use of advanced oxidation processes to improve the biodegradability … · processes to improve the...

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Use of Advanced OxidationProcesses to Improve the

Biodegradability of LandfillLeachates

Eric D. van Hullebusch (Associate Professor, UPE, France) and Mehmet A.Oturan (Full Professor, UPE, France)

Université Paris-Est, Laboratoire Géomatériaux et Environnement, EA 4508, 5 bdDescartes, 77454 Marne la Vallée Cedex 2, France. * E-mail : [email protected]

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Content• Context• Landfill leachates characteristics• Biological treatments• Physicochemical treatments• Advanced oxidation processes (AOP)

– Presentation of AOP’s– Why AOP’s?– Electro-fenton treatment– Enhanced biodegradability

• Integrated advanced oxidation process and biologicaltreatments

• Conclusions and futures perspectives

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Context• Leachates are defined as the aqueous effluent

generated as a consequence of rainwater percolationthrough wastes, biochemical processes in waste'scells and the inherent water content of wastesthemselves.

• Leachates may contain large amounts of organicmatter (biodegradable, but also refractory tobiodegradation), where humic-type constituents consistan important group, as well as ammonia-nitrogen,heavy metals, chlorinated organic and inorganicsalts.

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Context• The removal of organic material based on

– chemical oxygen demand (COD),– biological oxygen demand (BOD)

• and– ammonium

=> usual prerequisite before discharging the leachates intonatural waters.

• Toxicity analysis carried out using various testorganisms (Vibrio fisheri, Daphnia similes, Artemiasalina, Brachydanio rerio …) have confirmed thepotential dangers of landfill leachates and thenecessity to treat it so as to meet the standards fordischarge in receiving waters.Thomas et al., 2009, Journal of Toxicology and Environmental Health, Part B, 12:83-105

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Landfill leachatescharacteristics

From Kurniawan et al. (2010)J. Environ. Monit., 2010, 12,2032-2047

Low effluent biodegradability

60,94890-12-01-Methylnaphthalene

1,35991-57-62-methylnaphthalene

1,46485-01-8Phenanthrene

1,547100-02-74-Nitrophenol

2127-18-4Tetrachloroethylene

2117-84-0Dioctyl phthalate

2108-90-7Chlorobenzene

3100-42-5Styrene

3108-67-81,3,5-Trimethylbenzene

695-50-11,2-Dichlorobenzene

795-63-61,2,4-Trimethylbenzene

898-82-8Isopropylbenzene

991-20-3Naphthalene

14106-46-7p-Dichlorobenzene

2195-47-6o-Xylene

30100-41-4Ethylbenzene

71108-88-3Toluene

19999-87-6p-Cymene

Concentration inµg/lCAS n°Organic compound

0,43104-35-84-

Nonylphenolmonoethoxylate

0,512140-66-9p-tert-Octylphenol

0,539129-00-0Pyrene

0,60283-32-9Acenaphthene

0,784-66-2Diethyl phthalate

0,7541-73-11,3-Dichlorobenzene

0,742206-44-0Fluoranthene

0,92686-73-7Fluorene

Concentration inµg/lCAS n°Organic compound

Landfill leachates characteristics

Organic micropollutants concentrationfrom the mixed landfill leachatessolutionsFrom µg/l to ng/L concentration range

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0,34620427-84-34 Nonylphenoldiethoxylate

0,1742531-84-22-Methylphenanthrene

0,208120-12-7Anthracene


0,284-69-5diisobutyl phthalate

0,17234883-43-7PCB 8

0,16832598-10-0PCB 66

0,148832-71-33-MethyIphenanthrene

0,14635693-99-3PCB-52

0,1415862-07-4PCB 29

0,13132-65-0Dibenzothiophene

0,11537680-65-2PCB 18

0,11356-55-3Benz[a]anthracene


0,09237680-73-2PCB 101

Concentration inµg/lCAS n°Organic compounds Concentration

in µg/lCAS n°Organic compounds

0,04132598-14-4PCB 105

0,04331317-07-41-methyl-dibenzothiophene

0,04876-44-8Heptachlor

0,04931508-00-6PCB 118

0,06241464-39-5PCB 44

0,0784-74-2Dibutyl phthalate

0,0787372-88-54-methyl-dibenzothiophene

Organic micropollutants concentration from a mixed landfill leachates solutions

Landfill leachates characteristics

Main compounds: Chlorinated compounds,PAH, sulfur compounds, phenols andalkylated phenols, phthalate esters

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• Municipal landfill leachates: A significantsource for new and emerging pollutants ?

From Eggen et al., 2010, Science of the Total Environment, 408 (21) 5147-5157

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From Eggen et al., 2010, Science of theTotal Environment, 408 (21) 5147-5157

Relativedistribution of

compoundgroups

Total contentof organic

compounds

Based on GCpeak areas of theGC-MS full scan

analysis

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• Municipal landfill leachates: A significant sourcefor new and emerging pollutants ?– Emerging compounds identified in untreated leachates

samples at nanogram or microgram par liter levels• Chlorinated alkylphosphates• Carcinogenic flame retardant (TCPP)• Neurotoxin plasticizer (NBBS)• Insect repellent (DEET)• PFC’s• Pharmaceuticals• Personal care products such as NSAIDs (ibuprofen and

naproxen)• Polycyclic musk compounds

From Eggen et al., (2010) Science of the Total Environment, 408 (21) 5147-5157

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• Many emerging compounds are identified at higher levels inthe water phase then in the particles phase.

• Since they also seem to be rather persistent, they might bepose significant removal challenge in treatment processes.

• Therefore, Eggen et al. (2010) have shown that municipallandfill leachates may represent a significant source of concernfor legacy, new and emerging chemicals in groundwater.

• => Additional knowledge about the environmental fate andtoxicology of emerging compounds is necessary in order toaddress the need for improved treatment technologies forsustainable and efficient removal of these compounds.

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Conventional treatments

• Conventional landfill leachate treatments canbe classified into three major groups:– (a) leachate transfer: recycling and combined

treatment with domestic sewage,– (b) biodegradation: aerobic and anaerobic

processes– (c) chemical and physical methods: chemical

oxidation, adsorption, chemical precipitation,coagulation/flocculation, sedimentation/flotationand air stripping.

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Biological treatments• Due to its reliability, simplicity and high cost-effectiveness,

biological treatment (suspended/attached growth) is commonlyused for the removal of high concentrations of BOD.

• Biodegradation is carried out by microorganisms, which candegrade organics compounds to carbon dioxide and sludgeunder aerobic conditions and to biogas (a mixture comprisingchiefly CO2 and CH4) under anaerobic conditions.

• Biological processes have been shown to be very effective inremoving organic and nitrogenous matter from immatureleachate when the BOD/COD ratio has a high value (>0.5).

• With time, the major presence of refractory compounds(mainly humic and fulvic acids) tends to limit process'seffectiveness.

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Biological treatments

• Among the biological treatments, AS, SBRand UASB are the most frequently applied.

• These treatments are effective to– remove over 90% of COD with a concentration

ranging from 3500–26 000 mg.L-1,– to achieve 80% of NH3–N removal with a

concentration ranging from 100–1000 mg.L-1.

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• Aerobic treatment• In aerobic treatments, microbes consume

organic materials as their energy sources inthe presence of oxygen.

• In addition, an aerobic process oxidizesNH3–N into nitrate or biomass.

• The most common aerobic biologicaltreatments are AS, SBR, AL and RBC .

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• SBR• Recently SBR has been widely employed as

one of the most promising options for thebiological treatment of leachate.

• Basically SBR is an activated sludgetreatment in a reactor.

• This technique can capture solids andremove organic compounds in a vessel,eliminating the need for a clarifier.

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• SBR• There are five operating

phases in an SBRsystem:– filling,– reacting,– settling,– Drawing– idling.

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• SBR• This reactor design is ideally suited to nitrification–denitrification or

nitritation-anammox studies, as it provides an operational regimecompatible with a concurrent nitrification and the oxidation of organiccarbon.

• Between the filling and drawing phases, the operating conditions couldbe controlled by a periodical change of the concentration of O2,substrate and inorganic nutrients.

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Biological treatments• SBR

From Kurniawan et al. (2010) J. Environ. Monit., 2010, 12, 2032-2047

COD removal from 38 to 97 %NH3-N removal from 23 to 100 %

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Biological treatments• SBR• There are various advantages in using SBR for leachate

treatment such as:– the ease of operation and maintenance,– its ability to treat a wide range of contaminant loading in a single

reactor,– less sludge bulking,– tolerance to shock loading– no separate clarifiers required, thus reducing operational costs.

• In spite of its advantages, SBR has a variety of drawbacks suchas:– odor generation,– excess sludge production, as well as high energy consumption.

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Biological treatments• Anaerobic process.• In the anaerobic process, microbes are cultivated in the absence of

oxygen, while organics are converted by methanogenic bacteria toCO2, CH4 and other metabolite products as the end products.

• This treatment is preferable to provide energy, while simultaneouslyreducing greenhouse gas emissions.

• Due to the substantial amount of readily biodegradable VFAcompounds, anaerobic treatment is suitable for young leachate.

• Therefore, the most extensively applied anaerobic process for leachatetreatment is UASB.

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Biological treatments• Anaerobic process.

The UASB process was initially developed in The Netherlands in 1970-80 withthe following basic concepts: (i) the separation of the solid and gas phases fromthe liquid and (ii) the conversion of organic matter in the leachate into methaneas bioenergy.

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Biological treatments• Uflow anaerobic sludge blanket (UASB).• In recent years, the UASB reactor has gained global acceptance to

treat leachate with a COD concentration higher than 10000 mg.L-1.

• Basically, an anaerobic process requires a reactor containing wasteand bacteria responsible for the digestion process.

• When the waste enters the bottom of the reactor and flows upwardthrough a blanket of biologically formed granules, the microbes in thereactor form granules through self-immobilization of the bacteria cells.

• Concentrated waste in the form of sludge is then added into thereactor, where it is mixed with the reactor's contents to produce biogasas presented in the following reaction:

• (C6H10O5)n + nH2O → 3nCO2 + 3nCH4

– where n represents the coefficient of reaction of each molecule.

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Biological treatments• Uflow anaerobic sludge blanket (UASB).• Various parameters play major roles in enhancing the

effectiveness of a UASB reactor for leachatetreatment.– (i) the operating conditions (temperature, organic loading

rate, hydraulic retention time and the upflow velocity),– (ii) the influent characteristics (strength of leachate,

molecular size distribution),– (iii) the treatment system (reactor configuration, control

system),– (iv) the sludge bed characteristics.

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Biological treatments• Uflow anaerobic sludge blanket (UASB).• The UASB process for leachate treatment has several

advantages.– This technique enables the liquid, gas and solid phases in the

waste to be separated in one vessel without requiring a separatemechanical mixing and an additional settling unit.

– Unlike other biological processes, UASB has many competitiveadvantages in terms of its ability to treat the varying strength andcomposition of leachate.

– In addition, the sludge generated from the UASB process has goodsettling characteristics, provided that the sludge is not exposed toheavy mechanical agitation.

– Moreover, methane as the biogas produced under the anaerobiccondition is a new resource of energy.

• In spite of its benefits,– UASB can not cope with high loading rate variation.– In addition, it requires a long starting up period (2–8 months) for the

development of anaerobic granules and acclimatization.– These drawbacks may limit its application for leachate treatment.

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Physicochemical treatments

• Physical and chemical processes includereduction of suspended solids, colloidalparticles, floating material, color, and toxiccompounds by :– either flotation, coagulation/flocculation,

adsorption, chemical oxidation and air stripping.• Physical/chemical treatments for the landfill

leachate are used in addition at the treatmentline (pre-treatment or last purification) or totreat a specific pollutant (stripping forammonia).

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Advanced oxidation processesPresentation of AOP’s• Chemical oxidation is a widely studied method for the treatment

of effluents containing refractory compounds such as landfillleachate. Growing interest has been recently focused onadvanced oxidation processes (AOP).

• Most of them, except simple ozonation (O3), use a combinationof strong oxidants, e.g. O3 and H2O2, irradiation, e.g. ultraviolet(UV), ultrasound (US) or electron beam (EB), and catalysts, e.g.transition metal ions or photocatalyst.

Why AOP’s?• AOP, adapted to old or well-stabilized leachate, are applied to:

– oxidize organics substances to their highest stable oxidation statesbeing carbon dioxide and water (i.e., to reach completemineralization),

– improve the biodegradability of recalcitrant organic pollutants upto a value compatible with subsequent economical biologicaltreatment.

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Advanced oxidation processesList of typical AOP systems

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Advanced oxidation processes

From Renou et al., 2008

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Fenton’s reaction : H2O2 + Fe2+ Fe3+ + OH- + .OH

Electrochemistry : In situ synthesis of Fenton’s reagent

Organic

pollutants

CO2

• Electro-Fenton

• Fenton’s reaction assisted by electrochemistry

• Electrochemical advanced oxidation process

• In situ electrochemical generation of Fenton’s reagent (H202 + Fe(II))allowing the formation of •OH


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Electrochemical reactor: Open, cylindrical and non divided- Cathode:Carbon-felt - Anode: Pt, BDD or mixed metal oxides

• Reagent : compressed air / O2

• Catalyst : Fe3+ , Cu2+ , ... ( < 1 mM )


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OH.

Fe2+

Fe3+

e-

2 e-

H2O2

OH-

H+

H2O

2 e-

1/2 O2 + 2 H+

Oturan et al., J. Electroanal. Chem., 507 (2001) 96

Electro-Fenton: Electrocatalytic production of °OH


e-

Pt anode

Carbon feltcathode

stirring

Air

Thermometer

pH meter

Galvanostat

e-

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Mix of 8 French landfill leachates : mainly MSW, Industrial wastes

No need to add (Fe3+) I = 1 A

système EF : Carbon felt electrode / BDE

BEFORE AFTER

0

1000

2000

3000

4000

0 5 10 15 20

Temps (h)

CO

T (

mg

C L

-1)

0

20

40

60

80

100

120

1 2 3 4 5 6

COT

Taux

d'abattement

COT(%)

0 3 6 9 14 18

% a

batt

em

en

t C

OT

Durée du traitement (h)


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From Umar et al., (2010) Waste Management 30, 2113-2121

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Integrated advanced oxidation process(AOP) and biological treatments.

• In the past three decades (1976–2005), increasing scholarly interesthas been shown in the application of AOP such as ozonation, Fenton'soxidation to transform toxic pollutants into relatively harmlesssubstances.

• Among the AOPs reviewed, ozonation and the Fenton's oxidationare the most frequently investigated and commonly employed.

• However, other novel photo-oxidative technologies using UV LED as alight source or atomic layer deposit thin films as a photocatalyst arecurrently tested for its feasibility for leachate treatment.

• A combination of AOP and biological process enhances itstreatment performance for leachate. An almost complete CODremoval (98%) was attained by combining AS and Fenton's oxidation(COD: 7000 mg.L-1) and/or the AS and wet air oxidation (COD: 4140mg.L-1).

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Integrated advanced oxidation process(AOP) and biological treatments

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Conclusions and futureperspectives

• Several treatment strategies may bedesigned– For mature landfill

• AOP pre-treatment (enhance biodegradability) followedby UASB and/or SBR biological treatment

• Biological treatment (SBR or UASB) followed by AOPpost-treatment (removal of residual biorefractory COD)prior to release into sewer network or the environment

– Residual organic micropollutants and toxicityshould be evaluated prior discharges

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• Thank you for your attention

EMJD : Environmental Technologies forContaminated Solids, Soils and Sediments(ETeCoS3)

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Literature references• Renou et al. (2008) Landfill leachate treatment: Review and opportunity Journal

of Hazardous Materials, 150 (3), 468-493.• Umar et al. (2010) Trends in the use of Fenton, electro-Fenton and photo-

Fenton for the treatment of landfill leachate Waste Management, 30 (11), 2113-2121.

• Panizza et al. (2010) Electrochemical process for the treatment of landfillleachate. Journal of Applied Electrochemistry, 40 (10), 1721-1727.

• Wiszniowski et al. (2006) Landfill leachate treatment methods: A reviewEnvironmental Chemistry Letters, 4 (1), 51-61.

• De Morais and Zamora (2005) Use of advanced oxidation processes to improvethe biodegradability of mature landfill leachates Journal of Hazardous Materials,123 (1-3), 181-186.

• Thomas et al., (2009) Bioassays for the evaluation of landfill leachate toxicity.Jounral of Toxicology and Environmnetal Health, Part B 12, 12-83

• Kurniawan et al., (2010) Biological process for treatment of landfill leachate.Journal of Environmental Monitoring 12, 2032-2047.

• Eggen et al., (2010) Municipal lanfill leachates: A significant source for new andemergent pollutants. Science of the Total Environment 408, 5147-5157.

• Yalmaz and Ozturk (2001) Biological ammonia removal from anaerobically pre-treated landfill leachate in sequancing batch reactors (SBR). Water Science andTechnology 43, 307-314.

• Brillas et al. (2009) Electro-Fenton process and related electrochemicaltechnologies based on Fenton's reaction chemistry, Chem. Rev. 109,6570–6631.

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