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Intensification of landfill leachate treatment by advanced Fenton process using classical and statistical approach
Chemical Engineering & Processing: Process Intensification 133 (2018) 148–159
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Chemical Engineering & Processing: Process Intensification journal homepage: www.elsevier.com/locate/cep
Intensification of landfill leachate treatment by advanced Fenton process using classical and statistical approach Pranav H. Nakhate, Hrushikesh G. Patil, Kumudini V. Marathe
T
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Department of Chemical Engineering, Institute of Chemical Technology, Mumbai 400019, India
A R T I C LE I N FO
A B S T R A C T
Keywords: Advanced Fenton process (AFP) Landfill leachate One factor at a time (OFAT) Box-Behnken design model (BBD) Response surface methodology (RSM)
The intensification of complex landfill leachate treatment using advanced Fenton process (AFP) (H2O2 + Fe(II) + Ozone) was investigated with classical One Factor At a Time (OFAT) and Statistical Experimental Design (SED) approach. The Classical OFAT was employed to identify the range of operating parameters whereas SED using the Box-Behnken Design model (BBD) with Response Surface Methodology (RSM) was employed to optimise the operating parameters. In the OFAT model, the optimum dosage of operating parameter viz. Fe(II) (0.06 mol/L), H2O2 (0.6 mol/L), ozone (30 gm/m3) and pH (3) have shown COD and colour removal efficiency of 89.74% and 81.33% respectively within 120 min of reaction. Furthermore, in BBD, the optimum dosage at operating parameter viz. Fe(II) (0.06 mol/L), H2O2 (0.55 mol/L), ozone (25 gm/m3) and pH (3) have shown COD and colour removal efficiency of 89.74% and 82.9% respectively. SED model also confirms the correlation between factors and their responses in line with OFAT. The present intensification approach has helped to achieve efficient way for complex landfill leachate treatment compared to other published studies.
1. Introduction The human aggravation has consistently contributed to waste formation but this fact has been realized as a prominent issue only after massive demographic changes and industrialisation. The lack of solid waste management through proper channeling leads to some serious health concern [1]. Landfill waste disposal is the essential management strategy used by many countries due to its economic benefits [2,3]. According to central pollution control board India (CPCB), 7.80 million tonnes/annum of waste generated in India out of which 3.37 million tonnes/annum of waste goes to landfill (43.2%) [4]. This means roughly 0.2 to 0.6 kg per capita per day waste generated in India during 2014-15, depending upon the demographic size and shape and estimated to increase by 1.33% annually [4]. Despite that, one of the major environmental concern about landfill is the generation of leachate or water of precipitation which gets formed by rainwater draining through waste layer during the decomposition process [5]. Leachate may also get formed due to underground water which has been in contact with deposited waste as well as due to the biological activities carried out because of organic components from deposited waste [5,6]. Leachate is one of the hazardous effluent characterised by high concentrations of chemical oxygen demand (COD) (30,000–60,000 mg/ L) [7], biochemical oxygen demand (BOD) (4,000–6,000 g/L) [8,9],
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colour, heavy metals, ammonia (500–2000 mg/L) [9], humic acid, and toxic organic and inorganic salts [10]. The leachate composition may vary depending on the origin of wastes, types of waste, waste management and landfill age [11]. As the landfill age increases, the biodegradability ratio changes accordingly [8,12]. The juvenile leachate (< 5 years) usually characterised by having high BOD, COD and organic content values as well as higher biodegradability index (0.150.25) [9,12,13]. Matured leachate (< 5–7 years) on the other hand have much lower concentrations of biodegradable organic components due to anaerobic degradation, therefore, having lower biodegradability index (< 0.1) [6,14]. These complex characteristics of leachate cause hurdle in developing a comprehensible technique that can treat variously aged leachate, therefore combined sequential techniques have been studied recently, including flocculation-coagulation-adsorption, aerobic-anaerobic degradation and chemical oxidation [15–17]. Biological wastewater treatment processes like up-flow anaerobic sludge bioreactors (UFASB) etc. have been implemented for treatment of high strength effluents including juvenile leachate due to their cost-effective nature, high organic loading as well as their ammonia removal efficiency [18]. However, large COD quantity consumes a large amount of dissolved oxygen from effluents whereas colour being unamenable, blocks the sunlight leads to highly anaerobic condition [19]. Since the past two decade, physicochemical techniques for
Corresponding author. E-mail address: [email protected] (K.V. Marathe).
https://doi.org/10.1016/j.cep.2018.10.004 Received 22 June 2018; Received in revised form 1 October 2018; Accepted 7 October 2018 Available online 09 October 2018 0255-2701/ © 2018 Elsevier B.V. All rights reserved.
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estimation based on power dissipation, for future scale-up studies at effluent treatment plant (ETP) which may help in commercializing the process.
wastewater treatment have gained significant importance due to their high efficiency and low-cost approach. In 1980, the concept of an advanced oxidation process (AOP) was introduced for wastewater treatment after its successful implementation in potable water treatment [20,21]. AOP produces hydroxyl radicals OH ⦁ which are the most reactive oxidizing agent having an oxidation potential of 2.80 V against calomel electrode (reference electrode) [22]. Deng Y. and Zhao R. (2015) have done a detailed review on various AOP’s, their principles and their impacts on wastewater treatment, in which they mentioned that OH ⦁ are non-selective and reacts with various species with rate constants of 108-1010 M−1s−1. The main AOP which involves generation of OH ⦁ include ozone (O3), hydrogen peroxide (H2O2), etc. [21]. The integration of powerful oxidizing agents like oxygen (O2), O3, H2O2, Ultra-violet (UV) light, solar light, radiation, ultrasound, Fenton along with semiconductor catalysts [22–24] can be effective in increasing biodegradability as well as reducing COD and colour intensity of mature landfill leachate [6]. Fenton process has been widely used for the oxidation of different organic components from various wastewater stream as it contains high oxidation potential of 2.72 V [25]. It basically includes the mixture of H2O2 and ferrous salts (Fe(II)) from ferrous sulphate (FeSO4) which form a high concentration of OH ⦁ with rate constant between 53–76 M−1s−1 [25,26]. Other AOP’s are compelling in effluent treatment, however, Fenton process has significant performance as it can be operated at ambient temperature, the reagents can be available radially, safe to handle and do not require illumination [25]. The combination of Fenton process along with other oxidizing agents can improve the formation of OH ⦁ and can be termed as advanced Fenton process (AFP) [27]. A combination of Fenton process with UV radiation is called photo-Fenton process (PFP), incorporation of biological methods with electro-Fenton process, termed as Bio-electro-Fenton [28,29], whereas, in an electro-Fenton process (EFP) [30], both Fe(II) and H2O2 are electro generated via reduction on electrodes [31]. Extensive research can be observed in literature where PFP or EFP as a part of AFP was used for the treatment of landfill leachate [31–33], As discussed earlier, ozone itself has higher oxidation potential and selectivity towards organic pollutants but very few research articles have considered ozone as an oxidizing agent in association with Fenton process. several research papers have carried out ozonation either as a pre-treatment for Fenton experiments or post-Fenton experimentation to improve the treatment efficiency [34]. Composition and subsequent complexity of the effluent may hamper the utilisation quantity of ozone or Fenton process, if used as a single entity [35]. Moreover, use of AFP for the effluent treatment may decrease the operational cost based on energy consumption, enhance OH ⦁ availability and increase the COD reduction. Abu Amr, S. A. and Aziz Hamidi carried out the optimisation of stabilized landfill leachate using ozone/Fenton’s reagent in a single process for the first time. They studied operating parameters including ozone dosage, Fenton’s reagent ratio, pH and reaction time where the highest COD and colour reduction of 65% and 98% was observed respectively [36]. Abu Amr, S. A., and co-workers also carried out experiments to treat 20 L landfill leachate in order to investigate the efficiency of ozone/Fenton process in which they observed the highest COD and colour reduction of 78% and 98% respectively [35]. Therefore, it can be beheld that, in presence of Fenton’s reagent and ozone the rate of formation of OH ⦁ can be accelerated resulting into the degradation of organic components from landfill leachate [37]. The innovativeness of the present study lies in the incorporation of Fenton process with ozonation (H2O2 + Fe(II) + Ozone) in a single step to intensify “juvenile” landfill leachate treatment using OFAT for optimization of operating parameters including Fe(II) dosage, H2O2 dosage, ozone dosage, pH and reaction time. The statistical correspondence amongst individual factors like Fe(II) dosage, H2O2 dosage, and ozone dosage were evaluated using BBD with RSM. The treatment efficiency was evaluated in terms of COD and colour reduction. Moreover, lab scale dataset was developed along with approximate cost
2. Materials and methodology 2.1. Materials The chemical required for the AFP procedure viz. H2O2 (30% w/v), Ferrous sulphate heptahydrate (FeSO4.7H2O), Sulfuric acid (H2SO4), and Sodium hydroxide (NaOH) were obtained from SD fine chemicals limited, India. Ozonator of model Zeon 100 from Waterhouse, India was used for ozone generation with a constant output of 0.5 g/h (Max. 10 W electricity consumption). The Chemicals required for analysis purpose including Potassium Iodide (KI), Silver Sulphate (Ag2SO4), Mercury Sulphate (HgSO4), Potassium Dichromate (K2Cr2O7), Ferroin Indicator (0.025 M), Glucose, etc. were also purchased from SD fine chemicals Limited, India.
2.2. Leachate sampling The leachate sample was collected from Deonar dumping ground, located at eastern suburb of Mumbai city, India. It is India’s oldest and largest dumping ground with 132 ha (ha) of area and collection of almost 9000 tonnes of landfill wastes per day. Initial COD of landfill leachate was around 25,000 mg/L which was brought down to around 4000 mg/L ( ± 400) at end of UFASB in ETP using initial techniques. The landfill leachate sample was collected after UFASB reactor operation therefore, the sample was filtered prior to experimentation and stored in a dark area in order to avoid further decomposition. The collected leachate effluent contained high COD concentration of 3744 mg/L, total dissolved solids (TDS) concentration of 12,089 mg/L, the conductivity of 18.46 mS/cm, pH of 7.8 and reddish dark brown coloration due to the presence of complex landfill components showing the absorbance of 3.6 at 240 nm.
2.3. Experimental procedure The AFP experiments were performed employing both classical OFAT and SED approach. A jacketed three-neck glass reactor with a net volume of 500 mL incorporate with a gas inlet and outlet facilities were designed for AFP experimentation. The chemicals required for AFP were used without any further purification. The Fenton’s reagent was freshly prepared at every individual experiment by addition of appropriate amount of H2O2 and FeSO4.7H2O whereas ozone was generated from atmospheric oxygen via corona discharge technique using laboratory scale ozone generator. Firstly, 200 mL of landfill leachate sample with initial COD 3744 mg/L was taken into glass rector. Secondly, a known quantity of FeSO4.7H2O (for generation of Fe (II)) was added into the reactor followed by immediate addition of a known volume of H2O2. The sample was stirred vigorously at 1000 rpm on a magnetic stirrer for Fenton process whereas ozone was added into the closed reactor for AFP. The AFP experimentation was performed under constant stirring and at ambient temperature (303 K) whereas excess ozone was trapped in 1% KI solution outside the glass reactor. In classical OFAT approach, the impact of individual components was studied by varying their concentration. The Fe (II) concentration was varied from 0.02 mol/L to 0.1 mol/L, H2O2 concentration was varied from 0.1 mol/L to 1 mol/L, ozone dosage was varied from 10 g/m3 to 40 g/m3 whereas initial pH was varied from 3 to 9 using digital pH meter. After an appointed reaction time, 0.1 N NaOH was added to sample to adjust final pH at 7 approximately. The treated leachate sample was then filtered through 0.45 μm filter prior to analysis. 149
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error.
Table 1 Levels and independent values of BBD for landfill leachate treatment using AFP. Factor
Variable
3
Ozone dosage (g/m ) Fe++ concentration (mol/L) H2O2 concentration (mole/L)
X1 X2 X3
3. Results and discussion
Level Value −1
0
+1
10 0.01 0.1
25 0.06 0.55
40 0.1 1
3.1. Classical approach 3.1.1. Effect of Fe(II) on the removal of COD and colour Most of the research papers have discussed the COD and colour reduction of leachate sample by varying the molar ratio of Fe(II) and H2O2 [16,17,48,49]. In order to understand the impact of individual Fenton’s reagent parameter on landfill leachate treatment, Fe(II) and H2O2 concentrations were varied. The effect of Fe(II) ion concentration on COD and colour reduction was investigated by varying the amount of Fe(II) in Fenton’s reagent from 0.02 mol/L to 0.1 mol/L. Other operating parameters like ozone dosage of 30 g/m3, H2O2 dosage of 0.6 mol/L and pH of 3 were kept constant at standard value for initial runs. Highest COD reduction of 89.74% was perceived at 0.06 mol/L concentration of Fe(II) whereas higher colour reduction of 81.11% was also observed at λmax = 240 nm within 120 min. of reaction. The stabilization of COD and colour reduction was observed after 120 min (not presented in Figures) which is majorly due to the kinetics of Fenton’s reagent resulting in the complete consumption of Fe(II). Fe(II) reacts with excess H2O2 in order to form highly reactive OH ⦁ through electron transfer as shown in Eq. (3) below;
2.4. Experimental design RSM is a sophisticated statistical experimental design tool used for optimization of different processes. In the optimization of AFP process for the treatment of landfill leachate, the objective was to optimize the response surface which get influenced by different parameters as well as to identify the relationship between variable factors and their responses [38]. Box-Behnken design (BBD) with RSM was carried out to understand the effect of three independent variables i.e. ozone dosage (X1), Fe(II) concentration (X2) and H2O2 concentration (X3) using Design-Expert® software (Trial Version 7.0.0). It is very well reported that AFP processes are effective at acidic pH and as the pH increases, the treatment efficiency get decreases [39–41] which were also supported by the classical OFAT approach carried out at different pH earlier, therefore effect of pH was not considered for RSM study in order to avoid unnecessary experimental runs. The boundary conditions for all the three independent variables are given in Table 1 below. The total number of runs required by BBD is defined by N = 2 K (K-1) + C0, where K is the number of variables studied (3) and C0 is the number of central points (5) [42]. For present BBD with RSM study, 17 runs were carried out along with 5 replicates at the center of the design in order to excess pure error. The experimental data obtained from BBD (Table 1) were analysed and fitted into the second order polynomial equation (Eq. (1)) given below: k
y = b0 +
∑ bi xi + ∑ i=1
k=1
k
bii x i2
i=1
+
Fe (II ) + H2 O2 → Fe (III ) + OH ⦁ + OH−
The trend from Figs. 1 and 2 suggests that with an increase in Fe(II) concentration, the COD and colour reduction were also increased resulting in increased OH ⦁ concentration. These (OH ⦁) oxidises organic pollutants from leachate sample until the optimum value of 0.06 mol/L was reached. The decrease in COD and colour reduction beyond optimum Fe(II) concentration (< 0.06 mol/L) can be concluded with the fact that (OH ⦁) was scavenged by higher Fe(II) concentration, as shown in Eq. (4) below;
Fe (II ) + OH ⦁ → Fe (III ) + OH−
(4)
k
∑ ∑ i=1 j=i+1
Therefore, optimum Fe(II) concentration was selected for further reactions in order to avoid OH ⦁ scavenging [32]. Apparently, Fe(III) get produced while OH ⦁ scavenging process results into formation of iron sludge which increases operational cost.
bij x i x j (1)
Where, y is the predicted responses (COD and colour removal efficiencies in %), x i and x j are the independent variables, bi and bij are the coefficients that determine the influence of variable i and j in their response whereas bii determines the shape of the curve, b0 is the constant coefficient and k is the total number of variable studied [43–45].
3.1.2. Effect of H2O2 on the removal of COD and colour The effect of H2O2 concentration on the treatment of landfill leachate was studied under the similar experimental conditions by varying its concentration from 0.2 mol/L to 1 mol/L. The optimised Fe (II) concentration of 0.06 mol/L was selected whereas other operating parameters were kept standard. From Figs. 3 and 4, it can be seen that highest COD and colour reduction of 87.17% and 80.77% was observed respectively at 0.6 mol/L concentration of H2O2 within 120 min. of reaction. It can be noticed that as the concentration of H2O2 increases, COD and colour reduction likely increases similar to the trend observed in varying Fe(II) concentration mentioned above. At optimum condition, H2O2 strongly reacts with Fe(II) leading to the formation of OH ⦁ as mentioned in Eq. (3). COD and colour reduction stabilization was observed after 120 min (Not shown in Figure) due to unavailability of Fe (II) in the reaction. Indeed, excess H2O2 leads to OH ⦁ scavenging and formation of hydroperoxide ion (HO2−) and hydroperoxide radical (HO2⦁ ) as shown in Eq. (5) below (10).
2.5. Analytical methods The treatment efficiencies of AFP using classical and statistical approach were quantified by COD measurement and decolourisation. The samples were collected after an appropriate time interval and stored in the refrigerator at 4 °C after the addition of H2SO4 (≤ pH 2) in order to avoid further COD reduction [46]. COD was measured according to the standard protocol given by ISO 6060:1989, where samples were added into the vial along with dichromate and sulphuric acid reagents. The vials were digested in Hanna Instrument (HI)-839800 COD thermo-digester at 150 °C for 2 h. Decolourisation was observed using LMSP UV1900 Labman UV–vis double beam spectrophotometer. COD and colour treatment efficiencies (A) were calculated using the following equation (Eq. (2));
(B −B ) A (%) = 0 t × 100 B0
(3)
(2)
Where, B0 and Bt are the initial and final concentrations. The access amount of H2O2 was monitored by iodometric titration, mentioned elsewhere [47]. All the parameters for OFAT and BBD approach were measured in triplicate with an average 5% experimental
OH ⦁ + H2 O2 → HO2⦁ + H2 O
(5)
HO2⦁ + Fe (II ) → HO2− + Fe (III )
(6)
Fe(III) formed in the reaction (Eq. (6)) contributes to the iron sludge whereas remaining H2O2 may dissociate reversibly to form HO2− as mentioned below which further reacts with ozone in the generation of OH ⦁ . 150
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Fig. 1. Effect of Fe++ dosage on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; H2O2 dosage: 0.6 mol/L.
H2 O2 ⇌ HO2− + H+
(7) instead of OH− only from Eq. (3). This is further explained as shown in Eqs. (8)–(10). [51]
(7)
3.1.3. Effect of ozone and initial pH on the removal of COD and colour As we have discussed earlier, ozone itself is having higher oxidizing potential and reacts with pollutants selectively. To investigate the impact of ozone and pH on the removal of COD and colour from landfill leachate using AFP, ozone dosage was varied from 10 g/m3 to 40 g/m3 at a flow rate of 0.2-0.5 Liters per min (LPM) respectively, whereas initial pH was varied from 3 to 9 under the optimised condition. The pH of landfill leachate sample was maintained by using 0.1 N HCl and NaOH solutions prepared in DI water. It can be depicted from Figs. 5–8 that as with increased ozone dosage, COD and colour reduction was also increased. At 30 g/m3 ozone dosage (with ozone flow of 0.3 LPM), higher COD reduction and colour reduction of 87.17% and 81.11% was observed respectively. It has been discussed in the literature that O3/ H2O2 system can be effective only at higher pH due to the dominance of faster OH ⦁ production as a result of the reaction between OH− and O3 leading to decomposition of O3 [34,36,39,50]. In contradictory to that, higher COD reduction of 89.74% and higher colour reduction of 81.33% was observed at pH 3 in the AFP process. In this process, we believe that O3 likely reacts with excess HO2− formed from Eqs. (6) and
HO2− + O3 → HO2⦁ + O3⦁−
(8)
O3⦁− + H+ ⇌ HO3⦁
(9)
HO3⦁
→ O2 + OH ⦁
(10)
As a result of the overall reaction of O3 decomposition, 2 mol of OH ⦁ may get produced per mol of H2O2 and per 2 mol of O3 consumed. In addition to this, Chen et al. (2014) [52,53] have explained that Fe(II) oxidation rate is proportional to square of OH ⦁ concentration whereas H2O2 is proportion to OH ⦁ concentration only, therefore, as the pH of sample increases, Fe(II) and Fe(III) compete to react with HO2⦁ and forms hydroxyl complex like Fe(OH)++ instead of formation of OH ⦁ . 3.2. Statistical approach 3.2.1. RSM model validation & analysis of variance (ANOVA) After the optimization of AFP for landfill leachate treatment using classical OFAT approach, a statistical approach of RSM with BBD was also implemented in order to estimate the impact of an individual factor
Fig. 2. Effect of Fe++ dosage on colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; H2O2 dosage: 0.6 mol/L, λ max = 240 nm. 151
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Fig. 3. Effect of H2O2 dosage on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; optimised Fe++ dosage: 0.06 mol/L.
large p-value for LOF is preferred [45,54,55]. In the current scenario, the LOF value for COD reduction and colour reduction are 0.6507 and 0.1286 respectively indicating that LOF values are not significant hence the correlation between factors and their response. The coefficient of determination indicates variation in response predicted by the RSM model. At a higher value of R2 close to 1 is desired along with its reasonable agreement with adjusted R2 [56]. From Table 3, the R2 value of COD reduction and colour reduction was observed at 0.9977 and 0.9988 respectively which are close to 1 hence it satisfies the adjustment of quadratic model (Eqs. (11) & (12)) to the experimental data. Adjusted R2 values of COD reduction and the colour reduction was found to be 0.9947 and 0.9972 respectively which are close to the R2 values mentioned above, indicating the high significance of the model. AP is the ratio of predicted values from the design point to that of standard deviation (SD) of all predicted responses [56]. The AP value of any model needs to be more than 4 in order to confirm its adequate model discrimination. In the current study, the AP values of COD reduction and colour reduction are found to be 46.839 and 64.318 respectively which confirms that model can be significantly fitted and used for landfill leachate treatment. The predicted and actual values for COD reduction and colour reduction are mentioned in Table 2 where it can be interpreted that they are in good agreement with each other which can also be seen from Fig. 9(a) and (b) where it shows that most of the points follow the linear straight line.
as well as interaction between the factors. Different operating conditions were employed to identify the impact of variables on responses like COD and Colour removal. The experimental results are presented in Table 2 along with predicted and actual values of responses. The regression model equations based on experimental data using second order polynomial were developed for COD removal (Y1) and colour removal (Y2), mentioned below:
Y1 = 87.69 + 8.01 × X1 + 2.24 × X2 −11.54 × X3−0.64 × X1 × X2 −5.13 × X1 × X3 − 14.10 × X2 × X3−1.35 × X12 −18.53 × X22 × 24.29 × X32
(11)
Y2 = 81.90 + 8.07 × X1 + 2.16 × X2 −11.03 × X3−0.95 × X1 × X2 −4.97 × X1 × X3 − 14.15 × X2 × X3−31.66 × X12 −18.98 × X22 × 23.99 ×X32
(12)
The significance and adequacy of an experimental model are usually checked with adequate precision (AP), p-value, F value, and coefficient of determination (R2) [45,54] where the model and every model terms are significant at 95% confidence provided that p-values of F test are below 0.05. In the current study, ANOVA results of Eqs. (11) and (12), represented in Tables 2 and 3 demonstrated the p-value < 0.0001 for both COD reduction and colour reduction indicating that both models are significant. Lack of fit (LOF) in the p-value of F test indicates variation in data around the fitted model if the value is > 0.05, therefore, a
Fig. 4. Effect of H2O2 dosage on colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; optimised Fe++ dosage: 0.6 mol/L, λ max = 240 nm. 152
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Fig. 5. Effect of ozone dosage on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; Initial pH: 3; optimised Fe++ dosage: 0.06 mol/L, optimised H2O2 dosage: 0.6 mol/L.
Eqs. (5) and (6). Therefore, it can be concluded that both Fe(II) concentration and H2O2 concentration have significant interaction with each other in order to remove COD. Fig. 10(c) demonstrates surface response considering ozone (g/m3) and H2O2 (mol/L) as an independent variable. The COD reduction increment can be noted with increase in ozone dosage from 10 g/m3 to 25 g/m3 and H2O2 concentration from 0.1 mol/L to 0.55 mol/L. Beyond the optimum ozone dosage and H2O2 concentration, the decrease in COD reduction percentage was noted due to the fact that higher H2O2 concentration causes the OH ⦁ scavenging effect (mentioned earlier) whereas, at higher ozone dosage, excess ozone left unreacted and comes out from the reactor as a bubble. Therefore, both ozone dosage and H2O2 concentration have significant interaction with each other in order to remove COD.
3.2.2. Response surface plot analysis For understanding the effect of different individual variables as well as their interactive effects, a 3-dimensional plot was created based on the developed model. The generated plots represent the function of 2 variables at a time keeping another variable at a fixed value (center point) [57]. 3.2.2.1. Analysis of surface responses for COD removal. Fig. 10(a) represents surface response considering ozone (g/m3) and Fe(II) (mol/L) as an independent variables. It can be observed that COD reduction increases with an increase in Fe(II) concentration from 0.01 mol/L to 0.06 mol/L and ozone dosage from 10 g/m3 to 25 g/m3. For further increment in Fe(II) concentration and ozone dosage, the COD reduction percentage decreases due to the scavenging effect of excess Fe(II) concentration mentioned earlier in Eq. (4). Therefore, it can be concluded that both Fe(II) concentration and ozone dosage have significant interaction with each other in order to remove COD. Fig. 10(b) illustrates surface response considering Fe(II) (mol/L) and H2O2 (mol/L) as an independent variables. It can be observed that COD reduction increases with increase in Fe(II) concentration from 0.01 mol/L to 0.06 mol/L and H2O2 concentration from 0.1 mol/L to 0.55 mol/L. For further increase in Fe(II) concentration, the COD reduction percentage decreases due to the OH ⦁ scavenging effect whereas higher H2O2 concentration leads to OH ⦁ scavenging as well as formation of hydroperoxide ion (HO2−), hydroperoxide radical (HO2⦁ ) and Fe (III) which further contributes to the sludge formation as mentioned in
3.2.2.2. Analysis of surface responses for colour removal. Compare to COD reduction efficiency, AFP process is found to be slightly less efficient in colour reduction. It can be observed from Table 2 that AFP helps in reducing COD by 89.75% whereas colour by 82.91%. Fig. 11(a) shows the surface response by considering ozone dosage (g/m3) and Fe (II) (mol/L) concentration as an independent variable. It has been observed that as the ozone dosage increases from 10 g/m3 to 25 g/m3, and Fe(II) concentration from 0.01 mol/L to 0.06 mol/L, the colour reduction rate increases from 18.60% to 82.91% assuming the other parameter (H2O2) at an optimum concentration. As the ozone dosage and Fe(II) concentration increases to 40 g/m3 and 0.1 mol/L
Fig. 6. Effect of ozone dosage on colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; Initial pH: 3; optimised Fe++ dosage: 0.6 mol/L, optimised H2O2 dosage: 0.6 mol/L; λ max = 240 nm. 153
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Fig. 7. Effect of pH on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; optimised ozone dosage: 30 g/m3; optimised Fe++ dosage: 0.06 mol/L, optimised H2O2 dosage: 0.6 mol/L.
Fig. 8. Effect of pH on Colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; optimised ozone dosage: 30 g/m3; optimised Fe++ dosage: 0.06 mol/L, optimised H2O2 dosage: 0.6 mol/L; λ max = 240 nm. Table 2 Response values of different experimental conditions using BBD. Run No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Factor
Response
X1
X2
X3
% COD Recuction
Ozone (g/m3)
Fe++ (mol/L)
H2O2 (mol/L)
Actual
Predicted
Actual
Predicted
10.00 40.00 10.00 40.00 10.00 40.00 10.00 40.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00
0.01 0.01 0.10 0.10 0.06 0.06 0.06 0.06 0.01 0.10 0.01 0.10 0.06 0.06 0.06 0.06 0.06
0.55 0.55 0.55 0.55 0.10 0.10 1.00 1.00 0.10 0.10 1.00 1.00 0.55 0.55 0.55 0.55 0.55
25.641 43.5897 33.3333 48.7179 30.7692 56.4103 17.9487 23.0769 41.0256 71.7949 46.1538 20.5128 89.7436 87.1795 84.6154 87.1795 89.7436
26.92 44.23 32.69 47.44 30.45 56.73 17.63 23.40 40.06 72.76 45.19 21.47 87.69 87.69 87.69 87.69 87.69
18.6047 37.535 26.8908 42.0168 24.6499 49.8599 12.605 17.9272 34.7339 65.2661 40.8964 14.8459 81.5126 82.9132 81.5126 80.6723 82.9132
20.08 38.13 26.30 40.54 24.24 50.34 12.13 18.33 33.66 66.27 39.90 15.92 81.90 81.90 81.90 81.90 81.90
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% Colour Reduction
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reduction rate increases from 34.73% to 82.91% assuming the other parameter (ozone) at optimum concentration. As the Fe(II) and H2O2 concentration increases to 0.1 mol/L and 1 mol/L respectively, the colour reduction decreases to 14.84% due to excess OH ⦁ scavenging effect mentioned earlier. Fig. 11(c) demonstrates the surface response by considering ozone (g/m3) and H2O2 concentration as independent variable. It has been understood that as the ozone dosage increases from 10 g/m3 to 25 g/m3 and H2O2 concentration from 0.1 mol/L to 0.55 mol/L the colour reduction rate increases from 24.64% to 82.91% assuming the other parameter (Fe(II) concentration) at optimum concentration. The contour line at the center in Fig. 11(c) represents the optimum value. Perfect circular contour at the center indicates that both the variables have equal impact on colour reduction. As the ozone and H2O2 concentration increases to 40 g/m3 and 1 mol/L respectively, the colour reduction decreases to 17.92% due to excess OH ⦁ scavenging effect and saturation mentioned earlier.
Table 3 ANOVA Results and adequacy of quadratic model for COD and colour removal.
COD
Colour
Source
Sum of Square
Df
Mean Square
F Value
p-Value Prob < F
Model X1Ozone X2-Fe++ X3-H2O2 X1X2 X1X3 X2X3
11479.73 513.64
9 1
1275.53 513.64
335.32 135.03
< 0.0001 < 0.0001
X12
40.27 1065.09 1.64 105.19 795.53 4137.18
1 1 1 1 1 1
40.27 1065.09 1.64 105.19 795.53 4137.18
10.59 280.00 0.43 27.65 209.14 1087.62
0.0140 < 0.0001 0.5320 0.0012 < 0.0001 < 0.0001
X12
1445.05
1
1445.05
379.89
< 0.0001
2485.22 1 2485.22 653.34 X12 Residual 26.63 7 3.80 Lack of 8.22 3 2.74 0.60 Fit Pure 18.41 4 4.60 error SD = 1.95, R2 = 0.9977, Mean = 52.79, Adj. R2 PRESS = 160.26, Pred. R2 = 0.9861 Model 11497.08 9 1277.45 638.49 X1521.46 1 521.46 260.64 Ozone 1 37.19 18.59 X2-Fe++ 37.19 X3-H2O2 973.18 1 973.18 486.41 X1X2 3.62 1 3.62 1.81 X1X3 98.88 1 98.88 49.42 X2X3 800.40 1 800.40 400.05 4220.18 1 4220.18 2109.32 X12
X22
1517.43
1
1517.43
758.44
Significant
< 0.0001 0.6507
Not significant
3.3. Treatment efficiency
= 0.9947, AP = 46.839, < 0.0001 < 0.0001
The optimised parameter in AFP using classical OFAT approach were compared with other AOP’s including ozone/H2O2, Fenton process and ozonation. The results are demonstrated in Table 4, indicating maximum COD reduction of 89.74% using AFP whereas 81%, 76.92% and 69.23% COD reduction using ozone/H2O2, Fenton process and ozonation respectively. The optimum parameters obtained from classical OFAT and other AOP’s were analysed for their treatment efficiency. Treatment cost based on electric energy consumption plays important role in process economics. This treatment cost depends on the capacity of an individual system to reduce the undesired components (COD in this case) and time required to reduce the same. The process operation cost and energy efficiency for the hybrid system has been calculated based on energy consumption as follows [58]; For ozone process, Time required for treatment = 120 min, Initial COD = 3744 mg/L, Volume considered = 200 mL, Maximum power required for ozonation unit = 10 W, Final COD = 1152 mg/L. Therefore, power dissipation per unit volume (Power density) = 50 W/L i.e. 3, 60,000 J/L. The energy efficiency = amount of COD reduced / power dissipation = 7.2 × 10−3 mg/J. Further, the energy required for COD reduction = amount of initial COD/energy efficiency, i.e. 5.2 × 105 J/L = 0.15 kW h. In India, the cost for 1 kW h electricity varies according to the state and grid. Hence, by considering cumulative 9 Rs/ 1 kW h cost of electricity, 1.35 Rs.
Significant
0.0035 < 0.0001 0.2206 0.0002 < 0.0001 < 0.0001 < 0.0001
2422.28 1 2422.28 1210.70 < 0.0001 X32 Residual 14.01 7 2.00 Lack of 10.14 3 3.38 3.50 0.1286 Not Fit significant Pure 3.86 4 0.97 error SD = 1.41, R2 = 0.9988, Mean = 46.79, Adj. R2 = 0.9972, AP = 64.318, PRESS = 168.35, Pred. R2 = 0.9854
٭SD = Standard Deviation, Adj. R2= Adjusted R squared, AP = Adequate Precision, Pred. R2= Predicted R squared.
respectively, the colour reduction decreases to 42.01% due to supersaturation mentioned earlier. Fig. 11(b) illustrate the surface response by considering Fe(II) (mol/ L) and H2O2 concentration as independent variable. It has been seen that as the Fe(II) concentration increases from 0.01 mol/L to 0.06 mol/L and H2O2 concentration from 0.1 mol/L to 0.55 mol/L the colour
Fig. 9. Predicted Vs. Actual plot for COD reduction (a) and colour reduction (b). 155
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Fig. 10. The response surface plot of COD removal efficiency. Dependence of COD reduction (Y1) on ozone (X1) dosage, Fe++ (X2) and H2O2 concentration.
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Fig. 11. The response surface plot of Colour removal efficiency. Dependence of Colour reduction (Y1) on ozone (X1) dosage, Fe++ (X2) and H2O2 concentration.
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Table 4 Comparison of treatment efficiency between various systems based on electric energy consumption. System
Initial COD (mg/L)
COD Degradation achieved (%)
Energy efficiency (mg/J)
Energy required per unit volume (J/L)
Energy required (kWh)
Total cost related to power (Rs/L)
Chemical Cost (Rs)
Total cost (Rs)
Ref.
PhotoFenton ElectroFenton Fenton Ozone Ozone + H2O2 AFP
3800
80
1.4 × 10−3
2.7 × 106
0.75
6.75
7.19
13.94
1500
70
3.34 × 10−2
1.2 × 105
0.33
0.297
3.5
3.8
3744 3744 3744
77 69 81
8 × 10−3 7.2 × 10−3 1.98 × 10−3
4.68 × 105 5.2 × 105 1.89 × 106
0.13 0.15 0.525
1.17 1.35 4.72
6.3 – 4.11
7.47 1.35 8.83
(Primo et al., 2008) (Zhang et al., 2006) Current Study
3744
89
9.34 × 10−3
4.1 × 105
0.111
1.0
6.2
7.2
[8] F.N. Ahmed, C.Q. Lan, Treatment of land fi ll leachate using membrane bioreactors : a review, Desalination 287 (2012) 41–54, https://doi.org/10.1016/j.desal.2011.12. 012. [9] J.L. De Morais, P.P. Zamora, Use of advanced oxidation processes to improve the biodegradability of mature landfill leachates, J. Hazard. Mater. 123 (2005) 181–186, https://doi.org/10.1016/j.jhazmat.2005.03.041. [10] E. Taskan, H. Hasar, Effect of Different Leachate/Acetate Ratios in a Submerged Anaerobic Membrane Bioreactor (SAnMBR), Clean- Soil Air Water 40 (2012) 487–492, https://doi.org/10.1002/clen.201100291. [11] T.H. Christensen, P. Kjeldsen, P.L. Bjerg, D.L. Jensen, J.B. Christensen, A. Baun, H. Albrechtsen, G. Heron, Biogeochemistry of land ® ll leachate plumes, Appl. Geochem. 16 (2001) 659–718. [12] M.Z. Justin, M. Zupancic, Combined purification and reuse of landfill leachate by constructed wetland and irrigation of grass and willows, Desalination 6 (2009) 157–168, https://doi.org/10.1016/j.desal.2008.03.049. [13] K.Y. Foo, B.H. Hameed, An overview of landfill leachate treatment via activated carbon adsorption process, J. Hazard. Mater. 171 (2009) 54–60, https://doi.org/10. 1016/j.jhazmat.2009.06.038. [14] C. Wang, P. Lee, M. Kumar, Y. Huang, S. Sung, J. Lin, Simultaneous partial nitrification, anaerobic ammonium oxidation and denitrification (SNAD) in a fullscale landfill-leachate treatment plant, J. Hazard. Mater. 175 (2010) 622–628, https://doi.org/10.1016/j.jhazmat.2009.10.052. [15] D. Kulikowska, E. Klimiuk, The effect of landfill age on municipal leachate composition, Bioresour. Technol. 99 (2008) 5981–5985, https://doi.org/10.1016/j. biortech.2007.10.015. [16] S.K. Marttinen, R.H. Kettunen, K.M. Sormunen, R.M. Soimasuo, J.A. Rintala, Screening of physical – chemical methods for removal of organic material, nitrogen and toxicity from low strength landfill leachates, 46 (2002) 851–858. [17] E. Tauchert, S. Schneider, J.L. De Morais, P. Peralta-zamora, Photochemically-assisted electrochemical degradation of landfill leachate, Chemosphere 64 (2006) 1458–1463, https://doi.org/10.1016/j.chemosphere.2005.12.064. [18] H. Sun, Q. Yang, Y. Peng, X. Shi, S. Wang, S. Zhang, Advanced landfill leachate treatment using a two-stage UASB-SBR system at low temperature, J. Environ. Sci. 22 (2010) 481–485, https://doi.org/10.1016/S1001-0742(09)60133-9. [19] L.I. Hongjiang, Z. Youcai, S.H.I. Lei, G.U. Yingying, Three-stage aged refuse biofilter for the treatment of landfill leachate, J. Environ. Sci. 21 (2009) 70–75, https://doi. org/10.1016/S1001-0742(09)60013-9. [20] D.M. Bila, A.F. Montalv, A.C. Silva, M. Dezotti, Ozonation of a landfill leachate : evaluation of toxicity removal and biodegradability improvement, J. Hazard. Mater. 117 (2005) 235–242, https://doi.org/10.1016/j.jhazmat.2004.09.022. [21] Y. Deng, R. Zhao, Advanced oxidation processes (AOPs) in wastewater treatment, Curr. Pollut. Rep. 1 (2015) 167–176, https://doi.org/10.1007/s40726-015-0015-z. [22] F. Wang, D.W. Smith, M.G. El-din, Application of advanced oxidation methods for landfill leachate treatment—a review, J. Environ. Eng. Sci. 2 (2003) 413–427, https://doi.org/10.1139/S03-058. [23] C.B.C. Raj, H.L. Quen, Advanced oxidation processes for wastewater treatment : optimization of UV / H 2 O 2 process through a statistical technique, Chem. Eng. Sci. 60 (2005) 5305–5311, https://doi.org/10.1016/j.ces.2005.03.065. [24] H. Zhang, H. Jin, C. Huang, Optimization of Fenton process for the treatment of landfill leachate, J. Hazard. Mater. 125 (2005) 166–174, https://doi.org/10.1016/j. jhazmat.2005.05.025. [25] J.J. Pignatello, E. Oliveros, A. Mackay, Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton, 3389 (2007). doi:https://doi.org/10.1080/10643380500326564. [26] G.V. Buxton, C.L. Greenstock, P.W. Helman, A.B. Ross, Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (· OH /· O-) in aqueous solution, J. Phys. Chem. 17 (1988) 513–520. [27] A.G. Chakinala, D.H. Bremner, A.E. Burgess, K.C. Namkung, A modified advanced Fenton process for industrial wastewater treatment, Water Sci. Technol. 55 (2007) 59–65, https://doi.org/10.2166/wst.2007.390. [28] X. Li, S. Chen, I. Angelidaki, Y. Zhang, Bio-electro-Fenton processes for wastewater treatment : advances and prospects, Chem. Eng. J. 354 (2018) 492–506, https:// doi.org/10.1016/j.cej.2018.08.052. [29] A. Brink, C. Sheridan, K. Harding, Combined biological and advance oxidation processes for paper and pulp ef fl uent treatment, South Afr. J. Chem. Eng. 25
required to treat a 1 L sample. Based on this calculations, the cost for other processes like Fenton, Photo-Fenton, Electro-Fenton, AFP and ozonation + H2O2 have been calculated as shown in Table 4. The treatment cost required based on power dissipation was found to be less in case of Electro-Fenton, Fenton and Ozonation process, but the COD reduction capacity is found to be limited in those cases whilst, the COD reduction capacity was found to be better compared to other processes despite of slightly high cost. 4. Conclusion The process intensification of landfill leachate treatment was investigated using advanced Fenton process (AFP) (H2O2 + Fe(II) + Ozone). A correlative analysis between classical one factor at a time (OFAT) approach and statistical experimental design using a BoxBehnken model with response surface methodology (RSM) have provided well-founded results for COD reduction and colour reduction of landfill leachate. The predictions made using RSM were in good agreements with the OFAT approach indicating justifiability of optimised parameters used in the AFP method. Treatment efficiency has shown 89.74% and 81.33% of COD and colour reduction at the optimum condition when the AFP system was used, higher than that of other advanced oxidation processes (AOP’s). Therefore, based on optimum electric energy consumption and higher COD/ colour removal capability, AFP can be implemented for landfill leachate treatment. Acknowledgements We gratefully acknowledge the University Grant Commission (UGC) Gov. of India for availing financial support under the scheme F.25-1/ 2014-15 (BSR)/ No. F.5-64/2007 (BSR) and Bombay Municipal Corporation (BMC) for availing landfill leachate sample. References [1] L. Giusti, A review of waste management practices and their impact on human health, Waste Manage. 29 (2009) 2227–2239, https://doi.org/10.1016/j.wasman. 2009.03.028. [2] R.K. Rowe, Y. Yu, Clogging of finger drain systems in MSW landfills, Waste Manage. 32 (2012) 2342–2352, https://doi.org/10.1016/j.wasman.2012.07.018. [3] S. Renou, J.G. Givaudan, S. Poulain, F. Dirassouyan, P. Moulin, Landfill leachate treatment: review and opportunity, J. Hazard. Mater. 150 (2008) 468–493, https:// doi.org/10.1016/j.jhazmat.2007.09.077. [4] A. Nandan, B.P. Yadav, S. Baksi, D. Bose, Recent scenario of solid waste management in India, World Sci. News 66 (2017) 56–74. [5] O. Primo, M.J. Rivero, I. Ortiz, Photo-Fenton process as an efficient alternative to the treatment of landfill leachates, J. Hazard. Mater. 153 (2008) 834–842, https:// doi.org/10.1016/j.jhazmat.2007.09.053. [6] Mamalio-K. Barbara Pieczykolan, Izabela Plonka, Krzysztof barbusinski, Comparision of landfill leachate treatment efficiency using the advanced oxidation process, Arch. Environ. Prot. 39 (2013) 107–115, https://doi.org/10.2478/aep2013-0016. [7] T.A. Kurniawan, W. Lo, G.Y.S. Chan, Radicals-catalyzed oxidation reactions for degradation of recalcitrant compounds from landfill leachate, Chem. Eng. J. 125 (2006) 35–57, https://doi.org/10.1016/j.cej.2006.07.006.
158
Chemical Engineering & Processing: Process Intensification 133 (2018) 148–159
P.H. Nakhate et al.
[45] A.T. Nair, M.M. Ahammed, Coagulant recovery from water treatment plant sludge and reuse in post-treatment of UASB reactor effluent treating municipal wastewater, Environ. Sci. Pollut. Res. 21 (2014) 10407–10418, https://doi.org/10.1007/ s11356-014-2900-1. [46] E.P.A. (USA) EPA, Methods for Chemical Analysis of Water and Wastes, 1983. [47] H. Li, S. Zhou, Y. Sun, J. Lv, Application of response surface methodology to the advanced treatment of biologically stabilized landfill leachate using Fenton’ s reagent, Waste Manage. 30 (2010) 2122–2129, https://doi.org/10.1016/j.wasman. 2010.03.036. [48] M. Ahmadian, S. Reshadat, N. Yousefi, S.H. Mirhossieni, M.R. Zare, S.R. Ghasemi, N.R. Gilan, R. Khamutian, A. Fatehizadeh, Municipal leachate treatment by Fenton process : effect of some variable and kinetics, J. Environ. Public Health 2013 (2013) 1–6. [49] E. Atmaca, Treatment of landfill leachate by using electro-Fenton method, J. Hazard. Mater. 163 (2009) 109–114, https://doi.org/10.1016/j.jhazmat.2008.06. 067. [50] S.S.A. Amr, H.A. Aziz, M.N. Adlan, Optimization of stabilized leachate treatment using ozone / persulfate in the advanced oxidation process, Waste Manage. 33 (2013) 1434–1441, https://doi.org/10.1016/j.wasman.2013.01.039. [51] G. Merenyi, J. Lind, S. Naumov, C. von Sonntag, Reaction of ozone with hydrogen peroxide (peroxone process): a revision of current mechanistic concepts based on thermokinetic and quantum-chemical considerations, Environ. Sci. Technol. 44 (2010) 3505–3507. [52] R. Andreozzi, V. Caprio, A. Insola, R. Marotta, Advanced oxidation processes (AOP) for water purification and recovery, Catal. Today 53 (1999) 51–59, https://doi.org/ 10.1016/S0920-5861(99)00102-9. [53] Y. Chen, C. Liu, J. Nie, S. Wu, D. Wang, Removal of COD and decolorizing from landfill leachate by Fenton’ s reagent advanced oxidation, Clean Technol. Environ. Policy 16 (2014) 189–193, https://doi.org/10.1007/s10098-013-0627-1. [54] S. Ghafari, H.A. Aziz, M.H. Isa, A.A. Zinatizadeh, Application of response surface methodology (RSM) to optimize coagulation – flocculation treatment of leachate using poly-aluminum chloride (PAC) and alum, J. Hazard. Mater. 163 (2009) 650–656, https://doi.org/10.1016/j.jhazmat.2008.07.090. [55] S. Mohajeri, H.A. Abdul, M.H. Isa, M.A. Zahed, M.N. Adlan, Statistical optimization of process parameters for landfill leachate treatment using electro-Fenton technique, J. Hazard. Mater. 176 (2010) 749–758, https://doi.org/10.1016/j.jhazmat. 2009.11.099. [56] S.S. Moghaddam, M.R.A. Moghaddam, M. Arami, Coagulation / flocculation process for dye removal using sludge from water treatment plant : optimization through response surface methodology, J. Hazard. Mater. 175 (2010) 651–657, https://doi.org/10.1016/j.jhazmat.2009.10.058. [57] M. Ahmadi, F. Vahabzadeh, B. Bonakdarpour, E. Mofarrah, M. Mehranian, Application of the central composite design and response surface methodology to the advanced treatment of olive oil processing wastewater using Fenton’ s peroxidation, J. Hazard. Mater. 123 (2005) 187–195, https://doi.org/10.1016/j.jhazmat. 2005.03.042. [58] P. Thanekar, M. Panda, P.R. Gogate, Degradation of carbamazepine using hydrodynamic cavitation combined with advanced oxidation processes, Ultrason. -Sonochem. 40 (2018) 567–576, https://doi.org/10.1016/j.ultsonch.2017.08.001.
(2018) 116–122, https://doi.org/10.1016/j.sajce.2018.04.002. [30] V. Poza-Nogueiras, E. Rosales, M. Pazos, M.A. Sanroman, Accepted Manuscript, Chemosphere 201 (2018) 399–416, https://doi.org/10.1016/j.chemosphere.2018. 03.002. [31] M.A. Oturan, J. Peiroten, P. Chartrin, A.J. Acher, Complete destruction of p -nitrophenol in aqueous medium by electro-fenton method, Environ. Sci. Technol. 34 (2000) 3474–3479, https://doi.org/10.1021/es990901b. [32] H. Zhang, D. Zhang, J. Zhou, Removal of COD from landfill leachate by electroFenton method, J. Hazard. Mater. 135 (2006) 106–111, https://doi.org/10.1016/j. jhazmat.2005.11.025. [33] E. Kusvuran, O. Gulnaz, S. Irmak, O.M. Atanur, H.I. Yavuz, O. Erbatur, Comparison of several advanced oxidation processes for the decolorization of reactive Red 120 azo dye in aqueous solution, J. Hazard. Mater. 109 (2004) 85–93, https://doi.org/ 10.1016/j.jhazmat.2004.03.009. [34] S. Cortez, P. Teixeira, R. Oliveira, M. Mota, Evaluation of Fenton and ozone-based advanced oxidation processes as mature landfill leachate pre-treatments, J. Environ. Manage. 92 (2011) 749–755, https://doi.org/10.1016/j.jenvman.2010. 10.035. [35] S.S. Abu Amr, H.A. Aziz, M.N. Adlan, M.J.K. Bashir, Optimization of semi-aerobic stabilized leachate treatment using ozone /Fenton’s reagent in the advanced oxidation process, J. Environ. Sci. Health Part A Toxic/Hazard. Subst. Environ. Eng. 48 (2013) 720–729, https://doi.org/10.1080/10934529.2013.744611. [36] S.S. Abu Amr, H.A. Aziz, New treatment of stabilized leachate by ozone / Fenton in the advanced oxidation process, Waste Manage. 32 (2012) 1693–1698, https://doi. org/10.1016/j.wasman.2012.04.009. [37] M.S. Lucas, J.A. Peres, G.L. Puma, Treatment of winery wastewater by ozone-based advanced oxidation processes (O3, O3/UV and O3/ UV / H 2 O 2) in a pilot-scale bubble column reactor and process economics, Sep. Purif. Technol. 72 (2010) 235–241, https://doi.org/10.1016/j.seppur.2010.01.016. [38] N. Khoshnamvand, F.K. Mostafapour, A. Mohammadi, M. Faraji, Response surface methodology (RSM) modeling to improve removal of ciprofloxacin from aqueous solutions in photocatalytic process using copper oxide nanoparticles (CuO / UV), AMB Express. 8 (2018) 1–9, https://doi.org/10.1186/s13568-018-0579-2. [39] A. Duyar, K. Cirik, Textile wastewater treatment with ozone / Fenton process: effect of pH, K.S.U, J. Eng. Sci. 19 (2016) 76–81. [40] Y. Shen, Q. Xu, D. Gao, H. Shi, Degradation of an anthraquinone dye by ozone / Fenton : response surface approach and degradation pathway, Ozone Sci. Eng. 39 (2017) 219–232, https://doi.org/10.1080/01919512.2017.1301245. [41] Y.S. Jung, W.T. Lim, J.Y. Park, Y.H. Kim, Effect of pH on Fenton and Fenton ‐ like oxidation, (n.d.) 37–41. doi:https://doi.org/10.1080/09593330802468848. [42] M.A. Bezerra, R.E. Sanntelli, E.P. Oliveira, L.S. Villar, L.A. Escaleira, Response surface methodology (RSM) as a tool for optimization in analytical chemistry, 76 (2008) 965–977. doi:https://doi.org/10.1016/j.talanta.2008.05.019. [43] H. Zhang, Y. Li, X. Wu, Statistical experiment design approach for the treatment of landfill leachate by photoelectro-Fenton process, J. Environ. Eng. (2012) 278–286, https://doi.org/10.1061/(ASCE)EE.1943-7870.0000448. [44] M.J.K. Bashir, I.H. Farooqi, M.H. Isa, S.R.M. Kutty, Z.B. Awang, H.A. Aziz, S. Mohajeri, I.H. Farooqi, Landfill leachate treatment by electrochemical oxidation, Waste Manage. 29 (2009) 2534–2541, https://doi.org/10.1016/j.wasman.2009.05. 004.
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Chemical Engineering & Processing: Process Intensification journal homepage: www.elsevier.com/locate/cep
Intensification of landfill leachate treatment by advanced Fenton process using classical and statistical approach Pranav H. Nakhate, Hrushikesh G. Patil, Kumudini V. Marathe
T
⁎
Department of Chemical Engineering, Institute of Chemical Technology, Mumbai 400019, India
A R T I C LE I N FO
A B S T R A C T
Keywords: Advanced Fenton process (AFP) Landfill leachate One factor at a time (OFAT) Box-Behnken design model (BBD) Response surface methodology (RSM)
The intensification of complex landfill leachate treatment using advanced Fenton process (AFP) (H2O2 + Fe(II) + Ozone) was investigated with classical One Factor At a Time (OFAT) and Statistical Experimental Design (SED) approach. The Classical OFAT was employed to identify the range of operating parameters whereas SED using the Box-Behnken Design model (BBD) with Response Surface Methodology (RSM) was employed to optimise the operating parameters. In the OFAT model, the optimum dosage of operating parameter viz. Fe(II) (0.06 mol/L), H2O2 (0.6 mol/L), ozone (30 gm/m3) and pH (3) have shown COD and colour removal efficiency of 89.74% and 81.33% respectively within 120 min of reaction. Furthermore, in BBD, the optimum dosage at operating parameter viz. Fe(II) (0.06 mol/L), H2O2 (0.55 mol/L), ozone (25 gm/m3) and pH (3) have shown COD and colour removal efficiency of 89.74% and 82.9% respectively. SED model also confirms the correlation between factors and their responses in line with OFAT. The present intensification approach has helped to achieve efficient way for complex landfill leachate treatment compared to other published studies.
1. Introduction The human aggravation has consistently contributed to waste formation but this fact has been realized as a prominent issue only after massive demographic changes and industrialisation. The lack of solid waste management through proper channeling leads to some serious health concern [1]. Landfill waste disposal is the essential management strategy used by many countries due to its economic benefits [2,3]. According to central pollution control board India (CPCB), 7.80 million tonnes/annum of waste generated in India out of which 3.37 million tonnes/annum of waste goes to landfill (43.2%) [4]. This means roughly 0.2 to 0.6 kg per capita per day waste generated in India during 2014-15, depending upon the demographic size and shape and estimated to increase by 1.33% annually [4]. Despite that, one of the major environmental concern about landfill is the generation of leachate or water of precipitation which gets formed by rainwater draining through waste layer during the decomposition process [5]. Leachate may also get formed due to underground water which has been in contact with deposited waste as well as due to the biological activities carried out because of organic components from deposited waste [5,6]. Leachate is one of the hazardous effluent characterised by high concentrations of chemical oxygen demand (COD) (30,000–60,000 mg/ L) [7], biochemical oxygen demand (BOD) (4,000–6,000 g/L) [8,9],
⁎
colour, heavy metals, ammonia (500–2000 mg/L) [9], humic acid, and toxic organic and inorganic salts [10]. The leachate composition may vary depending on the origin of wastes, types of waste, waste management and landfill age [11]. As the landfill age increases, the biodegradability ratio changes accordingly [8,12]. The juvenile leachate (< 5 years) usually characterised by having high BOD, COD and organic content values as well as higher biodegradability index (0.150.25) [9,12,13]. Matured leachate (< 5–7 years) on the other hand have much lower concentrations of biodegradable organic components due to anaerobic degradation, therefore, having lower biodegradability index (< 0.1) [6,14]. These complex characteristics of leachate cause hurdle in developing a comprehensible technique that can treat variously aged leachate, therefore combined sequential techniques have been studied recently, including flocculation-coagulation-adsorption, aerobic-anaerobic degradation and chemical oxidation [15–17]. Biological wastewater treatment processes like up-flow anaerobic sludge bioreactors (UFASB) etc. have been implemented for treatment of high strength effluents including juvenile leachate due to their cost-effective nature, high organic loading as well as their ammonia removal efficiency [18]. However, large COD quantity consumes a large amount of dissolved oxygen from effluents whereas colour being unamenable, blocks the sunlight leads to highly anaerobic condition [19]. Since the past two decade, physicochemical techniques for
Corresponding author. E-mail address: [email protected] (K.V. Marathe).
https://doi.org/10.1016/j.cep.2018.10.004 Received 22 June 2018; Received in revised form 1 October 2018; Accepted 7 October 2018 Available online 09 October 2018 0255-2701/ © 2018 Elsevier B.V. All rights reserved.
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estimation based on power dissipation, for future scale-up studies at effluent treatment plant (ETP) which may help in commercializing the process.
wastewater treatment have gained significant importance due to their high efficiency and low-cost approach. In 1980, the concept of an advanced oxidation process (AOP) was introduced for wastewater treatment after its successful implementation in potable water treatment [20,21]. AOP produces hydroxyl radicals OH ⦁ which are the most reactive oxidizing agent having an oxidation potential of 2.80 V against calomel electrode (reference electrode) [22]. Deng Y. and Zhao R. (2015) have done a detailed review on various AOP’s, their principles and their impacts on wastewater treatment, in which they mentioned that OH ⦁ are non-selective and reacts with various species with rate constants of 108-1010 M−1s−1. The main AOP which involves generation of OH ⦁ include ozone (O3), hydrogen peroxide (H2O2), etc. [21]. The integration of powerful oxidizing agents like oxygen (O2), O3, H2O2, Ultra-violet (UV) light, solar light, radiation, ultrasound, Fenton along with semiconductor catalysts [22–24] can be effective in increasing biodegradability as well as reducing COD and colour intensity of mature landfill leachate [6]. Fenton process has been widely used for the oxidation of different organic components from various wastewater stream as it contains high oxidation potential of 2.72 V [25]. It basically includes the mixture of H2O2 and ferrous salts (Fe(II)) from ferrous sulphate (FeSO4) which form a high concentration of OH ⦁ with rate constant between 53–76 M−1s−1 [25,26]. Other AOP’s are compelling in effluent treatment, however, Fenton process has significant performance as it can be operated at ambient temperature, the reagents can be available radially, safe to handle and do not require illumination [25]. The combination of Fenton process along with other oxidizing agents can improve the formation of OH ⦁ and can be termed as advanced Fenton process (AFP) [27]. A combination of Fenton process with UV radiation is called photo-Fenton process (PFP), incorporation of biological methods with electro-Fenton process, termed as Bio-electro-Fenton [28,29], whereas, in an electro-Fenton process (EFP) [30], both Fe(II) and H2O2 are electro generated via reduction on electrodes [31]. Extensive research can be observed in literature where PFP or EFP as a part of AFP was used for the treatment of landfill leachate [31–33], As discussed earlier, ozone itself has higher oxidation potential and selectivity towards organic pollutants but very few research articles have considered ozone as an oxidizing agent in association with Fenton process. several research papers have carried out ozonation either as a pre-treatment for Fenton experiments or post-Fenton experimentation to improve the treatment efficiency [34]. Composition and subsequent complexity of the effluent may hamper the utilisation quantity of ozone or Fenton process, if used as a single entity [35]. Moreover, use of AFP for the effluent treatment may decrease the operational cost based on energy consumption, enhance OH ⦁ availability and increase the COD reduction. Abu Amr, S. A. and Aziz Hamidi carried out the optimisation of stabilized landfill leachate using ozone/Fenton’s reagent in a single process for the first time. They studied operating parameters including ozone dosage, Fenton’s reagent ratio, pH and reaction time where the highest COD and colour reduction of 65% and 98% was observed respectively [36]. Abu Amr, S. A., and co-workers also carried out experiments to treat 20 L landfill leachate in order to investigate the efficiency of ozone/Fenton process in which they observed the highest COD and colour reduction of 78% and 98% respectively [35]. Therefore, it can be beheld that, in presence of Fenton’s reagent and ozone the rate of formation of OH ⦁ can be accelerated resulting into the degradation of organic components from landfill leachate [37]. The innovativeness of the present study lies in the incorporation of Fenton process with ozonation (H2O2 + Fe(II) + Ozone) in a single step to intensify “juvenile” landfill leachate treatment using OFAT for optimization of operating parameters including Fe(II) dosage, H2O2 dosage, ozone dosage, pH and reaction time. The statistical correspondence amongst individual factors like Fe(II) dosage, H2O2 dosage, and ozone dosage were evaluated using BBD with RSM. The treatment efficiency was evaluated in terms of COD and colour reduction. Moreover, lab scale dataset was developed along with approximate cost
2. Materials and methodology 2.1. Materials The chemical required for the AFP procedure viz. H2O2 (30% w/v), Ferrous sulphate heptahydrate (FeSO4.7H2O), Sulfuric acid (H2SO4), and Sodium hydroxide (NaOH) were obtained from SD fine chemicals limited, India. Ozonator of model Zeon 100 from Waterhouse, India was used for ozone generation with a constant output of 0.5 g/h (Max. 10 W electricity consumption). The Chemicals required for analysis purpose including Potassium Iodide (KI), Silver Sulphate (Ag2SO4), Mercury Sulphate (HgSO4), Potassium Dichromate (K2Cr2O7), Ferroin Indicator (0.025 M), Glucose, etc. were also purchased from SD fine chemicals Limited, India.
2.2. Leachate sampling The leachate sample was collected from Deonar dumping ground, located at eastern suburb of Mumbai city, India. It is India’s oldest and largest dumping ground with 132 ha (ha) of area and collection of almost 9000 tonnes of landfill wastes per day. Initial COD of landfill leachate was around 25,000 mg/L which was brought down to around 4000 mg/L ( ± 400) at end of UFASB in ETP using initial techniques. The landfill leachate sample was collected after UFASB reactor operation therefore, the sample was filtered prior to experimentation and stored in a dark area in order to avoid further decomposition. The collected leachate effluent contained high COD concentration of 3744 mg/L, total dissolved solids (TDS) concentration of 12,089 mg/L, the conductivity of 18.46 mS/cm, pH of 7.8 and reddish dark brown coloration due to the presence of complex landfill components showing the absorbance of 3.6 at 240 nm.
2.3. Experimental procedure The AFP experiments were performed employing both classical OFAT and SED approach. A jacketed three-neck glass reactor with a net volume of 500 mL incorporate with a gas inlet and outlet facilities were designed for AFP experimentation. The chemicals required for AFP were used without any further purification. The Fenton’s reagent was freshly prepared at every individual experiment by addition of appropriate amount of H2O2 and FeSO4.7H2O whereas ozone was generated from atmospheric oxygen via corona discharge technique using laboratory scale ozone generator. Firstly, 200 mL of landfill leachate sample with initial COD 3744 mg/L was taken into glass rector. Secondly, a known quantity of FeSO4.7H2O (for generation of Fe (II)) was added into the reactor followed by immediate addition of a known volume of H2O2. The sample was stirred vigorously at 1000 rpm on a magnetic stirrer for Fenton process whereas ozone was added into the closed reactor for AFP. The AFP experimentation was performed under constant stirring and at ambient temperature (303 K) whereas excess ozone was trapped in 1% KI solution outside the glass reactor. In classical OFAT approach, the impact of individual components was studied by varying their concentration. The Fe (II) concentration was varied from 0.02 mol/L to 0.1 mol/L, H2O2 concentration was varied from 0.1 mol/L to 1 mol/L, ozone dosage was varied from 10 g/m3 to 40 g/m3 whereas initial pH was varied from 3 to 9 using digital pH meter. After an appointed reaction time, 0.1 N NaOH was added to sample to adjust final pH at 7 approximately. The treated leachate sample was then filtered through 0.45 μm filter prior to analysis. 149
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error.
Table 1 Levels and independent values of BBD for landfill leachate treatment using AFP. Factor
Variable
3
Ozone dosage (g/m ) Fe++ concentration (mol/L) H2O2 concentration (mole/L)
X1 X2 X3
3. Results and discussion
Level Value −1
0
+1
10 0.01 0.1
25 0.06 0.55
40 0.1 1
3.1. Classical approach 3.1.1. Effect of Fe(II) on the removal of COD and colour Most of the research papers have discussed the COD and colour reduction of leachate sample by varying the molar ratio of Fe(II) and H2O2 [16,17,48,49]. In order to understand the impact of individual Fenton’s reagent parameter on landfill leachate treatment, Fe(II) and H2O2 concentrations were varied. The effect of Fe(II) ion concentration on COD and colour reduction was investigated by varying the amount of Fe(II) in Fenton’s reagent from 0.02 mol/L to 0.1 mol/L. Other operating parameters like ozone dosage of 30 g/m3, H2O2 dosage of 0.6 mol/L and pH of 3 were kept constant at standard value for initial runs. Highest COD reduction of 89.74% was perceived at 0.06 mol/L concentration of Fe(II) whereas higher colour reduction of 81.11% was also observed at λmax = 240 nm within 120 min. of reaction. The stabilization of COD and colour reduction was observed after 120 min (not presented in Figures) which is majorly due to the kinetics of Fenton’s reagent resulting in the complete consumption of Fe(II). Fe(II) reacts with excess H2O2 in order to form highly reactive OH ⦁ through electron transfer as shown in Eq. (3) below;
2.4. Experimental design RSM is a sophisticated statistical experimental design tool used for optimization of different processes. In the optimization of AFP process for the treatment of landfill leachate, the objective was to optimize the response surface which get influenced by different parameters as well as to identify the relationship between variable factors and their responses [38]. Box-Behnken design (BBD) with RSM was carried out to understand the effect of three independent variables i.e. ozone dosage (X1), Fe(II) concentration (X2) and H2O2 concentration (X3) using Design-Expert® software (Trial Version 7.0.0). It is very well reported that AFP processes are effective at acidic pH and as the pH increases, the treatment efficiency get decreases [39–41] which were also supported by the classical OFAT approach carried out at different pH earlier, therefore effect of pH was not considered for RSM study in order to avoid unnecessary experimental runs. The boundary conditions for all the three independent variables are given in Table 1 below. The total number of runs required by BBD is defined by N = 2 K (K-1) + C0, where K is the number of variables studied (3) and C0 is the number of central points (5) [42]. For present BBD with RSM study, 17 runs were carried out along with 5 replicates at the center of the design in order to excess pure error. The experimental data obtained from BBD (Table 1) were analysed and fitted into the second order polynomial equation (Eq. (1)) given below: k
y = b0 +
∑ bi xi + ∑ i=1
k=1
k
bii x i2
i=1
+
Fe (II ) + H2 O2 → Fe (III ) + OH ⦁ + OH−
The trend from Figs. 1 and 2 suggests that with an increase in Fe(II) concentration, the COD and colour reduction were also increased resulting in increased OH ⦁ concentration. These (OH ⦁) oxidises organic pollutants from leachate sample until the optimum value of 0.06 mol/L was reached. The decrease in COD and colour reduction beyond optimum Fe(II) concentration (< 0.06 mol/L) can be concluded with the fact that (OH ⦁) was scavenged by higher Fe(II) concentration, as shown in Eq. (4) below;
Fe (II ) + OH ⦁ → Fe (III ) + OH−
(4)
k
∑ ∑ i=1 j=i+1
Therefore, optimum Fe(II) concentration was selected for further reactions in order to avoid OH ⦁ scavenging [32]. Apparently, Fe(III) get produced while OH ⦁ scavenging process results into formation of iron sludge which increases operational cost.
bij x i x j (1)
Where, y is the predicted responses (COD and colour removal efficiencies in %), x i and x j are the independent variables, bi and bij are the coefficients that determine the influence of variable i and j in their response whereas bii determines the shape of the curve, b0 is the constant coefficient and k is the total number of variable studied [43–45].
3.1.2. Effect of H2O2 on the removal of COD and colour The effect of H2O2 concentration on the treatment of landfill leachate was studied under the similar experimental conditions by varying its concentration from 0.2 mol/L to 1 mol/L. The optimised Fe (II) concentration of 0.06 mol/L was selected whereas other operating parameters were kept standard. From Figs. 3 and 4, it can be seen that highest COD and colour reduction of 87.17% and 80.77% was observed respectively at 0.6 mol/L concentration of H2O2 within 120 min. of reaction. It can be noticed that as the concentration of H2O2 increases, COD and colour reduction likely increases similar to the trend observed in varying Fe(II) concentration mentioned above. At optimum condition, H2O2 strongly reacts with Fe(II) leading to the formation of OH ⦁ as mentioned in Eq. (3). COD and colour reduction stabilization was observed after 120 min (Not shown in Figure) due to unavailability of Fe (II) in the reaction. Indeed, excess H2O2 leads to OH ⦁ scavenging and formation of hydroperoxide ion (HO2−) and hydroperoxide radical (HO2⦁ ) as shown in Eq. (5) below (10).
2.5. Analytical methods The treatment efficiencies of AFP using classical and statistical approach were quantified by COD measurement and decolourisation. The samples were collected after an appropriate time interval and stored in the refrigerator at 4 °C after the addition of H2SO4 (≤ pH 2) in order to avoid further COD reduction [46]. COD was measured according to the standard protocol given by ISO 6060:1989, where samples were added into the vial along with dichromate and sulphuric acid reagents. The vials were digested in Hanna Instrument (HI)-839800 COD thermo-digester at 150 °C for 2 h. Decolourisation was observed using LMSP UV1900 Labman UV–vis double beam spectrophotometer. COD and colour treatment efficiencies (A) were calculated using the following equation (Eq. (2));
(B −B ) A (%) = 0 t × 100 B0
(3)
(2)
Where, B0 and Bt are the initial and final concentrations. The access amount of H2O2 was monitored by iodometric titration, mentioned elsewhere [47]. All the parameters for OFAT and BBD approach were measured in triplicate with an average 5% experimental
OH ⦁ + H2 O2 → HO2⦁ + H2 O
(5)
HO2⦁ + Fe (II ) → HO2− + Fe (III )
(6)
Fe(III) formed in the reaction (Eq. (6)) contributes to the iron sludge whereas remaining H2O2 may dissociate reversibly to form HO2− as mentioned below which further reacts with ozone in the generation of OH ⦁ . 150
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Fig. 1. Effect of Fe++ dosage on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; H2O2 dosage: 0.6 mol/L.
H2 O2 ⇌ HO2− + H+
(7) instead of OH− only from Eq. (3). This is further explained as shown in Eqs. (8)–(10). [51]
(7)
3.1.3. Effect of ozone and initial pH on the removal of COD and colour As we have discussed earlier, ozone itself is having higher oxidizing potential and reacts with pollutants selectively. To investigate the impact of ozone and pH on the removal of COD and colour from landfill leachate using AFP, ozone dosage was varied from 10 g/m3 to 40 g/m3 at a flow rate of 0.2-0.5 Liters per min (LPM) respectively, whereas initial pH was varied from 3 to 9 under the optimised condition. The pH of landfill leachate sample was maintained by using 0.1 N HCl and NaOH solutions prepared in DI water. It can be depicted from Figs. 5–8 that as with increased ozone dosage, COD and colour reduction was also increased. At 30 g/m3 ozone dosage (with ozone flow of 0.3 LPM), higher COD reduction and colour reduction of 87.17% and 81.11% was observed respectively. It has been discussed in the literature that O3/ H2O2 system can be effective only at higher pH due to the dominance of faster OH ⦁ production as a result of the reaction between OH− and O3 leading to decomposition of O3 [34,36,39,50]. In contradictory to that, higher COD reduction of 89.74% and higher colour reduction of 81.33% was observed at pH 3 in the AFP process. In this process, we believe that O3 likely reacts with excess HO2− formed from Eqs. (6) and
HO2− + O3 → HO2⦁ + O3⦁−
(8)
O3⦁− + H+ ⇌ HO3⦁
(9)
HO3⦁
→ O2 + OH ⦁
(10)
As a result of the overall reaction of O3 decomposition, 2 mol of OH ⦁ may get produced per mol of H2O2 and per 2 mol of O3 consumed. In addition to this, Chen et al. (2014) [52,53] have explained that Fe(II) oxidation rate is proportional to square of OH ⦁ concentration whereas H2O2 is proportion to OH ⦁ concentration only, therefore, as the pH of sample increases, Fe(II) and Fe(III) compete to react with HO2⦁ and forms hydroxyl complex like Fe(OH)++ instead of formation of OH ⦁ . 3.2. Statistical approach 3.2.1. RSM model validation & analysis of variance (ANOVA) After the optimization of AFP for landfill leachate treatment using classical OFAT approach, a statistical approach of RSM with BBD was also implemented in order to estimate the impact of an individual factor
Fig. 2. Effect of Fe++ dosage on colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; H2O2 dosage: 0.6 mol/L, λ max = 240 nm. 151
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Fig. 3. Effect of H2O2 dosage on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; optimised Fe++ dosage: 0.06 mol/L.
large p-value for LOF is preferred [45,54,55]. In the current scenario, the LOF value for COD reduction and colour reduction are 0.6507 and 0.1286 respectively indicating that LOF values are not significant hence the correlation between factors and their response. The coefficient of determination indicates variation in response predicted by the RSM model. At a higher value of R2 close to 1 is desired along with its reasonable agreement with adjusted R2 [56]. From Table 3, the R2 value of COD reduction and colour reduction was observed at 0.9977 and 0.9988 respectively which are close to 1 hence it satisfies the adjustment of quadratic model (Eqs. (11) & (12)) to the experimental data. Adjusted R2 values of COD reduction and the colour reduction was found to be 0.9947 and 0.9972 respectively which are close to the R2 values mentioned above, indicating the high significance of the model. AP is the ratio of predicted values from the design point to that of standard deviation (SD) of all predicted responses [56]. The AP value of any model needs to be more than 4 in order to confirm its adequate model discrimination. In the current study, the AP values of COD reduction and colour reduction are found to be 46.839 and 64.318 respectively which confirms that model can be significantly fitted and used for landfill leachate treatment. The predicted and actual values for COD reduction and colour reduction are mentioned in Table 2 where it can be interpreted that they are in good agreement with each other which can also be seen from Fig. 9(a) and (b) where it shows that most of the points follow the linear straight line.
as well as interaction between the factors. Different operating conditions were employed to identify the impact of variables on responses like COD and Colour removal. The experimental results are presented in Table 2 along with predicted and actual values of responses. The regression model equations based on experimental data using second order polynomial were developed for COD removal (Y1) and colour removal (Y2), mentioned below:
Y1 = 87.69 + 8.01 × X1 + 2.24 × X2 −11.54 × X3−0.64 × X1 × X2 −5.13 × X1 × X3 − 14.10 × X2 × X3−1.35 × X12 −18.53 × X22 × 24.29 × X32
(11)
Y2 = 81.90 + 8.07 × X1 + 2.16 × X2 −11.03 × X3−0.95 × X1 × X2 −4.97 × X1 × X3 − 14.15 × X2 × X3−31.66 × X12 −18.98 × X22 × 23.99 ×X32
(12)
The significance and adequacy of an experimental model are usually checked with adequate precision (AP), p-value, F value, and coefficient of determination (R2) [45,54] where the model and every model terms are significant at 95% confidence provided that p-values of F test are below 0.05. In the current study, ANOVA results of Eqs. (11) and (12), represented in Tables 2 and 3 demonstrated the p-value < 0.0001 for both COD reduction and colour reduction indicating that both models are significant. Lack of fit (LOF) in the p-value of F test indicates variation in data around the fitted model if the value is > 0.05, therefore, a
Fig. 4. Effect of H2O2 dosage on colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; ozone output: 30 g/m3; Initial pH: 3; optimised Fe++ dosage: 0.6 mol/L, λ max = 240 nm. 152
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Fig. 5. Effect of ozone dosage on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; Initial pH: 3; optimised Fe++ dosage: 0.06 mol/L, optimised H2O2 dosage: 0.6 mol/L.
Eqs. (5) and (6). Therefore, it can be concluded that both Fe(II) concentration and H2O2 concentration have significant interaction with each other in order to remove COD. Fig. 10(c) demonstrates surface response considering ozone (g/m3) and H2O2 (mol/L) as an independent variable. The COD reduction increment can be noted with increase in ozone dosage from 10 g/m3 to 25 g/m3 and H2O2 concentration from 0.1 mol/L to 0.55 mol/L. Beyond the optimum ozone dosage and H2O2 concentration, the decrease in COD reduction percentage was noted due to the fact that higher H2O2 concentration causes the OH ⦁ scavenging effect (mentioned earlier) whereas, at higher ozone dosage, excess ozone left unreacted and comes out from the reactor as a bubble. Therefore, both ozone dosage and H2O2 concentration have significant interaction with each other in order to remove COD.
3.2.2. Response surface plot analysis For understanding the effect of different individual variables as well as their interactive effects, a 3-dimensional plot was created based on the developed model. The generated plots represent the function of 2 variables at a time keeping another variable at a fixed value (center point) [57]. 3.2.2.1. Analysis of surface responses for COD removal. Fig. 10(a) represents surface response considering ozone (g/m3) and Fe(II) (mol/L) as an independent variables. It can be observed that COD reduction increases with an increase in Fe(II) concentration from 0.01 mol/L to 0.06 mol/L and ozone dosage from 10 g/m3 to 25 g/m3. For further increment in Fe(II) concentration and ozone dosage, the COD reduction percentage decreases due to the scavenging effect of excess Fe(II) concentration mentioned earlier in Eq. (4). Therefore, it can be concluded that both Fe(II) concentration and ozone dosage have significant interaction with each other in order to remove COD. Fig. 10(b) illustrates surface response considering Fe(II) (mol/L) and H2O2 (mol/L) as an independent variables. It can be observed that COD reduction increases with increase in Fe(II) concentration from 0.01 mol/L to 0.06 mol/L and H2O2 concentration from 0.1 mol/L to 0.55 mol/L. For further increase in Fe(II) concentration, the COD reduction percentage decreases due to the OH ⦁ scavenging effect whereas higher H2O2 concentration leads to OH ⦁ scavenging as well as formation of hydroperoxide ion (HO2−), hydroperoxide radical (HO2⦁ ) and Fe (III) which further contributes to the sludge formation as mentioned in
3.2.2.2. Analysis of surface responses for colour removal. Compare to COD reduction efficiency, AFP process is found to be slightly less efficient in colour reduction. It can be observed from Table 2 that AFP helps in reducing COD by 89.75% whereas colour by 82.91%. Fig. 11(a) shows the surface response by considering ozone dosage (g/m3) and Fe (II) (mol/L) concentration as an independent variable. It has been observed that as the ozone dosage increases from 10 g/m3 to 25 g/m3, and Fe(II) concentration from 0.01 mol/L to 0.06 mol/L, the colour reduction rate increases from 18.60% to 82.91% assuming the other parameter (H2O2) at an optimum concentration. As the ozone dosage and Fe(II) concentration increases to 40 g/m3 and 0.1 mol/L
Fig. 6. Effect of ozone dosage on colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; Initial pH: 3; optimised Fe++ dosage: 0.6 mol/L, optimised H2O2 dosage: 0.6 mol/L; λ max = 240 nm. 153
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Fig. 7. Effect of pH on COD reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; optimised ozone dosage: 30 g/m3; optimised Fe++ dosage: 0.06 mol/L, optimised H2O2 dosage: 0.6 mol/L.
Fig. 8. Effect of pH on Colour reduction of landfill leachate via AFP. Constant ozone output: 0.5 g/h; optimised ozone dosage: 30 g/m3; optimised Fe++ dosage: 0.06 mol/L, optimised H2O2 dosage: 0.6 mol/L; λ max = 240 nm. Table 2 Response values of different experimental conditions using BBD. Run No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Factor
Response
X1
X2
X3
% COD Recuction
Ozone (g/m3)
Fe++ (mol/L)
H2O2 (mol/L)
Actual
Predicted
Actual
Predicted
10.00 40.00 10.00 40.00 10.00 40.00 10.00 40.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00
0.01 0.01 0.10 0.10 0.06 0.06 0.06 0.06 0.01 0.10 0.01 0.10 0.06 0.06 0.06 0.06 0.06
0.55 0.55 0.55 0.55 0.10 0.10 1.00 1.00 0.10 0.10 1.00 1.00 0.55 0.55 0.55 0.55 0.55
25.641 43.5897 33.3333 48.7179 30.7692 56.4103 17.9487 23.0769 41.0256 71.7949 46.1538 20.5128 89.7436 87.1795 84.6154 87.1795 89.7436
26.92 44.23 32.69 47.44 30.45 56.73 17.63 23.40 40.06 72.76 45.19 21.47 87.69 87.69 87.69 87.69 87.69
18.6047 37.535 26.8908 42.0168 24.6499 49.8599 12.605 17.9272 34.7339 65.2661 40.8964 14.8459 81.5126 82.9132 81.5126 80.6723 82.9132
20.08 38.13 26.30 40.54 24.24 50.34 12.13 18.33 33.66 66.27 39.90 15.92 81.90 81.90 81.90 81.90 81.90
154
% Colour Reduction
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reduction rate increases from 34.73% to 82.91% assuming the other parameter (ozone) at optimum concentration. As the Fe(II) and H2O2 concentration increases to 0.1 mol/L and 1 mol/L respectively, the colour reduction decreases to 14.84% due to excess OH ⦁ scavenging effect mentioned earlier. Fig. 11(c) demonstrates the surface response by considering ozone (g/m3) and H2O2 concentration as independent variable. It has been understood that as the ozone dosage increases from 10 g/m3 to 25 g/m3 and H2O2 concentration from 0.1 mol/L to 0.55 mol/L the colour reduction rate increases from 24.64% to 82.91% assuming the other parameter (Fe(II) concentration) at optimum concentration. The contour line at the center in Fig. 11(c) represents the optimum value. Perfect circular contour at the center indicates that both the variables have equal impact on colour reduction. As the ozone and H2O2 concentration increases to 40 g/m3 and 1 mol/L respectively, the colour reduction decreases to 17.92% due to excess OH ⦁ scavenging effect and saturation mentioned earlier.
Table 3 ANOVA Results and adequacy of quadratic model for COD and colour removal.
COD
Colour
Source
Sum of Square
Df
Mean Square
F Value
p-Value Prob < F
Model X1Ozone X2-Fe++ X3-H2O2 X1X2 X1X3 X2X3
11479.73 513.64
9 1
1275.53 513.64
335.32 135.03
< 0.0001 < 0.0001
X12
40.27 1065.09 1.64 105.19 795.53 4137.18
1 1 1 1 1 1
40.27 1065.09 1.64 105.19 795.53 4137.18
10.59 280.00 0.43 27.65 209.14 1087.62
0.0140 < 0.0001 0.5320 0.0012 < 0.0001 < 0.0001
X12
1445.05
1
1445.05
379.89
< 0.0001
2485.22 1 2485.22 653.34 X12 Residual 26.63 7 3.80 Lack of 8.22 3 2.74 0.60 Fit Pure 18.41 4 4.60 error SD = 1.95, R2 = 0.9977, Mean = 52.79, Adj. R2 PRESS = 160.26, Pred. R2 = 0.9861 Model 11497.08 9 1277.45 638.49 X1521.46 1 521.46 260.64 Ozone 1 37.19 18.59 X2-Fe++ 37.19 X3-H2O2 973.18 1 973.18 486.41 X1X2 3.62 1 3.62 1.81 X1X3 98.88 1 98.88 49.42 X2X3 800.40 1 800.40 400.05 4220.18 1 4220.18 2109.32 X12
X22
1517.43
1
1517.43
758.44
Significant
< 0.0001 0.6507
Not significant
3.3. Treatment efficiency
= 0.9947, AP = 46.839, < 0.0001 < 0.0001
The optimised parameter in AFP using classical OFAT approach were compared with other AOP’s including ozone/H2O2, Fenton process and ozonation. The results are demonstrated in Table 4, indicating maximum COD reduction of 89.74% using AFP whereas 81%, 76.92% and 69.23% COD reduction using ozone/H2O2, Fenton process and ozonation respectively. The optimum parameters obtained from classical OFAT and other AOP’s were analysed for their treatment efficiency. Treatment cost based on electric energy consumption plays important role in process economics. This treatment cost depends on the capacity of an individual system to reduce the undesired components (COD in this case) and time required to reduce the same. The process operation cost and energy efficiency for the hybrid system has been calculated based on energy consumption as follows [58]; For ozone process, Time required for treatment = 120 min, Initial COD = 3744 mg/L, Volume considered = 200 mL, Maximum power required for ozonation unit = 10 W, Final COD = 1152 mg/L. Therefore, power dissipation per unit volume (Power density) = 50 W/L i.e. 3, 60,000 J/L. The energy efficiency = amount of COD reduced / power dissipation = 7.2 × 10−3 mg/J. Further, the energy required for COD reduction = amount of initial COD/energy efficiency, i.e. 5.2 × 105 J/L = 0.15 kW h. In India, the cost for 1 kW h electricity varies according to the state and grid. Hence, by considering cumulative 9 Rs/ 1 kW h cost of electricity, 1.35 Rs.
Significant
0.0035 < 0.0001 0.2206 0.0002 < 0.0001 < 0.0001 < 0.0001
2422.28 1 2422.28 1210.70 < 0.0001 X32 Residual 14.01 7 2.00 Lack of 10.14 3 3.38 3.50 0.1286 Not Fit significant Pure 3.86 4 0.97 error SD = 1.41, R2 = 0.9988, Mean = 46.79, Adj. R2 = 0.9972, AP = 64.318, PRESS = 168.35, Pred. R2 = 0.9854
٭SD = Standard Deviation, Adj. R2= Adjusted R squared, AP = Adequate Precision, Pred. R2= Predicted R squared.
respectively, the colour reduction decreases to 42.01% due to supersaturation mentioned earlier. Fig. 11(b) illustrate the surface response by considering Fe(II) (mol/ L) and H2O2 concentration as independent variable. It has been seen that as the Fe(II) concentration increases from 0.01 mol/L to 0.06 mol/L and H2O2 concentration from 0.1 mol/L to 0.55 mol/L the colour
Fig. 9. Predicted Vs. Actual plot for COD reduction (a) and colour reduction (b). 155
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Fig. 10. The response surface plot of COD removal efficiency. Dependence of COD reduction (Y1) on ozone (X1) dosage, Fe++ (X2) and H2O2 concentration.
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Fig. 11. The response surface plot of Colour removal efficiency. Dependence of Colour reduction (Y1) on ozone (X1) dosage, Fe++ (X2) and H2O2 concentration.
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Table 4 Comparison of treatment efficiency between various systems based on electric energy consumption. System
Initial COD (mg/L)
COD Degradation achieved (%)
Energy efficiency (mg/J)
Energy required per unit volume (J/L)
Energy required (kWh)
Total cost related to power (Rs/L)
Chemical Cost (Rs)
Total cost (Rs)
Ref.
PhotoFenton ElectroFenton Fenton Ozone Ozone + H2O2 AFP
3800
80
1.4 × 10−3
2.7 × 106
0.75
6.75
7.19
13.94
1500
70
3.34 × 10−2
1.2 × 105
0.33
0.297
3.5
3.8
3744 3744 3744
77 69 81
8 × 10−3 7.2 × 10−3 1.98 × 10−3
4.68 × 105 5.2 × 105 1.89 × 106
0.13 0.15 0.525
1.17 1.35 4.72
6.3 – 4.11
7.47 1.35 8.83
(Primo et al., 2008) (Zhang et al., 2006) Current Study
3744
89
9.34 × 10−3
4.1 × 105
0.111
1.0
6.2
7.2
[8] F.N. Ahmed, C.Q. Lan, Treatment of land fi ll leachate using membrane bioreactors : a review, Desalination 287 (2012) 41–54, https://doi.org/10.1016/j.desal.2011.12. 012. [9] J.L. De Morais, P.P. Zamora, Use of advanced oxidation processes to improve the biodegradability of mature landfill leachates, J. Hazard. Mater. 123 (2005) 181–186, https://doi.org/10.1016/j.jhazmat.2005.03.041. [10] E. Taskan, H. Hasar, Effect of Different Leachate/Acetate Ratios in a Submerged Anaerobic Membrane Bioreactor (SAnMBR), Clean- Soil Air Water 40 (2012) 487–492, https://doi.org/10.1002/clen.201100291. [11] T.H. Christensen, P. Kjeldsen, P.L. Bjerg, D.L. Jensen, J.B. Christensen, A. Baun, H. Albrechtsen, G. Heron, Biogeochemistry of land ® ll leachate plumes, Appl. Geochem. 16 (2001) 659–718. [12] M.Z. Justin, M. Zupancic, Combined purification and reuse of landfill leachate by constructed wetland and irrigation of grass and willows, Desalination 6 (2009) 157–168, https://doi.org/10.1016/j.desal.2008.03.049. [13] K.Y. Foo, B.H. Hameed, An overview of landfill leachate treatment via activated carbon adsorption process, J. Hazard. Mater. 171 (2009) 54–60, https://doi.org/10. 1016/j.jhazmat.2009.06.038. [14] C. Wang, P. Lee, M. Kumar, Y. Huang, S. Sung, J. Lin, Simultaneous partial nitrification, anaerobic ammonium oxidation and denitrification (SNAD) in a fullscale landfill-leachate treatment plant, J. Hazard. Mater. 175 (2010) 622–628, https://doi.org/10.1016/j.jhazmat.2009.10.052. [15] D. Kulikowska, E. Klimiuk, The effect of landfill age on municipal leachate composition, Bioresour. Technol. 99 (2008) 5981–5985, https://doi.org/10.1016/j. biortech.2007.10.015. [16] S.K. Marttinen, R.H. Kettunen, K.M. Sormunen, R.M. Soimasuo, J.A. Rintala, Screening of physical – chemical methods for removal of organic material, nitrogen and toxicity from low strength landfill leachates, 46 (2002) 851–858. [17] E. Tauchert, S. Schneider, J.L. De Morais, P. Peralta-zamora, Photochemically-assisted electrochemical degradation of landfill leachate, Chemosphere 64 (2006) 1458–1463, https://doi.org/10.1016/j.chemosphere.2005.12.064. [18] H. Sun, Q. Yang, Y. Peng, X. Shi, S. Wang, S. Zhang, Advanced landfill leachate treatment using a two-stage UASB-SBR system at low temperature, J. Environ. Sci. 22 (2010) 481–485, https://doi.org/10.1016/S1001-0742(09)60133-9. [19] L.I. Hongjiang, Z. Youcai, S.H.I. Lei, G.U. Yingying, Three-stage aged refuse biofilter for the treatment of landfill leachate, J. Environ. Sci. 21 (2009) 70–75, https://doi. org/10.1016/S1001-0742(09)60013-9. [20] D.M. Bila, A.F. Montalv, A.C. Silva, M. Dezotti, Ozonation of a landfill leachate : evaluation of toxicity removal and biodegradability improvement, J. Hazard. Mater. 117 (2005) 235–242, https://doi.org/10.1016/j.jhazmat.2004.09.022. [21] Y. Deng, R. Zhao, Advanced oxidation processes (AOPs) in wastewater treatment, Curr. Pollut. Rep. 1 (2015) 167–176, https://doi.org/10.1007/s40726-015-0015-z. [22] F. Wang, D.W. Smith, M.G. El-din, Application of advanced oxidation methods for landfill leachate treatment—a review, J. Environ. Eng. Sci. 2 (2003) 413–427, https://doi.org/10.1139/S03-058. [23] C.B.C. Raj, H.L. Quen, Advanced oxidation processes for wastewater treatment : optimization of UV / H 2 O 2 process through a statistical technique, Chem. Eng. Sci. 60 (2005) 5305–5311, https://doi.org/10.1016/j.ces.2005.03.065. [24] H. Zhang, H. Jin, C. Huang, Optimization of Fenton process for the treatment of landfill leachate, J. Hazard. Mater. 125 (2005) 166–174, https://doi.org/10.1016/j. jhazmat.2005.05.025. [25] J.J. Pignatello, E. Oliveros, A. Mackay, Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton, 3389 (2007). doi:https://doi.org/10.1080/10643380500326564. [26] G.V. Buxton, C.L. Greenstock, P.W. Helman, A.B. Ross, Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (· OH /· O-) in aqueous solution, J. Phys. Chem. 17 (1988) 513–520. [27] A.G. Chakinala, D.H. Bremner, A.E. Burgess, K.C. Namkung, A modified advanced Fenton process for industrial wastewater treatment, Water Sci. Technol. 55 (2007) 59–65, https://doi.org/10.2166/wst.2007.390. [28] X. Li, S. Chen, I. Angelidaki, Y. Zhang, Bio-electro-Fenton processes for wastewater treatment : advances and prospects, Chem. Eng. J. 354 (2018) 492–506, https:// doi.org/10.1016/j.cej.2018.08.052. [29] A. Brink, C. Sheridan, K. Harding, Combined biological and advance oxidation processes for paper and pulp ef fl uent treatment, South Afr. J. Chem. Eng. 25
required to treat a 1 L sample. Based on this calculations, the cost for other processes like Fenton, Photo-Fenton, Electro-Fenton, AFP and ozonation + H2O2 have been calculated as shown in Table 4. The treatment cost required based on power dissipation was found to be less in case of Electro-Fenton, Fenton and Ozonation process, but the COD reduction capacity is found to be limited in those cases whilst, the COD reduction capacity was found to be better compared to other processes despite of slightly high cost. 4. Conclusion The process intensification of landfill leachate treatment was investigated using advanced Fenton process (AFP) (H2O2 + Fe(II) + Ozone). A correlative analysis between classical one factor at a time (OFAT) approach and statistical experimental design using a BoxBehnken model with response surface methodology (RSM) have provided well-founded results for COD reduction and colour reduction of landfill leachate. The predictions made using RSM were in good agreements with the OFAT approach indicating justifiability of optimised parameters used in the AFP method. Treatment efficiency has shown 89.74% and 81.33% of COD and colour reduction at the optimum condition when the AFP system was used, higher than that of other advanced oxidation processes (AOP’s). Therefore, based on optimum electric energy consumption and higher COD/ colour removal capability, AFP can be implemented for landfill leachate treatment. Acknowledgements We gratefully acknowledge the University Grant Commission (UGC) Gov. of India for availing financial support under the scheme F.25-1/ 2014-15 (BSR)/ No. F.5-64/2007 (BSR) and Bombay Municipal Corporation (BMC) for availing landfill leachate sample. References [1] L. Giusti, A review of waste management practices and their impact on human health, Waste Manage. 29 (2009) 2227–2239, https://doi.org/10.1016/j.wasman. 2009.03.028. [2] R.K. Rowe, Y. Yu, Clogging of finger drain systems in MSW landfills, Waste Manage. 32 (2012) 2342–2352, https://doi.org/10.1016/j.wasman.2012.07.018. [3] S. Renou, J.G. Givaudan, S. Poulain, F. Dirassouyan, P. Moulin, Landfill leachate treatment: review and opportunity, J. Hazard. Mater. 150 (2008) 468–493, https:// doi.org/10.1016/j.jhazmat.2007.09.077. [4] A. Nandan, B.P. Yadav, S. Baksi, D. Bose, Recent scenario of solid waste management in India, World Sci. News 66 (2017) 56–74. [5] O. Primo, M.J. Rivero, I. Ortiz, Photo-Fenton process as an efficient alternative to the treatment of landfill leachates, J. Hazard. Mater. 153 (2008) 834–842, https:// doi.org/10.1016/j.jhazmat.2007.09.053. [6] Mamalio-K. Barbara Pieczykolan, Izabela Plonka, Krzysztof barbusinski, Comparision of landfill leachate treatment efficiency using the advanced oxidation process, Arch. Environ. Prot. 39 (2013) 107–115, https://doi.org/10.2478/aep2013-0016. [7] T.A. Kurniawan, W. Lo, G.Y.S. Chan, Radicals-catalyzed oxidation reactions for degradation of recalcitrant compounds from landfill leachate, Chem. Eng. J. 125 (2006) 35–57, https://doi.org/10.1016/j.cej.2006.07.006.
158
Chemical Engineering & Processing: Process Intensification 133 (2018) 148–159
P.H. Nakhate et al.
[45] A.T. Nair, M.M. Ahammed, Coagulant recovery from water treatment plant sludge and reuse in post-treatment of UASB reactor effluent treating municipal wastewater, Environ. Sci. Pollut. Res. 21 (2014) 10407–10418, https://doi.org/10.1007/ s11356-014-2900-1. [46] E.P.A. (USA) EPA, Methods for Chemical Analysis of Water and Wastes, 1983. [47] H. Li, S. Zhou, Y. Sun, J. Lv, Application of response surface methodology to the advanced treatment of biologically stabilized landfill leachate using Fenton’ s reagent, Waste Manage. 30 (2010) 2122–2129, https://doi.org/10.1016/j.wasman. 2010.03.036. [48] M. Ahmadian, S. Reshadat, N. Yousefi, S.H. Mirhossieni, M.R. Zare, S.R. Ghasemi, N.R. Gilan, R. Khamutian, A. Fatehizadeh, Municipal leachate treatment by Fenton process : effect of some variable and kinetics, J. Environ. Public Health 2013 (2013) 1–6. [49] E. Atmaca, Treatment of landfill leachate by using electro-Fenton method, J. Hazard. Mater. 163 (2009) 109–114, https://doi.org/10.1016/j.jhazmat.2008.06. 067. [50] S.S.A. Amr, H.A. Aziz, M.N. Adlan, Optimization of stabilized leachate treatment using ozone / persulfate in the advanced oxidation process, Waste Manage. 33 (2013) 1434–1441, https://doi.org/10.1016/j.wasman.2013.01.039. [51] G. Merenyi, J. Lind, S. Naumov, C. von Sonntag, Reaction of ozone with hydrogen peroxide (peroxone process): a revision of current mechanistic concepts based on thermokinetic and quantum-chemical considerations, Environ. Sci. Technol. 44 (2010) 3505–3507. [52] R. Andreozzi, V. Caprio, A. Insola, R. Marotta, Advanced oxidation processes (AOP) for water purification and recovery, Catal. Today 53 (1999) 51–59, https://doi.org/ 10.1016/S0920-5861(99)00102-9. [53] Y. Chen, C. Liu, J. Nie, S. Wu, D. Wang, Removal of COD and decolorizing from landfill leachate by Fenton’ s reagent advanced oxidation, Clean Technol. Environ. Policy 16 (2014) 189–193, https://doi.org/10.1007/s10098-013-0627-1. [54] S. Ghafari, H.A. Aziz, M.H. Isa, A.A. Zinatizadeh, Application of response surface methodology (RSM) to optimize coagulation – flocculation treatment of leachate using poly-aluminum chloride (PAC) and alum, J. Hazard. Mater. 163 (2009) 650–656, https://doi.org/10.1016/j.jhazmat.2008.07.090. [55] S. Mohajeri, H.A. Abdul, M.H. Isa, M.A. Zahed, M.N. Adlan, Statistical optimization of process parameters for landfill leachate treatment using electro-Fenton technique, J. Hazard. Mater. 176 (2010) 749–758, https://doi.org/10.1016/j.jhazmat. 2009.11.099. [56] S.S. Moghaddam, M.R.A. Moghaddam, M. Arami, Coagulation / flocculation process for dye removal using sludge from water treatment plant : optimization through response surface methodology, J. Hazard. Mater. 175 (2010) 651–657, https://doi.org/10.1016/j.jhazmat.2009.10.058. [57] M. Ahmadi, F. Vahabzadeh, B. Bonakdarpour, E. Mofarrah, M. Mehranian, Application of the central composite design and response surface methodology to the advanced treatment of olive oil processing wastewater using Fenton’ s peroxidation, J. Hazard. Mater. 123 (2005) 187–195, https://doi.org/10.1016/j.jhazmat. 2005.03.042. [58] P. Thanekar, M. Panda, P.R. Gogate, Degradation of carbamazepine using hydrodynamic cavitation combined with advanced oxidation processes, Ultrason. -Sonochem. 40 (2018) 567–576, https://doi.org/10.1016/j.ultsonch.2017.08.001.
(2018) 116–122, https://doi.org/10.1016/j.sajce.2018.04.002. [30] V. Poza-Nogueiras, E. Rosales, M. Pazos, M.A. Sanroman, Accepted Manuscript, Chemosphere 201 (2018) 399–416, https://doi.org/10.1016/j.chemosphere.2018. 03.002. [31] M.A. Oturan, J. Peiroten, P. Chartrin, A.J. Acher, Complete destruction of p -nitrophenol in aqueous medium by electro-fenton method, Environ. Sci. Technol. 34 (2000) 3474–3479, https://doi.org/10.1021/es990901b. [32] H. Zhang, D. Zhang, J. Zhou, Removal of COD from landfill leachate by electroFenton method, J. Hazard. Mater. 135 (2006) 106–111, https://doi.org/10.1016/j. jhazmat.2005.11.025. [33] E. Kusvuran, O. Gulnaz, S. Irmak, O.M. Atanur, H.I. Yavuz, O. Erbatur, Comparison of several advanced oxidation processes for the decolorization of reactive Red 120 azo dye in aqueous solution, J. Hazard. Mater. 109 (2004) 85–93, https://doi.org/ 10.1016/j.jhazmat.2004.03.009. [34] S. Cortez, P. Teixeira, R. Oliveira, M. Mota, Evaluation of Fenton and ozone-based advanced oxidation processes as mature landfill leachate pre-treatments, J. Environ. Manage. 92 (2011) 749–755, https://doi.org/10.1016/j.jenvman.2010. 10.035. [35] S.S. Abu Amr, H.A. Aziz, M.N. Adlan, M.J.K. Bashir, Optimization of semi-aerobic stabilized leachate treatment using ozone /Fenton’s reagent in the advanced oxidation process, J. Environ. Sci. Health Part A Toxic/Hazard. Subst. Environ. Eng. 48 (2013) 720–729, https://doi.org/10.1080/10934529.2013.744611. [36] S.S. Abu Amr, H.A. Aziz, New treatment of stabilized leachate by ozone / Fenton in the advanced oxidation process, Waste Manage. 32 (2012) 1693–1698, https://doi. org/10.1016/j.wasman.2012.04.009. [37] M.S. Lucas, J.A. Peres, G.L. Puma, Treatment of winery wastewater by ozone-based advanced oxidation processes (O3, O3/UV and O3/ UV / H 2 O 2) in a pilot-scale bubble column reactor and process economics, Sep. Purif. Technol. 72 (2010) 235–241, https://doi.org/10.1016/j.seppur.2010.01.016. [38] N. Khoshnamvand, F.K. Mostafapour, A. Mohammadi, M. Faraji, Response surface methodology (RSM) modeling to improve removal of ciprofloxacin from aqueous solutions in photocatalytic process using copper oxide nanoparticles (CuO / UV), AMB Express. 8 (2018) 1–9, https://doi.org/10.1186/s13568-018-0579-2. [39] A. Duyar, K. Cirik, Textile wastewater treatment with ozone / Fenton process: effect of pH, K.S.U, J. Eng. Sci. 19 (2016) 76–81. [40] Y. Shen, Q. Xu, D. Gao, H. Shi, Degradation of an anthraquinone dye by ozone / Fenton : response surface approach and degradation pathway, Ozone Sci. Eng. 39 (2017) 219–232, https://doi.org/10.1080/01919512.2017.1301245. [41] Y.S. Jung, W.T. Lim, J.Y. Park, Y.H. Kim, Effect of pH on Fenton and Fenton ‐ like oxidation, (n.d.) 37–41. doi:https://doi.org/10.1080/09593330802468848. [42] M.A. Bezerra, R.E. Sanntelli, E.P. Oliveira, L.S. Villar, L.A. Escaleira, Response surface methodology (RSM) as a tool for optimization in analytical chemistry, 76 (2008) 965–977. doi:https://doi.org/10.1016/j.talanta.2008.05.019. [43] H. Zhang, Y. Li, X. Wu, Statistical experiment design approach for the treatment of landfill leachate by photoelectro-Fenton process, J. Environ. Eng. (2012) 278–286, https://doi.org/10.1061/(ASCE)EE.1943-7870.0000448. [44] M.J.K. Bashir, I.H. Farooqi, M.H. Isa, S.R.M. Kutty, Z.B. Awang, H.A. Aziz, S. Mohajeri, I.H. Farooqi, Landfill leachate treatment by electrochemical oxidation, Waste Manage. 29 (2009) 2534–2541, https://doi.org/10.1016/j.wasman.2009.05. 004.
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