank surrounded by a water jacket chamber for adjusting to the desired temperature (26 2 C). The recirculation tank was equipped with a mechanical stirrer (490 10 rpm) for mixing the tank content (3.5 l). Therefore, the pilot content of wastewater under treatment by considering the recirculation pump and fittings volume (1 l) reached 5.5 l. The recirculation flow rate (Qr) between the photochemical reactor and recirculation tank was controlled to 12 l/min by means of a centrifugal pump. A set of valves was applied for flow rate control
Measurement of BOD5, TP, TOC, and oil to samples was performed in accordance with the standard methods [34]. In the oil analysis, samples extracted by Freon solvent (1,1,2-trichlorotrifluoroethane; 99%, CAS Number 76-13-1) and standards (from 0 ppm to 100 ppm) for quantification were finally analyzed by Shimadzu IR-470 instrument [35]. For the COD analysis, raw and treated wastewater samples were spectrophotometrically tested by applying Hack Lange cuvette test (Hack Lang, Dusseldropf) and measured with a Hach Lange DR 5000 Model spectrophotometer (Hach Lange, Dusseldropf). The dissolved oxygen (DO) concentration and temperature were monitored by Waterproof DO 300 Dissolved Oxygen Meter. The pH adjustment and ORP checking were measured by WTW pH 330i pH & Redox messgerät im Koffer. The total dissolved solids (TDS) and electrical conductivity (EC) were obtained by WTW Cond 330i Conductivity Meter. The total organic carbon (TOC) was measured by a Shimadzu TOC-5000A TOC analyzer [18]. In addition, TPH analysis of samples from sampling and preservation to gas chromatography (GC) analysis performed in pursuant to Texas Natural Resource Conservation Commission (TNRCC-1005) with some modifications [36]. For this goal, the extracted samples were finally injected to A7890/C5975 GC–MS system (Agilent, USA) equipped with a CP-Sil 5 CB capillary column (30 m long, 0.25 mm ID, and 0.25 mm film). TPH standardization was performed with unleaded gasoline, and correlation for the achieved calibration curves is 0.99 as Eq. (4): y ¼ 9:8307x þ 1615:6
TPH concentration of the aqueous samples was obtained by using Eq. (5) [36]: C s ¼ ðC c V t DÞ=W s
Table 1 MWF wastewater characteristics. Parameter
Value
TPH (mg/l) COD (mg/l) TOC (mg/l) Oil & grease (mg/l) BOD5 (mg/l) BOD5/COD pH Suspended solids (mg/l) Turbidity (NTU)
3200 20 35000 500 5800 25 15500 500 280 17 0.008 4 9 0.2 5700 32 710 6
ð4Þ
ð5Þ
Cost analysis Power consumption was calculated using Eq. (6), developed by Bolton et al. [37]: EEO kWh m3 ¼
P t 1000 C V 60 log Cefinff
ð6Þ
where EEO: modified electrical energy per order that is the energy in kWh required for achieving 90% destruction of pollutants in 103 l
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Table 2 Chemical dosage used in DAF unit per 7 m3 of MWF wastewater under treatment. Chemical
FeCl3 (as coagulant)
Micronized CaCO3
NaOH
Poly-aluminum chloride (flocculant)
Hydrogen peroxide
80 kg
15 kg
18.5 kg
0.05 kg
2.75 kg
of wastewater, P: lamp power in kW, t: irradiation time in min, V: volume of the treated wastewater in liters, Cinf: influent COD concentration in mg/l, and Ceff: effluent COD concentration in mg/l. Chemical costs were estimated based on the trading price unit for H2O2 (30%) and FeSO47H2O to 103 l of the treated wastewater at the optimized condition (90% efficiency) of the photo-Fenton process. Results and discussion CA-DAF unit was operated with the condition mentioned above. Under this circumstance, treatment parameters in the effluent are presented in Table 3. Knowing the effluent quality at this treatment step, the study was progressing toward photo-Fenton experiments that were performed as a pilot-scale batch reactor. The purpose of these experiments was to obtain the suitable operational condition for the photo-Fenton process at the post-treatment of DAF in order to reduce the impact of final MWF effluent discharge into natural water streams (e.g., rivers) and resources (e.g., pools), or even the biological and membrane approaches to industrial wastewater treatment with higher goals (e.g., reuse). Effect of the initial pH value and reagents The pilot-scale unit was charged seven times, with DAF effluent for evaluation of the pH role in the process, particularly. Among the operated runs for each pH value (1.5, 2.5, 3, 4, 5.5, 7, 8.5, and 10) it was found that the optimum pH could be 2.5–3, since the removal rate reached to 70% and 74% to COD, respectively, and 73% and 78% to TPH, consistent with other studies based on Fenton reaction [6,28]. When the experiments were conducted in an acidic medium, the pH rapidly increased, whereas in an alkaline medium, it rapidly decreased. The first trend is likely to follow from Eq. (1), and hydrogen peroxide decomposes into OH and HO. The second trend was caused by H+ production through Eq. (7) [8,28,38]. Therefore, the components will be partially created to the right side of the equation, and as a final step, Fe3+ will be reacted with HO2 (Eq. (8)). Fe2+ production through Eqs. (2),(7), and (8) will help produce hydroxyl radicals and HO2 in pH value higher than 7, poorly so. However, these proceedings will have a minor role in increasing removal efficiency in extremely alkaline conditions.
Fe3þ þ H2 O2 þ hv ! Fe2þ þ HO2 þ Hþ k ¼ ð0:001 0:01 m1 s1 Þ
Fe3þ þ HO2 ! Fe2þ þ O2 þ Hþ
ð7Þ
1 1
k < 2 103 l mol
ð8Þ
s
Fig. 2. The effect of the initial pH value on the removal % of COD and TPH and DO concentration. Experimental condition for each run was: initial COD concentration = 506 mg/l, initial TPH concentration = 958 mg/l, retention time = 100 min, temperature = 26 2 C, [Fe2+] = 40 mg/l (or 0.273 mmol/l), H2O2 = 60 ml (1.9588 mol or 66.572 g), molar ratio weight ratio
H2 O2 TPH
H2 O2 = 7175, ½Fe2þ
weight ratio
H2 O2 COD
= 23.968,
= 69.5.
Fig. 2 illustrates that COD and TPH removal efficiencies have a general downward trend with increasing the pH from 2.5 to 10, while this trend was upward for pH 1.5–2.5. Despite these, the produced sludge (as Fe(OH)3) was partially increased with pH increasing, so that the highest sludge value was at pH 5–10, which could be due to the increase of available hydroxyl ions and greater precipitation of Fe3+ [39,40]. The sludge XRF is given in Fig. 3. Consistent with the results of previous studies of Fenton and photo-Fenton processes, various species of iron as a function of pH in the heterogeneous reaction can be considered as Table 4 [41,42]. Therefore, the maximum produced hydroxyl radicals was at a pH value close to 3, because FeOH2+(H2O)5 (or Fe2+) concentration as a semi-conductor with a higher light absorption coefficient than other species reached the maximum, which is crucial to the photoFenton reaction, resulting in photo-catalytic decomposition of hydrogen peroxide into H2O and O2 [16,38,41]. Moreover, the sludge formation was not observed at this pH range. By contrast, in the alkaline condition (pH 5) in the absence of Fe2+ and abundant Fe(OH)3 as a precipitation, chemical coagulation mechanism will be dominant to advanced oxidation mechanism with generation of OH, and under irradiating with ultraviolet light H2O2 is directly decomposed to H2O and O2 [16,40,43]. Under these conditions of the UV/H2O2 system, it was observed the DO concentration curve slowly increased. Overall, the H2O2 decomposition and DO concentration will be likely lower rather than photo-catalytic decomposition in acidic pH (as can be seen in Fig. 2), and as a result,
Table 3 The physico-chemical treatment parameters measured in DAF and photo-Fenton effluents, and removal efficiency to a–c (overall reduction). Parameter Unit
pH –
COD mg/l
BOD5 mg/l
BOD5/COD –
Oil mg/l
TPH mg/l
TOC mg/l
T-P mg/l
Turbidity NTU
ORP mV
TDS mg/l
506 49.5
110 36
0.217 0.726
35 5.6
958 35.4
143 37
0.09 <0.01
29.5 1.26
26 303
2060 2470
61 67.2 87.2
– – –
99.77 84 99.96
70 96.3 98.9
– >88.8 –
95.8 95.7 99.8
– – –
– – –
Value
a b
7.8 3
Removal efficiency %
a b c
– – –
98.5 90.2 99.85
97.5 74.1 99.3
a: by the current operation of DAF, b: by the optimized photo-Fenton.
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Fig. 3. The ferric iron sludge XRF reveals the high weight percentage of Fe3+ to other ions. The pH value was 8.5 and other experimental conditions were same with Fig. 2.
Table 4 The likely iron species as a function of the initial pH value in the photo-Fenton reaction (a heterogeneous reaction). pH
2
2–3 (or 2.7–3.2)
5
5
Species
[Fe(H2O)6]3+ or Fe3+
[Fe(OH)(H2O)5]2+ or Fe2+
[Fe(OH)2(H2O)4]+ or Fe+
Fe(OH)3 or Fe
catalyst amounts and OH production are reduced in solution at this pH range [1,41]. In the highly acidic condition (pH < 2), decrease of degradation rate was found owing to two possible reasons: (1) greater stability of hydrogen peroxide at this pH ranges and reduced reactivity with ferrous ion, that is influenced by the oxonium ions (H3O+) from to make electrophobic H2O2 [6,44], and (2) the scavenging of hydroxyl radical by H+ and inhibits the reaction of Fe3+ with H2O2 [8,16,39]. Then, OH and O2 generations are limited for these reasons. Owing to the small difference in removal rates between the two pH values, 2.5 and 3, and prevention of apparatus corrosions and lower acid consumption was considered pH 3 as the optimal value to following of this study. The effect of the reaction catalyst concentration (as Fe2+) on COD and TPH removal was investigated by adding FeSO4 solution in doses of 0–140 mg/l, while other reaction variables were fixed, including pH, H2O2 concentration, temperature, retention time, initial COD and TPH concentration as 3, 12.1 g/l, 26 2 C, 100 min,
506 mg/l, and 958 mg/l. The results of removal efficiency and residual concentration as a function of FeSO4 dose are illustrated in Fig. 4. According to this, an increase of 70 and 73.35% removals were respectively obtained to COD and TPH only by eking of FeSO4 40 mg/l, then, this rate in ferrous sulfate 100 mg/l with a minor increase reached to 80.8% and 88.5%. Hence, it can be deducted that OH generation and subsequently oxidation rate significantly rises simultaneously with enhancing of Fe2+ ion concentration in the reaction solution in lower FeSO4 doses according to Eq. (1). The Fe2 + usage in high concentrations as 40–100 mg/l FeSO4 leads to HO2 generation with a lower oxidation potential than hydroxyl radical through H2O2 decomposition [39]. In the very high ferrous sulfate or Fe2+ concentrations, organic matter degradation will be low for two possible reasons: (1) a negative reaction of the excess Fe2+ with hydroxyl radical, which is influenced by the scavenger features as Eq. (9), thus hindering COD and TPH oxidation by reducing OH [16], and (2) the brownish yellow turbidity formed in solution during the photo-Fenton process inhibits the ultraviolet radiation influence on H2O2 decomposition and some reactions such as Eq. (2), and assists lack of UV light absorption and excess Fe2+ in the solution [29]. As seen from Fig. 4, these factors are more important in concentrations greater than 100 mg/l (especially FeSO4 140 mg/l where removal is respectively diminished to 76.2 and 83.4% for COD and TPH).
Fe2þ þ OH ! Fe3þ þ OH
Fig. 4. The effect of FeSO4 doses on the degradation efficiency and residual effluent concentration of COD and TPH. Experimental condition for each run: initial COD concentration = 506 mg/l, initial TPH concentration = 958 mg/l, retention time = 100 min, pH = 3, temperature = 26 2 C, H2O2 = 60 ml (1.9588 mol or 66.572 g), weight ratio
H2 O2 COD
= 23.968, weight ratio
H2 O2 TPH
= 69.5.
k ¼ ð3:0 4:3Þ 108 M1 S1
ð9Þ
By contrast, post-treatment with UV light and hydrogen peroxide did not provide greater removal efficiency of 18 and 23.85% for COD and TPH. Under this condition, auto H2O2 decomposition affected by UV radiation along with minimum hydroxyl radical generation will be occurred. Accordingly, retention time 100 min, pH 3, and FeSO4 100 mg/l were selected optimal for analyzing of H2O2 effect. In order to complete the effect of process variables used for final purification of MWF wastewater hydrogen peroxide, doses of 0, 5.04, 9.03, 13.11, 17.15, and 20.17 g/l were examined with other fixed variables. The results of the removal and residual concentration are
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(AOP) based on H2O2. 1 H2 O2 ! O2 þ H2 O 2
H2 O2 þ OH ! H2 O þ HO2
Fig. 5. The effect of hydrogen peroxide doses on the degradation efficiency and residual concentration of COD and TPH. Experimental condition for each run: initial COD concentration = 506 mg/l, initial TPH concentration = 958 mg/l, retention time = 100 min, pH = 3, temperature = 26 2 C, [Fe2+] = 100 mg/l (or 0.6825 mmol/l).
ð10Þ
k ¼ ð1:2 4:5Þ 107 M1 S1
ð11Þ
After achieving the optimal condition as pH 3, FeSO4: 100 mg/l, and H2O2: 17.15 g/l to photo-Fenton system, it was appeared COD, TPH, oil, TOC, and turbidity could be reduced to 99% by combining the DAF unit and photo-Fenton. Therefore, this yield is superior to some hybrid approaches accomplished in MWF wastewater treatment, such as harmonisation of chemical and biological process with 92% COD and 86% TOC removals, a novel hybrid nano zarovalent iron initiated oxidation-biological degradation approach with 95.5% COD removal that studied by Jagadevan et al. [6,8]. Further, conventional separation processes (coagulation/ filtration) combined with sono-Fenton process with 90% removal efficiency was investigated by Painmanakul et al. [22].
illustrated in Fig. 5. The best COD and TPH reductions were achieved at an H2O2 dose of 17.15 g/l (85 ml in volume) with 90.2 and 96.3%, respectively. As seen in Fig. 5, oxidation reaction in H2O2 dose lower than 17.15 g/l is strongly dependent on the hydrogen peroxide concentration into solution and increasing the hydroxyl radical generation rate as a result thereof, so that, the COD and TPH degradation rates from 0 g/l H2O2 with 17.8 and 21.4% rose to 90.2 and 96.3% at this H2O2 concentration. In the concentration of 20.17 g/l H2O2, COD, and TPH degradation efficiencies decreased to 85.8 and 92.5%, likely as a result of the auto-decomposition hydrogen peroxide to O2 and H2O as Eq. (10), and the scavenging of hydroxyl radical by H2O2 from Eq. (11). This was consistent with the results of other studies [29,44,45]. Consequently, the optimal
The synergistic effect of FeSO4, H2O2, and UV The optimized photo-Fenton condition was separately assessed by the synergistic effect of FeSO4, H2O2, and UV in the COD and TPH removal. The removal efficiency only with UV/H2O2 and 17.15 g/l hydrogen peroxide was obtained 36.5% and 31.1% for COD and TPH, respectively. Under the H2O2/Fe2+ system or Fenton reaction, these values were as 45.3% and 44% to COD and TPH. Eventually, the reduction 20% was found in the context of these parameters by using UV/Fe2+. These results reveal that the Fenton reaction is the main reaction in the optimal condition only.
O2 2 O2 H2 O2 , TPH , and ½HFe2 2þ were favorable as 33.89, 17.9, and weight ratio for HCOD
The suitable biodegradability to industrial wastewater in BOD5/ COD (B/C) ratio higher than 0.4 will usually happen [4,29]. The raw MWF wastewater with a B/C ratio of 0.00781–0.00833 was highly non-biodegradable, increasing to 0.217 by the CA-DAF system, and increasing further to 0.726 after achieving optimal condition to
171.5, respectively. The weight ratio obtained for
H2 O2 ½Fe2þ
is same with
investigation carried out by Gunes [29] on removal of COD from oil recovery industry wastewater by the advanced oxidation process
Organic matters analysis
Fig. 6. GC–MS chromatograms of: (a) CA-DAF effluent and (b) final treated MWF wastewater by photo-Fenton process.
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Table 5 The significant organic pollutants identified in the effluent of CA-DAF unit by GC–MS analysis. Area (105)
Retention time (min)
Boiling point ( C)
Formula
Chemicals
Similarity (%)
1 2 3 4 5 6
5.739 10.286 10.754 11.281 11.838 12.480
174 272 243 254 302
C10H16 C16H26O C11H24O C16H34 C17H36 C21H14FeN2O3
86 98 65 83 73 79
0.78345 1.759 0.05663 0.50204 0.23485 0.66645
ND >99.9 0.34787 81 ND >99.9 0.25181 49.84 0.08899 62.1 0.01287 98
7 8 9 10 11 12 13 14 15
13.535 14.590 15.689 18.102 19.401 20.734 22.172 22.714 24.774
317 330 343 369 391 432 400 409 474
C18H38 C19H40 C20H42 C22H46 C24H50 C27H56 C24H38O4 C16H22O4 C33H68
Alpha-terpinene Phenol, 2,6-bis(1,1-dimethylethyl)-4-ethyl 1-Undecanol Hexadecane Heptadecane Iron, tricarbonyl (N-(phenyl-2-pyridyl methylene) benzenamine-N,N) Octadecane Nonadecane Eicosane Docosane Tetracosane Octacosane 1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester 1,2-Benzenedicarboxylic acid, mono(2-ethylhexyl) ester Tritriacontane
93 73 87 83 70 82 91 91 65
0.21103 0.52329 0.58189 0.62866 0.26959 0.69644 1.72665 549.18425 0.64618
0.05883 72.12 0.03483 93.34 0.02668 95.41 ND >99.9 0.01032 96.17 0.01018 98.54 ND >99.9 150.763 73 0.00427 97.82
Untreated
Removal (%) Treated
ND: non detected.
photo-Fenton process. Under this condition, the final effluent quality for COD, TPH, TOC, BOD5, and other parameters was obtained as Table 3. Development of biodegradability after post-treatment can be illustrated as the removal of bio-refractory organic compounds by gas chromatography–mass spectrophotometry (GC–MS) chromatogram and IR spectrum analysis of DAF and AOP effluents. In accordance with Fig. 6a, by GC–MS analysis more than ten organic compounds were detected in DAF effluent (see Table 5). These matters consisted in straight-chain paraffin (45%), aromatic organics (25%), alcohol (5%), and other hazardous organic pollutants (15%) that were compared with GC–MS data collected in the NIST library and from similar sources. The dominant organic matter detected included alpha-terpinene (0.14%), 2,6-bis(1,1dimethylethyl)-4-ethyl phenol (0.32%), bis(2-ethylhexyl) phthalate (0.31%), and mon (2-ethylhexyl) phthalate (99.12%), which are toxic and non-biodegradable, and can disrupt the biological processes of wastewater treatment. However, the low biodegradability of the MWF wastewater could be due to the presence of these compounds. By comparing the chromatograms (a) and (b) in Fig. 6, the sum of the organic compounds decreased significantly and removal efficiency for the named compound is 88.5%, on average, indicating that the performance of the photo-Fenton process in the optimal condition was acceptable, in accordance with studies based on the Fenton process [46]. Among these compounds, mono(2-ethylhexyl) phthalate was the most prominent detected matter with a chemical structure as illustrated in Fig. 6a, which was reduced 73%. This compound and other compounds detected in DAF effluent were consistent with the MWF patent formulations presented by Dihora et al. [47]. For the oil analysis, the CA-DAF effluent and optimized photoFenton was assessed by IR spectra in wavelength 2930 cm1 (as shown by dotted line) and based on transmittance percentage, as seen in Fig. 7. For comparison, Freon solvent was used as a blank solution with 0 mg/l oil and 73.3% transmittance to IR. The findings indicated that the applied AOP through 84% yield (Y ¼ cb c ) decreased oil concentration from 35 mg/l to 5.6 mg/l in the solution. Kinetic study Despite the heterogeneous composition of MWF wastewater, as well as the complexity of chemical compounds formed as intermediates during photo-Fenton oxidation, which render
impractical a detailed kinetic investigation of different singular reactions occurring during chemical oxidation, the disappearance of simple and complex organic compounds during the 100 min of oxidation in varied pH values could be described as pseudo firstorder reaction kinetics with regard to COD concentration, consistent with the data in Fig. 8. The reaction kinetics fitted well with R2 = 0.988. The applied kinetic model shows that the rate of reaction will be limited only by the concentration of OH in solution as a function of the initial pH value. The rate constants for reactions 0.01204, 0.00755, 0.003, and 0.001744 were obtained at pH values of 3, 5.5, 8.5, and 7, respectively, by Eq. (13). In the present study, a kinetic model will be used, following the assumption that COD degradation follows pseudo first-order kinetics Eq. (12) [43]. dCOD ¼ kt dt
ð12Þ
where k and t are the reaction rate constant, and reaction time, respectively. This equation can be integrated between t = 0 and t = t, yielding: ln
COD ¼ kt COD0
ð13Þ
where COD and COD0 are the final COD concentration after t min of reaction and the initial COD concentration of MWF wastewater or DAF effluent. Consequently, based on Fig. 8, and obtained rate constants, it was found that the decrease of pH value increases the pseudo firstorder rate constant. Also, in reaction times higher than 100 min, degradation is slow, which would be impractical from an economic perspective. Cost analysis Currently, the DAF effluent is discharged into the evaporation lagoon without any additional treatment. The economic cost of this disposal method with regard to operating and maintenance costs is almost $36/m3. Also, before applying the CA-DAF unit, the disposal cost by this procedure and incineration of the produced sludge was about $105/m3. For the cost analysis of a full-scale treatment system, various aspects should be considered, including capital, operating, and maintenance cost, and, depending on some factors, such as an applied treatment system, reactor configuration, operating
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Fig. 7. IR spectra of: (a) blank solution (0 mg/l), (b) photo-Fenton effluent (5.6 mg/l), and (c) CA-DAF effluent (35 mg/l).
biological reactor (with 92% efficiency) will respectively costs $86 and $139 per 1 m3 [1]. The sum of the costs shown in Table 6 was $26 per 1 m3 that nearly all of it is devoted to hydrogen peroxide, while at this compared investigation the electricity cost was dominant. Conclusion
Fig. 8. Pseudo first-order plot for the COD removal. Experimental condition was: initial COD = 506 mg/l, initial TPH = 958 mg/l, t (reaction time) = 100 min, tempera ture = 26 2 C, [FeSO4] = 40 ppm, [Fe2+] = 0.273 mmol/l, H2O2 = 60 ml (1.9588 mol or 66.572 g), molar ratio H 2 O2 TPH
H2 O2 = 7175, ½Fe2þ
weight ratio
H2 O2 COD
= 23.968, weight ratio
= 69.5.
Table 6 The operating costs for the studied UV/H2O2/Fe2+ system in optimal condition. Process components
Consumed
Costs ($ m3)
UV (kWh) FeSO4 (kg) H2O2 (kg)
6 0.01818 17.15
0.27 0.023 25.72
conditions, and the type of effluent to be treated [48]. In this case, cost analysis was performed for the optimized photo-Fenton process to estimate electrical energy by Eq. (6), and the amount of required chemicals by trade price. Therefore, EEO for UV lamp was achieved 6 kWh m3. The unit cost of chemicals added to the pilot and used electricity was as following: H2O2 (30%) $1.5 kg1, FeSO47H2O $1.3 kg1, $0.045 kWh1. The post-treatment costs per each cubic meter of MWF wastewater is presented in Table 6. Few studies have been done on the economic analysis of the MWF wastewater post-treatment with advanced oxidation processes. However, in the study conducted by MacAdam et al. it was found the use of the optimized UV/Fe2+/H2O2 system (as 0.165 g l1 Fe, 4 g l1 H2O2, pH 3) either as the main treatment process (with 85% efficiency) or as a polishing process post-pretreatment in a
In this study, post-treatment of MWF wastewater was assessed as a pilot-scale with the photo-Fenton process in following of the full-scale CA-DAF unit. Under optimized conditions by the initial pH value and Fenton reagents yielded a removal efficiency of 90% for COD and TPH, and favorable reduction to mono(2-ethylhexyl) phthalate and other non-biodegradable compounds. These findings were proven through the significantly low sludge production and maximum DO generation in the acidic medium. Also, the synergistic effect analysis in the optimal condition of photo-Fenton system constituents was obtained as H2O2/Fe2+ > UV/H2O2 > UV/Fe2 + . The kinetic study conducted through the COD degradation results showed it could well be fit using a pseudo first-order kinetic model. The post-treatment cost was estimated as approximately $26 per 1 m3 of DAF effluent. The findings indicate that the CA-DAF unit followed by photo-Fenton is an effective and practical method for treating MWF wastewater, owing to its high reduction efficiencies to organic parameters, so that the final effluent after photo-Fenton was highly biodegradable to non-biodegradable raw wastewater. Further investigations to complete this study can be done by (1) the bioassay study on the final effluent [49], (2) the effect of other catalysts instead of Fe2+, and (3) the aeration effect on photo-Fenton. References [1] J. MacAdam, H. Ozgencil, O. Autin, M. Pidou, C. Temple, S. Parsons, B. Jefferson, Environ. Technol. 33 (2012) 2741. [2] N. Hilal, G. Busca, F. Talens-Alesson, B.P. Atkin, Chem. Eng. Process.: Process Intensif. 43 (2004) 811. [3] C.C. Lee, Environmental Engineering Dictionary, Government Institutes, 2005. [4] A. Vahid, F. Mojtaba, S. Abbas, K. Reza, Casp. J. Appl. Sci. Res. 2 (2013). [5] D. Seo, H. Lee, H. Hwang, M. Park, N. Kwak, I. Cho, J. Cho, J. Seo, W. Joo, K. Park, Water Sci. Technol. 55 (2007) 251. [6] S. Jagadevan, M. Jayamurthy, P. Dobson, I.P. Thompson, Water Res. 46 (2012) 2395. ski, M. Załe˛ska-Radziwiłł, M. Łebkowska, D. Nowak, Arch. Environ. [7] A. Muszyn Contam. Toxicol. 52 (2007) 483. [8] S. Jagadevan, P. Dobson, I.P. Thompson, Bioresour. Technol. 102 (2011) 8783. [9] J.P. Byers, Metalworking Fluids, CRC Press, 2006. [10] C. Cheng, D. Phipps, R.M. Alkhaddar, Water Res. 39 (2005) 4051. [11] A. Teli, I. Vyrides, D.C. Stuckey, J. Chem. Technol. Biotechnol. 90 (2015) 507.
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010
G Model JIEC 3122 No. of Pages 9
M.M. Amin et al. / Journal of Industrial and Engineering Chemistry xxx (2016) xxx–xxx [12] J. Benito, A. Cambiella, A. Lobo, G. Gutiérrez, J. Coca, C. Pazos, Clean Technol. Environ. Policy 12 (2010) 31. [13] C. Remino, A. Attanasio, M. Gelfi, M. La Vecchia, R. Pedrazzani, Minimum quantity lubrication in turning: tool life tests, Technische Akademie Esslingen International Tribology Colloquium Proceedings 14 III (2004) 1497. [14] K. Bensadok, M. Belkacem, G. Nezzal, Desalination 206 (2007) 440. [15] K. Rajagopalan, T. Rusk, M. Dianovsky, Tribol. Lubr. Technol. 60 (2004) 38. [16] S.R. Pouran, A.A. Aziz, W.M.A.W. Daud, J. Ind. Eng. Chem. 21 (2015) 53. [17] E.B. Estrada-Arriaga, J.A. Zepeda-Aviles, L. García-Sánchez, Chem. Eng. J. 285 (2016) 508. [18] H. Hansson, F. Kaczala, M. Marques, W. Hogland, Int. J. Photoenergy 2012 (2012). [19] C. Feng, H. Sun, S. Li, M.K. Camarillo, W.T. Stringfellow, Y. Liang, Water Sci. Technol. 71 (2015) 1884. ski, M. Łebkowska, Pol. J. Environ. Stud. 14 (2005) 73. [20] A. Muszyn [21] S.M. Hoseini, M.M. Salarirad, M.R. Alavi Moghaddam, Desalin. Water Treat. 53 (2015) 300. [22] P. Painmanakul, T. Chintateerachai, S. Lertlapwasin, N. Rojvilavan, T. Chalermsinsuwan, N. Chawaloesphonsiya, O.-a. Larpparisudthi, Int. J. Environ. Earth Sci. 84 (2013) 128. [23] G. Bertanza, M. Collivignarelli, B. Crotti, R. Pedrazzani, Water Sci. Technol. 61 (2010) 227. [24] L.K. Wang, N.K. Shammas, W.A. Selke, D.B. Aulenbach, Flotation Technology, Springer, 2010. [25] R.F. De Sena, J.L. Tambosi, A.K. Genena, R. de F.P.M. Moreira, H.F. Schröder, H.J. José, Chem. Eng. J. 152 (2009) 151. [26] J. Rubio, M. Souza, R. Smith, Miner. Eng. 15 (2002) 139. [27] A.R., Dincer, V.-M., Sarria Muñoz, Coupled Advanced oxidation and biological processes for wastewater treatment (2003). [28] P. Bautista, A. Mohedano, J. Casas, J. Zazo, J. Rodriguez, J. Chem. Technol. Biotechnol. 83 (2008) 1323.
9
[29] N. Karakaya, E. Gunes, E. Gunes, Removal of COD from oil recovery industry wastewater by the advanced oxidation process (AOP) based on H2O2, Glob. Nest. J. 10 (2008) 31–38. [30] Y.H. Choi, S.U. Son, S.S. Lee, Sens. Actuators A: Phys. 111 (2004) 8. [31] A. Chindris, Degradation of refractory organic compounds in aqueous wastes employing a combination of biological and chemical treatments (2011). [32] J.E.F. Moraes, F.H. Quina, C.A.O. Nascimento, D.N. Silva, O. Chiavone-Filho, Environ. Sci. Technol. 38 (2004) 1183. [33] S.A.O. Galvão, A.L. Mota, D.N. Silva, J.E.F. Moraes, C.A. Nascimento, O. ChiavoneFilho, Sci. Total Environ. 367 (2006) 42. [34] L.S. Clesceri (Ed.), Standard Methods for the Examination of Water and Wastewater, 22nd ed., American Public Health Association, American Water Works Association & Water Environment Federation, Washington, 2012. [35] V. Roanoke, Evaluation of Oils and Grease and Total Petroleum Hydrocarbons in Industrial Laundry Effluents and Detergents, ETS Analytical Services, Inc., 1994 June 25. [36] Texas Natural Resource Conservation Commission Revision 03, 2001, June 1. [37] J.R. Bolton, K.G. Bircher, W. Tumas, C.A. Tolman, Pure Appl. Chem. 73 (2001) 627. [38] J.J. Pignatello, E. Oliveros, A. MacKay, Crit. Rev. Environ. Sci. Technol. 36 (2006) 1. [39] S. Karthikeyan, A. Titus, A. Gnanamani, A. Mandal, G. Sekaran, Desalination 281 (2011) 438. [40] M. Umar, H.A. Aziz, M.S. Yusoff, Waste Manag. 30 (2010) 2113. [41] J.L. Wang, L.J. Xu, Crit. Rev. Environ. Sci. Technol. 42 (2012) 251. [42] A.D. Bokare, W. Choi, J. Hazard. Mater. 275 (2014) 121. [43] M. Muruganandham, M. Swaminathan, Dyes Pigments 62 (2004) 269. [44] E. Elmolla, M. Chaudhuri, J. Hazard. Mater. 170 (2009) 666. [45] A. Rubio-Clemente, E. Chica, G.A. Peñuela, Water Air Soil Pollut. 226 (2015) 1. [46] J. Wei, Y. Song, X. Tu, L. Zhao, E. Zhi, Chem. Eng. J. 218 (2013) 319. [47] J.O. Dihora, J. Smets, T.A. Schwantes, P.D. Sands, Delivery particles, Google Patents, 2014. [48] R. Andreozzi, V. Caprio, A. Insola, R. Marotta, Catal. Today 53 (1999) 51. [49] M. Papa, R. Pedrazzani, G. Bertanza, Water Res. 47 (2013) 3679.
Please cite this article in press as: M.M. Amin, et al., Treatment of industrial wastewater contaminated with recalcitrant metal working fluids by the photo-Fenton process as post-treatment for DAF, J. Ind. Eng. Chem. (2016), http://dx.doi.org/10.1016/j.jiec.2016.10.010