Advanced Oxidation Processes for Wastewater Treatment

Beate GüntherInstitute for Geo ScienceJohannes Gutenberg University MainzTutor: Prof. Dr. R.-D. Wilken

Introduction

Oxidation-Reduction-ReactionTransfer of electrons (loss, gain)

Chemical Oxidation Main aim: Mineralization of organic compounds intoCO2 , H2O and harmless inorganic products

Oxidizing AgentEffects the oxidation of a substanceGets reduced

Quelle: DVGW Lehr-und Handbuch der Wasserversorgung Bd. 6 (2004) S.316

OH-radicale

Ozon

Hydrogen Peroxid

Permanganat

Oxygen

The higher the Redox-Potential, the higher the Oxidation-Power

Oxidizing Agents

Advanced Oxidation Processes (AOP) -Characteristics

same chemical feature: Production of OH-Radicals

Very reactive speciesAttack the most part of organic molecules Little selectivity of attack useful for an oxidant used in wastewater treatment

Work under ambient Conditions

AOP´s different reacting Systems e.g. :

Fenton-/Fenton-like Reactions, Ozone-Water-UV Systems, electrochemical OxidationDifferent combinations

Fenton Reaction

Producing OH radicals by means of addition of H2O2 to Fe²+ salts

Easy way to produce OH-RadicalFe non toxic, abundantNo special instrumentspH dependent (2,7-2,8)Neutralization - Flocks, Sludge (disposal problems)

Ozon-Water-System O3/H2O2 H2O2/UV O3/UV

O3 higher absorption yield than H2O2H2O2 is effective at wave lengths < 254nmSpecial instrumentsOzone generation is expensive

proaquaComparision of some AOP - Example

pH 3 u. 10 UV/O3 pH ?? UV/ H2O2 / Fe²+

Points to consider for O3/H2O2 - H2O2/UV - O3/UV

Influence of pHOH-Radical ScavengerLight wastingMass transfer limitationAdditional equipmentsCost evaluation

Capital costs, operating costs, maintenanceDepends on the nature and concentration of the pollutants, flow rate, reactor configuration

Boron Doped Diamond – Elektrode (EAOP)

•Covered with thin layer Diamond •Doped with Boron – make conductive•Bears a high over voltage (Material)•Generation of OH-Radicals direct from water

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BDD-Electrode

CSB-Abbau

0

200

400

600

800

1000

1200

0 50 100 150 200 250 300

Zeit t (min)

CSB

(mg/

l) I = 1,36 A

Nach Modell

bei I= 3,03

Material does not expendNo chemicals Water needs just a conductivityDegradation depends on current densityOptimal current density – depends on CODEasy to handleExpensive to produce

ConclusionsAOP´s high application

Drinking waterWaste waterIndustrial wastewaterSoil

Pretreatment for biological treatment

High potential (research)

Efficiency depends on character and concentration of pollutions

ReferencesS. Parsons Advanced oxidation processes for water and wastewater treatment, IWA Publishing(2004)

P. Bautista et al. Review: An overview of the application of Fenton oxidation to industrialwastewaters treatment, Journal of Chemical Biotechnology 83 (2008) 1323-1338

Ruppert UV/O3, UV/H2O2, UV/TiO2 and the Photo-Fenton Reaction Comparison of AdvancedOxidation Processes for Wastewater Treatment, Cosmosphere 28 (1994) 1147-1454

W.H. Glaze et al. The chemistry of water treatment processes involving ozone, hydrogen peroxideand ultraviolet radiation, Ozone Sci. Eng. 9 (1987) 335

R. Andreozzi et al. Advanced oxidation processes (AOP) for water purification and recovery, Catalysis Today 53 (1999) 51-59

C. Höfl et al. Oxidative degradation of AOX and COD by different advanced oxidation processes: A comparative study with two samples of pharmaceutical wastewater, Wat. Sci. Tech. Vol. 35 (1997) 257-264

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