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Table 10

Main results reported for the treatment of OMW by means of AOP combined with biological treatments

Advanced oxidation processes	Biological processes	Experimental conditions	Main results	References
Fenton's process	Anaerobic process	pH: 3.5 Temperature: 20 °C H₂O₂/Fe₂C ratio: 15:1 H₂O₂/COD ratio: 0.2	(i) Fenton's reagent leads to a 17.6 and 82.5% of COD and TPh reduction, respectively (ii) Anaerobic process leads to COD conversion between 52.6 and 74.0% (iii) Combined Fenton reagent/anaerobic digestion treatment leads to COD conversion between 63.6 and 88.0% (iv) Methane production ranged between 281 and 322 mL of CH₄/g COD removed	Amor et al. (2015)
Fenton's process and ozonation	Aerobic process	pH: 4.84 Temperature: 10, 20, 30 and 40 °C Fe²⁺/H₂O₂ ratio: 1:10, 1:15 and 1:20 Ozonation times: 1.8–8.7 h Ozone pressure: 0.35–1.21 kPa	(i) Fenton's reagent leads to 32.7 and 94% of COD and TPh reduction, respectively (ii) Ozonation process leads to 26.6 and 43.7% of COD and TPh reduction, respectively (iii) Combined Fenton reagent/anaerobic digestion treatment leads to a 84.2 and 81.3% of COD and TPh reduction, respectively (iv) Combined ozonation/anaerobic digestion treatment leads to a 72.5 and 94.8% of COD and TPh reduction, respectively	Beltran-Heredia et al. (2001)
Fenton's process	Aerobic process	pH: 3.5 H₂O₂/COD ratio: 0.20 H₂O₂/Fe²⁺molar ratio: 15	(i) Aerobic biodegradation alone leads to 83 and 61% of COD and TPh removal, respectively (ii) The combined process leads to 80.7 and 93.7% of COD and TPh removal, respectively	Lucas et al. (2013)
Fenton's process	Aerobic process	pH: 4.5–4.8 Temperature: 25 °C [Fe²⁺]: 0.5 g/L [H₂O₂]: 2, 4, 6, 8 g/L	The combined process leads to 79–94.77% and 36.66–73.33% of COD and TPh reduction, respectively	Kotsou et al. (2004)
Wet hydrogen peroxide catalytic oxidation (WHPCO)	Anaerobic process	pH: 2–5 Fe²⁺/H₂O₂ ratio: 1:10, 1:25 and 1:50 H₂O₂/COD ratio = 0.1:1.1, 0.1:2.2, 0.1:3.3 and 0.1:4.4	COD, BOD₅ and TOC removal rates of 75, 78 and 61%, respectively	El-Gohary et al. (2009)
Wet hydrogen peroxide catalytic oxidation (WHPCO)	Anaerobic process	pH: 5.2 Temperature: 25–50 °C [H₂O₂] = 2*10^–2 M (Al–Fe)PILC = 0.5 g/L	Reduction of the inhibition of the marine photobacteria Vibrio fischeri luminescence by 70%	Azabou et al. (2010)
Wet air oxidation (WAO)	Aerobic process	pH: 7 Temperature: 20 °C Treatment time: 10 h	Aerobic biodegradation of wet air oxidized TOPW leads to 77.1, 48.4 and 87% of COD, TC and TOC removal, respectively	Rivas et al. (2000)
Catalytic wet air oxidation (CWAO)	Anaerobic process	pH: 4.7–5.4 Temperature: 140 and 190 °C. Total air pressure: 70 bar	Removal efficiencies of 97 and 100% were obtained for TOC and TPh, respectively	Minh et al. (2008)
Electrochemical process	Anaerobic process	pH: 4.7–8.9 Temperature: 20 ± 2 °C Electrolysis charge: 10.4*10⁴ CL^–1 Supporting electrolyte KNO₃ concentrations: 0.1 M	(i) By using IrO₂ anode, 14, 91 and 85% removal rates of COD, TPh and color, respectively (ii) By using RuO₂ DSAs-type as anode, 99, 100 and 100% removal rates of COD, TPh and color, respectively	Gonçalves et al. (2012)
Electro-Fenton (EF)	Anaerobic process	pH: 4 [H₂O₂]: 0–1.5 g/L Current density: 1.25–10 A/dm²	(i) EF process leads to 65.8 and 33.1% of TPh and toxicity reduction, respectively (ii) In the combined process, total depuration of OMW has been achieved	Khoufi et al. (2006)
Electrochemical process	Aerobic process	pH: 4.5–5.0 [H₂O₂]: 0, 2.5 and 5.0%	(i) Aerobic biodegradation alone leads to 66–86 and 65% of COD and TPh removal, respectively (ii) The combined process leads to 96% of COD and TPh reduction	Kyriacou et al. (2005)
H₂O₂/UV Fenton'sreagent Photo-Fenton	Anaerobic process	pH: 12.6 Temperature: 20–35 °C. [Fe²⁺]: 2.410⁻³ and 4.810⁻³ M [H₂O₂]: 0.055–0.11 M	(i) The single UV radiation leads to 35 and 20% of COD and aromatic compounds removal, respectively (ii) The H₂O₂/UV system gives 41–76% of COD and 52% of aromatic compounds removal (iii) The combined process leads to 63–78% of COD reduction, and 277–282 mL CH₄/g COD removed for the methane yield coefficient	Benitez et al. (2001a)
Heterogeneous photocatalysis (TiO₂/UV)	Anaerobic process	pH: 4.8–7.5 Temperature: 37 °C Treatment time: 8–24 h	Over 90.8 ± 2.7%, 79.3 ± 1.9% and 50.3 ± 6.3% removal efficiencies of TPh, color and COD respectively	Costa & Alves (2013)
Ultrasound	Anaerobic process	pH: 5.14 Temperature: 35 ± 2 °C Power: 50–100 W Frequency: 20 kHz Power densities: 0.2 and 0.4 W/mL	(i) The application of ultrasound alone increased soluble chemical oxygen demand/total chemical oxygen demand SCOD/TCOD ratio from 0.59 to 0.79 (ii) An increase in methane production of 20% for ultrasound pretreated diluted OMW compared with the untreated one	Oz & Uzun (2015)
Ozonation	Anaerobic process	pH: 5.09–8 Treatment time: 1–7 h Temperature: 35 °C	(i) TPh and unsaturated lipids removal percentages up to 50% without variation of COD concentration (ii) Ozonated OMW have stronger inhibitory effect compared to untreated ones on methanogenic bacteria. Nevertheless, this effect is not present on acidogenic bacteria	Andreozzi et al. (1998)
Ozonation	Aerobic process	pH: 7 Temperature: 20 °C Ozone pressure: 1.69 and 1.73 kPa	(i) Ozonation followed by aerobic degradation leads to 84.6% of COD removal (ii) Aerobic degradation followed by ozonation leads to 81.8% of COD removal	Benitez et al. (1999a)
Ozonation	Aerobic process	pH: 13.5 Temperature: 28 ± 0.2 °C Ozone pressure: 0.82 and 1.22 kPa	(i) Single aerobic process leads to 80 and 75% of COD and TPh reduction, respectively (ii) Ozonation followed by aerobic degradation leads to 85 and 88% of COD and TPh reduction, respectively	Benitez et al. (2001b)
Ozonation, O₃/UV	Aerobic process	pH: 9.07–13.05 Temperature: 20 °C Ozone pressure: 4.70 kPa Flow-rate: 40 L/h	(i) Single ozonation process leads to 82–92% of COD reduction (ii) O₃/UV system leads to 88–96% of COD reduction (iii) Ozonation process followed by aerobic degradation leads to 96–97% of COD reduction	Benitez et al. (2002)
Ozonation	Aerobic process	pH: 13.5 Temperature: 28 ± 0.2 °C Ozone pressure: 0.82 and 1.22 kPa Flow-rate: 60 L/h	(i) Single aerobic process leads to 80 and 50–75% of COD and TPh reduction, respectively (ii) Ozonation followed by aerobic degradation leads to 85 of COD and 88% of TPh reduction	Benitez et al. (1999b)
Ozonation	Aerobic process	pH: 7–13.6 Temperature: 10, 20 and 30 °C Ozone pressure: 5.093 and 5.601 kPa Flow-rate: 125 L/h	(i) Single ozonation process leads to 55, 84 and 76% of COD, TPh and aromatic compounds reduction, respectively (ii) Single aerobic degradation leads to 90, 80 and 35% of COD, TPh and aromatic compounds reduction, respectively (iii) Aerobic degradation followed by ozonation process leads to 98.57, 97.6 and 95.82% of COD, TPh and aromatic compounds reduction, respectively	Beltran-Heredia et al. (2000a)
Ozonation	Aerobic process	pH: 4–9 Temperature: 10–30 °C Treatment time: 4–6 h Ozone pressure: 4.36 and 4.48 kPa	(i) Single ozonation process leads to 24–33 and 30–67% of COD and TPh reduction, respectively (ii) Ozonation followed by aerobic degradation leads to 82 and 76% of COD and TPh reduction, respectively	Beltran-Heredia et al. (2000b)
Ozonation	Aerobic process	pH: 4–10 Flow-rate: 20 L/h Acidic timing (min): 0–20, 155–165 Alkaline timing (min): 20–155, 165–180	(i) For TOPW, 87.4% of COD and 97.3% of TPh were removed (ii) For OMW, 99% of COD and 90% of TPh were removed	Rivas et al. (2001c)
Ozonation, O₃/UV	Aerobic process	pH: 3 Temperature: 25 °C Treatment time: 4–6 h Flow-rate: 35 L/h	(i) Ozonation followed by aerobic degradation leads to 87% of COD reduction (ii) Aerobic degradation followed by ozonation process leads to 80% of COD reduction (iii) O₃/UV followed by aerobic degradation leads to 90.7% of COD reduction (iv) Aerobic degradation followed by O₃/UV leads to 81.8% of COD reduction	Lafi et al. (2009)
Ozonation	Anaerobic process	pH: 7.5 Temperature: 35 °C Biological treatment time: 55 days Ozonation time: 30–240 min Ozone pressure: 1–4.9 kPa Flow-rate: 90 L/h	(i) Anaerobic digestion resulted 81, 95, 95% and 295 L CH₄/kg COD of COD, BOD₅, TPh removal and methane yield coefficient, respectively (ii) Ozonation post treatment leads to 16–52% of COD and 68–89% of TPh reduction	Beltran de Heredia & Garcia (2005)
Ozonation	Encapsulated biomass	pH:7–8.5 Temperature: 20–25 °C Treatment time: 1 h O₃ − 48 h biotreatment Flow-rate: 1 L/min	(i) Ozonation alone leads to 20% COD and 61% TPh removal (ii) The combined process leads to 36% COD and 61% TPh removal	Oz et al. (2018)

Advanced oxidation processes	Biological processes	Experimental conditions	Main results	References
Fenton's process	Anaerobic process	pH: 3.5 Temperature: 20 °C H₂O₂/Fe₂C ratio: 15:1 H₂O₂/COD ratio: 0.2	(i) Fenton's reagent leads to a 17.6 and 82.5% of COD and TPh reduction, respectively (ii) Anaerobic process leads to COD conversion between 52.6 and 74.0% (iii) Combined Fenton reagent/anaerobic digestion treatment leads to COD conversion between 63.6 and 88.0% (iv) Methane production ranged between 281 and 322 mL of CH₄/g COD removed	Amor et al. (2015)
Fenton's process and ozonation	Aerobic process	pH: 4.84 Temperature: 10, 20, 30 and 40 °C Fe²⁺/H₂O₂ ratio: 1:10, 1:15 and 1:20 Ozonation times: 1.8–8.7 h Ozone pressure: 0.35–1.21 kPa	(i) Fenton's reagent leads to 32.7 and 94% of COD and TPh reduction, respectively (ii) Ozonation process leads to 26.6 and 43.7% of COD and TPh reduction, respectively (iii) Combined Fenton reagent/anaerobic digestion treatment leads to a 84.2 and 81.3% of COD and TPh reduction, respectively (iv) Combined ozonation/anaerobic digestion treatment leads to a 72.5 and 94.8% of COD and TPh reduction, respectively	Beltran-Heredia et al. (2001)
Fenton's process	Aerobic process	pH: 3.5 H₂O₂/COD ratio: 0.20 H₂O₂/Fe²⁺molar ratio: 15	(i) Aerobic biodegradation alone leads to 83 and 61% of COD and TPh removal, respectively (ii) The combined process leads to 80.7 and 93.7% of COD and TPh removal, respectively	Lucas et al. (2013)
Fenton's process	Aerobic process	pH: 4.5–4.8 Temperature: 25 °C [Fe²⁺]: 0.5 g/L [H₂O₂]: 2, 4, 6, 8 g/L	The combined process leads to 79–94.77% and 36.66–73.33% of COD and TPh reduction, respectively	Kotsou et al. (2004)
Wet hydrogen peroxide catalytic oxidation (WHPCO)	Anaerobic process	pH: 2–5 Fe²⁺/H₂O₂ ratio: 1:10, 1:25 and 1:50 H₂O₂/COD ratio = 0.1:1.1, 0.1:2.2, 0.1:3.3 and 0.1:4.4	COD, BOD₅ and TOC removal rates of 75, 78 and 61%, respectively	El-Gohary et al. (2009)
Wet hydrogen peroxide catalytic oxidation (WHPCO)	Anaerobic process	pH: 5.2 Temperature: 25–50 °C [H₂O₂] = 2*10^–2 M (Al–Fe)PILC = 0.5 g/L	Reduction of the inhibition of the marine photobacteria Vibrio fischeri luminescence by 70%	Azabou et al. (2010)
Wet air oxidation (WAO)	Aerobic process	pH: 7 Temperature: 20 °C Treatment time: 10 h	Aerobic biodegradation of wet air oxidized TOPW leads to 77.1, 48.4 and 87% of COD, TC and TOC removal, respectively	Rivas et al. (2000)
Catalytic wet air oxidation (CWAO)	Anaerobic process	pH: 4.7–5.4 Temperature: 140 and 190 °C. Total air pressure: 70 bar	Removal efficiencies of 97 and 100% were obtained for TOC and TPh, respectively	Minh et al. (2008)
Electrochemical process	Anaerobic process	pH: 4.7–8.9 Temperature: 20 ± 2 °C Electrolysis charge: 10.4*10⁴ CL^–1 Supporting electrolyte KNO₃ concentrations: 0.1 M	(i) By using IrO₂ anode, 14, 91 and 85% removal rates of COD, TPh and color, respectively (ii) By using RuO₂ DSAs-type as anode, 99, 100 and 100% removal rates of COD, TPh and color, respectively	Gonçalves et al. (2012)
Electro-Fenton (EF)	Anaerobic process	pH: 4 [H₂O₂]: 0–1.5 g/L Current density: 1.25–10 A/dm²	(i) EF process leads to 65.8 and 33.1% of TPh and toxicity reduction, respectively (ii) In the combined process, total depuration of OMW has been achieved	Khoufi et al. (2006)
Electrochemical process	Aerobic process	pH: 4.5–5.0 [H₂O₂]: 0, 2.5 and 5.0%	(i) Aerobic biodegradation alone leads to 66–86 and 65% of COD and TPh removal, respectively (ii) The combined process leads to 96% of COD and TPh reduction	Kyriacou et al. (2005)
H₂O₂/UV Fenton'sreagent Photo-Fenton	Anaerobic process	pH: 12.6 Temperature: 20–35 °C. [Fe²⁺]: 2.410⁻³ and 4.810⁻³ M [H₂O₂]: 0.055–0.11 M	(i) The single UV radiation leads to 35 and 20% of COD and aromatic compounds removal, respectively (ii) The H₂O₂/UV system gives 41–76% of COD and 52% of aromatic compounds removal (iii) The combined process leads to 63–78% of COD reduction, and 277–282 mL CH₄/g COD removed for the methane yield coefficient	Benitez et al. (2001a)
Heterogeneous photocatalysis (TiO₂/UV)	Anaerobic process	pH: 4.8–7.5 Temperature: 37 °C Treatment time: 8–24 h	Over 90.8 ± 2.7%, 79.3 ± 1.9% and 50.3 ± 6.3% removal efficiencies of TPh, color and COD respectively	Costa & Alves (2013)
Ultrasound	Anaerobic process	pH: 5.14 Temperature: 35 ± 2 °C Power: 50–100 W Frequency: 20 kHz Power densities: 0.2 and 0.4 W/mL	(i) The application of ultrasound alone increased soluble chemical oxygen demand/total chemical oxygen demand SCOD/TCOD ratio from 0.59 to 0.79 (ii) An increase in methane production of 20% for ultrasound pretreated diluted OMW compared with the untreated one	Oz & Uzun (2015)
Ozonation	Anaerobic process	pH: 5.09–8 Treatment time: 1–7 h Temperature: 35 °C	(i) TPh and unsaturated lipids removal percentages up to 50% without variation of COD concentration (ii) Ozonated OMW have stronger inhibitory effect compared to untreated ones on methanogenic bacteria. Nevertheless, this effect is not present on acidogenic bacteria	Andreozzi et al. (1998)
Ozonation	Aerobic process	pH: 7 Temperature: 20 °C Ozone pressure: 1.69 and 1.73 kPa	(i) Ozonation followed by aerobic degradation leads to 84.6% of COD removal (ii) Aerobic degradation followed by ozonation leads to 81.8% of COD removal	Benitez et al. (1999a)
Ozonation	Aerobic process	pH: 13.5 Temperature: 28 ± 0.2 °C Ozone pressure: 0.82 and 1.22 kPa	(i) Single aerobic process leads to 80 and 75% of COD and TPh reduction, respectively (ii) Ozonation followed by aerobic degradation leads to 85 and 88% of COD and TPh reduction, respectively	Benitez et al. (2001b)
Ozonation, O₃/UV	Aerobic process	pH: 9.07–13.05 Temperature: 20 °C Ozone pressure: 4.70 kPa Flow-rate: 40 L/h	(i) Single ozonation process leads to 82–92% of COD reduction (ii) O₃/UV system leads to 88–96% of COD reduction (iii) Ozonation process followed by aerobic degradation leads to 96–97% of COD reduction	Benitez et al. (2002)
Ozonation	Aerobic process	pH: 13.5 Temperature: 28 ± 0.2 °C Ozone pressure: 0.82 and 1.22 kPa Flow-rate: 60 L/h	(i) Single aerobic process leads to 80 and 50–75% of COD and TPh reduction, respectively (ii) Ozonation followed by aerobic degradation leads to 85 of COD and 88% of TPh reduction	Benitez et al. (1999b)
Ozonation	Aerobic process	pH: 7–13.6 Temperature: 10, 20 and 30 °C Ozone pressure: 5.093 and 5.601 kPa Flow-rate: 125 L/h	(i) Single ozonation process leads to 55, 84 and 76% of COD, TPh and aromatic compounds reduction, respectively (ii) Single aerobic degradation leads to 90, 80 and 35% of COD, TPh and aromatic compounds reduction, respectively (iii) Aerobic degradation followed by ozonation process leads to 98.57, 97.6 and 95.82% of COD, TPh and aromatic compounds reduction, respectively	Beltran-Heredia et al. (2000a)
Ozonation	Aerobic process	pH: 4–9 Temperature: 10–30 °C Treatment time: 4–6 h Ozone pressure: 4.36 and 4.48 kPa	(i) Single ozonation process leads to 24–33 and 30–67% of COD and TPh reduction, respectively (ii) Ozonation followed by aerobic degradation leads to 82 and 76% of COD and TPh reduction, respectively	Beltran-Heredia et al. (2000b)
Ozonation	Aerobic process	pH: 4–10 Flow-rate: 20 L/h Acidic timing (min): 0–20, 155–165 Alkaline timing (min): 20–155, 165–180	(i) For TOPW, 87.4% of COD and 97.3% of TPh were removed (ii) For OMW, 99% of COD and 90% of TPh were removed	Rivas et al. (2001c)
Ozonation, O₃/UV	Aerobic process	pH: 3 Temperature: 25 °C Treatment time: 4–6 h Flow-rate: 35 L/h	(i) Ozonation followed by aerobic degradation leads to 87% of COD reduction (ii) Aerobic degradation followed by ozonation process leads to 80% of COD reduction (iii) O₃/UV followed by aerobic degradation leads to 90.7% of COD reduction (iv) Aerobic degradation followed by O₃/UV leads to 81.8% of COD reduction	Lafi et al. (2009)
Ozonation	Anaerobic process	pH: 7.5 Temperature: 35 °C Biological treatment time: 55 days Ozonation time: 30–240 min Ozone pressure: 1–4.9 kPa Flow-rate: 90 L/h	(i) Anaerobic digestion resulted 81, 95, 95% and 295 L CH₄/kg COD of COD, BOD₅, TPh removal and methane yield coefficient, respectively (ii) Ozonation post treatment leads to 16–52% of COD and 68–89% of TPh reduction	Beltran de Heredia & Garcia (2005)
Ozonation	Encapsulated biomass	pH:7–8.5 Temperature: 20–25 °C Treatment time: 1 h O₃ − 48 h biotreatment Flow-rate: 1 L/min	(i) Ozonation alone leads to 20% COD and 61% TPh removal (ii) The combined process leads to 36% COD and 61% TPh removal	Oz et al. (2018)

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