OZONATION COMBINED WITH MEMBRANE BIO-REACTOR FOR LANDFILL LEACHATE TREATMENT

by

Alia Chaturapruek

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering.

Examination Committee: Prof. C. Visvanathan (Chairman) Prof. Chongrak Polprasert Dr. Seung-Hwan Lee Nationality: Thai

Previous Degree: Bachelor of Engineering in Civil Engineering Prince of Songkla University Songkhla, Thailand Scholarship Donor: Her Majesty the Queen

Asian Institute of Technology School of Environment, Resources and Development

Thailand August 2003

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Acknowledgements The author would like to start this thesis with profound gratitude, great appreciation and indebtedness to her advisor, Prof. C. Visvanathan, for his valuable guidance, encouragement, support and stimulating ideas. His enthusiasm and systematic approach in completing the work challenged her to do her best. Prof. C. Visvanathan is not only academic assistance, but also sharing knowledge and professional experience to solve the problems that happen throughout the study period. Special thanks are extended to Prof. Chongrak Polprasert and Dr. Lee Seung-Hwan, the members of the examination committee, for their useful suggestions and comments, which have been a great help in attaining the objectives of this study. Acknowledgements are extended to SACWET and KIST project for their financial support for the research and equipment, without which completion of the thesis would have been difficult. The author wishes to present deepest sincere thanks to Ms. Sindhuja Sankaran and Mr. Periyathamby Kuruparan for their suggestions, helping and effort to edit my English writing. The author gives her deepest appreciation to Asian Institute of Technology (AIT) for providing the scholarship that made her able to pursue the master program at AIT. She also gives her deepest appreciation to staff member of the AIT Environmental Engineering Program, both laboratory and secretary sections. Words of thanks must also be conveyed to other advisees of Prof. C. Visvanathan both Master and Doctoral students for their cooperation, suggestion and discussion. Special thanks for her friends inside and outside AIT, especially Mr. Ekbordin for their company, friendship, encouragement, and help during her hard period of experiment. Finally, the author would like to express her deepest gratitude and dedicate this research work to her parents and brothers, whose love, assisted the author through difficult times and contributed to the success of this study.

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Abstract Landfill leachate consisting of refractory compounds has characteristics similar to

that of high-strength wastewater. The present treatment sequence includes Ammonia stripping process and Membrane Bioreactor (MBR) process scheme further required the development of post-treatment. Ozonation is one of the advanced oxidation processes which could be effective as a post biological treatment. A major advantage of the ozonation process is ability of ozone to oxidize and convert the non-biodegradable compounds into lower molecular weight compounds, which would enhance biodegradability. For this reason, a sequence of MBR and ozonation was developed in order to achieve maximum pollutant removal efficiency. The experiments were conducted in the laboratory scale experiments. The MBR system consists of yeast and bacterial systems. The effluents from both reactors were used for ozonation. The effect of ozone in terms of COD, TOC, Color, and BOD removal were determined. After the optimization of all parameters, the optimum conditions were used for combined MBR and ozonation system. The effect of ozone in the sludge of both the yeast and bacteria based MBR for sludge treatment and disposal was also studied. The results obtained from the experiments indicated that: A) The ozone transfer efficiency was low, which indicated the poor ability of ozone in the gas phase to transfer into the liquid phase. B) The optimum ozone concentration was found to be 75 mg/L for both effluents in terms of maximum COD, TOC, and Color removal. C) The optimum ozone contact time for yeast effluent was 90 minutes, where the COD, TOC, and Color removal efficiency were 49 %, 34.5 %, and greater than 95 %, respectively. The optimum ozone contact time for bacterial effluent was 45 minutes, where the biodegradability improvement indicated as BOD/COD ratio increased from 0.0342 to 0.0847. The COD, TOC, and Color removal efficiency for bacterial effluent at optimum condition were 39 %, 30 %, and greater than 95 %, respectively. D) The addition of Hydrogen Peroxide did not improve the removal efficiency of ozone. Thus, ozonation alone was used in the combined system. E) The overall COD removal efficiency of the combined system consisting of MBR and ozonation process was found slightly improved compared to original system. The efficiency increased from 79 % to 83.4 % for yeast and from 78.4 % to 82.5 % for bacterial system. F) Ozone was effective in sludge disintegration with a sludge reduction of 59 % and 28 % for yeast and bacterial sludge, respectively. Ozone also helped in improving the settleability and dewatering ability of sludge. From the overall results, it could be concluded that ozonation is an effective method as a post-biological treatment for landfill leachate especially in terms of color removal.

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Table of Contents

Chapter Title Page

Title Page i Acknowledgements ii

Abstract iii Table of Contents iv

List of Tables vi List of Figures vii List of Abbreviations x

1 Introduction 1

1.1 General 1 1.2 Objectives of the study 2 1.3 Scopes of the study 2

2 Literature Review 3

2.1 Introduction 3 2.1.1 Landfill leachate generation 3 2.1.2 Compositions and Characteristics of landfill leachate 4 2.1.3 Identification of organic substances and concentration 5

in municipal landfill leachate 2.1.4 Landfill leachate treatment and disposal 5

2.2 Application of Membrane Bioreactor in wastewater treatment 8 2.2.1 Membrane Bioreactor (MBR) process 8 2.2.2 Advantages, disadvantages, and comparison of MBR 9 with other processes

2.2.3 Application of MBR process in wastewater treatment 10 2.3 Application of chemical oxidation in wastewater treatment 11 2.3.1 General of chemical oxidation 11 2.3.2 Chemical oxidants used in wastewater treatment 12

2.3.3 Advantages of ozone in wastewater treatment 14 2.4 Application of ozone (O3) in wastewater treatment 14 2.4.1 Fundamental aspects and kinetics of O3 14

2.4.2 Kinetics studies for ozonation 15 2.4.3 Reaction of ozone with humic and fulvic acids

2.5 Ozonation and a combination of ozone with other 18 chemical oxidants in wastewater treatment specially landfill leachate treatment

2.6 Ozonation of sludge for sludge disposal 21 2.7 Advanced Oxidation Processes (AOPs) 23

3 Methodology 24

3.1 Overall experimental plan 24 3.2 Experimental setup 25

3.2.1 Membrane Bioreactor phase 25 3.2.2 Ozonation phase 25

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3.3 Batch study 28 3.3.1 Calibration 29

3.3.2 Effluent ozonation 31 3.3.3 Parameter optimization 33 3.3.4 Experimental implementation 34

3.4 Continuous study 38 3.4.1 Implementation of batch optimized parameter and 38

development of a continuous ozone system 3.4.2 Continuous experiment 38 3.4.3 Development of a sequence MBR and Ozonation 38

3.5 Ozonation of the sludge or MLSS from both yeast and 39 bacterial reactors

3.5.1 Sludge treatment in the mean of sludge reduction 39 3.5.2 Sludge treatment in term of reducing solid concentration 39

3.6 Analytical methods 41

4 Results and Discussions 43 4.1 Ozone Calibration studies 43

4.1.1 Determination of ozone in gas and liquid phase 43 4.1.2 Determination of the mass transfer and ozone transfer 45 efficiency 4.1.3 Ozone kinetic studies 47

4.2 Chemical oxidation of MBR effluent by Ozone (O3) 55 4.2.1 Effect of Ozonation on Yeast and Bacterial MBR effluent 55 4.2.2 Parameter Optimization 65

4.2.3 Effect of Ozonation on Optimum Ozone Condition 75 4.2.4 The Products after Ozonation 80

4.3 Chemical Oxidation of MBR effluent by Ozone plus Hydrogen 81 Peroxide (Perozone)

4.3.1 Determination of the waiting time after the addition of H2O2 82 4.3.2 Determination of H2O2 concentration in term of 83

H2O2/O3 ratio 4.3.3 Determination of Perozone Contact time 85 4.3.4 Comparison of the Efficiency between Ozone and Perozone 87

4.4 Continuous System by Combining MBR and Ozonation 90 4.4.1 Condition for Combined MBR and Ozonation 91 4.4.2 Organic Removal Efficiency from Combined System 91

4.5 Chemical Oxidation of the Mixed Liquor in MBR Reactors by Ozone 96 4.5.1 Effect of Ozonation on Sludge Minimization 97 4.5.2 Effect of Ozonation on the Solids Concentration 99

4.5.3 Effect of Ozonation on the Sludge Settleability 99

5 Conclusions and Recommendations 102 5.1 Conclusions 102

5.2 Recommendations for further study 104

Reference 106

Appendices 112

v

List of Tables

Table Title Page

2.1 Landfill leachate concentration ranges as a function 4 of the degree of landfill stabilization

2.2 Median concentration of organic substances found in municipal 5 landfill leachate

2.3 Comparative performances of various treatment processes 8 for landfill leachate treatment

2.4 Sludge productions for various wastewater treatment processes 10 2.5 The oxidation potential of various chemical oxidants 12 2.6 Ozonation of different kinds of wastewater and their treatment efficiency 20 3.1 Operating conditions for MBR and characteristics 24

of membrane module 3.2 Determination of k′ or pseudo first order rate constant at different 29

pH value 3.3 Determination of the rate constant or specific ozone utilization 29

rate and primary elimination degree of pollutant 3.4 Determination of ozonation factor 30 3.5 Characteristic of the effluent from both membrane bioreactors 31 3.6 Determination of optimum ozone dosage and contact time 33 3.7 Range of MWCO used in the experiment and their specification

3.8 Determination of optimum waiting time after 36 the addition for hydrogen peroxide 36

3.9 Determination of optimum perozone contact time 36 3.10 Determination of optimum recycle ratio 37 3.11 Determination of optimum ozone dosage 37 3.12 Analytical methods for parameters measurement 38 4.2 Ozone transfer efficiency at different feed gas ozone concentration 42 4.2 Ozone mass transfer coefficient at different feed gas 43 ozone concentration 4.4 Comparison of ozone transfer efficiency and ozone mass transfer 44

coefficient 4.5 The stability of dissolved ozone concentration or half-life with 47

different pH level and initial ozone concentration 4.6 Final COD concentration at 180 minutes ozone contact time 48 4.7 The summary of ozone reaction rate constant (k) based on TOC 49

and COD for four types of leachate 4.5 Membrane Resistance of different UF membranes used in 56

MWCO experiment 4.6 Comparison between the results obtained from 16 h 77

and 24 h HRT leachate 4.7 The comparison of COD removal efficiency between 91

original and combined system for both yeast and bacterial effluent 4.8 NH4-N determination in all steps of combined MBR and 93

Ozonation system 4.12 CST results of sludge before and after ozonation 97

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List of Figures

Figure Title Page

2.1 Landfill water balance 3 2.2 Submerged Membrane bioreactor with hollow fiber membrane 9 2.3 Reactivity of ozone in aqueous solution 14 2.4 The extreme forms of resonance structures in ozone molecules 14 2.5 Reaction diagram for ozone decomposition process 16 2.6 Effects of ozone dosage on characteristics of the ozonated sludge 20 2.7 Schematic diagram of the recirculation treatment process 21 3.1 Overall experimental plan 23 3.2 Schematic diagram of ozone generation by the corona discharge method 25 3.3 Schematic diagram of ozone column reactor 26 3.4 Schematic diagram of Experimental Setup 27 3.5 Schematic diagrams for the positions of pumping out 32 the filtrated or MLSS from MBR 3.6 Procedure for Molecular Weight Cut-Off experiment 35 3.7 Schematic diagram for ultrafiltration process for MWCO experiment 36 3.8 Schematic diagram for combined system (MBR + Ozonation)` 38 3.9 Reactor for sludge ozonation 39

4.1 Ozone concentrations in gas phase of the feed gas at different 41 oxygen flowrate and ozone voltage

4.3 Ozone concentrations in liquid phase at different ozone contact 41 time and initial ozone concentration

4.3 Ozone concentrations in off-gas at different contact time 43 4.4 Ozone concentrations at initial dissolved ozone concentration 45

of 0.02 mg/L at different pH value 4.9 Ozone concentrations at initial dissolved ozone concentration 45

of 0.04 mg/L at different pH value 4.10 Ozone concentrations at initial dissolved ozone concentration 46

of 0.06 mg/L at different pH value 4.11 Pseudo first order rate constant as a function of initial ozone 46

Concentration and pH condition 4.8 Comparison of half-life of ozone in different kind of water 47 4.9 The primary degree of pollutant elimination in term of TOC 48

at different contact time 4.10 The primary degree of pollutant elimination in term of COD 49

at different contact time 4.11 Reaction rate or specific ozone utilization rate constant in term 50

of TOC for four types of leachate at different contact time 4.12 Reaction rate or specific ozone utilization rate constant in 50

term of COD for four types of leachate at different contact time 4.13 Ozonation factor for four types of leachate as a function of 51

ozone contact time 4.14 Effect of ozone on COD removal efficiency at different ozone 53 dosage 4.15 Effect of ozone on TOC removal efficiency at different ozone dosage 53

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4.16 Effect of ozone on color removal efficiency at different ozone dosage 55 4.17 Color difference before and after ozonation for Yeast effluent 55 4.18 Color difference before and after ozonation for Bacterial effluent 55 4.19 Effect of Concentration Polarization on the membrane 57

permeate flux for YMBR and BMBR with and without stirring 4.20 Molecular weight distribution for yeast and bacterial effluent at 58

low and high ozone dosage in term of COD concentration 4.21 Molecular weight distribution for yeast and bacterial effluent 60

at low and high ozone dosage in term of TOC concentration 4.22 Effect of alkalinity on ozone consumption of bacterial effluent 61 from MBR 4.23 Effect of pH variation on COD degradation for yeast and 61 bacterial effluent 4.24 COD reduction for yeast effluent after ozonation at different 63

ozone concentration and contact time 4.25 COD reduction for bacterial effluent after ozonation 64

at different ozone concentration and contact time 4.26 TOC reduction for yeast effluent after ozonation at 64

different ozone concentration and contact time 4.27 TOC reduction for bacterial effluent after ozonation at different 65

ozone concentration and contact time 4.28 Color reduction for yeast effluent after ozonation at different 65

ozone concentration and contact time 4.29 Color reduction for bacterial effluent after ozonation at 66

different ozone concentration and contact time 4.30 COD degradation in dependence on ozone addition and volume load 67 4.31 The COD reduction and the increase of residual ozone with 68

contact time for Yeast effluent 4.32 The COD reduction and the increase of residual ozone 68

with contact time for Bacterial effluent 4.33 The change in COD and BOD after ozonation of yeast effluent 69 4.34 The change in COD and BOD after ozonation of bacterial effluent 69 4.35 BOD/COD ratio of yeast and bacterial effluent after ozonation 70 4.36 Specific ozone consumption in dependence on COD removal rate 72 4.37 TOC removal for yeast and bacterial effluent at different contact time 72 4.38 TOC variation as a function of COD for yeast and bacterial effluent 73 4.39 Color removal for yeast and bacterial effluent at different contact time 73 4.40 Molecular weight distribution in term of COD concentration at 74

optimum condition for both yeast and bacterial effluents 4.41 Molecular weight distribution in term of TOC concentration at 75

optimum condition for both yeast and bacterial effluents 4.42 Molecular weight distribution in term of Color at optimum 76

condition for both yeast and bacterial effluents 4.43 The reduction of pH after ozonation indicated the formation 78

of acids by-products 4.44 Variation in waiting time after the addition of H2O2 in terms 79

of COD removal 4.45 Variation in waiting time after the addition of H2O2 in terms 79

of TOC removal

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4.46 Variation in waiting time after the addition of H2O2 in terms 80 of color removal

4.47 Optimization of the H2O2/O3 ratio in terms of COD removal 81 4.48 Optimization of the H2O2/O3 ratio in terms of TOC removal 81 4.49 Optimization of the H2O2/O3 ratio in terms of color removal 82 4.50 Optimization of Perozone contact time in terms of COD removal 82 4.51 Optimization of Perozone contact time in terms of TOC removal 83 4.52 Optimization of Perozone contact time in terms of color removal 83 4.53 Optimization of Perozone contact time in terms of BOD5 83 4.54 The comparison of percentage COD degradation for yeast effluent 85 4.55 The comparison of percentage COD degradation for bacterial effluent 85 4.56 The comparison of TOC removed from yeast effluent 85 4.57 The comparison of TOC removed from bacterial effluent 86 4.58 The comparison of color removed from yeast effluent 86 4.59 The comparison of color removed from bacterial effluent 87 4.60 Continuous data of COD elimination from combined MBR 89

and ozonation for yeast system 4.61 Continuous data of COD elimination from combined MBR 89

and ozonation for bacterial system 4.62 COD of the leachate before and after ozonation of combined system 90 4.63 COD of the leachate before and after ozonation of original system 90 4.64 Overall COD concentration of original and combined system 92 4.65 The fate of yeast sludge after ozone treatment at various ozone dosages 94 4.66 The fate of bacterial sludge after ozone treatment at various 95 ozone dosages 4.67 Percentage of sludge reduction after ozonation at different ozone dosage 95 4.68 The change of MLVSS/MLSS ratio after applied different ozone dosage 96 4.69 Settle volume of bacterial sludge after 30 minutes in 97

different ozone dosage

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List of abbreviations

AOPs Advanced Oxidation Processes APO Advanced Photochemical Oxidation Processes ASP Activated Sludge Process BAF Biological Aerated Filter BMBR Bacterial Membrane Bioreactor BOD Biochemical Oxygen Demand COD Chemical Oxygen Demand CST Capillary Suction Time DS Dissolved Solid F/M Food to Microorganism ratio H2O2 Hydrogen Peroxide HRT Hydraulic Retention Time MBR Membrane Bioreactor MLSS Mixed Liquor Suspended Solid MLVSS Mixed Liquor Volatile Suspended Solid MW Molecular Weight MWCO Molecular Weight Cut-Off NH4

+-N Ammonia Nitrogen O2 Oxygen O3 Ozone OH Hydroxyl Radical RBCOD Rapidly Biodegradable COD RX Ratio of recirculation rate to an aeration tank volume x biomass

concentration in an aeration tank SRF Specific Resistance to Filtration SRT Sludge Retention Time SS Suspended Solid SV Sludge Volume TE Transfer Efficiency TKN Total Kjedahl Nitrogen TOC Total Organic Carbon TVA Total Volatile Acid UASB Upflow Anaerobic Sludge Blanket UF Ultrafiltration UMS Unsettlable micro-solids UV Ultraviolet VUV Vacuum ultraviolet YMBR Yeast Membrane Bioreactor

x

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Chapter 1

Introduction

1.1 General

Leachate is the water that percolates through the solid wastes in the landfill and leaches out the organic and inorganic constituents. These solid wastes undergo a number of simultaneous biological, physical, and chemical changes. Leachate is a high-strength wastewater, which has been recognized as one of the most concerned pollution source. Leachate mainly contains high concentration of organic contaminants, which are refractory and hardly biodegradable compounds. These compounds inhibit the performance of biological treatment process. It also contains high nitrogen (mainly ammonia or organic nitrogen), solids, halogenated hydrocarbon, and heavy metal. Variations in leachate composition occur for a wide range of reasons. The interactions between refuse composition, age of fill, hydrogeology of the site, climate, season, moisture routing through the fill all affect the leachate composition (Crawford and Smith, 1985). Collection and treatment of landfill leachate before discharge must be implemented in order to meet the required effluent standard.

Selection and design of a leachate treatment process depends on leachate quality,

final discharge requirement, and economical aspects. The present leachate treatment systems which mainly use biological treatment processes, for example Activated Sludge Process, Sequencing Batch Reactors, and Membrane Bio-Reactor cannot remove humic substance, COD, color, odor, and other refractory compounds which are presented in landfill leachate and therefore does not meet the discharge standards. Moreover, the major problem associated with the biological treatment process is the potential presence of toxic organics and heavy metals, which may interfere with metabolic processes and render this treatment approach ineffective (Shuckrow et al, 1982). In this study, two membrane bioreactors are used as biological treatment unit for treating leachate with Yeast and Bacterial population. The problems concern from this treatment unit is moderate COD removal efficiency and low color removal efficiency. Therefore, there is a need to develop a post treatment unit for landfill leachate treatment, to meet the required discharge standards.

Chemical oxidation as a post biological treatment by using Ozone and Ozone

combined with Hydrogen Peroxide (Perozone) as chemical oxidants have been proposed. The advantage of ozone and perozone over other chemical oxidants is the superior oxidizing power. With this strong oxidizing power, they have the potential for causing substantial changes to the nature of humic substances (Graham, 1999). Ozonation of leachate helps converting non-biodegradable compound into easily biodegradable compounds, which increase the biodegradability of leachate. Molecules break into smaller fragments, higher percentages of oxygen appear in these molecules (Marco et al, 1997). After ozonation, there will be an increase in biological oxygen demand without a significant reduction in chemical oxygen demand. Ozonation can easily destroy the parent compounds and some intermediates containing double bonds, which results in pollutant reduction. In order to evaluate advantages and risks of ozonation processes, kinetic data are needed to predict what products will remain in the leachate after the specific durations of ozonation. Kinetic data are also of importance for learning more about the environmental

1

behavior of ozone when absorbed in natural aquatic system (Hoigne and Bader, 1983) and for the decomposition and utilization of ozone.

The structure of organic substances is changed by chemical oxidation. Long-chain

humates that are hardly biodegradable are broken up and transformed to short-chain organic acids. These organic acids are difficult to degrade chemically but could easily degrade biologically (Steensen, 1997). Recent efforts have been made by recirculation the ozonated effluent back into biological treatment unit (Membrane Bio-Reactor, for this study) to treat the biologically degradable proportion of the compounds after ozonation. The effluent from biological treatment process tends to have less BOD and COD. Chemical oxidation requirements can be further decreased if the strategy of repeating the sequence chemical oxidation and biological treatment process several times has been used (Steensen, 1997). By doing this, the required effluent standard for landfill leachate can be achieved.

This study has two phases, namely: Membrane Bio-Reactor (MBR) phase and

Ozonation phase. It is focused on ozonation phase (ozone and perozone), which is the post treatment by using yeast and bacterial effluent from Membrane Bio-Reactor to start up the system. Both the filtrated effluent and the sludge or MLSS from Membrane Bio-Reactor are ozonated. Considering in term of sludge reduction, which is another application of ozonation, is done for the sludge ozonation experiment. After optimizing all parameters in ozonation phase from batch system, ozonated effluent is recirculated back to Membrane Bio-Reactor in continuous system. A sequence Membrane Bio-Reactor and ozonation is conducted for landfill leachate treatment in this study.

1.2 Objectives of the study

1. To develop the ozone calibration and kinetic studies prior to ozonation 2. To investigate the capability of using Ozone and Perozone as a post biological

treatment in order to increase the performance of the biological treatment process 3. To identify the optimal operational parameters in term of chemical oxidation

process efficiency. 4. Coupling the ozonation based chemical oxidation process and membrane bioreactor

for landfill leachate treatment 5. Application of ozonation of sludge treatment and disposal

1.3 Scopes of the study

1. Characteristics of ozone were determined by fundamental kinetic studies 2. The effluent from Membrane Bio-Reactor was fed to Ozone system, which has

been operated by the doctoral researcher 3. Both Filtrated and Mix Liquor Suspended Solid in both Yeast and Bacterial

Membrane Bio-Reactor were used in Ozone system 4. Ozone and Perozone were used as chemical oxidants 5. Parameter optimization was held in batch system and using batch optimized

parameters to start for continuous system

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3

Chapter 2

Literature Review

2.1 Introduction Landfill leachate is one of the most concerned pollution since it is defined as a high-strength wastewater. This problem is relating to leachate quantity and quality, gas production, and decomposition processes occurring in the landfill. Although controlling of leachate production is the best strategy to reduce pollution, one cannot avoid leachate generation that will occur even in carefully contained sites. Therefore, many treatment options for landfill leachate are taken into consideration for environmental and public health aspects. In this study, one of the treatment options is studied in order to achieve the best pollutant removal efficiency. 2.1.1 Landfill leachate generation When rainfall falls on the landfill site, the water can be separated into storm water runoff, evapotranspiration, or infiltration into the landfill. Leachate is produced when either infiltration or subsurface flow that contact with waste and exceed its field capacity. Leachate can be generated in otherwise dry or arid environments where groundwater is located far below the landfill site. The amount of leachate generated depends on many options including site climate, landfill morphology, waste depth, landfill surface conditions, and the operation of the facility (Reinhart and Townsend, 1997). This amount cannot be easily calculated, but “water balance method” has been used to indicate the volumes to be expected over a period. This method is presented in figure 2.1. Precipitation

Evapotranspiration

Storm water Runoff

Leachate Storage and Migration

Leachate Collection and Removal

Figure 2.1 Landfill water balance

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2.1.2 Compositions and Characteristics of landfill leachate The information of leachate characteristics is necessary for the control of landfill function and for the design and operation of leachate treatment facilities. When water is passed through the landfill waste, material is removed from the waste mass via mechanisms that include leaching of inherently soluble material, leaching of soluble products of biological and chemical transformation, and wash out of fines and colloids (Reinhart and Townsend, 1997). Characteristics of leachate can be broadly divided into four categories, which include physical characteristics, inorganic chemicals, organic chemicals, and toxicity (Crawford and Smith, 1985). The composition of landfill leachate at a particular time depends on many factors include type and composition of waste, rate of water infiltration, landfill design, operation, and age, the method by which it was emplaced, moisture content, climate, season, and the degree of stabilization. The variation of leachate composition may also result from environmental conditions at the time of sampling, during storage, and the precision of reported results may be affected to some extent by substances causing interference in standard analytical method (Robinson and Maris, 1979). Organic contaminants of leachate are primarily soluble refuse components or decomposition products of biodegradable fractions of waste. The concentrations of leachate components usually presented as a function of stabilization phase. In the early phase of waste degradation, leachate is characterized by high organic material, ammonium, and metals (Fe, Mn, Zn, Ca, Cu, Cd, Pb, Ni, Cr, and Hg) concentration as well as low pH. As the waste continues to degrade because of the ongoing microbial and physical/chemical processes within the landfill, the organic material (high molecular weight humic-like substances) and metals concentration gradually decreases, and the pH increases. In the early phase, 50-99 % of the organic material in leachate consists of low molecular weight fatty acids for example, aldehydes, amino acids, carbohydrates, peptides, humic acids, phenolic compounds, and fulvic acids. The fraction of unidentified organic materials increases with maturation of waste and leachate (Robinson and Maris, 1979). Landfill leachate concentration ranges as a function of the degree of landfill stabilization are presented in table 2.1. Table 2.1 Landfill leachate concentration ranges as a function of the degree of landfill stabilization (Reinhart and Townsend, 1997)

Parameter Phase II Transition

Phase III Acid

Formation

Phase IV Methane

Formation

Phase V Final

Maturation BOD (mg/L) 100-10,000 1,000-57,000 600-3,400 4-120 COD (mg/L) 480-18,000 1,500-71,000 580-9,760 31-900 TVA, mg/L as Acetic Acid 100-3,000 3,000-18,800 250-4,000 0

BOD/COD 0.23-0.87 0.4-0.8 0.17-0.64 0.02-0.13 Ammonia, mg/L-N 120-125 2-1,030 6-430 6-430

pH 6.7 4.7-7.7 6.3-8.8 7.1-8.8 Conductivity (μmhos/cm) 2,450-3,310 1,600-17,100 2,900-7,700 1,400-4,500

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2.1.3 Identification of organic substances and concentration in municipal landfill leachate There are many organic and inorganic compounds present in landfill leachate. Most of these compounds are toxic and harmful to human being. Identification of these compounds is necessary since it has the potential for water contaminant. Landfill leachate contains refractory compounds which are difficult to biodegrade and tend to have high molecular weight. Chain and Dewalle (1977) had conducted the experiment with two type of landfill leachate. Leachate I is produced in the acidification stage and leachate II in the methane fermentation stage. By using gel filtration, it has been reported that leachate I contained only a relative small amount of high molecular weight compounds which has only 0.5 % of the TOC. About 0.8 % of the TOC are the compounds with a molecular weight between 1,000 and 50,000 kDa. For leachate II, about 12 % of TOC could be attributed to compounds with a molecular weight over 50,000 kDa and 20 % with the compounds between 1,000 and 50,000 kDa. In general, low molecular weight compound has molecular weight less than 500 k Da, composed of easily degradable fatty acids. Medium molecular weight compound has molecular weight between 500 to 10,000 kDa composed of fulvic acids, or some humic acids, which are carboxylic, and hydroxyl groups. This is difficult to degrade and called refractory compound. High molecular weight compound has molecular weight more than 10,000 kDa which is humic substance. Organic compound usually found in landfill leachate are presented in table 2.2 Table 2.2 Median concentration of organic substances found in municipal landfill leachate (US. EPA, 1988)

Organic compounds Average

concentration (ppb)

Organic compounds Average

concentration (ppb)

Acrolein 270 Ethyl benzene 274 Benzene 221 bis (2-Ethylhexyl) phthalate 184

Bromomethane 170 Isophorone 1,168 Carbon tetrachloride 202 Lindane 0.020

Chlorobenzene 128 Methylene chloride 5,352 Chloroform 195 Methyl ethyl ketone 4,151

bis (Chloromethyl) ehter 250 Naphthalene 32.4 p-Crestol 2,394 Nitrobenzene 54.7

2,4 D 129 4-Nitrophenol 17 4,4-DDT 0.103 Pentachlorophenol 173

Di-n-butyl phthalate 70.2 Phenol 2,456 1,2 Dichlorobenzene 11.8 1,1,2,2-Tetrachloroethane 210 1,4 Dichlorobenzene 13.2 Tetrachloroethylene 132

Dichlorodifluoromethane 237 Toluene 1,016 1,1-Dichloroethane 1,715 Toxaphene 1 1,2-Dichloroethane 1,841 1,1,1-Trichloroethane 887

1,2-Dichloropropane 66.7 1,1,2-Trichloroethane 378 1,3-Dichloropropane 24 Trichloroethylene 187

Dietyl phthalate 118 Trichlorofluoromethane 56.1 2,4-Dimethyl phenol 19 1,2,3-Trichloropropane 230 Dimethyl phthalate 42.5 Vinyl chloride 36.1

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2.1.4 Landfill leachate treatment and disposal Leachate that is collected from the landfill site must be managed in proper ways in order to meet the effluent standard set by various authorities before discharging into the receiving water bodies. There may be exceptions where a suitable dilution is available for the untreated leachate. When this mean is not possible, the suitable treatment of leachate should be taken. The simplest method for leachate treatment is by discharging to a local wastewater treatment plant but this would create the possible impact of leachate on the treatment process. Pretreatment and flow equalization are often required. Another option for treating leachate is the construction of a treatment facilities onsite. This could reduce the cost of transportation and may lead to the specific objective of the particular landfill leachate. A key point to a design of leachate treatment facilities is that the leachate quantity and quality may vary greatly over the life of the landfill. The types of facilities are greatly influenced by the age and life of the tip and the economics of a system must be examined carefully. Specific problems inherent with treatment of landfill leachate are (Qasim and Chiang, 1994)

1) Landfill leachate is a high strength wastewater and magnitude of pollution potential which is hard for the selection and use of reliable treatment processes

2) Landfill leachate always has the changes from landfill to landfill. Therefore, the waste treatment techniques applicable for one site cannot be used to other locations. It should have the separate one that is suitable for each site.

3) The water that percolates through the landfill is depending on season climate and hydrology.

4) The chemical nature of the solids wastes at the landfill has a marked effect on the composition of leachate.

5) The quality and quantity of landfill leachate is fluctuated which occur both short and long term intervals. The treatment plant design should has the efficiency for treating young leachate and modify in the future depending on the landfill ages.

The options for leachate treatment can be described below.

2.1.4.1 Aerobic biological treatment Most of the organic material in leachate is readily biodegradable by aerobic biological oxidation together with pH adjustment and nutrient additions. It has been reported that the acidic phase is best suited for biological systems whist physical-chemical systems are better for old leachate (Boyle and Ham, 1974and Bull et al., 1983). For biological treatment, it implies transformation of particulate and soluble organic compounds to simpler organic compounds and biomass, usually separated from the liquid as biological sludge. The most common aerobic biological treatment methods are the activated sludge process, aerated lagoons, trickling filters, and rotating biological contactors. Activated sludge plants have been used to treat landfill leachate but data from full-scale plants is scarce and most of them are from laboratory or pilot scale plants. For greater than 90% removal of BOD5, the F/M ratio at 10 oC might be 0.25 kg BOD5/kg MLSS.day and up to 0.4 kg/kg.day at 20 oC (Crawford and Smith, 1985). For successful operation of an activated sludge plant, BOD:N:P should be greater than 100:5:1. Ammonium removals

6

of above 90% have generally been achieve with leachate with low fraction of readily biodegradable material when it is designed for nitrification. When it is designed for denitrification, nitrogen removal of up to 90% or more can be achieve (Kettunen et al., 1999). Chain and DeWalle (1977) determined from the laboratory experiments that treatment in an aerated lagoon at retention time in the range of 7 to 85 days could remove between 93 and 96.8 percent of the organic matter from a leachate having COD of almost 58,000 mg/L. It was concluded that aerobic biological treatment of leachate would not be successful at high organic loading and low retention time without addition of nutrients (Robinson and Maris, 1979). In addition to organic compound that require biological treatment, leachate contains inorganic dissolved solids (chloride, sodium), which experience limited removal by biological treatment, combination of biological and physico-chemical unit operation are preferred. 2.1.4.2 Anaerobic biological treatment Anaerobic biological treatment uses microorganisms, which grow in the absence of dissolved oxygen and convert organic material to carbon dioxide, methane, and other metabolic products. Although anaerobic treatments may appear to offer benefit over aerobic treatment because of biogas production, it has disadvantages of long retention time and high capital cost. The most common aerobic biological treatment methods are Upflow Anaerobic Sludge Blanket (UASB) reactors, Upflow anaerobic filter, or anaerobic digester. The result from laboratory scale has been reported that leachate with high BOD and COD would appear to require organic loading of around 1.0 kg COD/m3.day at 30 to 35 oC (Crawford and Smith, 1985). For UASB, soluble COD removal efficiency was consistently between 77% and 91% at hydraulic retention time of 24, 18, and 12h (Kennedy and Lentz, 2000). Boyle and Ham (1974) showed that greater than 90 percent removal of organic matter from leachate was possible by storage in anaerobic conditions for 10-12 days at temperatures of between 23 and 30 oC with organic loading of 1.05 kg COD/m3.day. For anaerobic treatment, ammonia removal is low but BOD removal can be significant with the methane collection and used to maintain the temperature in the process. 2.1.4.3 Physical and Chemical treatment As known, the composition of leachate changes as the waste stabilizes, resulting in a decrease in the proportion of organic compounds which are readily biodegradable. The effectiveness of biological leachate treatment processes decrease as waste stabilizes, physical and chemical techniques may become more appropriate. The methods involved the addition of chemicals to precipitate, coagulate, or oxidize inorganic fractions. Utilization of adsorption by activated carbon and ion exchange resins, and reverse osmosis membrane have been used. Many of these processes are used to remove residual soluble organic and inorganic materials from effluents produced by biological treatment of leachate. One of the chemical treatments by ozonation will be discussed in detail afterward. Other methods for landfill leachate treatment included treatment of leachate by recirculation through the landfill, land treatment, and treatment with sewage. These methods have been used for treating leachate in different conditions.

7

Table 2.3 Comparative performances of various treatment processes for landfill leachate treatment (Chian and DeWalle, 1977)

Characteristics of leachate Treatment

Processes Young (<5 yr)

Medium (5-10 yr)

Old (>10 yr)

Metals VOCs Nitrogen Priority Pollutants Solids

Membrane Processes Good Good Good Good Fair Good Good Good

Coagulation/ precipitation Poor Fair Poor Good NA Poor NA Good

Chemical Oxidation Poor Fair Fair NA Fair NA Good NA

Ion Exchange Poor Fair Fair Good NA Fair NA Good

Carbon absorption Poor Fair Good NA Good NA Good NA

Aerobic suspended growth and fixed film

Good Fair Poor Good Good Fair Fair Fair

Anaerobic suspended growth and fixed film

Good Fair Poor Good Good Fair Fair Fair

NA = not applicable 2.2 Application of Membrane Bioreactor in wastewater treatment 2.2.1 Membrane Bioreactor (MBR) process Membrane bioreactor is an innovative technology, which has been used to treat water and wastewater in recent years. This novel technology began over 30 years ago and membrane bioreactors have been used commercially for the last 20 years. Today, over 500 membrane bioreactor processes have been commissioned at full-scale to treat both industrial and municipal wastewaters, as well as for in-building treatment and re-use of grey water. The concept of MBR is by combining membrane technology with biological reactors for wastewater treatment. By using membrane for solid-liquid separation in biological unit, the replacement of secondary sedimentation tank is achieved. In the MBR, the entire biomass is confined within the system, providing both exact control of the residence time for the microorganisms in the reactor (solid retention time) and the disinfection of the effluent (Zoh and Stenstrom, 2002). A membrane is a material that one type of substance can pass more readily than others, thus presented the basis of separation process. It is manufactured in order to achieve the reasonable mechanical strength and can maintain a high throughput of a desired permeate with a high degree of

8

selectivity. The optimum geometry or configuration may have these characteristics (Stephenson et al., 2000)

1. A high membrane area to module bulk volume ratio 2. A high degree of turbulence for mass transfer promotion on the feed side 3. A low energy expenditure per unit product water volume 4. A low cost per unit membrane area 5. A design that facilitates cleaning 6. A design that permits modularization The MBR system can be categorized in two different configurations by allocation

of membrane module, which included the externally pressurized cross-flow MBR and the submerged MBR. The submerged MBR is superior to an externally pressurized cross-flow MBR in regard to power consumption and the simplicity of the installation because of the absence of recirculation pump (Yamamoto et al., 1989). In this study, the second type of MBR, which is the submerged MBR with hollow fiber membrane material, will be used for landfill leachate treatment. The figure of this type of MBR is presented in figure 2.2.

Effluent

AirInfluent

Hollow fiber membrane

Air diffuser

Leachate to be treated

Figure 2.2 Submerged Membrane bioreactor with hollow fiber membrane

2.2.2 Advantages, disadvantages, and comparison of MBR with other processes Every type of MBR processes has resulted in advantages over conventional biological treatment particularly in term of small footprint, process intensification, modular, and retrofit potential. Since MBR has produced high effluent quality and less sludge production, it has usually been used to replace conventional biological treatment. MBR can be operated at MLSS of up to 20,000 mg/L and as sludge settling is not required, submerged MBR can be up to 5 times smaller than a conventional ASP. The high biomass concentration in the MBR tank allows complete breakdown of carbonaceous material and

9

nitrification of municipal wastewater to be achieved within an average retention time of 3 hours. Sludge production is significantly reduced, compared to conventional ASP, as longer sludge ages are achievable according to the table 2.2 (Mayhew and Stephenson, 1997).

Table 2.4 Sludge productions for various wastewater treatment processes

Treatment processes Sludge production (kg/kg BOD)

Submerged MBR 0-0.3 Structured media biological aerated filter (BAF) 0.15-0.25

Trickling filter 0.3-0.5 Conventional activated sludge 0.6

Granular media BAF 0.63-1.06

MBR has advantages on treated water quality since it could receive higher organic loading rates and has higher removal efficiencies compared to other biological treatment processes. Gander et al (2000) has reported that submerged MBR can receive organic loading rate up to 0.39-0.7 kg BOD/m3.day (Plate and Frame) and 0.03-0.06 kg BOD/m3.day (Hollow Fiber). The removal efficiency of MBR can be up to 99%. Other than these advantages, MBR also has flexibility in operation because the control of SRT is independent of hydraulic retention time. Therefore, the system can be run at very long SRT, which enhance the growth of microorganism inside the reactor. Another feature of MBR technology is the ability of the membrane to remove pathogenic organisms, providing disinfection of the effluent. The membrane offers a physical barrier to the organisms that is unaffected by the influent quality. Reductions in bacteria and viruses of 4 -8 log have been reported (Kolega et al., 1991; Chiemchaisri et al., 1992; Gander et al., in press; Jefferson et al., 1998).

Since MBR has many advantages, it also has some disadvantages including the high cost and the problem of membrane fouling. Membrane fouling is the process by which a variety of species present in water increases the membrane resistance, which is the major obstacle for the application of membrane process. To overcome this problem, the options of pretreatment to remove foulants, promotion of turbulence, or reduction of the flux should be achieved (Stephenson et al., 2000).

2.2.3 Application of MBR process in wastewater treatment Nowadays, MBR process has been used in various wastewater treatment options as a secondary treatment. Sometimes, the combination of MBR with other post treatment process has been introduced. Huang and Qian (2000) has done the experiment by using synthetic wastewater treated with submerges MBR to investigate the organic removal performance. The results of the removal efficiencies of chemical oxygen demand (COD), total organic carbon (TOC), and biological oxygen demand (BOD) are 90, 94, and 95%, respectively with the initial COD, TOC, and BOD of 300-600, 110-125, 150-300 mg/L, respectively. They also conducted the experiment to find out behavior of soluble microbial products in MBR.

10

From the accumulation of TOC in the supernatant, macromolecules with MW > 100,000 accounted for 34%. This is decreased to 16% with the decrease of supernatant TOC whereas with MW < 30,000 increased from 33 up to 52%. The accumulation proved to be inhibitory towards the metabolic activity of the activated sludge, as well as contributing to the poor membrane permeability of the mixed liquor. Zoh and Stenstrom (2002) have investigated the experiment for the application of MBR for treating explosives process wastewater. For the anoxic MBR with the ceramic cross-flow ultrafiltration module was used to treat synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX. The wastewater consists of acetate, formate, and formaldehyde are used as a carbon source and nitrite and nitrate electron acceptors. The results have shown the removal efficiency of 90% carbon source, and approximately 90% of the stoichiometric amount of nitrate, 60% nitrite. The maximum volumetric organic loading rate was 0.72 kg COD/m3.day. Scholz and Fuchs (2000) have done the experiment to treat oily wastewater. Influent concentration was in range of 500-1,000 mg/L in term of hydrocarbon. Biomass concentration was up to 48g/L. A removal efficiency of 99.9% of fuel oil as well as lubricant oil could be achieved at the hydraulic retention time of 13.3 h. The maximum biodegradation of fuel oil is 0.82 g hydrocarbons/g MLVSS.day. TOC and COD removal efficiency are 94-96% for fuel oil and 97-98% for lubricant oil. 2.3 Application of chemical oxidation in wastewater treatment 2.3.1 General of chemical oxidation

Oxidation is a chemical reaction in which an element or ion is increased in positive valence, losing electrons to an oxidizing agent. To oxidize is to change a substance by chemical reaction by combining it with oxygen. Chemical oxidation has been used worldwide for the treatment of water and wastewater since its useful in oxidative degradation or transformation of a wide range of pollutants. Because the limitation of biological treatment process in the treatment of wastewater that are resistant to biodegradable or toxic, chemical oxidation was introduced since, it has the ability to convert the hardly biodegradable compounds into easily biodegradable compounds. Chemical oxidation is usually as a post biological treatment to improve the treatment efficiency. Due to the high cost and energy intensive, the application of chemical oxidation also has a limit. In order to achieve the higher removal efficiency, more chemical oxidation is required by the mean of stoichiometric. When consider the electrochemical potential, each chemical oxidant has different value of oxidation potential, which is defined as the ability to oxidize organic substance. The oxidation potential of various oxidants are presented in table 2.5.

11

Table 2.5 The oxidation potential of various chemical oxidants

Chemical oxidants Oxidation potential (Volts)

Fluorine (F) 3.03 Hydroxyl Radical (OH ) 2.80 Ozone (O3) 2.07 Hydrogen Peroxide (H2O2) 1.76 Permanganate (MnO4) 1.67 Chlorine Dioxide (ClO2) 1.50 Chlorine (Cl2) 1.36 Oxygen (O2) 1.23

Oxidizing reactions of interest in pollutant removal is OH or Hydroxyl Radical, a

byproduct of the Catalytic Oxidation process. OH is very unstable, thereby making it very aggressive or a free radical. The Hydroxyl or free radical occurs when ozone or hydrogen peroxide reacts with UV radiation and protolysis occurs. Although the Hydroxyl Radicals are short lived, they have a higher oxidation potential than ozone, chlorine, or hydrogen peroxide, and their unstable nature increases their reaction speed. A strong benefit of Catalytic Oxidation is the end products of CO2 and H2O. Catalytic Oxidation occurs by the following equation

Eq. 2.1 O3 + UV OH

Eq. 2.2 O3 + H2O2 + UV OH 2.3.2 Chemical oxidants used in wastewater treatment While chemical oxidation reactions are very common in wastewater treatment, the use of this for the remediation of waters contaminated by organic compounds is usually not feasible because of kinetic limitations. This problem can be overcome by the development of advanced oxidation processes (AOPs). By using this process, the overall rate of oxidation is greatly increased by the simple addition of oxidizing agents. AOPs generally involve generation and use of powerful but relatively nonselective transient oxidizing species. Typical oxidation processes for wastewater include Ozone, Hydrogen Peroxide, Chlorine, Chlorine Dioxide, UV radiation, and Wet oxidation. 2.3.2.1 Ozone (O3) Ozone can be used for both water and wastewater treatment. In the early period, ozone was used in water treatment for disinfection and color and odor removal. Nowadays, the use of ozone for wastewater treatment has been extended to many countries including Thailand. Ozone has the ability to convert organic compound into carbon dioxide and water, which help reducing the toxicity. Ozone has an oxidizing potential, which in many cases is sufficient to directly convert organic substances. It is effective to be used as a pretreatment to remove refractory compounds or in post treatment to increase the biodegradability. After the use of ozone for converting refractory compound, the BOD is increased without a significant reduction in COD. Since ozone has many advantages, it can be hazardous because the third unstable atom has a strong tendency to break away and attach itself to other substances. Therefore, many ozone treatments usually have ozone

12

trapped or ozone destroyer to trap the residual ozone in the exhaust gas from being emitted to the atmosphere. Oxidation of ozone is accelerated when a radical reaction occurs. By having the initiators such as OH-, H2O2, UV rays or certain organic compounds, the extremely reactive OHo radicals formed via intermediate reaction (Steensen, 1997). Since landfill leachate has high humic substances content, the oxidation by ozone is advantages since the initiator is presented in wastewater. The ozone reaction is slowed down by radical scavengers such as carbonates/hydro carbonates, or alkyl compounds (Staehelin and Hoigne, 1983). This radical scavenger can interrupt the chain reaction. 2.3.2.2 Hydrogen Peroxide (H2O2) Due to the low oxidation potential, H2O2 cannot be used alone. It needs to use together with ozone or UV in order to increase the oxidizing power. The use of catalysts such as iron salts (Gilbert and Bauer, 1987) or UV rays (Thomanetz and Rodwe, 1989) is essential. The most direct method for the generation of OH radicals is through the photo cleavage of H2O2. The primary process in the photolysis of H2O2 produces two OH radicals. This radical reacts quickly and unspecificly with organic compounds. 2.3.2.3 Chlorine, Chlorine Dioxide, and Hypochlorite These compounds are not used for chemical oxidation in wastewater treatment because they can produce toxic substances. 2.3.2.4 UV radiation The advanced photochemical oxidation processes (APO) can be divided into four groups: 1) Vacuum ultraviolet (VUV) photolysis, 2) Ultraviolet (UV)/oxidation processes, 3) the photo-Fenton process, and 4) sensitized APO processes. For the second group, most commercial UV/oxidation processes involve generation of OH through UV photolysis of conventional oxidants, including H2O2, and O3. UV on its own does oxidize certain organic compounds present in leachate. Due to the high cost of UV radiation, this method has the limitation. Some experiment was conducted by using UV/O3 to treat landfill leachate. The leachate is often biologically treated before photochemical treatment to reduce BOD. Biological treatment may also necessary after photochemical process because the conversion of refractory compounds into easily biodegradable compounds. For UV/O3 process with the initial COD of 900 mg/L, 8 m3/h of leachate, COD reduction is more than 90%. 2.3.2.5 Wet oxidation Wet oxidation occurs at high temperature and high pressure for 1 to 2 hours (Kylefors, 1997). Oxygen is used as the oxidizing agent. The sample is in liquid phase while oxygen is added as air or pure oxygen as high pressure. Copper is used as the catalyst for wet oxidation. The end products for this process are carbon dioxide, alcohols, ketones, aldehydes, and carboxylic acids.

13

2.3.3 Advantages of ozone in wastewater treatment Ozone has unique properties, which offer advantages in wastewater treatment which include (Francis and Evans, 1972)

- Ozone is a powerful oxidizing agent which has twice potential than chlorine. More complete oxidation can be expected from ozone than chlorination

- Ozone reactions are very rapid. Faster reaction times can me shorter contact times to reach required effluent contaminant level

- Ozone is a highly efficient germicide. This results in surer bactericidal and viricidal action with shorter contact times and less sensitive to pH and temperature than for chlorine.

- Ozone leaves a beneficial oxygen residual as a reaction product which results in increasing DO

- Oxidized or partially oxidized products are generally less toxic than chlorinated or unreacted species

Ozone can be used in several places in a wastewater treatment plant, for example

disinfection of the effluent, tertiary treatment which are reduction of COD and removal of BOD, increase DO, reduction of color and odor, decrease of turbidity. Ozone can also be used for sludge treatment for oxidizing of secondary sludge for partial or complete volatilization of organics, etc.

2.4 Application of ozone (O3) in wastewater treatment 2.4.1 Fundamental aspects of ozonation In an aqueous solution, ozone may act on various compounds (M) in two ways: by direct reaction with the molecular ozone, and by indirect reaction with the radical species that are formed when ozone decomposes in water (Hoigne and Bader, 1977). The two basic reactions of ozone in water are illustrated in figure 2.3

Figure 2.3 Reactivity of ozone in aqueous solution

+M Mox Direct Reaction

OH- OH M

M′ox Radical-Type Reaction

O3

The extreme forms of resonance structures in ozone molecules can be represented in figure 2.4 (Langlais et al., 1991)

O

O

O . .

δ+

δ-

..

. . . . . .

O

O .

δ+ δ-

. . . . . . .. ..

.

..

O. .

Figure 2.4 The extreme forms of resonance structures in ozone molecules

14

2.4.2 Kinetics studies for ozonation 2.4.2.1 Decomposition of ozone

The stability of dissolved ozone (or its half-life) is readily affected by pH, UV light, ozone concentration, and the concentration of radical scavengers (Tomiyasu et al., 1985). The decomposition rate, measured in the presence of excess radical scavengers, which prevent secondary reactions, is expressed by a pseudo first-order kinetic equation as described below.

[ ] [ ]3'

pH

3 OkdtOd

=⎟⎠

⎞⎜⎝

⎛− Eq. 2.3

[ ][ ] tkOO

ln '

pH03

3 =⎟⎟⎠

⎞⎜⎜⎝

⎛− Eq. 2.4

Where k′ = pseudo first-order rate constant for a given pH value The evolution reflects the fact that the ozone decomposition rate is first order with respect both ozone and hydroxide ions, resulting in an overall equation below

[ ] [ ][ ] [ ]−− ==⎟

⎠

⎞⎜⎝

⎛−

OHkkWhereOHOk

dtOd '

3pH

3 Eq. 2.5

Hoigné, Staehelin and Bader mechanism indicate that the decomposition of ozone

occurs in a chain process. The process includes initiation step 1, propagation steps 2 to 6, and break into chain reaction steps 7 and 8. The fundamental reactions can be described below (Langlais, 1991)

1) O3 + OH- → HO2 + O2

- k1 = 7.0*101 M-1s-1k1 Eq. 2.6

HO2 = hydroperoxide radical 1’) HO2 ↔ O2

- + H+ k2 (ionization constant) k2

Eq. 2.7 = 10-4.8 M

O2- = superoxide radical ion

2) O3 + O2

- → O3- + O2 k2 = 1.6*109 M-1s-1

k2 Eq. 2.8 O3

- = ozonide radical ion 3) O3

- + H+ ↔ HO3 k3 = 5.2*1010 M-1s-1k3

Eq. 2.9 k-3 = 2.3*102 s-1k-3

4) HO3 → OH + O2 k4 = 1.1*105 s-1

k4

Eq. 2.10

15

5) OH + O3 → HO4 k5 = 2.0*109 M-1 s-1k5 Eq. 2.11

6) HO4 → HO2 + O2 k6 = 2.8*104 s-1k6

Eq. 2.12

Eq. 2.13 7) HO4 + HO4 → H2O2 + 2O3 8) HO4 + HO3 → H2O2 + O3 + O2 Eq. 2.14 From all of the equations above, the diagram for the decomposition of ozone process can be developed as shown below

O2-

O3

O3-

HO3

OH

HO4

HO2

H2O

O2

H+

O2

2.4.2.2 Reaction kinetics of ozonation The transference of ozone gas into water is kinetically controlled, a fast zero order gas-liquid transfer is usually observed before the system reaches a saturated ozone concentration. The reaction kinetic of the pollutant can be determined after the saturated ozone is reached which the concentration of ozone is uniform in the liquid stream. The ozone consumption rate is determined solely by the rate of chemical reaction in the bulk. The overall degradation kinetic of the pollutant in term of molecular ozone and hydroxyl radical that is produced by the decomposition of ozone is follows the equation below

H2O

O2

-OH

O3

Chain Breakdown

Figure 2.5 Reaction diagram for ozone decomposition process

16

]OH][C[k]O][C[kdt

]C[dOH30

•+=−

Where [C] = the concentration of the pollutant [O3] = the concentration of ozone [OH ] = the concentration of hydroxyl radical k0 and kOH = kinetic rate constants Since ozone is offered in excess, the hydroxyl free radicals and ozone concentration in the solution are presumably close to constant which represent the steady state. Therefore, the equation above can be rearranged to the pseudo-first order equation where k is the overall or pseudo-first-order rate constant. Pseudo-first order equation is shown below (Chu and Ching, 2003)

Eq. 2.15

Eq. 2.16 ]C[k]C[]OH[OHk]3O[0kdt

]C[d−=⎟

⎠⎞⎜

⎝⎛ +−= •

The rate constant or specific ozone utilization rate, k can be obtained from the slope by plotting the relationship between ln(C/C0) and time.

t.kCCln

0

−=⎟⎟⎠

⎞⎜⎜⎝

⎛ Eq. 2.17

C and C0 are TOC concentration at time t and time 0, respectively; k is empirical

stoichiometry coefficient (time-1) (Langlais et al., 1991) Primary elimination degree of pollutant (α) is calculated from the equation below (Kornmuller et al., 1997b)

α = C Eq. 2.18

C0 2.4.2.3 Calculation of ozonation factor Calculate the ozone concentration in the feed gas before ozonation and in the off-gas after ozonation by Iodometric method. Ozonation efficiency depends on the mode of ozone introduction into the reactor and the nature of target pollutants. The overall ozonation factor can be considered as a comprehensive single parameter to evaluate the treatability of an organic substrate in aqueous phase by ozonation. The lower of the value of ozonation factor, the more the target compound is resistant to ozonation. Calculation of ozonation factor, not include the spontaneous self-decay of ozone, is as below (Teo et al., 2002)

Φ = [A]VA Eq. 2.19 [O3]f νf t – [O3]dVA – [O3]eνe t Where Φ = ozonation factor, mol A/mol O3, where A represents the substrate [A] = concentration of substrate mol/L VA = the volume of the treated aqueous phase, L

17

[O3]f = O3 concentration in the feed, mol/L [O3]d = O3 concentration dissolved in the reaction matrix, mol/L (This parameter is often be neglected) [O3]e = O3 concentration in the exhaust air stream, mol/L νf = flow rate of O3 feed, L/min νe = flow rate of exhaust air stream, L/min t = ozonation time, min

The ozonation need around 1/Φ times the ozone to achieve the given efficiency in terms of the settled experimental conditions. 2.4.3 Reaction of ozone with humic and fulvic acids Humic substance is used to represent natural dissolved organic component with high concentration that present in water. It is the result of the microbiological, chemical, and photochemical reactions that occur during the degradation and polymerization of vegetable matter. Fulvic acids are more soluble than humic acids which mainly in colloidal form (Langlais et al., 1991). 2.4.3.1 Ozone consumption Anderson et al.(1986) showed that semi batch ozonation of a phosphate-buffered fulvic acid induced a large consumption of ozone that increased with the ozone dosage applied. Reckhow (1984) observed the same phenomenon when using lower concentration of the same fulvic acids. The ozone consumption is dependent on the presence of bicarbonate ions in the solution. Bicarbonate stabilized the ozone in the water even in the presence of fulvic acids (Reckhow et al., 1986). It can be concluded that the presence of bicarbonate ions (as radical scavengers) stabilizes the ozone in fulvic acids solutions at a neutral pH, causing a lower rate of consumption compared with results obtained in the absence of bicarbonates. 2.4.3.2 Structural evolution ` The action of ozone with humic substances in a neutral pH solutions leads the following situation (Langlais et al., 1991)

- a slight abatement of TOC - a strong degradation of color and of UV absorbance - a slight decrease in the high apparent molecular weight fractions, and a slight

increase in the smaller fractions - a significant increase of the carboxylic functions - the formation of some identifiable ozonation products

2.5 Ozonation and a combination of ozone with other chemical oxidants in wastewater treatment specially landfill leachate As described in the above, landfill leachate contains humic substance, which can be defined as refractory compound. Only biological treatment cannot which resulted in the reduction of BOD cannot remove all the organic contaminants presented in leachate.

18

Ozonation as a post-biological treatment is one of the option to achieve the required effluent standard. Steensen (1997) has done the experiment by using three chemical oxidations processes, which are H2O2/UV, ozone, and ozone/fixed bed catalyst for landfill leachate treatment. It has been proposed that chemical oxidation has the advantage of the substances being almost completely converted. The resulted have been reported that for H2O2/UV, the percentage of COD degradation increased with the increase of H2O2 concentration. Up to COD degradation of 50%, H2O2 concentration is approximately 2 g H2O2 /g COD. As long as the minimum concentration of 500 mg H2O2/L is maintained, the oxygen level in the reactor stays above 5 mg/L. Additional oxygen dosages do not increase COD degradation. For ozone and ozone/fixed bed catalyst, the percentage of COD degradation is also increased with the increase of ozone dosage. Elimination rate of at least 80% was achieved. He resulted further with 0.8-1.8 kg ozone/ kg el COD, the catalyst reactor consumes less than the ozone reactor with 1.2-2.2 kg ozone/ kg el COD. He also developed the integration of a post-purification phase after chemical oxidation to increase the discharge quality at the same time with the reduction in oxidant consumption. In this unit, long chain humates that are hardly biodegradable are broken up and transformed to short chain organic acids. These compounds are difficult to degrade chemically but easily degradable biologically. The actual biologically degradable COD exceeds BOD5 by factor 2-3. Biological purification without recirculation results in ozone saving of approximately 20%, which can be increased by recirculation by 10-15%. Marttinen et al (2002) has investigated the screening of physical-chemical methods for removal of organic material, nitrogen, and toxicity from low strength landfill leachates. By using Nanofiltration to remove 52-66% COD, air stripping to remove 64-89% ammonia, and ozonation at 20oC to increase the concentration of rapidly biodegradable COB (RBCOD), but the proportion of RBCOD of total COD was still below 20%, indicating poor biological treatability. Ozone concentration in the feeding gas was 70-90 mg/L and is fed for 15-20 min with corresponding ozone doses of 0.08-0.50 mg O3/mg COD. With a dose of 0.50 mg O3/mg COD, the RBCOD value was almost double from the initial concentration. Beaman et al (1998) has reported substantial in crease in the biodegradability of methanogenic leachate, measured as increase of BOD/COD ratio, with ozone dose of 1.2 mg O3/mg COD. Barratt et al (1997) has done the advanced wastewater treatment with the impinging zone reactor, a reactor with intensively mixed with the ozone/oxygen mixture under atmospheric pressure and ambient temperature. The results show a decrease in hydraulic retention time of 10.3 vs. 3.3 h., a reduction of the O3/COD ratio of 3.2 vs. 1.8 kg/kg.

Chain and Dewalle (1976) have conducted the experiment on biological and physical/chemical treatment of landfill leachate. The results showed that COD removal was effective in young leachate due to the resistance of volatile fatty acids to ozone. Qasim and Chiang (1994) have reported of 22% COD reduction for old leachate.

Table 2.6 presented an advanced oxidation process with ozone and the combination

for different kinds of wastewater treatment.

19

Table 2.6 Ozonation of different kinds of wastewater and their treatment efficiency

Method of treatment

Type of wastewater Parameters % Removal References

O3

Phenolic compounds in

water TOC

40 % (60 min contact

time)

K.C. Teo, et al., 2002

O3 NOM TOC 33 % J.S. Park, et al., 2002

O3 Dye bath effluent TOC 28-40.5 % (Ozone dosage 2,340-2,970

mg/L, pH 7)

Idil Arslan Alaton, et al.,

2002

O3 + H2O2Aromatic

compounds TOC 40%

(70 min contact time)

A. Mokrini, et al., 1997

Pre- O3 + Slow sand filtration

Lake & river Color

70-80 % (5 mgO3/L)

74 % (2.5-3.5 mgO3/L)

52% (1.1-2.5 mgO3/L)

Nigel J. D. Graham, 1999

O3 Drinking water TOC 35 %

(60 min contact time)

H. Yasui and Y. Miyaji,

1992 O3 +

Chemical coagulation

Textile wastewater COD 16 % (Only O3)

45-50 % for PAC

Sheng H. Lin and Chi M. Lin, 1993

O3 + fix-bed catalytic

Propone oxide production wastewater

COD 45 %

(Ozone dosage 1.5 g/L)

F.P. Logemann and J. H. J.

Annee, 1997

O3Textile

wastewater Color COD

95 % 5-20 %

Frank Gähr, et al., 1994

O3

Naphthalene sulfonic acids in aqueous solution

COD TOC

40 % 20 %

Zhu Shiyun, et al., 2002

O3

1-Naphthalene, 1-5 Naphthalene and

3- Nitrobenzene sulphonic acids

TOC

40-60 % (pH 9) 60-70 % (pH 3) (90 min contact

time)

V. Calderara, et al., 2002

O3Textile

wastewater

Color COD BOD

80.9 % 87 %

25.1 % (35 h contact time)

C.M. Radetski, et

al., 2002

O3

2,4 Dichlorophenol

(Formic and acetic acid)

BOD/COD

0.4-0.5 (60 min contact

time) (COD decrease, BOD increase)

Antonio Marco, et al.,

1997

20

Method of treatment

Type of wastewater Parameter % Removal References

Sequential biological

treatment/O3

Log yard run-off

COD BOD

22 Increase 38 %

(30 min contact time)

Michael G. Zenaitis, et al., 2002

Sequential O3

/biological treatment

Log yard run-off

COD BOD

10 Increase 3 %

(30 min contact time)

Michael G. Zenaitis, et al., 2002

O3 Leachate BOD/COD 0.06-0.28 (O3 = 0.11 mg O3/mg

COD)

S.K. Marttinen, et

al., 2002 O3 + aerobic

biological degradation

Black- olive wastewater COD 42-55 %

Jesus Beltran-Heredia, et al., 2000

2.6 Ozonation of sludge for sludge disposal Feasibility of ozone treatment of sludge for sludge reduction and carbon source for denitrification has been investigated. Ahn, et al (2002) had reported that in term of overall sludge reduction 54% reduction of the total sludge mass could be achieved by ozone treatment at 0.2 g O3/g MLSS. Batch denitrification experiment showed that solubilized organics and the unsettlable micro-solids (UMS) could be utilized as carbon source for denitrification. The effects of ozone dosage on characteristics of the ozonated sludge can be described in figure 2.6.

0

19.6 23.932.7 31.5 27.7

0

35.1

20.129.2 42.9

0.8

13.8

25.7

13.711.7

9.6

99.2

63.94

45.6233.92 28

20.08

0%

20%

40%

60%

80%

100%

0 0.1 0.2 0.5 1 2

Ozone dose (g O3/g ss)

Solubilization Mineralization Unsettlable microparticles Residuals

Figure 2.6 Effects of ozone dosage on characteristics of the ozonated sludge

21

Collignin et al (1994); Weemaes et al (2000) have reported that sludge ozonation tends to increase the settleability of sludge. The settleability was estimated by measuring SV30 (% of sludge volume after 30 minutes settling) and it was improved by ozonation above 0.2g O3 /g DS. Muller et al (1998); Scheminski et al (2000); Weemaes et al (2000) reported that sludge filterability quantified by capillary suction time (CST) was deteriorated by ozone treatment. The specific resistance to filtration (SRF) was rapidly increased with ozone dose up to 0.2 g O3 /g DS and then decrease dramatically at an ozone dose of 0.5g O3 /g DS. This result was consistent with decrease in the micro-particle fraction at a relatively high ozone dose. Deleris et al studied about the minimization of sludge production in activated sludge process. Experiments have shown that 70% reduction in sludge production can be reached. Recycling of the ozonated sludge to the aeration tank induces a slight increase in effluent COD, but the biological treatment performance is maintained. The sludge was ozonated in the small perfectly mixed reactor with SRT of 10 days.

Yasui and Shibata (1994) have studied the approach to reduce excess sludge production in the activated sludge process. The results shown that the ozonation enhances biological degradation of the activated sludge. The amount of excess sludge is reduced to nearly zero when 1.2 kg/m3 of biomass is recirculated in a day from the biological stage to the ozonation stage at a BOD loading of 1.0 kg/m3.day. The schematic diagram in figure 2.7 was the study of the recirculation process. More biomass than excess sludge is recirculated from the aeration tank to the ozone contactor. A part of the biomass is mineralized by biological treatment via ozonation. The mineralized biomass would be equivalent to that generated from organic substrate contained in the wastewater.

Ozone treatment stage

BOD

Influent

Mineralization

Biomass generated from

influent Mineralization

Biomass generated from ozonated sludge

RX

Biomass to be

treated

BOD

Recirculation

Effluent

Biological treatment stage

Figure 2.7 Schematic diagram of the recirculation treatment process

22

2.7 Advanced Oxidation Processes (AOPs) Hydrogen Peroxide and UV radiation are likely to induce decomposition of ozone in water which generate highly reactive hydroxyl radicals. They are used to activate ozone in neutral pH water and when combined with ozone, provide advanced oxidizing treatment techniques. Hydrogen Peroxide (IV) is a weak acid. When combined with water, it partially dissociates into hydroperoxide ion (V) as below H2O2 + H2O ↔ HO2

- + H3O+ ka = 10-11.6 Eq. 2.20

Hydrogen Peroxide molecule reacts very slowly with ozone where hydroperoxide anion is highly reactive. As a result, the ozone decomposition rate by hydrogen Peroxide increases with increasing pH.

Given a known concentration of HO2-, it is seen that the O3 decomposition rate is

first order with respect to ozone and depends on the HO2- concentration. The kinetic

equation is shown below

]O['kdt

]O[d3

3 =−

Where k’ = pseudo first-order rate constant of ozone decomposition with H2O2 This development reflects an overall kinetic equation as shown

]HO[]O[''kdt

]O[d23

3 −=− Eq. 2.21

Where k’’ = second-order rate constant of ozone decomposition with H2O2 The hydroperoxide ions (HO2

-) consumed by ozone are very quickly. The rate at which the H2O2 is consumed by O3 then takes the following form

]O[]OH[kdt

]OH[d3t22

22 =− Eq. 2.22

23

24

Chapter 3

Methodology

3.1 Overall experimental plan The experimental plan can be divided into two main parts, which are batch study and continuous study. The overall experimental plan is presented in figure 3.1 Raw leachate

Pre-treatment

Effluent Membrane Bioreactor

Batch study

Ozone reactor calibration

study

Effluent ozonation

Ozonation of filtrate

Ozonation of MLSS

Parameter optimization

Batch optimized effluent

Continuous study

Implementation of batch optimized parameters

Development of a continuous ozone

system

Effluent recirculation

Development of a sequence MBR and ozone system until

achieve the maximum removal efficiency

Figure 3.1 Overall experimental plan

24

3.2 Experimental setup

The experimental setup could be divided into two phases, which are Membrane Bioreactor phase and Ozonation phase. 3.2.1 Membrane Bioreactor phase The experimental set up for this phase consists of two reactors, which were Yeast Membrane Bioreactor (YMBR) and Bacterial Membrane Bioreactor (BMBR). The effective volume for each reactor was 5 L with the diameter of 10 cm and the height of 130 cm. Each reactor was continuously aerated by compressed air via air diffuser to maintain aerobic condition. The effluent or filtrated was pump out from membrane at the top of the reactor. The reactor was operated with a periodic air backwashing and measuring transmembrane pressure as the condition for membrane cleaning. The information about operating condition and characteristics of membrane module are shown in the table below. Table 3.1 Operating conditions for MBR and characteristics of membrane module

Qout 7.5-8.0 L/d HRT 16 h MLSS 10,000-12,000 mg/L Membrane material Polyethylene Membrane type Hollow fiber Pore size 0.1 μm Surface area 0.42 m2

3.2.2 Ozonation phase The main components of ozonation phase were divided in the following three groups: ozone generator, ozone column reactor, and ozone scraper. 3.2.2.1 Ozone generator

Corona discharge method was used to generate ozone in the present experiment. This method is widely used as it produces a high concentration of ozone for the applied electrical energy

In corona discharge technique, a dry oxygen-containing gas (air or pure oxygen) is

passed between two electrically charged plates separated by a ceramic dielectric medium and a narrow discharge gap. Under these conditions, part of the oxygen is converted to ozone.

3O2 ↔ 2O3

The synthesis of ozone proceeds is based on the equilibrium reaction and the rate of

reaction increases rapidly above 35 oC. During the ozone generation, the heat produced by the generator has to be cooled. The schematic diagram of ozone generation by corona discharge is shown in the figure 3.2.

25

~

Heat

Heat

Discharge gap O2 O3

Electrode Dielectric

Electrode

Figure 3.2 Schematic diagram of ozone generation by the corona discharge method

The experiment was carried out by supplying dry pure oxygen via the ozone generator type OZ-7510. The generator employed the silent electric discharge principle in which a high-voltage alternating current was applied between two electrodes. It was an semi-industrial scale generator, which could generate ozone up to 10 g/h by oxygen feeding. The ozone concentration was 1-3 % by weight from dry air and the gas flowrate was 15 LPM... The solution was contacted by ozone via ceramic diffuser

3.2.2.2 Ozone column reactor

The reactor was designed as an ideal plug flow reactor, where ozone could

continuously introduce to the solution. Gaseous ozone was continuously fed into the reactor in both batch and continuous operation modes. The ozone column reactor consisted of two parts: the upper portion was constructed with glass column tube of 40 mm diameter and 160 cm length. The bottom part of the reactor was fixed with ceramic diffuser. The schematic diagram of the reactor is shown in Figure 3.2

3.2.2.3 Ozone Scraper

The excess ozone gas is transferred from the top of the ozone reactor to two bottles containing 2 % potassium Iodide (KI) neutral solution. KI will directly react with ozone in the off gas to prevent any ozone from being emitted to the atmosphere

26

160

80

4.0

6.5

∅ = 1

∅ = 3

∅ = 4

Ozone Generator

Drain port ∅ = 0.8

Sampling point ∅ = 0.8

Silicone tube ∅ = 0.8

12

Pure Oxygen inlet

Ozone outlet

Silicone tube ∅ = 0.8 Ceramic

diffuser ∅ 3

KI (2%)

V

OZZON OZONIZER

Figure 3.3 Schematic diagram of ozone column reactor (All dimensions are in cm)

27

Figure 3.4 Schematic diagram of Experimental Setup (Membrane Bioreactor and Ozone System)

Oxygen

Residue Ozone Destroyer

KI 2%

Yeast effluent

Bacterial effluent

Sample Point

O2

Level Control

Tank Yeast Bact.

Ozone Generator

Raw leachate

tank

KI 2%

Level Control

Tank

O3

3.3 Batch study

Most of the experiments were conducted in batch study. The purpose of this study was to optimize the operating parameters, which was used further as the optimized parameters in continuous study.

Drain Water Cooling

Water Ozonated leachate

(Recirculation)

Air

OZZON OZONIZER

V

28

3.3.1 Calibration This part of the experiment was done prior to the experiment to find out the characteristics of the ozone generated. Initially, the ozone generator was calibrated in the gas and liquid phase and after that, the mass transfer and ozone transfer efficiency was computed to define the characteristic of ozone. 3.3.1.1 Measurement of ozone in the gas phase

Applied ozone dosage in the gas phase was determined by analyzing the amount of ozone in the gases being fed to the ozone contactor coupled with knowledge of the (ozone-containing) gas and liquid (to be treated) flowrates. Ozone concentration in the gas phase was determined by Iodometric method (APHA, 1998) by using 2% potassium Iodide solution to determine the amount of residual ozone in the gas phase. The amount of ozone produced was transferred to react with KI directly. The iodide liberated was then treated with 0.2 mole of sodium thiosulfate redundant solution (Rice et.al, 1986 and Langlais et.al, 1991). For each flowrate of dry oxygen with variation of ozone contact time and supply voltage, the yield of ozone per one unit of oxygen utilized could be calculated by potassium iodide method. The stoicheometric of the chemical reaction is shown below (Langlais et.al, 1991)

The reaction of ozone with potassium iodide

O3 + 2I- + H2O I2 + O2 + 2(OH-) Eq. 3.1

The released iodine is titrated with sodium thiosulfate

I2 + 2S2O32- 2I- +S4O6

2- Eq. 3.2

3.3.1.2 Measurement of ozone in the liquid phase

Dissolved ozone concentration in water was determined by spectrophotometric method with the HP 8452A Diode-Array Spectrophotometer. The method involved oxidation of a buffered iodine solution and spectrophotometry measurement of the tri-iodine ion liberated by ozone. The general description for this method was ozone reacted with the neutral potassium iodide; iodine was in the complexes tri-iodine form. The concentration of tri-iodine liberated was determined spectrophotometrically at the wavelength of 352 nm (Shechter, 1973)

3.3.1.3 Determination of the mass transfer and ozone transfer efficiency

After applying ozone, the ozone concentration in the feed gas (O3 feed gas) and ozone

in the aqueous phase (O3 aqueous) were measured. The transfer efficiency of ozone was calculated by determining the difference between the ozone applied to the reactor and the ozone in the off gas and aqueous phase. The equation for calculation is shown below (Langlais et.al, 1991)

Ozone Transfer Efficiency (%) = O3 aqueous x 100 Eq. 3.3 O3 feed

29

When the stream containing pure ozone was contacted with a wastewater, there was a mass transfer from the gas to liquid phase. By using dissolution method (Langlais et.at, 1991), the ozone mass transfer could be calculated by the following equation

Ln (CL

* - CL) = - KLa x t Eq. 3.4

Where CL* and CL are the equilibrium ozone concentration (mg/L) and ozone

concentration in aqueous phase (mg/L) at time t, respectively. KLa is ozone mass transfer coefficient (time-1) and t is contact time (time).

3.3.1.4 Determination of ozone kinetic rate constant

1) Determination of pseudo first order rate constant (k’) for to ozone decomposition at different pH

Table 3.2 Determination of k’ or pseudo first order rate constant at different pH value

Time (min) O3

(mg/L) 0 1 3 5 7 10 15 20 25 30

45 k′0,45 k′1,45 k′3,45 k′5,45 k′7,45 k′10,45 k′15,45 k′20,45 k′25,45 k′30,4560 k′0,60 k′1,60 k′3,60 k′5,60 k′7,60 k′10,60 k′15,60 k′20,60 k′25,60 k′30,6075 k′0,75 k′1,75 k′3,75 k′5,75 k′7,75 k′10,75 k′15,75 k′20,75 k′25,75 k′30,75

The pH was varied during the ozonation and its relationship with k′ (s-1) was

established. The pH used in the experiment was 2, 4, 7, 9, 11.

2) Determination of the reaction rate constant or specific ozone utilization rate and the primary degree of pollutant elimination (α) (Ozone concentration = 75 mg/L)

Table 3.3 Determination of the rate constant or specific ozone utilization rate and primary elimination degree of pollutant (α)

Time (min) Types of leachate

15 30 60 90 180 Yeast effluent at

HRT = 16h with a given [C0] or TOC0

kY16, 15 and αY16, 15

kY16, 30 and αY16, 30

kY16, 60 and αY16, 60

kY16, 90 and αY16, 90

kY16, 180 and αY16, 180

Bacterial effluent at HRT = 16h with a

given [C0] or TOC0

kB16, 15 and αB16, 15

kB16, 30 and αB16, 30

kB16, 60 and αB16, 60

kB16, 90 and αB16, 90

kB16, 180 and αB16, 180

Yeast effluent at HRT = 24h with a given [C0] or TOC0

kY24, 15 and αY24, 15

kY24, 30 and αY24, 30

kY24, 60 and αY24, 60

kY24, 90 and αY24, 90

kY24, 180 and αY24, 180

Bacterial effluent at HRT = 24h with a

given [C0] or TOC0

kB24, 15 and αB24, 15

kB24, 30 and αB24, 30

kB24, 60 and αB24, 60

kB24, 90 and αB24, 90

kB24, 180 and αB24, 180

30

3) Determination of ozonation factor for yeast and bacterial effluent (Ozone concentration = 75 mg/L)

Table 3.4 Determination of ozonation factor

Time (min) Type of leachate

15 30 60 90 180 Yeast effluent at HRT = 16h with a given [A] ΦY16, 15 ΦY16, 30 ΦY16, 60 ΦY16, 90 ΦY16, 180

Bacterial effluent at HRT = 16h with a given [A] ΦB16, 15 ΦB16, 30 ΦB16, 60 ΦB16, 90 ΦB16, 180

Yeast effluent at HRT = 24h with a given [A] ΦY24, 15 ΦY24, 30 ΦY24, 60 ΦY24, 90 ΦY24, 180

Bacterial effluent at HRT = 24h with a given [A] ΦB24, 15 ΦB24, 30 ΦB24, 60 ΦB24, 90 ΦB24, 180

3.3.2 Effluent ozonation Landfill leachate in this study was taken from Pathumthani Sanitary Landfill (Pathumthani province, Thailand) and Ramindra Transfer Station (Bangkok, Thailand). It was characterized and mixed in order to simulate a medium-age leachate. The raw leachate had NH3 1,600-1,800 mg/L, TKN 1,800-2,000 mg/L, and COD 7,000-9,000 mg/L. 3.3.2.1 Effluent from Membrane Bioreactors (MBR)

At present, raw leachate was pre-treated with Ammonia stripping to remove

ammonia. Leachate that was pre-treated by this process would have the ammonia removal efficiency of 90%. The ammonia stripped leachate was fed to MBR which consist of two reactor which were

1) Yeast Membrane Bioreactor (YMBR) which using yeast in biological

process 2) Bacterial Membrane Bioreactor (BMBR) which using mixed bacteria

population in biological process

The efficiency from the reactors averaged between 65-70% COD removal.

3.3.2.2 Chemical Oxidants In this study, two chemical oxidants were used prior to their strong oxidizing

potential. Chemical oxidants had ability to convert long chain humates to short chain, which increased the biodegradability of the substance presented in leachate. Chemical oxidants that involve in the chemical oxidation process are as followed.

1) Ozone (O3) with the oxidizing power of 2.07 V was sufficient to directly convert organic substances. Ozone was generated from ozone generator as described above.

2) Hydrogen peroxide combined with ozone (Perozone) with the strong

oxidizing power of 3.06 V, perozone was developed as chemical oxidant in

31

order to get the benefit from its strong oxidizing power together with the strategy to reduce ozone consumption. Perozone allowed an increase of COD removal of refractory compounds (Panpanit, 2001) In this study, various concentration ratios of hydrogen peroxide and ozone was implemented to find out the optimum parameters.

3.3.2.3 Chemical oxidation process

1) Ozonation of the filtrate or supernatant from both membrane bioreactors

The effluent from membrane bioreactor was filtrated through the membrane

module by air bubble pressurized in the aerobic condition of the biological process. Each sample from each reactor was ozonated to find out the optimum parameters and compared the efficiency between these two reactors. The characteristic of the filtrate effluent from MBR, which was pre-treated with ammonia stripping, is shown in table 3.5.

Table 3.5 Characteristic of the effluent from both membrane bioreactors

Parameters Yeast Effluent Bacterial effluent BOD (mg/L) 60-120 240-260 COD (mg/L) 2,195-3,081 2,143-3,143 NH3 (mg/L) 115-395 45-367 TKN (mg/L) 126-521 67-473 Color (ADMI) 219-336 449-621

2) Ozonation of the Mix Liquor Suspended Solid (MLSS) from both membrane bioreactors

The purpose for the ozonation of the sludge was for sludge reduction and the

supernatant of the ozonated sludge, which was consist of solubilized organics and micro-particles was proved to be an effective carbon source for denitrification (Ahn et.al, 2002). Recycling of the ozonated sludge to the MBR induced a slight increase in effluent COD, but the biological treatment performance was maintained (Deleris, et.al)

In this study, the MLSS of the two reactors was maintained at average 10,000-

12,000 mg/L. The effluent was taken out from the reactor at the middle height of the reactor. A fraction of the mixed liquor was ozonated equivalent to the volume of sludge wasted to maintain the SRT in the MBR. The ozonated mixed liquor or sludge was returned to the MBR in an attempt to increase the biodegradability by transforming high molecular compounds to the lower molecular weights entities.

The figure of the position for pumping out the filtrate and MLSS from MBR to the

ozone reactor is shown below

32

Figure 3.5 Schematic diagrams for the positions of pumping out the filtrate or MLSS from MBR

Ozone generator

KI Sample point

Ozone reactor

MBR

MLSS Filtrate

Recirculation 3.3.3 Parameter optimization 3.3.3.1 Optimization of the ozone and perozone contact time

It is necessary to maintain a higher residence time in the biological reactor for

recirculation of the ozonated effluent back to MBR. If no option of recirculation back to MBR, the residence time in the ozone reactor could be equal to or less than in MBR. The further consideration for this study was half-life or the stability of dissolved ozone in the column. It was an advantage if the optimum time that the ability to degrade the substance not increase could be found. After a certain time (half-life) after contacting ozone or perozone with leachate, there was no change in effluent degradation. Therefore, the optimum contact time in term of effluent degradation rate and economic feasibility could be achieved.

3.3.3.2 Optimization of the waiting time after addition of hydrogen peroxide

H2O2 had a better efficiency if the waiting time after addition of H2O2 before the

reaction is done. The purpose for doing this was to ensure homogeneity of H2O2 in the solution to be treated. This modified approach could increase COD removal efficiency of the effluent. In this study, the trial of the waiting time was implemented before ozonation. Sample was collected before the addition of H2O2, during and after the ozonation. It should be noted that the sample should be mixed for the duration of the waiting time and then put in the ozone column.

33

3.3.3.3 Optimization of the H2O2 concentration

In order to achieve this, the voltage and the waiting time should be fixed. For each trial, adjust the addition range of H2O2 until the optimum value was achieved by considering the removal efficiency and economical aspect that ozone consumption could be reduced.

3.3.3.4 Optimization for ozone and perozone dosage

In order to achieve this, the contact time and the addition of H2O2 should be fixed.

The procedure was done by trial with the different in ozone dosage until the optimum value was achieved, again by considering the removal efficiency and economical aspect. 3.3.4 Experimental implementation

For membrane filtrated and bioreactor mixed liquor, ozone was used as chemical oxidants. The contact time and ozone dosage given in table 3.5 were used to optimize the conditions for ozonation. The optimum parameters were determined in term of COD, TOC, and Color removal efficiency. BOD/COD was also used to determine optimum conditions. The higher the BOD/COD ratio obtained, the better efficiency of chemical oxidation unit to convert refractory compounds into easily biodegradable compounds. During ozonation, chemical oxidants were continuously supplied to react with the leachate. 3.3.4.1 Ozone as chemical oxidant

Table 3.6 Determination of optimum ozone dosage and contact time

Ozone dosage (mg/L) Contact

time (min)

Batch No.

15 30 45 60 75 90 180

1 45 45 45 45 45 45 45 2 60 60 60 60 60 60 60 3 75 75 75 75 75 75 75

After getting the optimum ozone dosage and contact time, the structural conversion

before and after ozonation was determined through Molecular Weight Cut-Off (MWCO) experiment.

1) Determination of initial membrane resistance

Membrane resistance was conducted to find out the efficiency of the new

membrane. It was measured by filtrating distilled water through the membrane using Nitrogen gas at two bars pressure. The volume of the permeate from membrane was measured using an electronic balance taking density of water equal to 1 kg/L. Membranes with five different molecular weight namely 50 k Da, 10 k Da, and 5 k Da, 3.5 kDa, and 1 kDa was used in the experiment. The diameter of each membrane is 7.6 cm. Membrane resistance was calculated with the formula given below.

34

mRTMPJμ

=

Eq. 2.23

J = Filtration flux (L/m2.h) TMP = Transmembrane pressure (kPa) μ = Dynamic viscosity = 0.798*10-3 N.s/m2 at 27 oC Rm = Membrane Resistance (m-1) 2) Molecular Weight Cut-Off (MWCO) experiment

In order to separate the organic molecules of the leachate on the basis of their

molecular weight, Molecular Weight Cut-Off experiment was performed. Using flat sheet circular ultrafiltration membrane (UF) with the 7.6 cm diameter in a 300 mL cell. The five types of UF membranes with the molecular weight cut-off ranges is presented in table 3.5. Nitrogen gas was applied to pressurize the ultrafiltration cell at 2 bars for Koch membrane and 4 bars for Desal membrane. The compositions of the leachate in term of their molecular weight were separated into six groups included 1) MW > 50 kDa, 2) MW 10-50 kDa, 3) MW 5-10 kDa, 4) MW 3.5-5 kDa, 5) MW 1-3.5 kDa, and 6) MW < 1kDa. The procedures for MWCO experiment were as follow:

1. Using 100 mL of leachate as an initial volume to fraction with UF at MW 50 kDa

by using Nitrogen gas at 2 bars for 30 minutes. 2. The volume of retentate was kept and could be represented the fraction of MW >

50 kDa. The sample was used for further analysis.

3. The volume of permeate was used as an initial volume for UF at MW 10 kDa. The same procedures were performed with UF membrane of the corresponding MW of 5 kDa, 3.5 kDa, and 1 kDa but pressurize with Nitrogen gas at 4 bars instead of 2 bars for the last two UF.

4. Leachate at each MW fraction was analyzed for COD, TOC, BOD/COD, and Color

before and after ozonation at optimum conditions.

Table 3.7 Range of MWCO used in the experiment and their specification

MWCO (kDa) Specification 50 Koch membrane M-100, 0030883 series 10 Koch membrane K-131, 0030880 series 5 Koch membrane K-328, 0030896 series

3.5 Desal GK series 1.0 Desal GE series

35

The procedure for molecular weight distribution is shown below

100 mLof leachate

MW 50 kDa

Permeate

Retentate of MW > 50 kDa

MW 10 kDa

Permeate

Retentate of MW 10- 50 kDa

MW 5 kDa

Permeate

Retentate of MW 5-10 kDa

MW 3.5 kDa

Permeate

Retentate of MW 3.5-5 kDa

MW 1 kDa

Permeate at MW < 1 kDa

Retentate of MW 1-3.5 kDa

Figure 3.6 Procedure for Molecular Weight Cut-Off experiment

The schematic diagram for ultrafiltration process for MWCO experiment is showed in figure 3.7

36

P Leachate addition

Pressurization, N2

Stirring mechanism

Membrane placement

Magnetic stirrer

Permeate

Figure 3.7 Schematic diagram for ultrafiltration process for MWCO experiment 3.3.4.2 Ozone combined with hydrogen peroxide (perozone) as chemical oxidant

1) Determination of optimum waiting time after the addition for hydrogen peroxide

The optimum waiting time after the addition for hydrogen peroxide was determined

by using optimum ozone dosage and contact time from table 3.3

Table 3.8 Determination of optimum waiting time after the addition for hydrogen peroxide

Waiting time (min) Batch No. H2O2/O3

ratio = 0.1 H2O2/O3

ratio = 0.3 H2O2/O3

ratio = 0.5 H2O2/O3

ratio = 0.7 1 0 0 0 0 2 10 10 10 10 3 20 20 20 20 4 30 30 30 30

2) Determination of optimum perozone contact time

Optimum perozone contact time was determined using optimum ozone dosage and optimum H2O2 concentration with optimum waiting time obtained from previous experiment

37

Table 3.9 Determination of optimum perozone contact time

Batch No. Perozone contact time (min) 1 15 2 30 3 45 4 60 5 75 6 90 7 180

3) Effect of pH during ozonation process

Alkalinity represents the presence of carbonate or bi-carbonates which was the

radical scavenger during ozonation. The ozone consumptions at different alkalinity condition (controlled by pH value) were determined. The experiment was conducted using optimum ozone or perozone dosage and contact time. The varied pH used were 2, 3, 4, 7, and 11.

3.4 Continuous study

In the continuous study, batch optimized effluent, which was obtained from yeast or bacteria effluent was fed into the ozone reactor as feeding.

3.4.1 Implementation of batch optimized parameter and development of a continuous

ozone system After batch study, all optimized parameters were used for the initial condition of

the continuous system. These included ozone dosage and ozone contact time. The development of the continuous system was considered. The effluent from MBR was fed in batch mean to the ozone column. Leachate was recirculated many times in the sequence of MBR and ozonation until achieve the maximum removal efficiency.

3.4.2 Continuous experiment After ozonation, the option for the recirculation of ozonated effluent back into

MBR was taking into consideration. The purpose for doing this was to increase the removal efficiency of the effluent at the same time, the chemical requirements for chemical oxidation could be lessen. Using batch optimized parameter as initial values for starting up the continuous experiment. The schematic diagram for combined system was showed in figure 3.8.

3.4.3 Development of a sequence MBR and Ozonation system

When the optimum recirculation rate was achieved, the treated effluent from MBR

was sent to ozonation system again. This sequence was done several times until the maximum removal efficiency in term of COD was achieved.

38

.

Ozone generator

KI

Ozone reactor

MBR

Recirculation (O3 leachate)

O3

Mixed tank (Raw LL+O3 LL)

MBR effluent

Figure 3.8 Schematic diagram for combined system (MBR + Ozonation)

3.5 Ozonation of the sludge or MLSS from both yeast and bacterial reactors 3.5.1 Sludge treatment in the mean of sludge reduction

The effects of sludge ozonation were determined in terms of mineralization (total

COD change), solubilization (soluble COD change), and changes in residual solid characteristics (total and residual SS). The experiment was conducted by varying ozone dosage in the range of 0, 0.01, 0.02, 0.1, 0.2, and 0.5 mgO3/mgSS. Determined the conversion of the fraction before and after ozonation in term of mineralization, solubilization, unsettlable microparticles, and residuals. Ozonation on sludge was effective in reducing sludge production by the mechanisms of degradation of suspended solid into soluble form and mineralization this soluble organic matter. 3.5.2 Sludge treatment in term of reducing solid concentration

The concentration of solid was reduced from the degradation of organic matter by ozonation. The solid concentration reduced when increasing ozone dosage. The ratio of MLVSS/MLSS was determined with the variation of ozone dosage. The ozone dosage used was in the range of 0, 0.01, 0.02, 0.1, 0.2, and 0.5 mgO3/mgSS. As sludge ozonation tended to increase the settleability of sludge, sludge volume index for each ozone dosage was determined. Ozone had the ability to overcome the floc structure inside sludge which resulted in the increasing of sludge settleabiltiy.

39

In this experiment, the ozone reactor for sludge treatment was design. An effective volume of 0.3 L/d was considered from then rate of sludge drained per day from MBR. Completely mixed condition was maintaining by magnetic stirrer mechanism. The detail design for sludge reactor is illustrated in figure 3.9.

Magnetic stirrer

O3 out

Feed for continuous

system

Sampling point

Option for recirculation in

continuous system

O3 in

Diffuser

18

12

∅ 0.8

∅ 0.8

∅ 0.8

∅ 0.5

∅ 0.8

∅ 0.5

∅ 2.5

Column diameter 6

Figure 3.9 Reactor for sludge ozonation (All dimension are in cm)

2

2

8

Rubber

Fix

4

40

3.6 Analytical methods

The analytical method in this study was followed the Standard Methods (APHA et.al, 1998). The samples were collected to measure at the different conditions. For BOD, COD, TKN, TOC, color, and pH, they were measured before, after ozonation and after post-biological treatment to see the conversion from the process. For alkalinity, it was measured before ozonation because alkalinity was radical scavenger. Ozone would react with carbonate before humic substance, which resulted in high chemical oxidant requirements. For suspended solid, it was measured only when taking the MLSS effluent from MBR because SS was very low in filtrated effluent. For MWCO, it was measured before and after ozonation to see the fraction of the compound that was changed during ozonation. The analytical methods for parameters measurement, range, and interference are shown in table 3.12 Table 3.12 Analytical methods for parameters measurement

Parameters Methods Range Interference References Ozone concentration in gas phase (mg/L)

Iodometric method - H2O2, organic peroxides, chlirine APHA, 1998

Ozone concentration in liquid phase (mg/L)

Spectrophotometric method

- Color, turbidity, the presence of organic matter

Shechter, 1973

BOD (mg/L) Oxi Top bottles 0-4,000 Depend on the operating condition

German standard

COD (mg/L) Potassium Dichromate Digestion (Closed reflux method)

- Chloride

APHA, 1998

TKN (mg/L) Digestion method - Chloride APHA, 1998TOC (mg/L) Combustion method 0-20,000 ppm

High concentration of non - volatile organic compound

APHA, 1998

Color (ADMI) Spectrophotometric method

Depend on the limitation of the spectrophotometer

Turbidity

APHA, 1998

MWCO (kDa) Membrane filtration method

Depends on the molecular weight of membrane material.

Suspended solids

Slater, 1985, Gourdon, 1989, and

Huang, 2000

41

Parameters Methods Range Interference References Alkalinity (mg/L as CaCO3)

Titration method - Soaps, oily matter, suspended solids, or precipitates

APHA, 1998

SS (mg/L) Glass Fiber Filtration Disc

- Floating particles, oil and grease, high concentration of calcium, magnesium, chloride, and/or sulfate.

APHA, 1998

pH pH meter 1-14 - APHA, 1998

42

Chapter 4

Results and Discussions

4.1 Ozone Calibration studies The calibration of ozone generator was done prior to ozonation in order to determine ozone concentration in gas and liquid phase. By maintaining a constant gas to liquid flow ratio, the increase of the ozone transfer into liquid was almost directly proportional to the ozone concentration in feed gas. Calibration of ozone was done by varying the oxygen flowrate and power voltage of the ozone generator at different ozone contact time. Ozone concentration in off-gas occurred when ozone was applied into solution after a period of time. Another objective for ozone calibration was to determine the characteristics of ozone at specific operational conditions. These were defined by the determination of the ozone mass transfer and ozone transfer efficiency. 4.1.1 Determination of ozone in gas and liquid phase In this study, ozone was generated by corona discharge method. The generated ozone was calibrated in order to determine the exact amount of ozone concentration in gas phase. The analytical method for ozone concentration measurement in gas phase was done by Iodometric method (APHA, 1998). Ozone was applied directly to 2% Potassium Iodide (KI) solution. Iodide ion was oxidized to iodine by ozone and the liberated iodine was titrated with sodium thiosulfate to a starch endpoint. The reaction of ozone with potassium iodide is as follows.

O3 + 2I- + H2O I2 + O2 + 2OH- Eq. 4.1

The released iodine is titrated with sodium thiosulfate

I2 + 2S2O32- 2I- +S4O6

2- Eq. 4.2

The details of experiment results for determination of ozone in gas phase are shown in tables B-1 to B-6 of Appendix B. The calibration results presented in Figure 4.1 showed the proportional increase in ozone concentration with an increase in voltage. The results indicated that higher ozone concentration could be achieved with lower oxygen flowrate. The ozone could only be generated from the voltage higher than 160 volts due to the limitation in ozone generator. The trend of the results from this experiment was lower than the results reported by the manufacturer by approximately 20 %. The probable reasons for this difference might be from the analytical techniques. Ozone gas analyzer equipment and Iodometric method were used for the determination of ozone in gas phase for the ozone company and this experiment, respectively. The appropriate ozone concentrations that were used for all the experiment for this thesis study was 45, 60, and 75 mg/L.

43

40

45

50

55

60

65

70

75

80

160 170 180 190 200 210 220

Voltage (V)

Ozo

ne c

once

ntra

tion

(mg/

L)

0.2 L/min 0.4 L/min 0.6 L/min 0.8 L/min 1.0 L/min

Figure 4.1 Ozone concentrations in gas phase of the feed gas at different oxygen flowrate

and ozone voltage

After passing ozone gas into distilled water in the reactor, ozone concentration in liquid phase was monitored with time. The spectrophotometric method was used to determine dissolved ozone concentration in liquid phase (Shechter, 1973). The initial ozone concentrations in feed gas applied to determine ozone concentration in liquid phase were 45 mg/L, 60 mg/L, and 75 mg/L. The ozone contact time varied from 0.5 to 30 minutes. Ozone concentration in liquid phase was automatically calculated from spectrophotometer as indicated in Figure B-6 of Appendix B. The results of ozone concentration in liquid phase are in tables B-7 and B-8 of Appendix B. Figure 4.2 shows the concentration of ozone in liquid phase at different contact time.

00.010.020.030.040.050.060.07

0 5 10 15 20 25 30

Contact time (min)

Ozo

ne c

once

ntra

tion

in

liqui

d ph

ase

(mg/

L)

Ozone = 45 mg/L Ozone = 60 mg/L Ozone = 75 mg/L

Figure 4.2 Ozone concentrations in liquid phase at different ozone contact time and initial

ozone concentration

44

The above figure indicated the residual ozone concentration remained in water solution with different ozone contact time. From the results, ozone concentration in liquid phase followed the stoichiometric assumption. The higher of the ozone concentration in feed gas applied, the higher of ozone transferred into distilled water. The concentration of ozone transferred up to the theoretical limit defined by Henry’s law. Ozone concentration increased in the first period, which was in the first five minutes after applied ozone and decreased after this contact time for every initial ozone concentration. This followed the theory of ozonation which said that after applied ozone for a period of time, part of ozone would transfer into exhaust gas, which would further reduce ozone after applied ozone for a period of time. Part of ozone also decomposed in the solution, which was another reason for the reduction of ozone concentration. The ozone concentration level examined was 0-0.063 mg/L. This could be concluded that most of the ozone was transferred into the off-gas while only small amount remained in the liquid phase.

4.1.2 Determination of the mass transfer and ozone transfer efficiency In all processes of ozonation, ozone concentration in feed gas (O3 feed) and ozone concentration in the off-gas (O3 out) must be measured and the transfer efficiency must be calculated. Ozone transfer efficiency (TE) was the percentage of the applied ozone that goes into the solution under the specific conditions. TE was calculated by determining the difference between ozone concentration applied to the reactor and ozone concentration in off-gas as given in the equation 4.3. Off-gas flow losses were typically less than 10 percent of feed gas flow when product gas ozone concentration was low to moderate (Langlais, et al., 1991)

%100x]O[

]O[]O[%),TE(EfficiencyTransfer

feed3

out3feed3

⎥⎥⎦

⎤

⎢⎢⎣

⎡ −= Eq. 4.3

In this experiment, ozone concentration of 45, 60, and 75 mg/L in feed gas at ozone

contact time of 0.5, 1, 3, 5, 7, 10, 15, 20, 25, and 30 minutes were used. The ozone transfer efficiency was average in all of the experiment. The results of ozone transfer efficiency are presented in Table 4.2. The details of experimental results are presented in Tables B-9 to B-11 of Appendix B. Table 4.2 Ozone transfer efficiency at different feed gas ozone concentration

Ozone concentration in feed gas (mg/L) Ozone transfer efficiency (TE), % 45 54.1 60 58.2 75 50.7

Average TE (%) 54.3 The parameters that affect the transfer efficiency are water temperature, gas to liquid ratio, and contactor pressure. Ozone was more soluble in cold water than hot water (Meyer and Mazzei). The transfer efficiency of 54.3% is considered low. This could be because of the effect of the temperature during summer (27oC-32 oC) while conducting this experiment. Figure 4.3 showed the results of ozone concentration in off-gas as a function of ozone contact time. When contact time increased, the ozone applied in feed gas was transferred into off-gas, which leaded to the increase of the concentration in off-gas.

45

During the first period of ozonation, ozone applied was directly transferred into off-gas which lead to the dramatically increase of ozone concentration in off-gas. After an approximately 5 minutes contact time, the ozone reaction began which lead to the almost constant ozone concentration in off-gas. The more the ozone applied in feed gas, the more the ozone in off-gas.

Dissolved ozone concentration in liquid phase was determined The feed gas concentration varied from 45, 60, and 75 mg/L. Ozone concentration was determined in 1 L of distilled water after ozone contact time of 0.5, 1, 3, 5, 7, 10, 15, 20, 25, and 30 minutes. The solubility of ozone in water at temperature of approximately 30 oC was 0.14 (ratio of mg/L in water to mg/L in gas). The dissolution method for the determination of the mass transfer is given in followed Equation 3.4. The results of the mass transfer were presented in Table 4.3. The range of the mass transfer varied with the time and initial ozone concentration. The average value was used as the representative results of the transfer coefficient. Table 4.4 showed the comparison of the ozone transfer efficiency and ozone mass transfer coefficient. The coefficient result from this study was slightly higher than the experiments conducted by the other researchers. The results of mass transfer efficiency are in Tables B-12 to B-14 of Appendix B. Table 4.3 Ozone mass transfer coefficient at different feed gas ozone concentration

Ozone concentration in feed gas (mg/L) Ozone mass transfer coefficient (KLa, s-1) 45 0.01478 60 0.01710 75 0.01889

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35

Contact time (min)

Ozo

ne c

once

ntra

tion

in o

ff-g

as

(mg/

L)

Ozone conc. = 45 mg/L Ozone conc. = 60 mg/LOzone conc. = 75 mg/L

Figure 4.3 Ozone concentrations in off-gas at different contact time

46

Table 4.4 Comparison of ozone transfer efficiency and ozone mass transfer coefficient (Panpanit, 2001)

Type of ozone

reactor

Temperature (oC)

Ozone in feed gas (mg/L)

Aqueous

Ozone transfer

efficiency (%)

Ozone mass

transfer coefficient

(s-1)

Reference

Bubble column 28-30 oC 75 Distilled

water 54.3 0.01889 Present study

Bubble column 17-18 oC 10.2 Distilled

water 90 0.00689 Biri, 1997

Batch reactor 20 oC 14.4 Ultra pure

water 49 0.01 Roche, et al., 1994

Bubble column 28-30 oC 33 Distilled

water 63 0.0077 Panpanit, 2001

4.1.3 Ozone kinetic studies When ozone was used to treat the landfill leachate, kinetic data are important and must be known in order to predict the products that remain in water after specific period of ozonation. It is also necessary for one to know about the environmental behavior of ozone when absorbed into water. When ozone gas was bubbled into landfill leachate, kinetics of the reaction was determined for the overall reaction as a function of flow and chemical parameters. In this study, the characteristics of ozone were defined by the determination of ozone decomposition rate. This data could be used to find out the optimum conditions of ozonation. From the results of the organic removal efficiency, specific ozone utilization rate or ozone reaction rate constant was obtained. This data was used to predict the amount of pollutant remained in the solution after applied ozone and the rate of the reaction. The primary degree of pollutant elimination was also determined in order to find out the ability of ozone to treat leachate at different conditions. All of these kinetic data must be calculated prior to the application of ozone for all wastewater treatment. 4.1.3.1 Determination of ozone decomposition rate constant In general, when ozone reacts with landfill leachate, only part of ozone reacts directly with dissolved solutes. The remaining part may decompose before reaction and initiate reactive secondary oxidants such as hydroxyl radicals (OH ) (Chu and Ching, 2003). The decomposition of ozone in water was based on phenomenological descriptions of overall kinetics found for pure water (Staehelin and Hoigne, 1982). Primary decomposition of ozone produced free radical, which could react further with ozone to yield more free radicals. This situation could also accelerate the decomposition of ozone. The decomposition of ozone yields the decomposition rate constant and the half-life of ozone (the time that the ozone concentration decrease to half of the initial concentration). In this experiment, distilled water was used to find out the ozone concentration in liquid phase at different ozone contact time. The stability of dissolved ozone or its half-life was readily affected by pH. The ozone decomposition rate constant or pseudo first order rate constant was a linear function of pH, therefore, the ozone decomposition rate was a first order with respect to both ozone and hydroxide ions (Langlais et al., 1991)

47

The initial ozone concentrations dissolved in distilled water were set at 0.02, 0.04, and 0.06 mg/L at normal pH of 6 (pH of distilled water used). The pH varied was 2, 6, 7, and 11. The decomposition rate was expressed by a pseudo first order kinetic equation as illustrated in Equations 2.3, 2.4 and 2.5. Figures 4.4, 4.5, and 4.6 show the results of ozone concentration in distilled water at different pH condition and initial ozone concentration. The ozone contact time varied was 0.5, 1, 3, 5, 7, 10, 15, 20, 25, and 30 minutes. Ozone concentration in liquid phase was measured. The details of the experiment results are in Tables B-15 to B-27 of Appendix B.

ypH=7 = 0.0379x

ypH=6 = 0.0287x

ypH=2 = 0.0253x

ypH=11 = 0.0407x

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 5 10 15 20 25 30 35Time (min)

-{ln

([O

3]/[O

3]0)

}

pH = 2 pH = 6 pH = 7 pH = 11

Figure 4.4 Ozone concentrations at initial dissolved ozone concentration of 0.02 mg/L at

different pH value

ypH=7 = 0.0395x

ypH=6 = 0.035x

ypH=2 = 0.0271x

y pH=11= 0.0425x

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 5 10 15 20 25 30 35Time (min)

-{ln

([O

3]/[O

3]0)

}

pH = 2 pH = 6 pH = 7 pH = 11

Figure 4.5 Ozone concentrations at initial dissolved ozone concentration of 0.04 mg/L at

different pH value

48

ypH=7 = 0.0419xypH=6 = 0.0386x

ypH=2 = 0.0279x

ypH=11 = 0.044x

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 5 10 15 20 25 30 35Time (min)

-{ln

([O

3]/[O

3]0)

}pH = 2 pH =6 pH = 7 pH = 11

Figure 4.6 Ozone concentrations at initial dissolved ozone concentration of 0.06 mg/L at

different pH value

A summary of the results for pseudo first order rate constant is presented in figure 4.7. On the basis of these results, it could be assumed that the pH-dependent decomposition of ozone was due to a reaction that is kinetically controlled by hydroxide concentration. The rate constant increased when the initial ozone dissolved in water increased. It also increased when the ozone condition was getting into alkaline condition as indicate by the increase of pH value.

3

4

5

6

7

8

2 3 4 5 6 7 8 9 10 11pH

k' (*

10-4

s-1)

[O3]o = 0.02 mg/L [O3]o = 0.04 mg/L [O3]o = 0.06 mg/L

Figure 4.7 Pseudo first order rate constant as a function of initial ozone concentration and pH condition

The stability of dissolved ozone or its half-life (t1/2) is presented in Table 4.5. It

could be concluded that the half-life of ozone decreased when pH increased (from approximately 30 minutes at pH of 2 to 15 minutes at pH of 11). Hydroxide ion enhanced the self-decomposition of ozone. A faster decay rate contributed by free radical oxidation

49

at high pH levels. This situation was obviously observed by the low absorbance value at high pH level of the solution measured by spectrophotometer. Half-life of ozone also decreased when the initial ozone concentration increased. The equation for half-life is as followed.

t1/2 = ln2 Eq. 4.4 k′

Table 4.5 The stability of dissolved ozone concentration or half-life with different pH level and initial ozone concentration

Half-life, t1/2 of dissolved ozone (min) pH [O3]0, pH 6 = 0.02 mg/L [O3]0, pH 6 = 0.04 mg/L [O3]0, pH 6 = 0.06 mg/L

2 27.4 25.6 24.8 6 24.2 19.80 17.96 7 18.29 17.55 16.54 11 17.03 16.31 15.75

The stability of ozone also depended on the quality of water solution. Rice (1986) indicated that the purer of the water, the lower the concentration of ozone-demanding constituents was presented. This could be the reason for long half-life period. Rice also presented the half-life of ozone in different kind of water. The comparison of these data was illustrated in Figure 4.8. All of half-life data measured at 20 oC but 30 oC was used for present study. From the result, half-life could also be affected by water temperature.

010203040506070

Distilled waterin present study

Double distilledwater

Distilled water Tap water Low hardnessgroundwater

Filtered waterfrom lake

Hal

f-lif

e of

ozo

ne (m

in)

Figure 4.8 Comparison of half-life of ozone in different kind of water

4.1.3.2 Determination of the reaction rate constant and the primary degree of pollutant elimination The reaction rate or specific ozone utilization rate constant were determined according to the stoichiometric assumption for ozone in wastewater treatment. The pollutant in leachate (as presented in term of COD and TOC concentration) decreased after applied ozone for different contact time. Four different types of leachate used for the

50

determination of reaction rate constant were Yeast and Bacterial effluent from MBR at Hydraulic Retention Time (HRT) of 16 and 24 hours, each. The contact time varied from 15, 30, 60, 90, and 180 minutes. The pH of Yeast MBR and Bacterial MBR were controlled at 3.6 and 7.5, respectively. The maximum removal efficiencies at contact time of 180 minutes for all types of leachate are presented in Table 4.6.

The rate of TOC and COD removal efficiency increased when increasing contact time. It could be concluded that bacterial effluent had higher pollutant removal (both TOC and COD) than yeast for both HRT of 16 and 24 hours. Ozone had higher efficiency in removing COD in leachate than TOC. This meant that ozone had little effect on TOC mineralization, resulting in less transformation of carbon compounds presented in leachate to carbon dioxide. The degree of primary pollutant elimination, as presented in Equation 2.18, in term of TOC and COD are shown in Figures 4.9 and 4.10, respectively. This result indicates the trend of leachate degradation during ozonation with ozone dosage of 75 mg/L. During the first minutes, a high TOC and COD concentration results in a lower degradation rate. Wenzel et al, (1998) indicated that this situation is caused by the higher extent of ozone consumption. Table 4.6 Final COD concentration at 180 minutes ozone contact time

Types of landfill leachate TOC concentration (mg/L)

COD concentration (mg/L)

Yeast effluent (HRT 16 h)* 490 960 Bacterial effluent (HRT 16 h)** 215 519 Yeast effluent (HRT 24 h)*** 703 1,295

Bacterial effluent (HRT 24 h)**** 388 664 * Initial TOC concentration for yeast at 16 h-HRT = 796 mg/L, COD = 2,138 mg/L ** Initial TOC concentration for bacteria at 16 h-HRT = 650 mg/L, COD = 1,938 mg/L *** Initial TOC concentration for yeast at 24 h-HRT = 1,122 mg/L, COD = 2,664 mg/L ***** Initial TOC concentration for bacteria at 24 h-HRT = 786 mg/L, COD = 2,260 mg/L

0

0.2

0.4

0.6

0.8

1

0 30 60 90 120 150 180

Contact time (min)

Deg

ree

of p

rim

ary

pollu

tant

elim

inat

ion

(TO

C/T

OC

0)

Yeast at HRT = 16 h Bact. at HRT = 16 hYeast at HRT = 24 h Bact. at HRT = 24 h

Figure 4.9 The primary degree of pollutant elimination in term of TOC at different contact

time

51

0

0.2

0.4

0.6

0.8

1

0 30 60 90 120 150 180

Contact time (min)

Deg

ree

of p

ollu

tant

el

imin

atio

n (C

OD

/CO

D0)

Yeast at HRT = 16 h Bact. at HRT = 16 hYeast at HRT = 24 h Bact. at HRT = 24 h

Figure 4.10 The primary degree of pollutant elimination in term of COD at different

contact time

The effect of initial solute concentration on the oxidation rate is shown in Figures 4.11 and 4.12. When applied the first order kinetic reaction rate equation as presented in Equation 2.17, the results showed the linear relationship between the natural logarithm of the pollutant concentration based on initial concentration and contact time. The slope of the relationship represented the reaction rate constant. The higher of the reaction rate constant, the higher the removal efficiency. The summarized reaction rate constant is shown in Table 4.7. It was obviously observed that bacterial effluent had higher reaction rate constant, which mean that ozone could degrade organic pollutant presented in bacterial effluent better than yeast effluent. The reaction rate constant was in the range of 0.003–0.008 min-1, which was considered low reaction rate. In order to achieve high pollutant removal efficiency, more ozone had to be applied where we also need to consider the economical aspect. Another option was by the combination of chemical oxidation process with biological treatment. The details of this option were discussed in the next part of the experiment. Wenzel et al, (1998) had conducted the experiment with landfill leachate and their results showed that the initial TOC concentration of 450 mg/L has been lowered approximately to 293 mg/L (35 % degradation) and 135 mg/L (70 % degradation) after a reaction time of 5 and 65 minutes, respectively. The details of the experiment are presented in Tables B-28 to B-31 of Appendix B.

Table 4.7 The summary of ozone reaction rate constant (k) based on TOC and COD for four types of leachate

Types of landfill leachate k (min-1) based on TOC k (min-1) based on COD Yeast effluent (HRT 16 h) 0.0032 0.0053

Bacterial effluent (HRT 16 h) 0.0071 0.0076 Yeast effluent (HRT 24 h) 0.003 0.0045

Bacterial effluent (HRT 24 h) 0.0044 0.0065

52

The results showed that the condition from Membrane Bioreactor at HRT of 16 h had higher reaction rate than HRT of 24 h. This meant that ozone could easier react with the organic pollutant presented in the first type of leachate than the last one. However, this parameter was not the main reason for the optimization conditions but it was the indicator for one to know the characteristic of ozone to degrade the organic pollutant.

y = 0.0071x

y = 0.0044x

y = 0.0032x

y = 0.003x

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 30 60 90 120 150 180 210

Contact time (min)

-ln (T

OC

/TO

C 0)

Yeast at HRT = 16 h Bact. at HRT = 16 hYeast at HRT = 24 h Bact. at HRT = 24 h

Figure 4.11 Reaction rate or specific ozone utilization rate constant in term of TOC for four types of leachate at different contact time

y = 0.0076x

y = 0.0065x

y = 0.0053x

y = 0.0045x

00.20.40.60.8

11.21.41.6

0 30 60 90 120 150 180 210

Contact time (min)

- ln

(CO

D/C

OD

0)

Yeast at HRT = 16 h Bact. at HRT = 16 hYeast at HRT = 24 h Bact. at HRT = 24 h

Figure 4.12 Reaction rate or specific ozone utilization rate constant in term of COD for four types of leachate at different contact time

53

4.1.3.3 Determination of ozonation factor The ozone concentration in feed gas applied to the reactor and the concentration in off-gas was measured by Iodometric method. Based on the assumption that most of residual ozone concentration in the reaction matrix was transfer into off-gas, this parameter could be neglected in the calculation. According to the ozone consumption and the mass balance of the pollutant participating in the reaction, ozonation factor could be calculated from Equation 2.19. Ozonation factor was considered to evaluate the treatability of organic substrate in aqueous phase. The lower the ozonation factor, the more the target compound was resistant to ozonation. This statement was true if the pollutant load were the same due to the higher in ozone consumption. If the pollutant loas was not the same, the ratio of ozonation factor to organic load was determined. In this study, ozonation factor was determined in four different types of leachate. TOC concentration was used to represent the concentration of substrate, indicated in the equation. Ozone at feed gas concentration of 75 mg/L was used and the volume of leachate to be treated was set at 1 L. By varying ozone contact time from 15, 30, 60, 90, and 180 minutes, the results of ozonation factor was shown in figure 4.13 which did not include the spontaneous self-decay of ozone. The details of the experimental results are presented in Tables B-32 and B-33 of Appendix B.

0.0

0.5

1.0

1.5

2.0

0 30 60 90 120 150 180

Contact time (min)

Ozo

natio

n fa

ctor

Yeast at HRT = 16 h Bacteria at HRT = 16 hYeast at HRT = 24 h Bacteria at HRT = 24 h

Figure 4.13 Ozonation factor for four types of leachate as a function of ozone contact time

From the results of ozonation factor, bacterial effluent had lower ozonation factor than yeast, but initial TOC concentration in bacteria was lower. This could be the reason of low ozonation factor in bacteria. The Hydraulic Retention Time of 24 hours in MBR process had higher ozonation factor than that of HRT 16 hours. From all the results, it could not be concluded which one was more resistant to ozonation than another due to the difference in pollutant load. Teo et al. (2002) had conducted the experiment for the ozonation of p-chlorophenol in water. Their results showed that at 30 minutes ozone contact time with ozone concentration of 13.1 mg/L, ozonation factor was considered to be 0.23. This means that the ozonation of p-chlorophenol needed around 1/0.23 = 4.3 times the ozone to achieve the given efficiency in term of settled experimental conditions.

54

4.2 Chemical oxidation of MBR effluent by Ozone (O3) As ozone is a powerful chemical oxidant for water and wastewater treatment, its application is spread worldwide in many fields. Baig and Liechti (2001) had indicated the uses of ozone to recycle marina aquaria waters, to eliminate cyanides in the metal finishing industry, to reduce color from textile industry, to destroy phenol and hydrocarbons in refinery industry, and finally to remove COD in landfill leachate which is the main objective for this study. Ozone had been used for wastewater containing biorefractory compounds that do not easily degrade by biological treatment process (Karrer, et al., 1997). Ozone also has the advantage in its characteristic that contains elements like oxygen to avoid the creation of secondary pollutant, as is the case for chlorine containing oxidants.

The objectives of this study were focused on the organic removal efficiency in leachate measured in term of COD and TOC. As ozonation gives the satisfactory results in transforming high molecular weight compounds into low molecular weight compounds which increase the biodegradability of organic substances, BOD/COD was the parameter used for this assumption. Respirometric experiment was another method for biodegradability study. The conversion of slowly biodegradable COD to readily biodegradable COD before and after ozonation was the indicator to prove this ability of ozonation. Only 10-30 % of color was removed from the leachate in MBR process and ozonation was most appropriate method used to remove color of MBR effluent to meet the required standard. To evaluate the performance of the ozonation, various parameters were optimized prior to using the process in the continuous study.

4.2.1 Effect of Ozonation on Yeast and Bacterial MBR effluent The effluents from MBR process ever after treatment contained high organic content which resulted in high COD and TOC concentration. Ozonation had the ability in partial degradation of the substances which enhancing the biodegradability of leachate by cleavage of aromatic structures and dissociating the carbon-halogen, carbon-carbon single and double bonds (Ince, 1998). Biodegradability experiment and the results from MWCO experiment helped to prove this conversion. Effect of ozonation on color removal efficiency was the most obviously observed parameters while conducting the experiment. The details for all of these experiments are discusses in the following parts. 4.2.1.1 Effect of Ozonation on COD and TOC removal efficiency Ozone has an oxidizing potential which in many cases was sufficient to directly convert organic substances (Steensen, 1997). A partial or complete destruction of the high molecular contaminants can be achieved which results in COD and TOC reduction. As an increase of the ozone dosage, the higher was the reduction in concentration of COD and TOC. In this experiment, ozone contact time was fixed to 30, 60, and 90 minutes. The ozone concentration generated from ozone generator was varied from 45, 60, and 75 mg/L. The results obtained in the Figure 4.14. The detail of the calculation is mentioned in Table C-1 of Appendix C.

55

1000

1200

1400

1600

1800

2000

2200

45 50 55 60 65 70 75

Ozone concentration (mg/L)

CO

D c

once

ntra

tion

(mg/

L)

Yeast effluent at 30 min Bacterial effluent at 30 minYeast effluent at 60 min Bacterial effluent at 60 minYeast effluent at 90 min Bacterial effluent at 90 min

Figure 4.14 Effect of ozone on COD removal efficiency at different ozone dosage

350

450

550

650

750

45 50 55 60 65 70 75

Ozone concentration (mg/L)

TO

C c

once

ntra

tion

(mg/

L)

Yeast effluent at 30 min Bacterial effluent at 30 minYeast effluent at 60 min Bacterial effluent at 60 minYeast effluent at 90 min Bacterial effluent at 90 min

Figure 4.15 Effect of ozone on TOC removal efficiency at different ozone dosage

From the results, the percentage organic compounds reduction varied with ozone dosage in term of both COD and TOC concentration. This followed the stoichiometric assumption of ozone to treat all kinds of wastewater. The initial COD before ozonation of yeast and bacteria are 2,138 and 1,938 mg/L, respectively. COD removal efficiency for yeast increased from 6 % at contact time of 30 minutes (45 mg/L) to 41 % at contact time of 90 minutes (75 mg/L). For bacteria, the COD removal efficiency increased from 3% to 39 % at contact time of 30 (45 mg/L) and 90 minutes (75 mg/L), respectively. The initial TOC concentration before ozonation for yeast was 796 mg/L and 650 mg/L for bacteria. The removal efficiency of TOC for yeast increased from 3% at contact time 30 minutes (45

56

mg/L) to 38 % at contact time 90 minutes (75 mg/L). Similar observation was found in bacteria where the TOC removal efficiency increased from 9.16 % to 40.8 % at contact time 30 minutes (45 mg/L) and 90 minutes (75 mg/L), respectively. A COD reduction of 20 % was observed after ozonation at ozone dosage of 800 mgO3/L (0.15 gO3.gCOD-1) for landfill leachate treatement indicated by Ledakowicz and Kaczorek, 2001. Geenens, et al. (1999) obtained nearly same rate for COD removal of 30 % with a specific ozone consumption of 1-2 g/g COD for landfill leachate of initial COD concentration of 895 mg/L. These supported that ozone result mainly in a partial oxidation. The difference of the ozone consumption was due to the age of landfill leachate play a role in determining the organic content and its degradation potential. The intermediates formed during ozonation are quite difficult to degrade, which required much higher ozone dosage to achieve complete oxidation to yield carbon dioxide and water. In term of TOC reduction, the same situation could be observed. Wenzel, et al. (1999) had conducted the experiment with landfill leachate by using ozone dosage in the range of 10 g.h-1 to 54 g.h-1. They obtained the 16 % TOC reduction for reaction time of 60 minutes and 89 % reduction for reaction time of 480 minutes. It could be concluded that both COD and TOC reduction could be increased by increasing ozone dosage to yield complete oxidation. However, the economical aspect should also be considered for this situation. 4.2.1.2 Effect of Ozonation on Color removal efficiency Humic substances were the main compounds that caused the color in landfill leachate. They are generally classified as: 1) humin, 2) humic acid, and 3) fulvic acid (Latifoglu and Gurol, 2003). Humic substances contribute almost a fraction of 50 % to the natural organic matter in water. They were poorly defined heterogeneous group of non-volatile organic species that was difficult for analysis and characterization (Graham, 1999). Color in leachate came mainly from dissolved organic compound that comprise the organic carbon and organic color components. Ozone had the ability to cleave the unsaturated bonds in aromatic moieties found in humic materials, thereby decreasing the color (Rittmann, et al., 2002). The reactions between these two components occurred through direct reactions involving molecular ozone or by indirect reactions involving radical oxidation that were produced from ozone decomposition. Ozonation causeed the substantial structural changes of humic substance which resulted in a strong and rapid decrease in color. The products formed by ozonation will be discussed in the later part of the study. The effluents from both reactors (Yeast and Bacteria) still had high degree of color contaminants which not meet the color standard. Ozonation was used to decolorize these effluents at a certain dosage. Color determination by colorimetric method using spectrophotometer in ADMI unit (APHA, 1998) was conducted to determine the change in color from ozonation. The effluents were ozonated at three different ozone concentrations of 45, 60, and 75 mg/L. The ozone contact time was fixed at 30, 60, and 90 minutes. The results od decolorization obtained are illustrated in Figure 4.16 and the details of the calculation is shown in Table C-1 of Appendix C.

57

020406080

100120140160180200

45 50 55 60 65 70 75

Ozone concentration (mg/L)

Col

or (A

DM

I)

Yeast effluent at 30 min Bacterial effluent at 30 minYeast effluent at 60 min Bacterial effluent at 60 minYeast effluent at 90 min Bacterial effluent at 90 min

Figure 4.16 Effect of ozone on color removal efficiency at different ozone dosage

Ozone had great ability to remove color in landfill leahcate. The initial color for yeast effluent was in the range of 300±50 ADMI and bacteria between 400±50 ADMI. Ozone could remove color up to 96 % for both yeast and bacterial effluent after ozone dosage of 75 mg/L, 90 minutes. The increased of the ozone dosage (both ozone concentration and contact time) gave the significant reduction in color of leachate. The color removal efficiency ranged from 79 % to 96 % when ozone dosage was increased from the concentration of 45 mg/L, 30 minutes to concentration of 75 mg/L, 90 minutes for yeast effluent. The same phenomenon occured for bacterial effluent where the efficiency increased from 62 % to 96 % when ozone dosage was increased as yeast. Rittmann et al. (2002) had conducted the experiment to treat color groundwater by ozonation followed by biofiltration. They obtained 69 %, 81 %, and 83 % of color reduction after ozone of 1.0, 1.4, and 1.8 g O3/g C, respectively. Koyuncu, et al (2001) has also used ozone to remove color of textile wastewater with the efficiency of 83 % after ozonation for 20 minutes (6.1 gO3) and increased to 96 % after 50 minutes contact time. This showed that significant increase in contact time could enhance color removal as found in our study. Figure 4.17 and Figure 4.18 show the different between the colors of leachate samples before and after ozonation for yeast and bacterial effluent. More than 95 % of color reduction could be obtained from ozonation at optimum condition.

Figure 4.17 Color difference before and Figure 4.18 Color difference before and

after ozonation for Yeast effluent after ozonation for Bacterial effluent

Before After Before After

58

4.2.1.3 Effect of Ozonation on Molecular Weight Distribution In order to classify the range of molecular weight of the leachate sample, Molecular Weight Cut-Off (MWCO) experiment was used with Ultrafiltration membrane (UF). As ozone causes a slight decrease in the high apparent molecular weight fractions and a slight increased in the smaller fractions, fractionation of the organic matter before and after ozonation could give the obvious justification. For these experiment, TOC, COD, and Color were measured in each fraction. The percentage of organic substances with a different MW range in the total amount, in term of TOC, COD, and Color, was calculated using the mass balance concept (Huang et al., 2000). Five different types of UF membranes ranging from 50,000 Da, 10,000 Da, 5,000 Da, 3,500 Da, and 1,000 Da. were used in the experiment.

1) Initial Membrane Resistance Permeate or filtration flux and initial membrane resistance were measured by filtering distilled water through new UF membrane. The relationship between filtration flux and transmembrane pressure was linear and membrane resistance could be calculated from the slope of this linear relationship followed equation 4.5

mRTMPJμ

=

Eq. 4.5

J = Filtration flux (L/m2.h) TMP = Transmembrane pressure (kPa) μ = Dynamic viscosity = 0.798*10-3 N.s/m2 at 27 oC Rm = Membrane Resistance (m-1) The results of membrane resistance are showed in table 4.8. The detail of membrane resistance calculation and graphs are showed in Tables C-2 to C-9 and Figures C-1 to C-8 of Appendix C. Table 4.8 also shows the results of the difference in membrane resistance between new membrane and used membrane Table 4.8 Membrane Resistance of different UF membranes used in MWCO experiment

Membrane Resistance (Rm, m-1) Types of UF membranes New membrane Used membrane

MW 50,000 Da 7.784 E+12 2.064 E+13 MW 10,000 Da 5.852 E+12 1.846 E+13 MW 5,000 Da 2.408 E+13 4.505 E+13 MW 35,00 Da 1.131 E+14 - MW 1,000 Da 1.804 E+14 -

From the results, membrane resistance tends to increase with the decrease in molecular weight of the membrane except for MW 10 kDa. The reason might be because the MW 10 kDa membrane has higher porosity than MW 50 kDa membrane resulting in lower resistance. When compared the membrane resistance of new and used membrane, membrane resistance increases 1.5-3 times after using membrane once as indicted in the table. Even though using distilled water (high purity), the effect from the micro molecule

59

inside caused the different in filtration flux which results in the increase of membrane resistance. The fouling layer consisted of a dark brown deposit, represented suspended and colloidal matter in the high molecular weight ranges (Slater et al., 1985)

2) The role of stirring on membrane permeate flux in MWCO experiment The result of the difference between MWCO experiment with and without stirring is showed in Figure 4.19 for YMBR and BMBR. The details of the calculation are presented in Tables C-10 to C-13 of Appendix C. The result showed the difference in membrane filtration flux in term of COD concentration. For YMBR, the fraction of MW > 50 kDa was the majority (63 %) when done without stirring but this fraction was eliminated by stirring which made the majority part shift to MW 3.5-5 kDa (51 %). This could be due to the accumulation of higher molecular weight in the membrane as described above. It could be observed that the fraction of MW 5-10 kDa and MW 3.5-5 kDa increased after stirred the sample and overall COD concentration was also reduced. For BMBR, we could observe the same trend of conversion which the molecular weight range of 50 kDa was reduced after stirring. The fraction of MW 3.5-5 kDa increased to become the majority part of this sample which is of 52 % of the total. The fraction of MW 1-3.5 kDa and MW < 1 kDa could be observed in this condition.

0

200

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800

1000

1200

1400

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1800

YMBR without stir YMBR with stir BMBR without stir BMBR with stir

CO

D c

once

ntra

tion

(mg/

L)

MW > 50 kDa MW 10-50 kDa MW 5-10 kDaMW 3.5-5 kDa MW 1-3.5 kDa MW < 1 kDa

Figure 4.19 Effect of Concentration Polarization on the membrane permeate flux for

YMBR and BMBR with and without stirring

60

The experiment without stirring could cause the major change of the COD fraction as the results indicated above. Even micro molecule in the solution could cause this problem. Therefore, agitation by stirring the solution during the experiment must not be neglected.

3) Effect of landfill leachate Ozonation with low and high ozone dosage

The effluent from both yeast and bacterial MBR were ozonated with low and high ozone dosage in order to identify the partial degradation of ozone with leachate. For low ozone dosage, ozone concentration of 45 mg/L at contact time 30 minutes for both yeast and bacterial effluent. For high ozone dosage, ozone concentration of 75 mg/L at contact time 90 minutes for yeast effluent and at contact time 45 minutes for bacterial effluent. The detail of the calculation is presented in Tables C-14 to C-17 of Appendix C. The results of molecular weight distribution for yeast effluent and bacterial effluent in term of COD concentration is showed in Figure 4.20

0

200

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600

800

1000

1200

1400

1600

1800

YMBR OzonatedYMBR at 45mg/L, 30 min

OzonatedYMBR at 75mg/L, 90 min

BMBR OzonatedBMBR at 45mg/L, 30 min

OzonatedBMBR at 75mg/L, 45 min

CO

D c

once

ntra

tion

(mg/

L)

MW > 50 kDa MW 10-50 kDa MW 5-10 kDaMW 3.5-5 kDa MW 1-3.5 kDa MW < 1 kDa

Figure 4.20 Molecular weight distribution for yeast and bacterial effluent at low and high

ozone dosage in term of COD concentration

61

From the results, total COD concentration reduced when increasing ozone dosage. For low ozone dosage of yeast effluent, there was not much changed in COD concentration after ozonation since the amount of ozone was insufficient to convert the higher molecular weight fraction to lower fraction. The decreased in COD occurred from partial oxidation of ozone for treating leachate. Most of the fraction after ozonation still be in the same range as before ozonation which mostly in the range of MW > 50 kDa (70 %) for low ozone dosage. For bacterial effluent at low ozone dosage, the significant change was obtained. In this case, the fraction of MW > 50 kDa was reduced and there was the increase in fraction of MW 10-50 kDa to be the main fraction (38 %). The fraction of MW 5-10 kDa was also decreased and caused the increase in the fraction of MW 3.5-5 kDa and MW 1-3.5 kDa. When compared between yeast and bacterial effluent at low ozone dosage, bacteria seem to be easy to degrade than yeast since the percentage of fraction conversion was higher in bacteria than yeast. For high ozone dosage of yeast effluent, the substantial change of conversion fraction occurred which the MW >50 kDa was completely degraded to the lower fraction. The majority of this ozonated yeast was in the range of 3.5-5 kDa (47 %) which shifted from MW > 50 kDa before ozonation. The overall COD concentration was also decreased. One could observe that there was the mineralization of high molecular weight fraction to low MW fraction (MW<1 kDa) since there was the increase of this fraction during ozonation. For bacterial effluent, all the fraction of MW > 50 kDa was also converted into low MW compounds. Most of the leachate was in the range of MW 3.5-5 kDa (48 %). The fraction of MW 1-3.5 kDa increased together with the appearance of MW < 1 kDa. TOC was another parameters used in the MWCO studies. The molecular weight distribution in term of TOC concentration is presented in Figure 4.21 and the detail of the calculation is in Tables C-19 to C-23 of Appendix C. The results showed that 59 % of YMBR effluent was above MW 50 kDa. This fraction reduced to 52 % after ozonation with 45mg/L for 30 minutes and was eliminated after ozonation with 75 mg/L for 90 minutes. It could be observed that the fraction of MW 5-10 kDa and MW 3.5-5 kDa increased significantly after ozonation in high ozone dosage. The higher of the ozone dosage caused the mineralization for the low molecular weight fraction (MW < 1 kDa) as seen in the reduction of this fraction with an increased of ozone dosage. For BMBR, 57 % of the fraction of MW > 50 kDa reduced to 31 % after ozonation with low ozone dosage and was eliminated after ozonation with high ozone dosage. The majority fraction of BMBR before ozonation was in MW > 50 kDa, which shifted to MW 10-50 kDa (39 %) and MW 3.5-5 kDa (46 %) after ozonation with low and high ozone dosage, respectively. The overall TOC reduction increased with the increase of ozone dosage for both yeast and bacterial effluent.

The effect of ozonation in raw leachate in molecular weight distribution was also studied. In this experiment, raw leachate was the leachate before treating in MBR system. Raw leachate used was medium aged landfill leachate (5-10 years). The composition in leachate contained refractory compounds, which was hardly biodegradable by nature. The results showed that 87 % of raw leachate was in the range of MW > 50 kDa. Only 5.5 % and 8 % of raw leachate were in the range of MW 10-50 kDa and MW < 5 kDa, respectively. The results indicated that most of the compounds in raw leachate were high molecular weight compounds having a characteristic of humic substance. This humic substance was formed by microbiological processes from intermediate products of the biodegradation of polymeric organic compounds such as lignin (Gourdon et al., 1989).

62

Slater, et al (1985) had conducted the experiment on molecular weight distribution of young landfill leachate. Their results showed that 76 % of leachate TOC was below MW 500 kDa. About 4 % and 14 % were in molecular weight range of MW 0.5-10 kDa and MW 1-10 kDa, respectively. This meant that most of the fraction of young leachate was low molecular weight fraction which consisted of alcohols and organic acids. Gourdon, et al (1989) did the similar experiment for young landfill leachate and indicated that most of the fraction was below MW 0.5 kDa (95%). From all the results, MWCO experiment was able to identify the molecular weight distribution of the leachate sample, which showed the substantial conversion of the molecular weight distribution in young, and medium aged landfill leachate.

0

100

200

300

400

500

600

700

YMBR OzonatedYMBR at 45mg/L, 30 min

OzonatedYMBR at 75mg/L, 90 min

BMBR OzonatedBMBR at 45mg/L, 30 min

OzonatedBMBR at 75mg/L, 45 min

TO

C c

once

ntra

tion

(mg/

L

MW > 50 kDa MW 10-50 kDa MW 5-10 kDaMW 3.5-5 kDa MW 1-3.5 kDa MW < 1 kDa

Figure 4.21 Molecular weight distribution for yeast and bacterial effluent at low and high

ozone dosage in term of TOC concentration

4) Effect of pH and alkalinity on Ozonation Ozone reacts with organic compounds in water and wastewater by two mechanisms, which were direct oxidation by ozone molecule and indirect oxidation by hydroxyl radicals. The ozonation pathway strongly depended on the characteristics of the wastewater to be treated (Alaton et al, 2002). Since pH was one of the characteristics which effect ozonation, one should consider the effect of pH as an initial condition for ozonation. As pH was related to alkalinity of the water solution, the effect of alkalinity on ozonation must be taken into consideration. Steensen (1997) indicated that carbonated and bi-carbonate were the radical scavenger of ozonation which resulted in an increase of ozone consumption. Carbonate and bi-carbonate are referred by alkalinity. The effect of

63

alkalinity in term of ozone consumption is presented in Figure 4.22. Adjusting pH of the leachate varied the alkalinity. The leachate used in this experiment was bacterial effluent from MBR which has initial pH of around 7.6. Yeast effluent had no alkalinity since its pH was around 3.6. In this experiment, pH variation from 2, 4, 5.5, 7.6, and 11 resulted in alkalinity of 0, 0, 1,477, 1,493, and 1,523 mg/L as CaCO3, respectively. The results indicated that alkalinity did not cause much different on ozone consumption even at high alkalinity. When considering in term of organic degradation, the effect of alkalinity on COD degradation was studied. Leachate from both yeast and bacterial effluent were used to adjust pH. For YMBR, varied pH from 3.6 (initial pH of YMBR), 7, and 11. For BMBR, varied pH from 3.5, 7 (initial pH of BMBR), and 11. COD degradation was determined after ozonation of 30 mg/L at contact time 45 minutes. The results showed in Figure 4.23. The detail of calculation for the effect of alkalinity on ozone consumption is presented in Table C-24 of Appendix C and the detail of the effect of pH on COD degradation is in Table C-25 of Appendix C.

1200

1300

1400

1500

1600

0 200 400 600 800 1000 1200 1400

Alkalinity (mg/L as CaCO3)

Ozo

ne c

onsu

mpt

ion

(mg

Ozo

ne)

Figure 4.22 Effect of alkalinity on ozone consumption of bacterial effluent from MBR

1500

2000

2500

3000

2 4 6 8 10

pH

CO

D c

once

ntra

tion

(mg/

L)

12

Yeast effluent Bacterial effluent

Figure 4.23 Effect of pH variation on COD degradation for yeast and bacterial effluent

64

From the results of COD degradation, there were two things that effect the rate of ozonation. First was the formation of hydroxyl radical (OH ) that was enhanced at high pH (alkaline condition). Increasing the pH in the ozonation system would result in a higher OH production rate due to the Equation 4.6 to Equation 4.8 as followed (Alaton et al, 2002)

Eq. 4.6 O3 + OH- O3 - + OH

Eq. 4.7 O3

- O2 + O -

Eq. 4.8 O - + H+ OH

The second thing that affects the rate of ozonation was the presence of carbonate and bi-carbonate (radical scavenger) which accelerated the ozone decomposition rate and was enhanced at alkaline condition (high pH). The results showed that COD reduction did not have the significant difference in all pH variation due to the effect of the hydroxyl radical formation and the presence of radical scavenger played their role simultaneously during ozonation or the carbonate/bi-carbonate was low concentration. Therefore, in this experiment, there was no need to adjust the pH of both yeast and bacterial effluent for ozonation in all experiment.

Alaton, et al (2002) had conducted the experiment on advanced oxidation of dyebath effluent. Their results in pH variation showed that 17% of TOC reduction was found at pH 3 while 28 % was found at pH 7. The increase to pH 11 did not further improve the ozonation process due to the fact that the additional OH scavenging effect of carbonate and bi-carbonate present in the reaction solution compensated the acceleration of ozone of ozone decomposition to OH at alkaline pH. The optimum pH condition was found at pH 7 where the radical type reaction becomes effective and simultaneously the inhibiting effect of radical scavenger is not played a role much. Logemann and Annee (1997) had observed the effect of carbonate and bi-carbonate concentration during ozonation by the addition of sodium bicarbonate. They found that the percentage of COD conversion were 86, 83, and 76 % at the sodium carbonate concentration of 0, 1,260, and 2,260 mg/L, respectively. This could be concluded that even at extreme bicarbonate concentrations, the COD conversion only slightly decreases. 4.2.2 Parameter Optimization When advanced oxidation process using ozone had been studied, the oxidant dosage is chosen in such a way that they cause only partial mineralization (Ledakowicz and Kaczorex, 2001), which result in an increase of biodegradability of the leachate to be treated. This biodegradable fraction would be suitable to treat by biological treatment process. In order to achieve this, much lower ozone dosage was required than the complete oxidation which therefore lower the capital costs and operating costs of the process. In this section, optimum conditions and parameters optimization was obtained to treat leachate biologically after ozonation. This optimum condition involved the increase of the biodegradability of the leachate as well as the color reduction. The biodegradability of the leachate was described in term of BOD/COD ratio. In order to achieve the optimum condition, the parameters to be measured were COD, TOC, BOD, and Color. The optimum

65

condition as ozone concentration and contact time was determined in term of all above mentioned parameters. 4.2.2.1 Optimization of Ozone Concentration From the results of ozone calibration study, desired ozone concentration could be fixed by adjusting the oxygen flowrate and the voltage of ozone generator. Vary the ozone concentration from 45, 60, and 75 mg/L. The ozone contact time in this experiment varied from 30, 60, and 90 minutes. Parameters to be analyzed were COD, TOC, and Color. The optimum condition was the condition that obtained the maximum COD, TOC, and color reduction.

For yeast and bacterial effluent, the results of COD concentration are presented in Figure 4.24 and Figure 4.25. The value obtained indicated that the increase of ozone concentration (from 45 mg/L to 75 mg/L) resulted in the reduction of COD concentration. This was the same as increasing the ozone contact time with mean that ozone dosage was increased. The initial COD concentration for yeast effluent was 2,140 mg/L. The percentage of COD for yeast reduced from 5.7 % at ozone concentration of 45 mg/L, 30 minutes to 41.4 % at ozone concentration of 75 mg/L, 90 minutes. For bacterial effluent that had an initial COD concentration of 1,940 mg/L was reduced 3.1% at ozone concentration of 45 mg/L, 30 minutes to 39 % at ozone concentration of 75 mg/L, 90 minutes.

COD reduction was caused by the degradation of organic matter presented in leachate which mostly leads to the formation of low molecular weight acids as acetic acid or oxalic acid (Karrer et al., 1997). From the results, bacterial effluent had higher percentage of COD degradation than yeast. This means that the compound in bacterial effluent ias easy to be degraded than yeast effluent. The detail of the calculation is presented in Table C-1 of Appendix C

2018 1810 1705

1775 16011392

1392 1357 1253

0

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1000

1500

2000

2500

COD (mg/L)

45 60 75

90

60

30

Ozone concentration (mg/L)

Contact time (min)

Figure 4.24 COD reduction for yeast effluent after ozonation at different ozone

concentration and contact time

66

1879.2 1809.6 1670.4

1531.21461.6 1426.8

1600.81322.4

1183.2

0

500

1000

1500

2000

COD (mg/L)

45 60 75

90

60

30

Ozone concentration (mg/L)

Contact time (min)

Figure 4.25 COD reduction for bacterial effluent after ozonation at different ozone concentration and contact time

When consider in term of TOC concentration, the reduction of TOC concentration was the same trend as COD which the increased of ozone dosage (both ozone concentration and contact time) caused the increase of TOC removal efficiency. The decomposition of organic matter in the leachate sample caused this reduction. The results of TOC concentration after ozonation for yeast and bacterial effluent are showed in Figure 4.26 and Figure 4.27. The TOC reduction rate was low in the first period of increasing the ozone concentration and the rate increased when ozone concentration shifted to 75 mg/L. The initial TOC concentration for yeast was 796 mg/L. The percentage of TOC reduction was increased from 2.6 % at ozone concentration of 45 mg/L, 30 minutes to 32 % at ozone concentration of 75 mg/L, 90 minutes. For bacterial effluent with initial TOC concentration of 743 mg/L, percentage TOC reduction increased from 1.3 % at ozone concentration of 45 mg/L to 28.8 % at ozone concentration of 75 mg/L, 90 minutes. The same observation was obtained which yeast was easy to degrade than bacteria since the percentage of TOC reduction for yeast was higher than bacteria. The detail of the calculation is showed in Table C-1of Appendix C.

775.0 766.1 728.5

712.2 661.0 640.0

623.0 621542.4

0

200

400

600

800

TOC (mg/L)

45 60 75

90

60

30

Ozone concentration (mg/L)

Contact time (min)

Figure 4.26 TOC reduction for yeast effluent after ozonation at different ozone concentration and contact time

67

590.8553.4

526.6565.1

510.7473.6

530.1 472.6

384.8

0.0

200.0

400.0

600.0

TOC (mg/L), Bacteria

45 60 75

90

60

30

Ozone concentration (mg/L)

Contact time (min)

Figure 4.27 TOC reduction for bacterial effluent after ozonation at different ozone concentration and contact time

Color reduction after ozonation indicated effectiveness of ozone for oxidation. Ozone resulted in an oxidation of humic substance which caused color in landfill leachate. The results of color reduction during ozonation are presented in Figure 4.28 and Figure 4.29. For yeast effluent with initial color of 330 ADMI, percentage of color reduction increased from 78 % at ozone concentration of 45 mg/L, 30 minutes to 96 % at ozone concentration of 75 mg/L, 90 minutes. For bacterial effluent with initial color of 430 ADMI, percentage of color reduction increased from 60 % at ozone concentration of 45 mg/L, 30 minutes to 96 % at ozone concentration of 75 mg/L, 90 minutes. The results indicated that high color removal efficiency was achieved even at low ozone dosage. The expected color removal efficiency of more than 95 % was achieved at ozone concentration of 75 mg/L, 90 minutes. The detail of the calculation is showed in Table C-1 of Appendix C

7264

52

49

23 28

2818 13

0

20

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60

80

Color (ADMI)

45 60 75

90

60

30

Ozone concentration (mg/L)

Contact time (min)

Figure 4.28 Color reduction for yeast effluent after ozonation at different ozone concentration and contact time

68

173

127

72

5130 34

45 21 160

50

100

150

200

Color (ADMI)

45 60 75

9060

30

Ozone concentration (mg/L)

Contact time (min)

Figure 4.29 Color reduction for bacterial effluent after ozonation at different ozone concentration and contact time

From all of the results obtained from COD, TOC, and Color determination, the optimum ozone concentration could be observed. The optimum ozone concentration was the concentration of ozone that caused the highest COD, TOC, and Color reduction. When the ozone concentration was increased from 45 mg/L to 75 mg/L, the removal of COD, TOC, and Color determination significantly increased. Therefore, it was more appropriate to take the maximum ozone concentration of 75 mg/L as optimum ozone concentration for this study. 4.2.2.2 Optimization of Ozone Contact Time After obtained the optimum ozone dosage from the previous experiment, optimum ozone contact time was determined by fixing optimum ozone concentration of 75 mg/L. In this experiment, ozone contact time was varied from 0 (before ozonation), 15, 30, 45, 60, 75, 90, and 180 minutes. Parameters analyzed were COD, TOC, BOD, Color, pH, and Ozone residual. As the optimum ozone concentration was emphasized on maximum COD, TOC, and Color removal efficiency, optimum ozone contact time was also based on it. Ozone contact time was optimized based on the focus of the study to increase the biodegradability of the leachate. At this optimum condition, biodegradability of the leachate sample would increase with desirable TOC and Color removal efficiency. COD concentration at the optimum contact time would not be considered as it would be removed further in the Membrane Bioreactor which will be discussed in detail later in this chapter. BOD/COD ratio was used to represent the biodegradability of the leachate sample. The higher of BOD/COD ratio, the great is the biodegradability of compound to be treated by biological mean.

69

1) Effect of Contact Time Variation on the Degradation of COD

The percentage COD removal efficiency with respect to ozone dosage applied to treat leachate sample was considered. The results obtained in Figure 4.30 shows the increase of percentage COD degradation with ozone dosage applied. The detail of calculation is presented in Tables C-26 to C-27 of Appendix C.

0

20

40

60

80

0 1 2 3 4 5

Ozone dosage (mg Ozone/mg COD)

% C

OD

Rem

oval

YMBR BMBR

Figure 4.30 COD degradation in dependence on ozone addition and volume load

From the results for yeast effluent with initial COD concentration of 2,138 mg/L,

the maximum COD reduction of 55 % was achieved at ozone dosage of 3.8 mg Ozone/mg COD or at ozone contact time of 180 minutes. For bacteria effluent with initial COD concentration of 1,938 mg/L, the maximum COD removal efficiency of 73 % was obtained at the same contact time, which was 180 minutes, or equal to ozone dosage of 4.2 mg ozone/mg COD. It could be concluded that the percentage COD removal efficiency increased with the increase of ozone dosage. From the results, bacterial effluent had the better COD removal efficiency than yeast since the percentage of COD degradation was higher. Steensen (1997) had conducted the experiment on the ozonation of leachate with initial COD of around 1,000 mg/L and BOD5 < 10 mg/L. At least 80 % of COD degradation was obtained with ozone dosage of 2 mg Ozone/mg COD. The increase of the ozone addition above 3 mg ozone/mg COD did not result in an increase of degradation rate.

When applied ozone into the reactor for leachate treatment, the ozone in feed gas

was transferred in to water solution. Ozone was used to decompose the organic matter inside the leachate. After the degradation, only small amount of ozone would remain in the leachate sample and most of the ozone was transferred into off-gas as residual ozone. The residual ozone concentration was measured by reacting with 2% KI solution and followed the Iodometric method the same as for ozone concentration in feed gas. During ozonation as COD reduced when contact time was getting increased, ozone mass residual in off-gas increased. The more the ozone dosage applied to the reactor, the more of ozone residual in off-gas. As COD decreased, the utilization of ozone decreased and thus there was an increase in residual ozone. The result is presented in Figure 4.31 and Figure 4.32 and the detail of calculation is in Tables C-26 to C-27 of Appendix C.

70

01000

2000

3000

0 15 30 45 60 75 90 180Contact time (min)

CO

D (m

g/L

)

0200400600800

Ozo

ne

Res

idua

l (m

g O

zone

)

COD (mg/L) Ozone Residual (mg Ozone)

Figure 4.31 The COD reduction and the increase of residual ozone with contact time for Yeast effluent

0500

100015002000

0 15 30 45 60 75 90 180Contact time (min)

CO

D (m

g/L

)

0200400600800

Ozo

ne R

esid

ual

(mg

Ozo

ne)

COD (mg/L) Ozone Residual (mg Ozone)

Figure 4.32 The COD reduction and the increase of residual ozone with contact time for Bacterial effluent

From the results, the rate of ozone mass residual in off-gas increased rapidly in the

first period of ozonation (around 45 minutes for yeast and 30 minutes for bacteria). The possible reason was that due to the reaction of ozone molecule with the compound in leachate which consumed small amount ozone. Only partial degradation of ozone occurred during this period which converted the high molecular weight compounds in to lower molecular weight compounds. After this period, the degradation was completed but COD reduction and ozone consumption still proceed. This result indicated that after the first period of degradation, ozone continued to react presumably by further oxidizing of the by-product that occurred from primary oxidation. This by-product was more difficult to degrade which consumed more ozone than in the first period which resulted in the lower of ozone residual in off-gas. Lopez, et al (1998) reported the increase of ozone residual in off-gas for the ozonation of Azo dyes. They obtained the reduction of COD together with the decay of Fast-Violet-B (FVB) during ozonation. The reasons of the increase of ozone residual could be explained due to the complete degradation within ten minutes and to continuation of ozone comsumption for the oxidation of FVB degradation by-products. Panpanit (2001) reported the similar results that ozone residual gradually increased with increasing contact time. His experiment was conducted for the ozonation of Oil/Water Emulsion. The possible reason was due to the ethoxylate group of nonionic emulsion that was inert to ozone. Its products were difficult to degrade with ozone, which resulted in an increase of ozone residual similar to the present study.

71

2) Effect of Contact Time Variation on the Biodegradability of the Leachate

The biodegradability of leachate was described in terms of BOD/COD ratio. Ozone results in the improvement of biodegradability of the leachate sample by partial mineralization the compounds in the leachate. This enhanceed the biodegradability by cleavage aromatic structures to low molecular weight substances. The results of COD and BOD after ozonation are showed the Figure 4.33 and Figure 4.34. The detail of calculation is in Tables C-28 to C-29 of Appendix C.

0500

1000150020002500

0 15 30 45 60 75 90 180

Contact time (min)

CO

D (m

g/L

)

0

20

40

60

80

BO

D5 (

mg/

L)

COD (mg/L) BOD5 (mg/L)

Figure 4.33 The change in COD and BOD after ozonation of yeast effluent

0

500

1000

1500

2000

2500

0 15 30 45 60 75 90 180

Contact time (min)

CO

D (m

g/L

)

020406080100120140

BO

D5 (

mg/

L)

COD (mg/L) BOD5 (mg/L)

Figure 4.34 The change in COD and BOD after ozonation of bacterial effluent

From the results of yeast effluent, BOD5 reduced after ozonation occurred for all the contact time. This meant that the biodegradability of yeast effluent after ozonation was not improved. The COD reduction was due to the degradation of organic matter inside the aqueous solution which therefore, resulted in the decrease of BOD5 after ozonation. The possible reasons for this might be because yeast effluent consisted of the compounds that

72

could be directly mineralized and leaded to the end products. Therefore, there was no intermediate compound that was easily degradable. The maximum BOD5 reduction obtained at 180 minutes contact time which equal to 98 % BOD5 reduction. For bacterial effluent, BOD5 increased after ozonation after contact time of 15, 30, and 45 mg/L and reduced after this contact time. BOD5 increased 46 %, 31 %, and 40 % after contact time of 15, 30, and 45 minutes, respectively. The increased of BOD5 after a certain contact time resulted in the increase of the biodegradability of the compounds to be treated. As ozone reacted with humic material and other complex substances in leachate, it caused substantial structural changes in the humic substance. This resulted in the slight decrease in the high apparent molecular weight fractions and a slight increase of the smaller fractions. Ozone resulted in the formation of carboxylic functions and other by-products (Graham, 1999). After contact time of 45 minutes, BOD5 decreased with the reduction of 94 % at contact time of 180 minutes. The possible reason could be due to primary degradation leading to more biodegradable by-products of organic acids and aldehydes. Ozone continued to react, probably oxidizing primary by-products. Such a secondary degradation of ozone leaded to the formation of less biodegradable intermediates which are resistant to further degradation. This could explain the decrease in BOD5 after 45 minutes contact time. Karrer, et al. (1997) had conducted an experiment for the ozonation of landfill leachate. He reported that BOD5 of the biologically pretreated leachate increased from 30 to 140 mg/L within 20 minutes contact time at ozone dosage of 90 mg/L and decreased after this contact time. Marco, et al (1997) reported the similar experiment for 2,4-dichlorophenol ozonation, they obtained the results that BOD/COD increased from 0.07 to the ratio of 0.45 due to the increase in BOD along with the decrease COD. The biodegradability of the bacterial effluent was described in term of BOD/COD ratio. The results presented in Figure 4.35 showed the increase of this ratio after ozonation only for bacterial effluent. This situation was not observed in yeast effluent since its biodegradability was not enhanced after ozonation. The detail of calculation is in Tables C-28 to C-29 of Appendix C.

0.000.010.020.030.040.050.060.070.080.09

0 15 30 45 60 75 90 105 120 135 150 165 180

Contact time (min)

BO

D/C

OD

YMBR BMBR

Figure 4.35 BOD/COD ratio of yeast and bacterial effluent after ozonation

73

The increased of BOD/COD ratio after ozonation was due to the slight increase of BOD and the slight decrease of COD. BOD/COD of bacterial effluent increased from 0.0342 to the maximum ratio of 0.0847 at contact time 45 minutes and decreased to the ratio of 0.0081 at contact time of 180 minutes. As the biological system could further degrade the biodegradable components, ozonation was stopped at the maximum BOD/COD ratio to send it back to MBR process. From this experiment, the optimum ozone contact time for bacterial effluent was achieved based on maximum increase of BOD/COD ratio which was at contact time of 45 minutes, when the improvement in BOD/COD was 60 %. For yeast effluent, as no biodegradability enhancement was observed after ozonation, the optimum ozone contact time was based on the maximum in COD, TOC, and Color removal efficiency. This has made yeast effluent achieved the optimum contact time of 90 minutes where the economical aspect and practical situation were also considered. The COD, TOC, and Color removal efficiency for yeast effluent at contact time 90 minutes were 49 %, 34.5 %, and 95 %, respectively. Even though at contact time of 180 minutes obtained the maximum removal efficiency, it was not economic and difficult under practical condition.

3) Effect of Ozonation on Specific Ozone Consumption When ozone was applied to treat the leachate sample, the specific ozone consumption, which described in terms of mg ozone/ mg COD removed was determined. This parameter indicated the amount of ozone consumed for each COD removed. The higher of the ozone consumption, the more difficult of target compound in leachate to be treated. The result of specific ozone consumption is showed in Figure 4.36 and the detail of calculation is presented in Table C-30 of Appendix C. The result indicated that specific ozone consumption increased along with contact time. At optimum ozone condition for yeast (75 mg/L, 90 minutes), specific ozone consumption was 3.32 mg ozone/mg COD to achieve COD degradation of 49.2 %. For bacterial effluent at optimum ozone condition (75 mg/L, 45 minutes), specific ozone consumption was 2.37 mg ozone/mg COD to achieve % COD removal of 32.7 %. Less ozone was consumed in bacterial effluent due to the lower COD degradation achieved. Geenens, et al (1999) did the experiment on advanced oxidation by using ozone of landfill leachate with initial COD of 900 mg/L. Specific ozone consumption of 1-2 g ozone/g COD removed was obtained to achieve COD oxidation of 30%. Steensen (1997) was also reported that 1.2-2 kg ozone/kg COD removed was used to achieve COD degradation of approximate 70 % for landfill leachate with initial COD of 1,000 mg/L.

01234567

0 10 20 30 40 50 60 70 8

% COD removal

Spec

ific

Ozo

ne c

onsu

mpt

ion

(m

g O

zone

/mg

CO

D R

emov

al)

0

YMBR BMBR

Figure 4.36 Specific ozone consumption in dependence on COD removal rate

74

4.2.3 Effect of Ozonation on Optimum Ozone Condition At optimum ozone condition, some parameters were not optimized because experiment emphasized mainly in the condition that could improve the biodegradability. At optimum condition for bacterial effluent, COD of 1,305 mg/L was not the main consideration since this parameter would be optimized after the sequential recirculation of ozonated leachate back to Membrane Bioreactor. TOC and Color were the other important parameters that should be considered after ozonation. These parameters tended to reduce to the certain value after ozonation. In this section, the effect of ozonation on optimum condition would consider TOC and Color removal efficiency, and molecular weight distribution. 4.2.3.1 Effect of the Optimum Ozone Condition on TOC Removal Efficiency After the reaction of ozone with leachate sample, the result of the TOC degradation was obtained. This reduction was due to the oxidation of organic compounds which caused TOC in leachate. The result of TOC reduction after different ozone contact time is presented in Figure 4.37 and the detail of calculation is in Table C-31 of Appendix C. From the result of yeast effluent with initial TOC of 796 mg/L, the maximum percentage reduction of 38.5 % had been reported. At optimum ozone condition for yeast effluent (75 mg/L, 90 minutes), it was obtained TOC reduction in the value of 34.5 %. For bacterial effluent with initial TOC concentration of 743 mg/L, ozone could degrade to highest degradation of 71 % at contact time of 180 minutes. At optimum condition for bacteria, TOC removal of 30 % was achieved. It could be seen that bacterial effluent degraded TOC better than yeast since the percentage TOC removal was higher in bacteria than yeast. Teo, et al (2002) did the experiment on ozonation of p-chlorophenol with initial TOC concentration of 138 mg/L. They achieved 60 % TOC reduction at ozone contact time of 60 minutes with ozone dosage of 13.1 mg/L. The rate of TOC degradation was high in the first period of ozonation due to the partially degraded of organic compound to more easily biodegradable compound which resulted in the fast conversion. After the certain contact time, the rate of TOC removal decreased due to the formation of primary by-products which was difficult to degrade and that resulted in slow TOC conversion.

0100200300400500600700800900

0 15 30 45 60 75 90 105 120 135 150 165 180

Contact time (min)

TO

C (m

g/L

)

YMBR BMBR

Figure 4.37 TOC removal for yeast and bacterial effluent at different contact time

75

0200400600800

1000

500 700 900 1100 1300 1500 1700 1900 2100 2300COD (mg/L)

TO

C (m

g/L

)YMBR BMBR

Figure 4.38 TOC variation as a function of COD for yeast and bacterial effluent

Figure 4.38 showed the linear variation in TOC as a function of COD during oxidation. This means that during ozonation, the organic matter was progressively oxidized through to mineralization. A 49 % reduction in COD to reach the final value of 1,135 mg/L (after contact time of 90 minutes) gave a 35 % TOC removal for yeast effluent. For bacterial effluent, 33 % reduction in COD to reach the final value of 1,305 mg/L (after contact time of 45 minutes) gave a 30 % TOC removal. Baig and Liechti (2001) had conducted the experiment on ozonation of landfill leachate with initial COD and TOC were 400 and 150 mg/L, respectively. Ozone of 1.6 g ozone/g COD was applied and the result obtained was 60 % reduction in COD to reach the final value of 150 mg/L gave a 60 % TOC removal. The greater COD removal compared to TOC removal could be in leachate, not all the carbon containing compounds are oxidized. 4.2.3.2 The Effect of the Optimum Ozone Condition on Color Removal Efficiency Due to the loss of aromaticity and depolymerization of organic matter presented in leachate, the rapid decreased in color obtained after ozonation in different ozone contact time. Ozone had the ability to oxidize humic substances, which caused color and results in color removed. The result of color reduction after ozonation with respect to ozone contact time is showed in Figure 4.39 and the detail of calculation is in Table C-32 of Appendix C.

0100200300400500

0 15 30 45 60 75 90 105 120 135 150 165 180

Contact time (min)

Col

or (A

DM

I)

YMBR BMBR

Figure 4.39 Color removal for yeast and bacterial effluent at different contact time

76

From the results, the excellent color removal efficiency was achieved for both yeast and bacterial effluent (> 95 % removed) at ozone contact time of 180 minutes. Bacterial effluent had initial color higher than yeast but the rate of color removal was slightly better than yeast. The possible reason could be that bacterial effluent consists of some color causing compounds that is easier to be removed than yeast. From both effluents, the rate of color removal was rapid during the first period of contact time variation (from 15 to 75 minutes) and the color did not obviously reduce after this contact time. Although the ozone dosage was high or applied in excess, the lowest color unit after ozonation would not reach zero due to the presence of fine particles, which remained in the aqueous solution and caused color. At optimum condition for yeast and bacteria, color reductions were equal to 95 % and 90 %, respectively. 4.2.3.3 The Effect of the Optimum Ozone Condition on Molecular Weight Distribution After getting the optimum ozone condition, molecular weight distribution of the leachate at optimum condition should be determined. It could be used to prove the structural change in term of molecular weight of the compounds. MWCO experiment was used to determine molecular weight distribution of the compound before and after ozonation at optimum condition. Determined COD, TOC, and Color in each molecular weight fraction. These parameters could describe the concentration load in each different fraction. Figure 4.40, Figure 4.41, and Figure 4.42 show the molecular weight distribution in term of COD, TOC, and Color, respectively. The detail of calculation is presented in Tables C-12 to C-13 and C-33 to C-42 of Appendix C

0

200

400

600

800

1000

1200

1400

1600

1800

YMBR Ozonated YMBRat 75 mg/L, 90

min

BMBR Ozonated BMBRat 75 mg/L, 45

min

CO

D c

once

ntra

tion

(mg/

L)

MW > 50 kDa MW 10-50 kDa MW 5-10 kDaMW 3.5-5 kDa MW 1-3.5 kDa MW < 1 kDa

Figure 4.40 Molecular weight distribution in term of COD concentration at optimum

condition for both yeast and bacterial effluents

77

From the result of yeast effluent before and after ozonation, the majority fraction in YMBR (before ozonation) was in MW 3.5-5 kDa (51 %). After ozonation, this fraction was still the majority fraction of the leachate after ozonation (51 %). There was the slight increase of the fraction of MW 10-50 kDa and MW 1-3.5 kDa. The overall COD concentration decreased from 1,427 mg/L to 1,159 mg/L after ozonation at this optimum condition. This could have explained why there was no biodegradability improvement for yeast after ozonation. This was due to no obviously conversion of the structure as presented in term of molecular weight. Although the majority fraction of MW 3.5-5 kDa was presented in bacterial effluent before and after ozonation, the substantial conversion of the molecular weight occurred. The fraction of MW > 50 kDa was reduced and compensated with the fraction of MW 10-50 kDa. This could be the reason for the biodegradability enhancement after ozonation at optimum condition. The compounds in the molecular weight range of 10-50 kDa could be intermediates from primary oxidation which were easily biodegraded. The overall COD reduced from 1,615 mg/L to 1,291 mg/L occurred after ozonation.

0

100

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300

400

500

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YMBR Ozonated YMBRat 75 mg/L, 90

min

BMBR Ozonated BMBRat 75 mg/L, 45

min

TO

C c

once

ntra

tion

(mg/

L)

MW >50 kDa MW 10-50 kDa MW 5-10 kDaMW 3.5-5 kDa MW 1-3.5 kDa MW < 1 kDa

Figure 4.41 Molecular weight distribution in term of TOC concentration at optimum condition for both yeast and bacterial effluents

78

From the results of TOC concentration, exactly the same situation with COD concentration obtained in this experiment. The majority fraction of all kinds of leachate presented here was the fraction of MW 3.5-5 kDa. The overall TOC concentration in yeast effluent reduced from 760 mg/L to 537 mg/L. For bacterial effluent, the overall TOC concentration was also reduced from 606 mg/L to 568 mg/L at the optimum ozone condition. For the results of color of each fraction, a significant reduction of color after ozonation was obtained. For yeast effluent, the majority before ozonation was in the range of MW 3.5-5 kDa (50 %). After ozonation, almost all color in different fractions was eliminated. The majority after ozonation was in the same range of 3.5-5 kDa (54 %). For bacterial effluent, the majority fraction was the same as yeast which increased from 50 % before ozonation to 53 % after ozonation.

0

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YMBR Ozonated YMBRat 75 mg/L, 90 min

BMBR Ozonated BMBRat 75 mg/L, 45 min

Col

or (A

DM

I)

MW > 50 kDa MW 10-50 kDa MW 5-10 kDaMW 3.5-5 kDa MW 1-3.5 kDa MW < 1 kDa

Figure 4.42 Molecular weight distribution in term of Color at optimum condition for both yeast and bacterial effluents

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4.2.3.4 Re-check the Optimum Condition with the Effluent from MBR of 24 h-HRT Due to the change of the Hydraulic Retention Time (HRT) of Membrane Bioreactor from HRT of 16 h to HRT of 24 h, all the previous experiments needed to be re-check with the effluent of 24 h-HRT. The results obtained in previous experiment were done with 16 h-HRT leachate. At that moment, the HRT had adjusted to 24 h and would be used further in the continuous system. However, the trend of the results obtained from 16 h-HRT leachate did not have the significant change to 24 h-HRT leachate. However, to confirm this, there was the need to re-check the optimum ozone condition between this two leachate. Table 4.9 presents the comparison between the leachate of HRT 16 h. and 24 h. From the results, it was indicated that COD and TOC concentration in 24 h-HRT leachate was higher than 16 h-HRT leachate before and after ozonation of both effluents. The possible reason for this was due to the sudden change in HRT of the MBR system, the microorganism inside the reactor needed time to be acclimatized with the new conditions. Therefore, the system had not been stable yet and the results obtained were not consistent. BOD5 of yeast and bacterial effluent at 24 h-HRT was lower than that of 16 h-HRT. This means that, as HRT was longer, degradation of organic matter should better decomposition which resulted in lower BOD5. For color, there was no significant difference between 16 h and 24 h HRT leachate. Table 4.9 Comparison between the results obtained from 16 h and 24 h HRT leachate

Types of leachate

COD (mg/L)

BOD5 (mg/L) BOD/COD TOC

(mg/L) Color

(ADMI) YMBR16 h 2,138 58.1 0.0273 796 330 YMBR 24 h 2,776 20 0.00353 1,165 332

O3 YMBR 16 h 1,087 5.6 0.00515 521 17

O3 YMBR 24 h 1,737 4.2 0.00242 1,012 16 BMBR 16 h 1,938 66.3 0.0342 743 430 BMBR 24h 1,970 47.9 0.0243 866 531

O3 BMBR 16 h 1,305 110.6 0.0847 521 42

O3 BMBR 24 h 1,558 115.1 0.0739 852 53

4.2.4 The Products after Ozonation After the reaction of ozone with the compounds inside leachate, there was the products formation which some effect on further degradation. These products included the intermediate after primary degradation and the by-product of primary degradation. Graham (1999) indicated that after ozonation, the by-products formed were mainly aldehydes (formaldehyde, acetaldehyde, glyoxal, methylglyoxal) and carboxylic acids (formic, acetic, glyoxylic, pyruvic and ketomalonic acids). Glyoxalic acid and hydrogen peroxide have been identified as fulvic acid by-products. He also reported that the by-products comprise solely low molecular weight aldehydes whose formation increased with ozone dosage. In present study, pH determination after ozonation at different contact time was mentioned in Figure 4.43. The detailed of calculation is in Table C-43 of Appendix C.

80

2345678

0 15 30 45 60 75 9

Contact time (min)

pH

0

YMBR BMBR

Figure 4.43 The reduction of pH after ozonation indicated the formation of acids by-products

From the results, pH of both yeast and bacterial effluent dropped after ozonation. For yeast effluent, the initial pH was low, therefore, the rate of pH dropped was small which equal to the decrease of 0.58 pH units (from pH of 3.52 to pH of 2.94) at contact time of 90 minutes. For bacterial effluent, it could be observed the fast drop of pH which equal to the decrease of 2.44 pH units (from pH of 7.14 to pH of 4.7) at contact time of 90 minutes. The reduction of pH indicated the formation of acids as by-products after ozonation. For yeast effluent, the result of pH indicated that there was not much formation of acid by-products which is easily biodegradable. Therefore, the biodegradability of the sample after ozonation did not much improved. On the other hand, bacterial effluent indicated the large amount of acid by-products which leaded to the enhancing of the biodegradability after ozonation. The rate of pH drop was slow in the first 45 minutes (the optimum ozone contact time). Due to the increase of the biodegradability during this period of time, it meant that the acid by-products formed during this period tended to have low molecular weight and consisted of easily biodegradable compounds.

Yasui and Miyaji (1992) reported that after ozonation, pH decreased through

ozonation. These could be attributed to the generation of assimilable organic acids by ozonation. They also analyzed the amount of carboxylic acids formation. Their results indicated that carboxylic formation increases as the ozonation proceeded. Lopez, et al (1998) has indicated the reduction of pH after ozonation. He reported a fast decrease of 4 pH units (from 11 to 7) that occurred in the first 30 minutes followed by a slower decrease of only one pH unit during the remaining 60 minutes ozonation. Their results also indicated the formation of acid as by-products after ozonation. 4.3 Chemical Oxidation of MBR effluent by Ozone plus Hydrogen Peroxide (Perozone)

The addition of Hydrogen Peroxide (H2O2) to induce the decomposition of ozone in water was one of the processes in Advanced Oxidation Processes. Hydrogen Peroxide was a weak acid, when applied together with ozone, it could generate highly reactive hydroxyl radicals. This addition was used to activate ozone with its ability to provide advanced oxidizing techniques (Langlais et al., 1991) Craig, et al (1994) indicated that the

81

conversion of ozone to hydroxyl radical (OH ) by the addition of H2O2 could often be used to increase oxidation rates and efficiency especially for compounds which were not readily degraded by ozone alone. In this experiment, optimization of various parameters was done to obtain the most effective condition. The optimizing of the parameters was focused in terms of the waiting time after the addition of H2O2, Perozone dosage, and Perozone contact time. All the experiments were conducted with 16 h-HRT leachate for both yeast and bacterial effluent. 4.3.1 Determination of the waiting time after the addition of H2O2

The efficiency of H2O2 would be increased if there were the waiting time after the addition of H2O2. This was to ensure the homogeneity of H2O2 in the solution. The optimum conditions from ozone experiment were used for both yeast and bacterial effluent. For yeast effluent, optimum ozone condition was at O3 concentration of 75 mg/L and contact time of 90 minutes, whereas for bacterial effluent, optimum ozone condition was at O3 concentration of 75 mg/L, contact time of 45 minutes. The waiting time was varied from 0, 10, 20, and 30 minutes after the addition of H2O2. Used H2O2 concentration at the ratio of H2O2/O3 = 0.3. The efficiency was measured in terms of COD, TOC, and Color removal. The results are showed in Figure 4.44 to Figure 4.46 and the detail of calculation is in Tables D-1 to D-2 of Appendix D.

1000

1100

1200

1300

1400

1500

0 10 20

Waiting time after adding H2O2 (min)

CO

D (m

g/L

)

30

Yeast Bacteria

Figure 4.44 Variation in waiting time after the addition of H2O2 in terms of COD removal

500550600650700

0 10 20

Waiting time after adding H2O2 (min)

TO

C (m

g/L

)

30

Yeast Bacteria

Figure 4.45 Variation in waiting time after the addition of H2O2 in terms of TOC removal

82

02040

6080

0 10 20Waiting time after adding H2O2 (min)

Col

or (A

DM

I)

30

Yeast Bacteria

Figure 4.46 Variation in waiting time after the addition of H2O2 in terms of color removal

From the results of experiments, the optimum waiting time after the addition of H2O2 was the condition that could achieve the highest removal efficiency in term of COD, TOC, and Color. The results indicated that the optimum waiting time for yeast effluent is at the waiting time of 30 minutes. At this condition, COD was reduced from 2,036 mg/L (YMBR) to 1,120 mg/L (41% removed). TOC was removed 25 % from the value of 778 mg/L to 584 mg/L. For color reduction, after the oxidation with perozone, color was removed to the same value in all waiting time which was 10 ADMI (97% removed). For bacterial effluent, the optimum waiting time was 20 minutes which resulted in the highest removal efficiency. The percentage of 37 % of COD was degraded from the value of 1,963 mg/L (BMBR) to 1,227 mg/L. For TOC concentration with the initial TOC of 777 mg/L, 21 % was removed at this waiting time to the value of 613 mg/L. The color removal efficiency of 91 % was achieved which reduced from 438 ADMI to 41 ADMI. Thus, for yeast and bacterial effluent, 30 minutes and 20 minutes were considered optimums waiting time, respectively. 4.3.2 Determination of H2O2 concentration in term of H2O2/O3 ratio

Hydrogen Peroxide should be added in the optimum dosage which would lead to the generation of active hydroxyl radical. If the addition exceeded the optimum range, it would increase scavenging of hydroxyl radicals while offering no extra oxidation efficiency. Another effect is due to the remaining excessive residual effluent H2O2

concentration (Adams et al, 1994). The H2O2 concentration was usually described in term

of H2O2/O3 ratio which indicated the amount of H2O2 used per unit of ozone applied. In this experiment, the optimum ozone condition and optimum waiting time from the previous experiment was used. H2O2/O3 ratio was varied from 0.1, 0.2, 0.3, 0.4, and 0.5. Determine COD, TOC, and Color after the oxidation of leachate with perozone was determined. The results obtained are illustrated in Figure 4.47 to Figure 4.49 and the details of calculation are showed in Tables D-4 to D-4 of Appendix D.

From the results obtained from yeast effluent, COD decreased from 2,036 mg/L to

1,109 mg/L (46 % degradation) after the addition of H2O2 in the H2O2/O3 ratio of 0.2. After this ratio, COD removed tended to increase again. The possible reason could be the remaining H2O2 residue after the increase of H2O2 concentration. This resulted in an increased of COD concentration. For TOC, the TOC concentration reduced from 778 mg/L

83

with a maximum removal of 14 % to 669.5 mg/L at H2O2/O3 ratio of 0.3. After this condition, TOC was increased in the same trend as COD concentration. For color removal, 97 % of color removal efficiency was obtained at H2O2/O3 ratio of 0.1, 0.2, and 0.3. While considering all these parameters and their removal efficiencies, the optimum H2O2/O3 ratio was obtained at H2O2/O3 of 0.2. The result of COD degradation at this optimum condition was 14 %.

For bacterial effluent, the highest COD removal efficiency of 38 % was achieved at

H2O2/O3 ratio of 0.2 which reduced from 1,963 mg/L to 1,218 mg/L. For TOC removal efficiency, the concentration was reduced from 777 mg/L to 694 mg/L (10.6 %) at H2O2/O3 of 0.3. After this ratio, TOC increased due to the formation of by-products and the H2O2 residue. Color was removed to the highest of 91 % at H2O2/O3 of 0.5 which reduced from 438 ADMI to 38 ADMI. As far as all the removed efficiencies are concerned (more emphasis in COD removal efficiency), H2O2/O3 of 0.2 was the optimum condition which has TOC removal of 10.3 % and color removal efficiency of 89 %. There was no significant change in COD, TOC, and Color while varying the H2O2/O3 ratio for both yeast and bacterial effluent. This is similar to the study done by Geenens, et al (1999) which said that peroxide dosage greater than 1,000 ppm did not improve the biodegradability, while treating a leachate of COD of 900 mg/L and BOD5

of 43 mg/L.

1000

1500

2000

2500

0 0.1 0.2 0.3 0.4 0.5

H2O2/O3

CO

D (m

g/L

)

Yeast Bacteria

Figure 4.47Optimization of the H2O2/O3 ratio in terms of COD removal

600650700750800

0 0.1 0.2 0.3 0.4 0.5

H2O2/O3

TO

C (m

g/L

)

Yeast Bacteria

Figure 4.48 Optimization of the H2O2/O3 ratio in terms of TOC removal

84

0100200300400500

0 0.1 0.2 0.3 0.4 0.5

H2O2/O3

Col

or (A

DM

I)Yeast Bacteria

Figure 4.49 Optimization of the H2O2/O3 ratio in terms of color removal

Nelieu, et al (2000) had conducted the experiment on the degradation of Atrazine into Ammeline by perozone. They reported that 2.9x10-5 mol/min of H2O2 (H2O2/O3 ratio of 0.7) was the optimum condition regarding the degradation rate of Atrazine in pure or natural waters. They obtained that 91 % of Atrazine reacted after 15 minutes of treatment and disappeared after 30 minutes. 4.3.3 Determination of Perozone Contact time

After getting the optimum waiting time and H2O2 concentration, the optimization of perozone contact time was done. Optimum waiting time and H2O2/O3 ratio for both effluents were used for this study. For yeast effluent, the contact time was varied from 30, 45, 60, 75, and 90 minutes. For bacterial effluent, the waiting time was varied from 15, 30, 45, 60, and 90 minutes. The variation in contact time was considered from the optimum ozone contact time. COD, TOC, color, and BOD5 were determined. The results are presented in Figure 4.50 to Figure 4.53 and the detail of calculation is in Tables D-5 to D-6 of Appendix D.

1000120014001600180020002200

0 15 30 45 60 75 9 Perozone contact time(min)

CO

D (m

g/L

)

0

Yeast Bacteria

Figure 4.50 Optimization of Perozone contact time in terms of COD removal

85

0200400600800

1000

0 15 30 45 60 75 9

Perozone contact time (min)

TO

C (m

g/L

)

0

Yeast Bacteria

Figure 4.51 Optimization of Perozone contact time in terms of TOC removal

0100200300400500

0 15 30 45 60 75 9

Perozone contact time (min)

Col

or (A

DM

I)

0

Yeast Bacteria

Figure 4.52 Optimization of Perozone contact time in terms of color removal

0

20

40

60

80

0 20 40 60 80 1

Perozone contact time (min)

BO

D5 (

mg/

L)

00

YMBR BMBR

Figure 4.53 Optimization of Perozone contact time in terms of BOD5

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As far as BOD5 removal was considered, there was no case where BOD5 increased after ozonation. This meant that the biodegradability of the compound was not improved. BOD5 for both yeast and bacterial effluent decreased after ozonation in all contact time. When considered in terms of COD removal efficiency, COD decreased to the highest of 41 % after contact time of 90 minutes for yeast effluent. The same observation was obtained for bacterial effluent with the maximum COD degradation of 42 %. It could be concluded that the concentration of COD and BOD5 decreased after ozonation due to the degradation of organic matter inside leachate. This situation leaded to the formation of less biodegradable compounds (BOD5 decrease) but these compounds continued slow degradation which resulted in reduction of COD concentration. For TOC removal efficiency in yeast effluent, 21 % of the reduction was obtained at contact time of 90 minutes. Color was removed to the maximum color removal of 95 % after perozone contact time of 90 minutes. For bacterial effluent, the highest TOC reduction was achieved at contact time of 90 minutes with the rate of 20 %. Color was reduced 95 % after contact time of 90 minutes. From these results, if could be said that the higher of the perozone contact time, the higher of the removal efficiency in terms of COD, TOC, and Color. From all the experments, the optimum Perozone contact time was 90 minutes for both yeast and bacterial effluent.

By considering the pH for Perozone, after the addition of Hydrogen Peroxide, pH significantly decreased to acidic condition. For yeast effluent with initial pH of 3.75, after the addition of H2O2 for 30 minutes and 90 minutes, pH dropped to 2.18 and 1.73, respectively. For bacterial effluent with initial pH of 7.81, after the addition of H2O2 for 15 minutes and 90 minutes, pH dropped to 3.71 and 1.80, respectively. The pH dropped after the addition of H2O2 into the range around 2-4, making the Perozone experimental condition as acidic.

Steensen (1997) had reported that the optimum pH for Perozone condition was in the range of 2-4. Thus, we could say that the optimum pH in our experiment was obtained. An as low as possible concentration of radical scavengers was essential. Therefore, for the effective oxidation, alkalinity has to be completely reduced prior to oxidation. Alaton (2002) had also reported that Perozone condition was more sensitive to the scavenging effect of carbonate at higher pH than ozonation. For ozonation process, the effect of radical scavenger was partially compensated by the increased hydroxyl radical formation. Kim, et al (1997) had conducted the experiment to treat landfill leachate by Fenton reaction. They obtained that 70 % of COD was removed at a pH of 3 whereas only 20 % of the COD was eliminated at a pH of 8.2. 4.3.4 Comparison of the Efficiency between Ozone and Perozone The removal efficiency in terms of COD, TOC, and Color between ozone and perozone was compared. The results on COD removal are showed in Figure 4.54 and Figure 4.55 for yeast and bacterial effluent, respectively. The details of calculation are in Tables D-7 to D-8 of Appendix D.

87

01020304050

0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0Ozone dosage (mg ozone/mg COD)

% C

OD

de

grad

atio

n

Yeast (Ozone) Yeast (Perozone)

Figure 4.54 The comparison of percentage COD degradation for yeast effluent

0204060

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25Ozone dosage (mg ozone/mg COD)

% C

OD

de

grad

atio

n

Bacteria(Ozone) Bacteria (Perozone)

Figure 4.55 The comparison of percentage COD degradation for bacterial effluent

From the results of yeast effluent in term of COD removal efficiency, ozone alone seemed to have the better COD removal efficiency than yeast. Only in some ozone dosage that perozone had a better efficiency. The maximum COD degradation for ozone was 49 % while perozone achieved only 41 %. This trend was the same for bacterial effluent since the percentage COD removed was higher in ozone than perozone. The highest COD removal rate for ozone was 60 % while only 41 % was achieved by perozone. By consider in terms of TOC concentration between ozone and perozone, the results obtained was illustrated in Figure 4.56 and Figure 4.57 and the details of calculation are in Tables D-9 to D-10 of Appendix D.

-10

10

30

50

0 1 2 3 4 5Ozone dosage (mg ozone/mg TOC)

% T

OC

deg

rada

tion

6

Yeast (Ozone) Yeast (Perozone)

Figure 4.56 The comparison of TOC removed from yeast effluent

88

01020304050

0 1 2 3 4 5 6

Ozone dosage (mg ozone/mg TOC)

% T

OC

deg

rada

tion

Bacteria (Ozone) Bacteria (Perozone)

Figure 4.57 The comparison of TOC removed frombacterial effluent

The results from TOC determination was indicated that TOC removal efficiency was better by using only ozone than perozone for both yeast and bacterial effluent. For yeast effluent, ozone achieved the maximum 35 % of TOC removal efficiency while perozone obtained only 21 %. For bacterial effluent, the highest TOC removal was 48 % using only ozone while only 20 % was reported for perozone. By looking in term of color removal efficiency, only for yeast effluent that perozone could achieve better removal efficiency. The maximum of color removal of 95 % was achieved in both ozone and perozone. For bacterial effluent, ozone had the better color reduction than perozone in all ozone dosage. The maximum of 97 % was achieved by ozone while 95 % was obtained from perozone. The results of color removal efficiency were presented in Figure 4.58 and Figure 4.59 and the details of calculation are in Tables D-11 to D-12 of Appendix D

020406080

100

0 2 4 6 8 10 12 14

Ozone dosage (mg ozone/color)

% C

olor

rem

oval

Yeast (Ozone) Yeast (Perozone)

Figure 4.58 The comparison of color removed from yeast effluent

89

020406080

100

0 1 2 3 4 5 6 7 8 9 10Ozone dosage (mg ozone/color)

% C

olor

rem

oval

Bacteria (Ozone) Bacteria (Perozone)

Figure 4.59 The comparison of color removed from bacterial effluent

In conclusion, perozone did not play a role in the improvement of the removal efficiency compared to using only ozone. However, the difference between the ability of both oxidants was not significant. The possible reason could be that the specific compounds in landfill leachate used in the experiment which inhibited the efficiency of preozone to form reactive hydroxyl radical. Leachate might also consist of the other kinds of radical scavenger which resulted in less formation of hydroxyl radical. Another reason might be because the remaining of Hydrogen Peroxide residue after the addition into the solution (Alaton, 2002). This could cause the increase in COD and TOC after the certain peroxide concentration. From these results, it could be concluded that it would be better to use the condition obtained using ozone alone instead of perozone for continuous system. The condition obtained here was from 16 h-HRT leachate. To maintain the condition exactly the same with continuous system, all the conditions need to be re-checked with 24 h-HRT leachate. The optimum ozone condition would be used in the continuous system which will be discussed in the next section. 4.4 Continuous System by Combining MBR and Ozonation Ozone is an expensive chemical oxidant. Thus, low ozone dosage can ensure sufficient chemical changes of biorefractory compounds to enhance the biodegradability (Baig and Liechti, 2001). To provide considerable cost advantage, partial ozonation could be applied to the effluent after MBR process. The ozonation of organic matter mostly leaded to the formation of low molecular weight acids as acetic acid or oxalic acid and are easily biodegradable (Karrer et al., 1997). It was economic and logical to send the ozonated sample back to MBR process again for biological treatment of biologically degradable sample. Because biological treatment was much cheaper than chemical treatment both in term of investment and operating costs, this supports that it was more interesting to combined MBR and ozonation for landfill leachate treatment. Karrer, et al (1997) had also reported that the microorganisms in a combined process with controlled the addition of ozone started to adapt to the removal of the original feed components which were not biologically degraded initially. Therefore, the longer a combined process, the less ozone was necessary to obtain the desired degradation level.

90

4.4.1 Condition for Combined MBR and Ozonation There were two options for combined MBR and ozonation. The first option was to be done in continuous system. The HRT for original MBR was 24 h and for ozonation time required were 45 minutes for bacterial effluent and 90 minutes for yeast effluent. In the practical work, the effective volume of the leachate to be ozonated was 1 L. By considering leachate flowrate and HRT for ozonation system, the volume of leachate to be ozonated was only 100 mL in single run. This was not possible in the real work because of hydraulic problem. Due to this problem, it leaded to the second option where ozonation was done in batch system. This option was operated by mixing the raw leachate with ozonated leachate in the ratio of Raw leachate:Ozonated leachate = 2:1 for both yeast and bacterial effluent. The optimum ozone condition for yeast and bacterial effluent were used in the combined system (75 mg/L, 90 minutes for yeast and 75 mg/L, 45 minutes for bacteria). The leachate flowrate of the original MBR system was 5 L/d for both reactors. The flowrate for raw leacahte in combined system would maintain the same which was 5 L/d. Therefore, the flowrate of ozonated leachate was fixed at 2.5 L/d. The total flowrate for combined system was shifted to 7.5 L/d. The organic load for combined system was maintained the same as original. By considering in term of BOD5 load of yeast reactor, the BOD5 load was 6,000 ± 12.5 mg BOD5. For bacterial reactor, BOD5 load was maintained as 6,000 ± 250 mg BOD5.When considered in term of COD, COD load for yeast reactor was maintained at 27,500 ± 3,750 mg COD while bacterial reactor was 30,000 ± 2,500 mg COD. The value of COD load increased but the COD concentration decreased in combined system. The example of calculation is in A-10 of Appendix A. 4.4.2 Organic Removal Efficiency from Combined System Ozonation resulted in a significant biodegradability enhancement due to the partial oxidation of residual biorefractory organic compounds. To take advantage of this effect, the ozonated leachate was sent back to MBR in order to increase the organic removal efficiency together with reduced ozone consumption. The efficiency was considered in term of COD removal efficiency. The results obtained are discussed in detail in the following parts. 4.4.2.1 COD removal efficiency of MBR system

The combined system was operated for one month. During the first period of operation, the concentration of COD of influent to MBR system and effluent out of MBR system was fluctuating. The first phase of operation (10 days) used only the effluent from original MBR system for ozonation. The reason for this was to obtain a short period acclimatization of microorganism to the mixed system. The second phase of operation used the effluent from combined MBR system to ozonation and recycled back to MBR system again. This could be said that the new recirculation was started and a sequence operating of MBR-Ozonation was obtained. The results are illustrated in Figure 4.60 and Figure 4.61. The details of calculation were in Table E-1 of Appendix E

91

Influent, YMBR Effluent, YMBR

0100020003000400050006000700080009000

0 5 10 15 20 25 30 35Operating day (days)

CO

D (m

g/L

)Start recirculation

Figure 4.60 Continuous data of COD elimination from combined MBR and ozonation for yeast system

0

2000

4000

6000

8000

10000

12000

0 5 10 15 20 25 30 35Operating day (days)

CO

D (m

g/L

)

Influent, BMBR Effluent, BMBR

Start recirculation

Figure 4.61 Continuous data of COD elimination from combined MBR and ozonation for

bacterial system

Figures above give the evolution of the COD in leachate and effluent after MBR system. It could be observed that there was no significant change of COD removal efficiency from combined system. This situation was observed from both reactors. The possible reason was due to the variation of COD concentration in the influent. The consistency in the influent COD concentration was not observed, but leaded to the nearly constant COD concentration of the effluent. The COD concentration of influent during the first period of operation (before recirculation) was observed to be more consistent than after recirculation. This might be because the COD concentration after ozonation was not much varied as after recirculation. From the results, the operating period was too short to evaluate the change of the effluent quality for the combined system.

From original MBR system, COD removal efficiency for yeast system was 66 % and the efficiency of 74 % was obtained from bacterial system. After the combination of MBR and ozonation for yeast system, the rate of efficiency increased to 71.2 %. The slight

92

increased of removal efficiency to 75.4 % was observed. It could be concluded that the combination system slightly improved the effluent quality from MBR system. This was due to the compounds inside leachate had been converted into easily biodegradable compound by ozonation. Thus, the combined leachate was suitable to degrade biologically. The reason for the slight change of the effluent was due to the difference in the volume and organic load of the influent of combined system. 4.4.2.2 COD removal efficiency of Ozonation system

The MBR effluent from combined system was ozonated for both yeast and bacteria. The optimum ozone conditions obtained from previous experiment were used. After recirculation the ozonated effluent back to MBR, COD concentration was measured in MBR effluent and ozonated effluent. The efficiency of ozonation in removing COD was determined. The result is showed in Figure 4.62 and the detail of calculation is in Table E-2 of Appendix E.

0500

10001500200025003000

YMBR Ozonated YMBR BMBR Ozonated BMBR

CO

D (m

g/L

)

Range of COD

Figure 4.62 COD of the leachate before and after ozonation of combined system

From the results, yeast effluent after ozonation had lower COD than bacterial effluent. Ozone could remove 1,027 mg/L of COD in yeast effluent and 593 mg/L of COD in bacterial effluent. This was due to the ozone dosage applied for yeast effluent (4,050 mg O3) was two times higher than bacterial effluent (2,025 mg O3). The deviation in the figure indicates the maximum and minimum COD concentration in each sample. The efficiency of ozonation in COD removal was compared with the original MBR system. The result of COD in original system was illustrated in Figure 4.63 and the detail of calculation is in Table E-3 of Appendix E.

0500

100015002000250030003500

YMBR Ozonated YMBR BMBR Ozonated BMBR

CO

D (m

g/L

)

Range of COD

Figure 4.63 COD of the leachate before and after ozonation of original system

93

From the results, yeast effluent could be removed COD in the value of 1,090 mg/L and bacterial effluent could removed 330 mg/L of COD concentration. If compared with combined system, it could be concluded that the effluent from combined system could be removed COD better than original system only for bacterial effluent. Almost two times of COD concentration could be removed from combined system in bacterial effluent. Due to ozone had the ability to convert compounds inside bacterial effluent into easily biodegradable compounds. This kind of compound was easy to degrade even by biological or chemical process. This was leaded to the result that COD of bacterial effluent was two times removed from combined process. For yeast effluent, the compound inside was difficult to degrade because there was no biodegradability enhancement after ozonation. COD removal efficiency was not improved for yeast system. Another observation was the variation in COD concentration of combined and original process. The higher of the variation in combined process compared with original system was due to the fluctuation of the MBR influent and effluent as indicated in the previous part. Bacterial effluent was more fluctuated than yeast effluent. 4.2.2.3 Overall COD Removal Efficiency The COD removal efficiency of the whole system was determined. COD concentration in raw leachate after ammonia stripping and COD of ozonated effluent were used to compare the efficiency of the system. The efficiency of the combined system was compared with original system. Baig and Liechti (2001) indicated that the combination of chemical and biological treatment process could lead to an extensive COD removal together with a reduced ozone need. This statement was true because COD removal efficiency was improved after combined system. Thus, ozone dosage required to achieve the desired was also reduced. The comparison of the efficiency was done and the result obtained is presented in Table 4.10. Table 4.10 The comparison of COD removal efficiency between original and combined system for both yeast and bacterial effluent (COD of raw leachate = 8,400 mg/L)

Yeast Bacteria Types of leachate Original

system Combined

system Original system

Combined system

Final COD after ozonation (mg/L) 1,765 1,391 1,814 1,473

Overall COD removal efficiency (%) 79.0 83.4 78.4 82.5

% COD improvement 4.4 4.1 Specific ozone

consumption (mg O3 /mg COD removed)

3.72 3.94 6.13 3.41

From the results, the final COD concentration from combined system was lower

compared to original system. The COD removal efficiency was increased 4.4 % for yeast system and 4.1 % for bacterial system. It could be concluded that overall COD reduction was improved though not significant. For specific ozone consumption, there was no improvement in yeast system due to the compounds inside was hardly biodegradable compounds which was proved from the above experiment. The substantial reduction in

94

specific ozone consumption of bacteria was obtained. The ozone consumption was reduced half from original system to combined system. The reduction in specific ozone consumption leaded to the lower operating cost of ozonation. Steensen (1997) had reported the reduction of ozone consumption from the combination of chemical-biological process to treat landfill leachate. He obtained that biological purification without recirculation in ozone saving of approximately 20 % which could be increased by recirculation by 10-15%. From the results, overall COD concentration of combined system is illustrated in Figure 4.64.

8,400

Raw leachate

Raw leachate

MBR

8,400 Bacteria

Ozonation

2,144

Combined system

Yeast

Ozonation

2,855

Combined system 8,400

Raw leachate 1,765 1,814

MBR MBR

6,194 6,642

Ozonation

2,418 2,067

1,391 1,473

Ozonation

Figure 4.64 Overall COD concentration of original and combined system 4.2.2.4 Effect of Ozone on Ammonia Nitrogen (NH4-N) Removal Efficiency

NH4-N was one of the parameters concerned in landfill leachate treatment due to the high level of ammonia presented. In this experiment, NH4-N was removed by ammonia stripping process. This unit operation could remove NH4-N up to 80 %. The effect of ozone on NH4-N removal efficiency was studied. NH4-N from MBR effluent and ozonated effluent were determined. The optimum ozone condition was used in this study. The experiment also checked the NH4-N in all steps pf combined system. The results obtained is presented in Table 4.11.

95

Table 4.11 NH4-N determination in all steps of combined MBR and Ozonation system

Sample NH4-N (mg/L) % Removal Total removal (%) Raw LL before stripped 1,890 - - Raw LL after stripped 369.6 80.4 80.4 Combined yeast Inf. 142.8 61.4 92.4 Combined bact inf 148.4 59.8 92.1

Yeast effluent 67.8 52.5 96.4 Bact effluent 121.5 19.7 93.7

O3 Yeast 0 100 100 O3 Bact 19.18 83.9 99.0

• % Removal compared the efficiency between each step of treatment • Total removal compared the efficiency with the first step of treatment

From the results, NH4-N could be removed prior to biological treatment. The

ammonium reduction in this system was reduced significantly with the step-wise of treatment. The ammonia stripping process could remove ammonia up to 80%. For the influent of the combined system, ammonia removal was around 92% for both reactors because the influent here was the mixing between raw leachate and ozonated leachate which had low ammonia. The MBR system could remove ammonia 52.5 % for yeast reactor but only 19.7 % ammonia removal in bacterial reactor. The possible reason for this might be due to the pH of the leachate treated in each reactor. Yeast had pH of 3.6 and Bacteria had pH of 7.5. At low pH, ammonia was in the form of NH4

+ which could be used by microorganism inside the reactor. At high pH, ammonia was in the form of NH3 instead. For ozonation at optimum condition (75 mg/L, 90 min for yeast and 75 mg/L, 45 min for bacteria), ammonia reduction could be up to 84 % for bacterial effluent and could be completely eliminated for yeast effluent. This means that ozone had high efficiency in removing ammonia and the efficiency increased with ozone contact time and initial ozone concentration. The reduction of ammonia by ozonation up to 80 % was reported by Gierlich and Kollbach (1998). The ammonia oxidation by ozonation most likely resulted from the superposition of the direct reaction produced by molecular ozone and the indirect reaction of hydroxyl radicals formed by the decomposition of ozone (Langlais et al., 1991).

4.5 Chemical Oxidation of the Mixed Liquor in MBR Reactors by Ozone The mixed liquor inside MBR reactors or could be called “sludge” was used to ozonated. The effect of ozone when it was used to treat sludge was investigated. The first objective of the sludge ozonation was to reduce the amount of sludge production. This issue was important in the wastewater treatment plant with conventional activated sludge process where there was the excess biomass produced. Therefore, the ability of ozone to reduce the excess sludge production was developed. This problem was not faced with Membrane Bioreactor process where the less amount of sludge was produced. However, the effect of ozone on sludge minimization was studied and will be discussed in the next part. Another aspect of sludge ozonation was to enhance the settleability of the sludge. This ability was due to the total amount of sludge was reduced. Thus, the ability of the sludge to settle was improved. The objective of recirculation the ozonated sludge back to MBR had brought to the interest since the biodegradability of sludge was enhanced which could be biologically oxidized by biological treatment. This approach was not studied in the present study due to the limit of time for research study.

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4.5.1 Effect of Ozonation on Sludge Minimization Organic matter decomposition during the ozonation of sludge could be described in two mechanisms. One was solubilization due to degradation of suspended solids and second was mineralization due to oxidation of soluble organic matter (Ahn et al., 2002) The effect of ozone on sludge was determined in term of mineralization, solubilization, unsettleable microparticle (UMS), and residual solid. The extent of minerization by measuring the total COD (TCOD) and the extent of solubilization was obtained by measuring soluble COD (SCOD). For UMS fraction, it was described as the COD of the supernatant after settle from settleability test. This UMS fraction caused the reduction in sludge filterability as measured in term of capillary suction time. Muller et al. (1998) reported that sludge filterability was deteriorated by ozonation. The fraction of residual solid was subtracted from TCOD, SCOD, and UMS. The less of the residual sludge, the less of sludge production. The experiment was conducted by using the mixed liquor or sludge of yeast and bacterial culture. Due to the less amount of sludge to be drained out each day (300 mL/day), the amount of sludge was not sufficient for ozonation by variation in ozone dosage. The overcome this problem, the sludge which was drained out from the reactors everyday was collected in a container which provided sufficient aeration. According to this, the amount of biomass presented which measured in term of MLSS and MLVSS would increase due to the death of the microorganism. This was not effect the experiment because it was emphasized only the effect of ozonation on sludge which considered the characteristics of sludge before and after ozonation. Thus, these data was not the representative of the characteristics of sludge from inside the reactors. Ozone concentration was varied according to MLSS concentration. The ozone dosage varied from 0, 0.02, 0.05, 0.1, 0.2, and 0.5 mg O3/mg SS. Separated each fraction by measuring in term of COD concentration. Mineralization was TCOD changed, solubilization was SCOD changed, UMS was COD of filtered particles of the supernatant after settlement, and Residual solid was TCOD-SCOD-UMS. The results obtained are illustrated in Figure 4.65 and Figure 4.66. The details of calculation are in Tables F-1 to F-2 of Appendix F

0

25.9 20.70

3.4 6.910.3

13.8 20.7

24.1

20.728.4

34.532.8

41.475.965.5

52.637.9

27.617.2

12.110.3 17.20%

20%

40%

60%

80%

100%

0 0.02 0.05 0.1 0.2 0.5Ozone dose (mgO3/mgSS)

Solubilization Mineralization Unsettleable microparticles Residuals

Figure 4.65 The fate of yeast sludge after ozone treatment at various ozone dosages

97

018.6 14.3

0

14.3 14.3 8.6

14.3 15.730.0

20.0 21.420.7

21.4 27.9

70.060.0 57.1 62.1

45.7 42.1

7.15.7 8.60%

20%

40%

60%

80%

100%

0 0.02 0.05 0.1 0.2 0.5

Ozone dose (mgO3/mgSS)

Solubilization Mineralization Unsettleable microparticles Residuals

Figure 4.66 The fate of bacterial sludge after ozone treatment at various ozone dosages

From the results obtained, solubilization fraction increased after ozonation due to the degradation of organic matter to the highest at ozone dose of 0.2 mgO3/mgSS for both yeast and bacterial sludge. After this ozone dosage, solubilization fraction decreased which was converted into mineralization fraction. Mineralization fraction reached the highest value at high ozone dosage (0.5 mgO3/mgSS for both sludge). The fraction of unsettled micro particle was dominant for yeast sludge at every ozone dosage. This could be the cause for the unsettlement ability of yeast sludge when conducted settleability experiment.

The result of percentage sludge reduction is presented in Figure 4.67. According from the results, percentage of sludge reduction was low in bacterial sludge which achieved the highest reduction of 28 % at ozone dosage of 0.5 mgO3/mgSS. Yeast sludge had higher percent of sludge reduction than bacteria which achieved the highest of 59 % at ozone dosage of 0.5 mgO3/mgSS. The desired ozone dosage for sludge reduction was depended on the objective. If the organic-rich solubilized and unsettled fraction of ozonated sludge could be used as a carbon source for nitrification, a substantial reduction of sludge could be achieved at the dosage that made the predominant in those fractions (Ahn et al., 2002).

010203040506070

0 0.1 0.2 0.3 0.4 0.5 0.6Ozone dose (mgO3/mgSS)

% S

ludg

e R

educ

tion

Yeast sludge Bacterial sludge

Figure 4.67 Percentage of sludge reduction after ozonation at different ozone dosage

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4.5.2 Effect of Ozonation on the Solids Concentration The degradation of suspended solids continuously increased with ozone dose while the degree of solubilization symptomatically increased (Ahn et al., 2002). The difference between degradation and solubilization resulted in mineralization. The change of MLSS and MLVSS after ozonation was measured. The result of MLSS/MLVSS ratio after different ozone dosage is presented in Figure 4.68 and the detail of calculation is in Table F-3 of Appendix F.

0.3

0.4

0.5

0.6

0.7

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5Ozone dose (mgO3/mgSS)

ML

VSS

/ML

SS

Yeast sludge Bacterial sludge

Figure 4.68 The change of MLVSS/MLSS ratio after applied different ozone dosage

From the results, the ratio of MLVSS/MLSS increased after the reaction of ozone.

This could be concluded that ozone helped degrade the suspended solid which resulted in the decreased of MLSS. The decreased of suspended solid resulted in the increased of soluble fraction. Some of the soluble fraction was converted into mineralization form which could be the cause for the increased of MLVSS after some dosage of ozonation. This could be said that ozonation could reduce the amount of sludge generated from the system. The highest MLVSS/MLSS ratio which obtained from yeast sludge was 0.62 while the bacterial sludge had the highest ratio of 0.51. Yeast seemed to have higher degree of degradation than bacteria. From the experiment, it could be observed that there was the change in color of sludge after ozonation only for yeast system. This could be one of the reasons that yeast has higher degree of solid degradation than bacteria. 4.5.3 Effect of Ozonation on the Sludge Settleability The settleability of sludge could be improved by the addition of ozone. Ozone could overcome the bridging or diffuse floc structure associated with excessive biomass concentration. The microorganism presented in sludge had lower density after ozonation compared to before ozonation (Kamiya and Hirotsuji, 1998). This would be the cause for the enhancement of the sludge settleability. In the experiment, the measurement of sludge settleability was done in the mean of Diluted Sludge Volume Index (DSVI) (Jenkins, et al). Because the sludge used in the experiment was not the representative of the sludge inside reactors, therefore the settleability was measured in term of final volume after 30 minutes settle period based on DSVI method. The result is presented in Figure 4.69 and the detail of calculation is in Table F-4 of Appendix F.

99

800

1000

1200

1400

1600

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5Ozone dosage (mg O3/mg SS)

Sett

le V

olum

e (m

L)

Figure 4.69 Settle volume of bacterial sludge after 30 minutes in different ozone dosage

From the results, the settle volume of the sludge after ozonation was better than before ozonation (at ozone dosage 0 mg O3/mg SS) for all ozone dosage. The results indicated that the settleability was not improved after ozone dosage of 0.02 mg O3/mg SS. The possible reason was due to the increase of the amount of suspended solid after some ozone dosage which was the cause for the more difficult of the sludge to settle. The settleability of sludge was observed only for bacterial sludge. This situation was not found for yeast sludge due to the high amount of UMS fraction as indicated above which caused the dispersion in yeast sludge. Ahn et al (2002), observed the improvement of sludge settleabiltiy after ozone dosage of 0.2 gO3/g DS for conventional activated sludge. The same situation was obtained by Kamiya and Hirotsuji (1998) which indicated that the ratio of SVI after and before ozonation decreased with increasing ozone dose. They obtained 60 % of the relative SVI reduction at an ozone dose of 9.5 mg O3/g MLSS and that the sludge settling characteristics were extremely improved. The possible reason that in this experiment obtained the unexpected results could be from the low quality of sludge characteristics. One of the parameters that was used to identify the quality of sludge was Capillary Suction Time (CST) CST was the measurement of the ability of sludge in dewatering process. The lower of the CST, the easier of the solubilized fraction of the sludge to be separated from the solid phase. In this experiment, CST measurement was conducted by using C.S.T. Apparatus (Triton-type 16 s). Determine CST for sludge before and after ozonation at ozone concentration of 75 mg/L, 45 minutes for both yeast and bacterial sludge. The results obtained are presented in Table 4.12 and the detail of calculation is in Table F-5 of Appendix F. Table 4.12 CST results of sludge before and after ozonation

CST (s/g SS) Types of sludge Before ozonation After ozonation

Yeast sludge 316.5 219.0 Bacterial sludge 323.7 215.2

From the results, it could be conclude that ozone could improve the ability of sludge in dewatering process. The decrease of CST value was due to the reduction of unsettleable micro particle that presented in the sludge after ozonation. From the results, yeast sludge could reduce CST of 97.5 s/g SS and bacterial sludge could reduce 108.5 s/g SS. The reason for the higher reduction of CST in bacterial sludge than yeast sludge was

100

due to the lower of unsettleable micro particle in bacterial sludge after ozonation as indicated in the previous section. However, CST value after ozonation was still high. The lower of the CST, the better of the filterability of the sludge. The good CST should be around 1-20 s/g SS. The results obtained indicated the low quality of both sludge in dewatering ability. Thus, CST was not the indicator parameter for indicating the effect of ozone in both yeast and bacterial sludge. After the recirculation of ozonated sample back to MBR system, the sludge characteristics were improved. After one month of the operation of combined system, the filterability of sludge was improved. The sludge was taken from both reactors after one month of recirculation. The results indicated that CST of yeast sludge reduced to 127 s/g SS while CST of bacterial sludge reduced to 10 s/g SS. This indicated that the ability of sludge in dewatering properties was improved after one month of the combined system was operated. Bacterial sludge still indicated the better dewatering ability than yeast sludge.

101

102

Chapter 5

Conclusion and Recommendations

5.1 Conclusions The conclusions based on the objectives of the study are summarized as follows: 1. The first objective prior to other studies was calibration and kinetic studies by

considering the fundamental aspect of ozone. The conclusions of this objective are as follows

1.1) The results on ozone concentration in liquid phase indicated that most of the ozone was transferred into the off-gas while only a small amount remained in the liquid phase. This ensured that the residual ozone in liquid phase could be neglected.

1.2) The average ozone transfer efficiency obtained from the experiment was quite low (54.3 %), which could be as an effect of water temperature, size of diffuser, and gas to liquid ratio.

1.3) The ozone decomposition rate constant increased with pH and initial ozone concentration applied. The maximum was obtained at pH 11 while minimum was obtained at pH 2.

1.4) Half-life of ozone decreased with an increase in pH and initial ozone concentration. Half-life was 30 minutes at pH 2 while it was 15 minutes at pH 11.

1.5) The rate of TOC and COD removal efficiency increased while increasing the contact time. The organic removal efficiency was higher in the bacterial effluent than yeast effluent and higher in 16h HRT compared to that of 24h HRT. Higher reaction rate constant indicates easier degradation of various compounds.

2. The second objective was to investigate the capacity of ozone and perozone to

increase the performance of the biological treatment process. The conclusions of this objective are as follows

2.1) The COD, TOC, and Color removal efficiency increased with increased in ozone contact time and ozone dosage.

2.2) The majority fraction in both yeast and bacterial effluent before ozonation was MW > 50 kDa which shifted after ozonation to the range of MW 3.5-5 kDa. This shows the breakdown of the high molecular weight compounds into low molecular weight after ozonation.

2.3) pH and alkalinity did not play an significant role in ozonation in the present study due to the simultaneous role of radical scavenger and the production of hydroxyl radical. The pH for yeast ozonation was pH 3.6 and bacterial ozonation was pH 7.5.

103

3. The third objective was to identify the optimum operational parameters in terms of removal efficiency for chemical oxidation process. The conclusions for this objective are as follows

3.1) The optimum ozone concentration was found at 75 mg/L for both yeast and bacterial effluent where maximum COD, TOC, and Color removal efficiency could be obtained. 3.2) The optimum ozone contact time obtained was at 90 minutes for yeast effluent with COD removal efficiency of 49%. The optimum ozone contact time was at 45 minutes for bacterial effluent considering the improvement in biodegradability in terms of BOD/COD from 0.0342 to 0.0847, which was suitable for biologically degradation.

3.3) At optimum ozone condition, yeast and bacterial effluent had TOC removal of 34.5 % and 30%, respectively. The color removal efficiency of yeast and bacterial effluent at optimum condition was greater than 95 %.

3.4) The products after ozonation were mainly in the form of acid by-products which is indicated by a decrease in pH when the ozone dosage was increased.

3.5) The optimum waiting time after the addition of H2O2 for yeast effluent was 30 minutes but 20 minutes for bacterial effluent.

3.6) The optimum H2O2/O3 ratio was found to be 0.2 for both yeast and bacterial effluent.

3.7) The optimum perozone contact time was 90 minutes for both effluents where there was a maximum COD, TOC, and Color removal efficiency.

3.8) When efficiency of ozone and perozone was compared, the removal efficiency in terms of COD, TOC, and Color did not improve. Thus, ozone alone was used for the continuous system.

4. The fourth objective was to couple ozonation and membrane bioreactor for landfill

treatment. The conclusions for this objective are as follows

4.1) COD removal efficiency of MBR system after recirculation slightly increased compared with the original system. The COD removal efficiency improved from 66% to 74% for the yeast system and 71.2% to 75.4 % for the bacterial system.

4.2) COD removal efficiency of ozonation system improved after recirculation. The COD removal efficiency of ozonated effluent increased compared to the original system with a value of 4.3 % for yeast effluent and 13.3 % for bacterial effleunt.

4.3) The overall COD removal efficiency was slightly increased with a value of 4.4 % for yeast and 4.1 % for bacterial system. The reduction in ozone consumption was observed only in the bacterial system.

104

5. The fifth objective was the application of ozone for sludge treatment. The conclusions for this objective are as follows

5.1) Ozone had the ability in reduce the sludge production by degradation of organic matter. A maximum of 59% sludge reduction was observed in yeast sludge while 28% was obtained for bacterial sludge. 5.2) The degradation of suspended solids increased with ozone dosage. This resulted in reduction of biomass concentration in the sludge 5.3) Sludge settleability improved after ozone application for a specific dosage. This was due to the ability of ozone to overcome the diffuse floc structure inside the sludge. CST also improved after the application of ozone for sludge treatment.

5.2 Recommendations for further study

1. Ozone generator used in the experiment should have wide range of concentration. This will be useful to study the effect of ozone concentration in low and high ozone dosage.

2. The design of the ozone column reactor should concern foaming problem typically

found in landfill leachate treatment. Increasing the surface area of the reactor or install the mechanical impeller to break the foam can solve this problem.

3. The method for the determination of ozone concentration in liquid phase should be

standardized. Thus, the presence of color in the sample will not interfere with the measurement.

4. Ozone gas analyzer should be installed within the reactor in order to reduce the workload on measuring of ozone concentration in the gas phase.

5. The types of membrane for MWCO experiment should be made of the same type of

material. This can help to maintain the similar condition in all cases and thus, the results can be easily compared. The membrane with molecular weight of 500 Da and lower are recommended for ozonated sample.

6. The operation of Membrane Bioreactor should be well stabilized which will make

the results valuable and comparable.

7. If the standard discharge is required, the development of post treatment after ozonation is recommended. This can be done by sending to the municipal wastewater treatment plant or by the mean of dilution.

8. Specific fraction of the leachate should be analysed and its change after ozonation

should be further studies

9. The bandwidth of the raw leachate quality should be proper maintained due to the consistency requirement.

10. Oxygen Uptake Rate (OUR) experiment should be conducted in order to

investigate the biodegradability and biokinetic study of the sludge.

105

11. Toxicity test should be implemented for the leachate samples before and after ozonation for indicating the effect of ozonation on leachate sample.

12. Parameter Size Distribution for sludge before and after ozonation should be studied

for the change that effected from ozone.

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Appendix A

Example of Calculation

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Appendix A: Examples of calculation A-1 Calculation of ozone concentration

1.1 Determination of ozone concentration in gas phase by Iodometric method At oxygen flowrate = 0.6 L/min, voltage of ozone generator = 200 V Vary ozone contact time from 1, 3, and 5 minutes At contact time 1 minute, volume of Na2S2O3 = 17.3 mL At contact time 3 minute, volume of Na2S2O3 = 51.9 mL At contact time 5 minute, volume of Na2S2O3 = 89.8 mL

Ozone Demand, OD (mg/min) = A*N*24

T A = mL of Na2S2O3 = 89.8 mL (CT = 5 minutes) N = Normality of Na2S2O3 used = 0.106 N T = Ozone contact time (min) = 5 minutes

Ozone Demand = 89.8 mL*0.106 N*24 5

= 45.69 mg/min

Ozone concentration (mg/L) = OD AF

AF = Air/Oxygen flowrate = 0.6L/min Ozone concentration = 45.69 mg/min = 76.2 mg/L 0.6 L/min Average ozone concentration = (73.4+73.4+76.2) = 75 mg/L 3 1.2 Determination of ozone concentration in liquid phase by

Spectrophotometric method

This part is automatically calculated by spectrophotometer with the equation

Ozone concentration (mg/L) = 0.0426 *Absorbance The value of 0.0426 obtained from standard curve of absorbance vs iodine (or ozone) concentration

114

A-2 Calculation of ozone transfer efficiency

For ozone concentration in feed gas = 75 mg/L at ozone contact time = 3 minutes For ozone in off-gas (O3 out), Normality of Na2S2O3 used = 0.625 N,

Volume of Na2S2O3 = 4.1 mL

Ozone Demand = 4.1 mL* 24*0.625 N = 20.5 mg/min 3 min

Ozone concentration = 20.5 mg/min = 34.2 mg/L

0.6 L/min

Transfer Efficiency = (75 mg/L)-(34.2 mg/L) * 100 % = 54.4 % 75 mg/L

By varying ozone contact time for ozone in feed gas of 75 mg/L, average ozone transfer efficiency can be obtain below

Avg. transfer efficiency = (60+73.3+54.4+37.7+36.2+35.7+45.4+63.2) = 50.7 % 8

A-3 Calculation of ozone mass transfer coefficient Determine equilibrium ozone concentration in liquid phase by using ozone solubility data

CL* = S x Cg

Where: Cg = ozone concentration in gas phase

S = Solubility ratio of ozone as a function of water temperature (Langlais, et al., 1991 obtained from Rawson, 1953) Table A-1 Solubility data of ozone as a function of water temperature

Temperature (oC) Solubility ratios (mg/L in water to mg/L in gas) 9.6 0.39 14.5 0.29 20.3 0.21 25.5 0.17 30.5 0.14 35.0 0.12 39.0 0.07

%100x]O[

]O[]O[%),TE(EfficiencyTransfer

feed3

out3feed3 −=

115

At ozone concentration in feed gas = 75 mg/L (Cg) Temperature = 30 oC (summer season), solubility ratio = 0.14, therefore:

CL* = 75 mg/L * 0.14 = 10.5 mg/L By substituting CL* into the formula below, ozone mass transfer coefficient was determined

ln (CL* - CL) = -KLa x t Where:

CL = Ozone concentration in liquid phase at time t (mg/L) KLa = Ozone mass transfer coefficient (sec-1) t = Ozone contact time (sec) For ozone contact time = 3 minutes (180 seconds) From the experiment, ozone concentration in liquid phase = 0.0629 mg/L

ln (10.5-0.0629) = -KLa x 180 sec KLa = - 0.01303 sec-1

A-4 Calculation of ozone decomposition rate constant Measure ozone concentration in liquid phase by spectrophotometer after applied ozone into water solution as the time passed. At ozone concentration in feed gas = 75 mg/L, contact time = 1minute (pH =6) Ozone concentration in liquid after applied ozone = 0.0565 mg/L ([O3]0) At ozone contact time = 3 minutes, ozone concentration = 0.0495 mg/L (([O3]t)

- ln {[O3]t/[O3]0}= - ln (0.0495/0.0565) = 0.1331 Plot the graph between - ln {[O3]t/[O3]0}and contact time, the slope obtained from this graph is ozone decomposition rate constant (k′ = 6.43*10-4 s-1, for this condition)

Half-life of ozone (t1/2) = ln2 k′

= ln2 (6.43*10-4 s-1*(1/60))

= 17.96 minute A-5 Calculation of the reaction rate constant and the primary degree of pollutant elimination

Using real wastewater (leachate at different condition), determined TOC and COD concentration at different ozone contact time For yeast effluent from MBR (HRT = 24h), at ozone contact time = 30 minutes TOC = 998 mg/L (TOC0 = 1,122 mg/L) and COD = 2,437 mg/L (COD0 = 2,664 mg/L) Primary degree of pollutant elimination in term of TOC = TOCt/TOC0 = 998/1,122 = 0.89

116

Primary degree of pollutant elimination in term of COD = CODt/COD0 = 2,437/2,664 = 0.915 For ozone reaction rate constant or ozone utilization rate constant, plot the graph between -ln (TOCt/TOC0) or - ln (CODt/COD0) and contact time. The slope obtained from this graph is ozone reaction rate constant

- ln (TOCt/TOC0) = -ln (998/1,122) = 0.1168

- ln (CODt/COD0) = -ln (2,437/2,664) = 0.0891

k (based on TOC) = 0.003 min-1 and k (based on COD) = 0.0043 min-1 A-6 Calculation of ozonation factor

Determine ozone concentration in off-gas by Iodemetric method the same as for feed gas For yeast effluent from MBR (HRT = 24h) at ozone contact time = 30 minutes, ozone concentration in off-gas = 15.92 mg/L Used TOC concentration to be the representative of the concentration of the substrate which is equal to 1,122 mg/L The volume of leachate to be treated = 1L based on the assumption that ozone residual in aqueous phase is transferred into off-gas (this value can be neglected). Ozonation factor (Φ) can be calculated as below

Φ = [A]VA [O3]f νf t – [O3]dVA – [O3]eνe t [A] = concentration of substrate = 1,122 mg/L VA = the volume of the treated aqueous phase = 1L [O3]f = O3 concentration in the feed gas = 75 mg/L [O3]d = O3 concentration dissolved in the reaction matrix (neglected) [O3]e = O3 concentration in the exhaust air stream = 15.92 mg/L νf = flow rate of O3 feed = 0.6 L/min νe = flow rate of exhaust air stream = 0.6 L/min t = ozonation time = 30 minutes Φ = (1,122 mg/L*1L)

(75 mg/L*0.6L/min*30min)-(15.92 mg/L*0.6L/min*30min) = 0.518

117

A-7 Calculation of initial membrane resistance

From the equation

mRTMPJμ

=

For membrane with molecular weight of 50 kDa (Diameter = 7.6 cm) μ = Dynamic viscosity = 0.798*10-3 N.s/m2 at 27 oC At TMP = 101 kPa, the volume of the filtrated = 32.9 mL and filtration time = 5 minutes Surface area of membrane = π*D2 = π*(7.6*10-2)2 = 0.004536 m2 4 4 Filtration flux (J) can be calculated as below

J = (32.9 mL*60 ) (5 min*1000*0.004536 m2)

= 87.03 L/m2.h

From the relationship between filtration flux and TMP as shown in figure C-1, thus the slope of the graph = 1.7255. Membrane resistance (Rm) can be calculated as below

Rm = 1.7255*1010*3600 7.98 = 7.784*1012 m-1 A-8 Calculation of ozone consumption

Due to the small number of ozone residual in liquid phase, this value can be neglected, thus the calculation of ozone consumption is as below

Ozone consumption (mg O3) = (Ozone in feed gas) – (Ozone in off-gas)

Ozone concentration in feed gas = 75 mg/L (oxygen flowrate = 0.6 L/min) For bacterial effluent at contact time of 45 minutes, ozone concentration in off-gas = 19.72 mg/L, thus Ozone consumption = (75 mg/L*0.6 L/min*45 min)-(19.72 mg/L* 0.6 L/min*45 min)

= 1,492.5 mg O3

A-9 Calculation of the volume of H2O2 addition Specific weight of H2O2 (35% V/V) = 1.13 or 1,130 g/L At ozone concentration of 75 mg/L (45 mg O3/min), H2O2/O3 ratio = 0.2, thus

Volume of H2O2 added = (0.2*45 mg O3/min*100) * 1000 (1,130 g/L*35*1000) = 0.0228 mL/min At contact time of 45 min, mL of H2O2 addition = 0.00228 mL/min*45 min = 1.024 mL

118

A-10 Calculation of organic load in terms of BOD5 and COD for combined system

BOD5 load For MBR (initial system), BOD5 = 1,200 mg/L, flowrate = 5 L/d BOD5 load = (1,200 mg/L*5L/d) = 6,000 mg BOD5 Bacterial reactor For combined system, BOD5 from ozonation = 100 mg/L, assume 50% recycle (2.5 L) BOD5 load = (1,200 mg/L*5L/d)+(100mg/L*2.5L) = 6,250 mg BOD5

= 6,000 ± 250 mg BOD5 Yeast reactor For combined system, BOD5 from ozonation = 5 mg/L, assume 50% recycle (2.5 L) BOD5 load = (1,200 mg/L*5L/d)+(5 mg/L*2.5L) = 6,012.5mg BOD5

= 6,000 ± 12.5 mg BOD5 COD load For MBR (initial system), COD = 5,500 mg/L, flowrate = 5 L/d COD load = (5,500 mg/L*5L/d) = 27,500 mg COD Bacterial reactor For combined system, COD from ozonation = 1,500 mg/L, assume 50% recycle (2.5 L) BOD5 load = (5,500 mg/L*5L/d)+(1,500mg/L*2.5L) = 31,250 mg COD

= 27,500 ± 3,750 mg COD Yeast reactor For combined system, COD from ozonation = 1,000 mg/L, assume 50% recycle (2.5 L) COD load = (5,500 mg/L*5L/d)+(1,000mg/L*2.5L) = 30,000 mg COD

= 30,000 ± 2,500 mg COD Because the load from ozonation is low if compare with the total load therefore, it can be assumed that the BOD5 and COD load are maintained.

119

Appendix B

Results of ozone calibration and ozone kinetic study

120

Appendix B: Results of ozone calibration and ozone kinetic study 1. Results of ozone calibration study

1.1 Calibration of ozone concentration in gas phase

Table B-1 Ozone concentration in gas phase at oxygen flowrate = 0.2 L/min (12 L/h)

Voltage (V) Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone concentration

(mg/L) 220 1 6.0 15.84 79.2

3 17.6 15.49 77.4 5 22.5 11.88 59.4

Mean 72.0 Ozone concentration reported by manufacturer (mg/L) 110.4

% error 34.8

200 1 7.3 19.27 96.4 3 17.9 15.75 78.8 5 28.0 14.78 73.9

Mean 83.0 Ozone concentration reported by manufacturer (mg/L) 89.7

% error 7.45

180 1 5.1 13.46 67.3 3 15.70 13.82 69.1 5 29.1 15.34 76.7

Mean 71.0 Ozone concentration reported by manufacturer (mg/L) 75.9

% error 6.42

160 1 4.2 11.09 55.4 3 14.70 12.94 64.7 5 26.3 13.89 69.4

Mean 63.2 Ozone concentration reported by manufacturer (mg/L) 56.9

% error 11.04

121

Table B-2 Ozone concentration in gas phase at oxygen flowrate = 0.4 L/min (24 L/h)

Voltage (V) Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone concentration

(mg/L) 220 1 11.60 30.6 76.6

3 35.1 30.9 77.2 5 56.3 29.7 74.3

Mean 76.0 Ozone concentration reported by manufacturer (mg/L) 112.1

% error 32.2

200 1 11.10 29.3 73.3 3 32.6 28.7 71.7 5 55.9 29.5 73.8

Mean 72.9 Ozone concentration reported by manufacturer (mg/L) 94.9

% error 23.1

180 1 10.15 26.8 67.0 3 29.2 25.7 64.1 5 52.9 27.9 69.8

Mean 67.0 Ozone concentration reported by manufacturer (mg/L) 81.9

% error 18.25

160 1 10.20 26.9 67.3 3 28.4 25.0 62.5 5 45.1 23.8 59.5

Mean 63.1 Ozone concentration reported by manufacturer (mg/L) 75.9

% error 16.85

122

Table B-3 Ozone concentration in gas phase at oxygen flowrate = 0.6 L/min (36 L/h)

Voltage (V) Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone concentration

(mg/L) 220 1 19.0 48.3 80.6

3 56.6 48.0 80.0 5 93.5 47.6 79.3

Mean 80.0 Ozone concentration reported by manufacturer (mg/L) 99.5

% error 19.63

200 1 17.3 44.0 73.4 3 51.9 44.0 73.4 5 89.8 45.7 76.2

Mean 74.3 Ozone concentration reported by manufacturer (mg/L) 91.4

% error 18.75

180 1 15.0 39.6 66.0 3 44.9 39.5 65.8 5 82.2 43.4 72.3

Mean 68.0 Ozone concentration reported by manufacturer (mg/L) 85.7

% error 20.6

160 1 13.90 36.7 61.2 3 39.8 35.0 58.3 5 69.5 36.7 61.1

Mean 60.2 Ozone concentration reported by manufacturer (mg/L) 79.4

% error 24.1

123

Table B-4 Ozone concentration in gas phase at oxygen flowrate = 0.8L/min (48 L/h)

Voltage (V) Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone concentration

(mg/L) 220 1 11.40 58.3 72.9

3 34.9 59.5 74.3 5 57.2 58.5 73.1

Mean 73.4 Ozone concentration reported by manufacturer (mg/L) 100.1

% error 26.6

200 1 10.05 51.4 64.2 3 31.5 53.6 67.0 5 54.7 55.9 69.9

Mean 67.0 Ozone concentration reported by manufacturer (mg/L) 87.5

% error 23.4

180 1 14.50 36.9 46.1 3 55.6 47.2 58.9 5 93.6 47.6 59.5

Mean 54.9 Ozone concentration reported by manufacturer (mg/L) 76.8

% error 28.5

160 1 14.90 37.9 47.4 3 43.1 36.6 45.7 5 68.7 35.0 43.7

Mean 45.6 Ozone concentration reported by manufacturer (mg/L) 60.4

% error 24.5

124

Table B-5 Ozone concentration in gas phase at oxygen flowrate = 1.0 L/min (60 L/h)

Voltage (V) Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone concentration

(mg/L) 220 1 14.85 75.9 75.9

3 44.5 75.8 75.8 5 78.0 79.8 79.8

Mean 77.2 Ozone concentration reported by manufacturer (mg/L) 94.5

% error 18.37

200 1 12.85 65.7 65.7 3 42.4 72.3 72.3 5 60.4 61.7 61.7

Mean 66.6 Ozone concentration reported by manufacturer (mg/L) 86.3

% error 22.8

180 1 9.2 47.0 47.0 3 34.1 58.1 58.1 5 57.8 59.1 59.1

Mean 54.7 Ozone concentration reported by manufacturer (mg/L) 71.8

% error 23.7

160 1 8.95 45.8 45.8 3 25.5 43.5 43.5 5 42.8 43.8 43.8

Mean 44.3 Ozone concentration reported by manufacturer (mg/L) 58.0

% error 23.5

125

0.0020.0040.0060.0080.00

100.00120.00

0 2 4 6

Contact time (min)

Ozo

ne c

once

ntra

tion

(mg/

L)

220 V 200 V 180 V 160 V

0.00

20.00

40.00

60.00

80.00

100.00

0 2 4 6

Contact time (min)

Ozo

ne c

once

ntra

tion

(mg/

L)

220 V 200 V 180 V 160 V

0.00

20.00

40.00

60.00

80.00

100.00

0 2 4 6

Contact time (min)

Ozo

ne c

once

ntra

tion

(mg/

L)

220 V 200 V 180 V 160 V

0.00

20.00

40.00

60.00

80.00

0 2 4 6Contact time (min)

Ozo

ne c

once

ntra

tion

(mg/

L)

220 V 200 V 180 V 160 V

0.00

20.00

40.00

60.00

80.00

100.00

0 2 4 6

Contact time (min)

Ozo

ne c

once

ntra

tion

(mg/

L)

220 V 200 V 180 V 160 V

Table B-6 Ozone concentrations in gas phase of ozone feed gas at selected values

Voltage (V) Oxygen flowrate (L/min)

Ozone Demand (mg/min)

Ozone concentration (mg/L)

160 0.8 36.5 45 160 0.6 36.1 60 200 0.6 44.6 75

Figure B-1 Ozone concentration at oxygen flowrate = 0.2 L/min

Figure B-2 Ozone concentration at oxygen flowrate = 0.4 L/min

Figure B-3 Ozone concentration at oxygen flowrate = 0.6 L/min

Figure B-4 Ozone concentration at oxygen flowrate = 0.8 L/min

Figure B-5 Ozone concentration at oxygen flowrate = 1.0 L/min

126

1.2 Calibration of ozone concentration in liquid phase Table B-7 Calibration curve of ozone in liquid phase measured by spectrophotometer

Ozone concentration (mg/L) Absorbance 0.0024 0.038 0.0048 0.049 0.0072 0.101 0.012 0.182 0.024 0.427 0.048 0.949 0.072 1.484 0.096 2.088 0.120 3.184

y = 23.458xR2 = 0.9721

0

0.5

1

1.5

2

2.5

3

3.5

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Ozone concentration (mg/L)

Abs

orba

nce

Figure B-6 Calibration curve for ozone concentration in liquid phase

Table B-8 Results of ozone concentration in liquid phase

Ozone concentration in liquid phase (mg/L) Contact time (min) At O3 in feed gas

= 45 mg/L At O3 in feed gas

= 60 mg/L At O3 in feed gas

= 75 mg/L 0 0 0 0

0.5 0.01465 0.00814 0.00984 1 0.01917 0.01563 0.0469 3 0.0229 0.0269 0.0629 5 0.0298 0.0283 0.0596 7 0.0298 0.0251 0.0564 10 0.0315 0.0263 0.0519 20 0.0287 0.0282 0.0458 30 0.0227 0.0262 0.0391

127

2. Results of ozone transfer efficiency Table B-9 ozone transfer efficiency for ozone in feed gas = 45 mg/L

Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone conc. in off-gas (mg/L)

Ozone transfer efficiency (%)

0.5 0.4 12.0 15.0 66.7 1 0.4 6.0 7.5 83.3 3 3.2 16.0 20.0 55.6 5 6.8 20.4 25.5 43.3 7 9.5 20.4 25.4 43.5 10 13.7 20.5 25.6 43.1 20 27.6 20.7 25.8 42.6 30 32.5 16.3 20.3 54.9

Average ozone transfer efficiency (%) = 54.1 Table B-10 ozone transfer efficiency for ozone in feed gas = 60 mg/L

Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone conc. in off-gas (mg/L)

Ozone transfer efficiency (%)

0.5 0 0 0 83.3 1 0.2 6.0 10.0 70.8 3 0.7 10.5 17.5 63.9 5 2.6 13.0 21.7 51.7 7 5.8 17.4 29.0 47.0 10 8.9 19.1 31.8 47.9 20 12.5 18.8 31.3 47.1 30 25.4 19.1 31.8 54.2

Average ozone transfer efficiency (%) = 58.2 Table B-11 ozone transfer efficiency for ozone in feed gas = 75 mg/L

Contact time (min) mL of Na2S2O3

Ozone Demand (mg/min)

Ozone conc. in off-gas (mg/L)

Ozone transfer efficiency (%)

0.5 0.6 18.0 0 60.0 1 0.8 12.0 30.0 73.3 3 4.1 20.5 20.0 54.4 5 9.4 28.1 34.2 37.7 7 13.4 28.7 46.8 36.2 10 19.3 29.0 47.9 35.7 20 32.8 24.6 48.3 45.4 30 33.1 16.55 40.9 63.2

Average ozone transfer efficiency (%) = 50.7

128

3. Results of ozone mass transfer coefficient Table B-12 Ozone mass transfer for ozone in feed gas = 45 mg/L (CL* = 6.3 mg/L) Contact time (sec) CL ln(CL*-CL) KLa (s-1)

30 0.01465 1.838 -0.0613 60 0.01917 1.838 -0.0306

180 0.0229 1.837 -0.01021 300 0.0298 1.836 -0.00612 420 0.0298 1.836 -0.00437 600 0.0315 1.836 -0.00306

1,200 0.0287 1.836 -0.001530 1,800 0.0227 1.837 -0.001021

Average KLa = -0.01478 s-1

Table B-13 Ozone mass transfer for ozone in feed gas = 60 mg/L (CL* = 8.4 mg/L) Contact time (sec) CL ln(CL*-CL) KLa (s-1)

30 0.00814 2.127 -0.0709 60 0.01563 2.126 -0.0354

180 0.0269 2.125 -0.01181 300 0.0283 2.125 -0.00708 420 0.0251 2.125 -0.00506 600 0.0263 2.125 -0.00354

1,200 0.0282 2.125 -0.001771 1,800 0.0262 2.125 -0.001181

Average KLa = -0.01710 s-1

Table B-14 Ozone mass transfer for ozone in feed gas = 75 mg/L (CL* = 10.5 mg/L) Contact time (sec) CL ln(CL*-CL) KLa (s-1)

30 0.00984 2.350 -0.0783 60 0.0469 2.347 -0.0391

180 0.0629 2.345 -0.01303 300 0.0596 2.346 -0.00782 420 0.0564 2.346 -0.00559 600 0.0519 2.346 -0.00391

1,200 0.0458 2.347 -0.001956 1,800 0.0391 2.348 -0.001304

Average KLa = -0.01889 s-1

129

4. Results of ozone decomposition or pseudo first order rate constant

Table B-15 At O3 = 45 mg/L, 1 min (pH = 2) Table B-16 At O3 = 45 mg/L, 1 min (pH = 6)

Time (min)

Ozone conc. (mg/L) - ln {[O3]/[O3]0} Time

(min) Ozone conc.

(mg/L) - ln {[O3]/[O3]0}

0 0.0578 0 0 0.01960 0 1 0.0558 0.0351 1 0.01921 0.0200 3 0.0526 0.0949 3 0.01793 0.0888 5 0.0500 0.1447 5 0.01683 0.1525 7 0.0473 0.2008 7 0.01576 0.2179 10 0.0438 0.2785 10 0.01436 0.3113 15 0.0387 0.4016 15 0.01227 0.4685 20 0.0344 0.5183 20 0.01031 0.6425 25 0.0310 0.6226 25 0.00959 0.7153 30 0.0279 0.7298

30 0.00895 0.7843

Table B-17 At O3 = 45 mg/L, 1 min (pH = 7) Table B-18 At O3 = 45 mg/L, 1 min (pH = 11)

Time (min)

Ozone conc. (mg/L) - ln {[O3]/[O3]0} Time

(min) Ozone conc.

(mg/L) - ln {[O3]/[O3]0}

0 0.00443 0 0 0.000724 0 1 0.00413 0.0696 1 0.000660 0.0921 3 0.00392 0.1225 3 0.000639 0.1249 5 0.00362 0.2016 5 0.000575 0.2302 7 0.00324 0.3136 7 0.000511 0.3480 10 0.00294 0.4102 10 0.000469 0.4350 15 0.00247 0.5839 15 0.000383 0.6357 20 0.00204 0.7731 20 0.000320 0.8180 25 0.001704 0.9554 25 0.000277 0.9611 30 0.001491 1.0890

30 0.000213 1.2235

Table B-19 At O3 = 75 mg/L, 1 min (pH = 2) Table B-20 At O3 = 75 mg/L, 1 min (pH = 6)

Time (min)

Ozone conc. (mg/L) - ln {[O3]/[O3]0} Time

(min) Ozone conc.

(mg/L) - ln {[O3]/[O3]0}

0 0.1134 0 0 0.0565 0 1 0.1107 0.0243 1 0.0539 0.0473 3 0.0962 0.1641 3 0.0495 0.1331 5 0.0961 0.1659 5 0.0457 0.2119 7 0.0895 0.2362 7 0.0420 0.2975 10 0.0800 0.3483 10 0.0377 0.4046 15 0.0715 0.4615 15 0.0320 0.5701 20 0.0627 0.5931 20 0.0276 0.7178 25 0.0596 0.6433 25 0.0240 0.8569 30 0.0544 0.7338

30 0.0210 0.9917

130

Table B-21 At O3 = 75 mg/L, 1 min (pH = 7) Table B-22 At O3 = 75 mg/L, 1 min (pH = 11)

Time (min)

Ozone conc. (mg/L) - ln {[O3]/[O3]0} Time

(min) Ozone conc.

(mg/L) - ln {[O3]/[O3]0}

0 0.0313 0 0 0.00426 0 1 0.0297 0.0513 1 0.00405 0.0513 3 0.0272 0.1396 3 0.00366 0.1508 5 0.0250 0.2228 5 0.00341 0.2231 7 0.0230 0.3061 7 0.00307 0.3285 10 0.0203 0.4320 10 0.00275 0.4385 15 0.01691 0.6156 15 0.00226 0.6349 20 0.01419 0.7914 20 0.00183 0.8440 25 0.01150 1.0011 25 0.001491 1.0498 30 0.01010 1.1315

30 0.001193 1.2730

Table B-23 At O3 = 75 mg/L, 5 min (pH = 2) Table B-24 At O3 = 75 mg/L, 5 min (pH = 6)

Time (min)

Ozone conc. (mg/L) - ln {[O3]/[O3]0} Time

(min) Ozone conc.

(mg/L) - ln {[O3]/[O3]0}

0 0.1214 0 0 0.0530 0 1 0.1106 0.0929 1 0.0504 0.0512 3 0.1074 0.1230 3 0.0456 0.1498 5 0.0983 0.2109 5 0.0420 0.2315 7 0.0942 0.2538 7 0.0387 0.3149 10 0.0845 0.3621 10 0.0345 0.4279 15 0.0785 0.4358 15 0.0288 0.6100 20 0.0703 0.5465 20 0.0242 0.7858 25 0.0629 0.6572 25 0.0204 0.9524 30 0.0586 0.8079

30 0.01747 1.1100

Table B-25 At O3 = 75 mg/L, 5 min (pH = 7) Table B-26 At O3 = 75 mg/L, 5 min (pH = 11)

Time (min)

Ozone conc. (mg/L) - ln {[O3]/[O3]0} Time

(min) Ozone conc.

(mg/L) - ln {[O3]/[O3]0}

0 0.0464 0 0 0.000639 0 1 0.0441 0.051 1 0.000596 0.0690 3 0.0400 0.1484 3 0.000554 0.1431 5 0.0364 0.242 5 0.000533 0.1823 7 0.0333 0.333 7 0.000426 0.4055 10 0.0293 0.459 10 0.000383 0.5108 15 0.0239 0.665 15 0.000311 0.7202 20 0.0200 0.843 20 0.000264 0.8835 25 0.01674 1.019 25 0.000213 1.0986 30 0.01363 1.225

30 0.000183 1.2494

131

Table B-27 Pseudo first order rate constant at different initial ozone concentration as a function of pH

5. Results of ozone reaction rate constant or specific ozone utilization rate and

primary elimination degree of pollutant Table B-28 Results of ozone reaction rate constant and primary elimination degree of pollutant for Yeast effluent from MBR at HRT = 16 h

Contact time (min)

TOC (mg/L) or C1

- ln (C1/C0,1) α1,

C1/C0,1

COD (mg/L) or C2

- ln (C2/C0,2) α2,

C2/C0,2

0 796 0 1 2138 0 1 15 781 0.020 0.980 1859 0.1399 0.869 30 737 0.0773 0.926 1773 0.1871 0.829 60 617 0.254 0.776 1311 0.489 0.613 90 521 0.423 0.655 1132 0.633 0.531 180 490 0.486 0.615 960 0.801 0.449

Max % Removal 38.5 55.1

Table B-29 Results of ozone reaction rate constant and primary elimination degree of pollutant for Bacterial effluent from MBR at HRT = 16 h

Contact time (min)

TOC (mg/L) or C1

- ln (C1/C0,1) α1,

C1/C0,1

COD (mg/L) or C2

- ln (C2/C0,2) α2,

C2/C0,2

0 650 0 1 1938 0 1 15 628 0.0344 0.966 1746 0.1042 0.901 30 527 0.211 0.810 1538 0.231 0.793 60 474 0.317 0.728 1468 0.278 0.758 90 385 0.525 0.592 769 0.925 0.397 180 215 1.109 0.330 519 1.317 0.268

Max % Removal 67.0 73.2

pH [O3]0 (mg/L) k′ (*10-4 s-1) [O3]0

(mg/L) k′ (*10-4 s-1) [O3]0 (mg/L) k′ (*10-4 s-1)

2 0.06 4.22 0.1 4.52 0.1 4.65 6 0.02 4.78 0.04 5.83 0.06 6.43 7 0.004 6.31 0.03 6.58 0.05 6.98 11 0.0007 6.78 0.004 7.08 0.0006 7.33

132

Table B-30 Results of ozone reaction rate constant and primary elimination degree of pollutant for Yeast effluent from MBR at HRT = 24 h

Contact time (min)

TOC (mg/L) or C1

- ln (C1/C0,1) α1,

C1/C0,1

COD (mg/L) or C2

- ln (C2/C0,2) α2,

C2/C0,2

0 1122 0 1 2664 0 1 15 1094 0.0253 0.975 2589 0.0284 0.972 30 998 0.1168 0.890 2437 0.0891 0.915 60 898 0.223 0.800 1980 0.297 0.743 90 772 0.374 0.688 1676 0.464 0.629 180 703 0.467 0.627 1295 0.722 0.486

Max % Removal 37.3 51.4

Table B-31 Results of ozone reaction rate constant and primary elimination degree of pollutant for Bacterial effluent from MBR at HRT = 24 h

Contact time (min)

TOC (mg/L) or C1

- ln (C1/C0,1) α1,

C1/C0,1

COD (mg/L) or C2

- ln (C2/C0,2) α2,

C2/C0,2

0 786 0 1 2260 0 1 15 704 0.110 0.896 2133 0.0582 0.943 30 641 0.204 0.816 1610 0.339 0.712 60 545 0.365 0.694 1322 0.537 0.585 90 503 0.445 0.641 1241 0.599 0.549 180 388 0.707 0.493 664 1.225 0.294

Max % Removal 50.7 70.6

133

6. Results of ozonation factor Table B-32 Ozonation factor for Yeast and Bacterial effluent from MBR at HRT = 16h

Yeast at HRT = 16h Bacteria at HRT = 16h Contact time (min) O3 in off-gas

(mg/L) Ozonation

factor O3 in off-gas

(mg/L) Ozonation

factor 15 13.98 1.450 20.1 1.316 30 19.04 0.791 26.9 0.751 60 14.57 0.366 15.31 0.303 90 10.47 0.229 10.74 0.187 180 6.76 0.108 7.26 0.089

Table B-33 Ozonation factor for Yeast and Bacterial effluent from MBR at HRT = 24h

Yeast at HRT = 24h Bacteria at HRT = 24h Contact time (min) O3 in off-gas

(mg/L) Ozonation

factor O3 in off-gas

(mg/L) Ozonation

factor 15 11.0 1.948 11.0 1.364 30 15.92 1.055 26.4 0.898 60 14.83 0.518 15.09 0.364 90 10.81 0.324 10.33 0.225 180 6.63 0.152 7.08 0.107

134

Appendix C

Results of chemical oxidation of MBR effluent by Ozone (O3)

135

Appendix C: Results of chemical oxidation of MBR effluent by Ozone (O3)

1. Effect of Ozonation on COD and TOC removal efficiency Table C-1 Results of COD, TOC, and Color removal efficiency after ozonation at different ozone dosage and contact time

Yeast Ozone concentration

(mg/L) Contact time

(min) COD (mg/L) TOC (mg/L) Color (ADMI)

45 90 1,392 623.0 28 60 90 1,357 621.0 18 75 90 1,253 542.4 13 45 60 1,775 712.2 49 60 60 1,601 661.0 23 75 60 1,392 640.0 28 45 30 2,018 775.0 72 60 30 1,810 766.1 64 75 30 1,705 728.5 52

Bacteria Ozone concentration

(mg/L) Contact time

(min) COD (mg/L) TOC (mg/L) Color (ADMI)

45 90 1,601 530.1 45 60 90 1,322 472.6 21 75 90 1,183 384.8 16 45 60 1,531 565.1 51 60 60 1,462 510.7 30 75 60 1,427 473.6 34 45 30 1,879 590.8 173 60 30 1,810 553.4 127 75 30 1,670 526.6 72

2. Effect of ozone on molecular weight distribution 2.1 Initial Membrane Resistance

Table C-2 Initial Membrane Resistance for MWCO 50 kDa

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 32.9 87.0 5 202 59.6 157.7 5 303 71.8 189.9 5 404 108.5 287.0 5 505 115.2 304.7

Membrane Resistance (m-1) 7.784 E+12

136

Table C-3 Initial Membrane Resistance for MWCO 10 kDa

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 32.9 44.2 5 202 59.6 102.4 5 303 71.8 174.1 5 404 108.5 267.2 5 505 115.2 348.4

Membrane Resistance (m-1) 5.852 E+12

Table C-4 Initial Membrane Resistance for MWCO 5 kDa

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 7.2 19.0 5 202 13.8 36.5 5 303 21.4 56.6 5 404 28.1 74.3 5 505 35.8 94.7

Membrane Resistance (m-1) 2.408 E+13 Table C-5 Initial Membrane Resistance for MWCO 3.5 kDa

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 1.2 3.17 5 202 2 5.29 5 303 4 10.58 5 404 5.2 13.76 5 505 7.1 18.78

Membrane Resistance (m-1) 1.131 E+14 Table C-6 Initial Membrane Resistance for MWCO 1 kDa

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 0 0 5 202 0 0 5 303 0.2 0.529 5 404 2 5.29 5 505 3.1 8.20

Membrane Resistance (m-1) 1.804 E+14

137

y = 1.7255x - 51.196R2 = 0.9648

0

100

200

300

400

500

600

0 50 100 150 200 250 300 350

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-1 Initial membrane resistance for MWCO 50 kDa

y = 1.2973x + 60.111R2 = 0.9931

0100200300400500600

0 50 100 150 200 250 300 350 400

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-2 Initial membrane resistance for MWCO 10 kDa

y = 5.3367x + 2.8759R2 = 0.9994

0

200

400

600

0 10 20 30 40 50 60 70 80 90 100

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-3 Initial membrane resistance for MWCO 5 kDa

138

y = 25.076x + 44.309R2 = 0.9851

0

200

400

600

0 2 4 6 8 10 12 14 16 18 20

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-4 Initial membrane resistance for MWCO 3.5 kDa

y = 38.98x + 193.7R2 = 0.8372

0100200300400500600

0 2 4 6 8 10

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-5 Initial membrane resistance for MWCO 1 kDa

2.2 Membrane Resistance of the used membrane Table C-7 Membrane Resistance for MWCO 50 kDa after used

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 15.9 42.1 5 202 27.8 73.5 5 303 32.7 86.5 5 404 40.0 105.8 5 505 50.8 134.4

Membrane Resistance (m-1) 2.064 E+13

139

Table C-8 Membrane Resistance for MWCO 10 kDa after used

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 9.8 25.9 5 202 20.8 55.0 5 303 30.4 80.4 5 404 38.6 102.1 5 505 47.4 125.4

Membrane Resistance (m-1) 1.846 E+13

Table C-9 Membrane Resistance for MWCO 5 kDa after used

Time (min) TMP (kPa) Volume (mL) Filtration flux, J (L/m2.h)

5 101 4.6 12.2 5 202 8.7 23.0 5 303 12.8 33.9 5 404 15.2 40.2 5 505 20.3 53.7

Membrane Resistance (m-1) 4.505 E+13

y = 4.5746x - 101.65R2 = 0.9824

0100200300400500600

0 20 40 60 80 100 120 140 160

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-6 Membrane resistance for MWCO 50 kDa after used

y = 4.092x - 15.238R2 = 0.9967

0100200300400500600

0 20 40 60 80 100 120 140

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-7 Membrane resistance for MWCO 10 kDa after used

140

y = 9.9863x - 22.446R2 = 0.9913

0100200300400500600

0 10 20 30 40 50 60

Filtration flux (L/m2.h)

TM

P (k

Pa)

Figure C-8 Membrane resistance for MWCO 5 kDa after used

2.2 The role of stirring on membrane permeate flux in MWCO experiment Table C-10 COD concentration in each fraction based on molecular weight for YMBR (without stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD

Yeast 100 2,076 2,076 1,538 >50 k 51.4 1,882 967 62.9

10-50 k 0 0 0 0 5-10 k 19.7 1,330 262 17.04 3.5-5 k 12.9 1,233 159 10.34 1-3.5 k 11.8 1,038 122.5 7.96

<1 k 4.2 649 27.2 1.77

Table C-11 COD concentration in each fraction based on molecular weight for BMBR (without stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD

Bact. 100 1,946 1,946 1,646 >50 k 50.4 1,817 916 55.6

10-50 k 7.9 2,206 1,74.3 10.6 5-10 k 38.6 1,363 526 32.0 3.5-5 k 3.1 973 30.2 1.8 1-3.5 k 0 0 0 0

<1 k 0 0 0 0

141

Table C-12 COD concentration in each fraction based on molecular weight for YMBR (with stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD

Yeast 100 1,996 1,996 1,427 >50 k 0 0 0 0

10-50 k 2.2 1,742 38 2.68 5-10 k 38.4 1,487 571 40.0 3.5-5 k 52.3 1,402 733 51.4 1-3.5 k 4.1 1,133 46 3.25

<1 k 3 1,274 38 2.68

Table C-13 COD concentration in each fraction based on molecular weight for BMBR (with stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD

Bact. 100 1,911 1,911 1,615 >50 k 19.4 1,657 321 19.9

10-50 k 0 0 0 0 5-10 k 19.2 1,742 334 20.7 3.5-5 k 50.2 1,657 832 51.5 1-3.5 k 9.9 1,062 105 6.51

<1 k 1.3 1,699 22 1.37

2.3 Effect of ozone on molecular weight distribution with low and high ozone dosage in terms of COD concentration

Table C-14 COD concentration in each fraction based on molecular weight for O3 Yeast at ozone conc. of 45 mg/L, 30 minutes (without stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD O3 Yeast 100 2,018 2,018 1,479

>50 k 65.8 1,557 1,025 69.3 10-50 k 3.7 0 0 0 5-10 k 13.1 1,492 195 13.2 3.5-5 k 6.2 1,427 89 6.0 1-3.5 k 10.4 1,492 155 10.5

<1 k 0.8 1,946 15 1.1

142

Table C-15 COD concentration in each fraction based on molecular weight for O3 Bact at ozone conc. of 45 mg/L, 30 minutes (without stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD O3 Bact 100 1,879 1,879 1,424 >50 k 31.4 1,427 448 31.5

10-50 k 37 1,492 552 38.8 5-10 k 14.7 1,363 200 14.1 3.5-5 k 10.1 1,427 144 10.1 1-3.5 k 6.8 1,168 79 5.6

<1 k 0 0 0 0 Table C-16 COD concentration in each fraction based on molecular weight for O3 Yeast at ozone conc. of 75 mg/L, 90 minutes (without stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD O3 Yeast 100 1,200 1,200 1,029

>50 k 0 0 0.0 0 10-50 k 6.4 909 58 5.65 5-10 k 30.9 982 303 29.3 3.5-5 k 45.4 1,054 479 46.5 1-3.5 k 16.7 1,054 176 17.11

<1 k 0.6 1,091 7 0.64 Table C-17 COD concentration in each fraction based on molecular weight for O3 Bact at ozone conc. of 75 mg/L, 45 minutes (without stirrer)

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD O3 Bact 100 1,563 1,563 1,328 >50 k 0 0 0 0

10-50 k 12 1,273 153 11.50 5-10 k 19.5 1,200 234 17.61 3.5-5 k 45.4 1,418 644 48.5 1-3.5 k 22.4 1,273 285 21.5

<1 k 0.7 1,818 13 0.96

143

2.4 Effect of ozone on molecular weight distribution with low and high ozone dosage in terms of TOC concentration

Table C-18 TOC concentration in each fraction based on molecular weight for YMBR (without stirrer)

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC

Yeast 100 796.3 796.3 663.4 >50 k 51.4 765.2 393.3 59.3

10-50 k 0 0 0 0 5-10 k 19.7 613.6 120.9 18.2 3.5-5 k 12.9 518.7 66.9 10.1 1-3.5 k 11.8 466.4 55.0 8.3

<1 k 4.2 648 27.2 4.1 Table C-19 TOC concentration in each fraction based on molecular weight for BMBR (without stirrer)

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC

Bact 100 650 650 596.5 >50 k 50.4 671.5 338.4 56.7

10-50 k 7.9 758 59.9 10.03 5-10 k 38.6 477.6 184.4 30.9 3.5-5 k 3.1 446.4 13.84 2.32 1-3.5 k 0 0 0 0

<1 k 0 0 0 0

Table C-20 TOC concentration in each fraction based on molecular weight for O3 Yeast at ozone conc. of 45 mg/L, 30 minutes (without stirrer)

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC O3 Yeast 100 775 775 599.1

>50 k 50 626.3 313.2 52.3 10-50 k 19.5 565 110.2 18.4 5-10 k 13.1 558.9 73.2 12.2 3.5-5 k 6.2 563.5 34.9 5.8 1-3.5 k 10.4 617.4 64.2 10.7

<1 k 0.8 421.2 3.4 0.6

144

Table C-21 TOC concentration in each fraction based on molecular weight for O3 Bact at ozone conc. of 45 mg/L, 30 minutes (without stirrer)

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC O3 Bact 100 733.5 733.5 586.4 >50 k 31.4 575.8 180.8 30.8

10-50 k 37 626.4 231.8 39.5 5-10 k 14.7 586.2 86.2 14.69 3.5-5 k 10.1 553.6 55.9 9.54 1-3.5 k 6.8 466.5 31.7 5.41

<1 k 0 0 0 0 Table C-22 TOC concentration in each fraction based on molecular weight for O3 Yeast at ozone conc. of 75 mg/L, 90 minutes (without stirrer)

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC O3 Yeast 100 637.6 737.6 657.9

>50 k 0 0 0 0 10-50 k 6.4 539.3 34.5 5.25 5-10 k 30.9 572.2 176.8 26.9 3.5-5 k 45.4 576.7 261.8 39.8 1-3.5 k 16.7 488.3 81.5 12.40

<1 k 0.6 478.35 2.87 0.44 Table C-23 TOC concentration in each fraction based on molecular weight for O3 Bact at ozone conc. of 75 mg/L, 45 minutes (without stirrer)

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC O3 Bact 100 100 605.1 605.1 >50 k 0 0 0 0

10-50 k 12 12 556.6 66.8 5-10 k 19.5 19.5 556.9 108.6 3.5-5 k 45.4 45.4 545.7 247.7 1-3.5 k 22.4 22.4 500.3 112.1

<1 k 0.7 0.7 592.7 4.1 3. Effect of pH and alkalinity on Ozonation Table C-24 Effect of Alkalinity on ozone consumption of O3 Bact. at O3 concentration = 75 mg/L, 45 minutes

pH mL of 0.02 N H2SO4

Alkalinity (mg/L as CaCO3)

mL of Na2S2O3 (0.641 N)

Ozone in off-gas (mg/L)

Ozone consumption (mg ozone)

2 - 0 34.4 19.6 1,495.8 4 - 0 33.1 18.86 1,515.8 5 4.3 86 35.6 20.284 1,477.3

7.69 23 468 34.6 19.72 1,492.5 11 69.1 1,382 32.6 18.58 1,523.5

145

Table C-25 Effect of pH variation on COD degradation for yeast and bacterial effluent at ozone concentration = 30 mg/L, contact time = 45 minutes

pH COD (mg/L) Yeast effluent

pH COD (mg/L) Bacterial effluent

3.63 (normal pH for yeast)

2,399 3.50 1,714

7.05 2,742 6.98 (normal pH for bacteria)

1,684

11.01 2,313 11.01 1,714

4. Parameter optimization 4.1 Effect of contact time variation on the degradation of COD Table C-26 Effect of contact time variation on the degradation of COD for yeast effluent at ozone concentration of 75 mg/L

Yeast

Contact time (min)

COD (mg/L)

% COD Degradation

Ozone mass in

feed (mg ozone)

Ozone dosage (mg ozone/mg

COD)

Ozone mass

residual (mg ozone)

0 2,138 - - - - 15 1,858 13.07 675 0.316 125.8 30 1,773 17.07 1,350 0.632 342.7 45 1,687 21.1 2,025 0.947 502.4 60 1,311 38.7 2,700 1.263 524.5 75 1,168 45.4 3,375 1.579 560.4 90 1,087 49.2 4,050 1.895 565.5 180 960 55.1 8,100 3.79 730.5

Table C-27 Effect of contact time variation on the degradation of COD for bacterial effluent at ozone concentration of 75 mg/L

Bacteria

Contact time (min)

COD (mg/L)

% COD Degradation

Ozone mass in

feed (mg ozone)

Ozone dosage (mg ozone/mg

COD)

Ozone mass

residual (mg ozone)

0 1,938 - - - - 15 1,617 16.58 675 0.348 180.9 30 1,668 13.96 1,350 0.697 484.2 45 1,305 32.65 2,025 1.045 527.2 60 1,468 24.26 2,700 1.393 551.0 75 1,362 29.72 3,375 1.741 573.5 90 769 60.33 4,050 2.090 580.0 180 519 73.22 8,100 4.179 783.6

146

4.2 Effect of contact time variation on the biodegradability of the leachate Table C-28 Effect of contact time variation on the biodegradability of the leachate for yeast effluent at ozone dosage of 75 mg/L

Yeast

Contact time (min) COD (mg/L) BOD5 (mg/L) BOD/COD 0 2,138 58.1 0.02716 15 1,858 40.8 0.02196 30 1,773 8.4 0.00474 45 1,687 5.6 0.00332 60 1,311 6.3 0.00481 75 1,168 6.0 0.00514 90 1,087 5.6 0.00515 180 960 1.4 0.00146

Table C-29 Effect of contact time variation on the biodegradability of the leachate for bacterial effluent at ozone dosage of 75 mg/L

Bacteria

Contact time (min) COD (mg/L) BOD5 (mg/L) BOD/COD 0 1,938 66.3 0.03421 15 1,617 122.1 0.07552 30 1,668 94.9 0.05691 45 1,305 110.6 0.08472 60 1,468 14.9 0.01015 75 1,362 12.8 0.00940 90 769 10.3 0.01340 180 519 4.2 0.00809

4.3 Effect of ozonation on specific ozone consumption Table C-30 Effect of ozonation on specific ozone consumption for yeast and bacterial effluent at ozone concentration of 75 mg/L

Specific ozone consumption (mg O3/mg COD removed) Contact time (min)

Yeast Bacteria 0 0 0 15 1.97 1.54 30 2.76 3.20 45 3.38 2.37 60 2.63 4.57 75 2.90 4.86 90 3.32 2.97 180 6.26 5.16

147

5. Effect of ozonation on optimum ozone condition 5.1 Effect of the optimum ozone condition on TOC removal efficiency Table C-31 Effect of ozone on TOC removal efficiency for yeast and bacterial effluent at optimum ozone condition

TOC (mg/L) % TOC Removal Contact time

(min) Yeast Bacteria Yeast Bacteria

0 796.3 742.7 - - 15 780.5 628.4 1.980 15.39 30 737.1 526.6 7.43 29.1 45 699.4 520.8 12.17 29.9 60 617.8 473.6 22.4 36.2 75 537.5 450.2 32.5 39.9 90 521.4 384.8 34.5 48.2 180 489.6 214.6 38.5 71.1

5.2 Effect of the optimum ozone condition on Color removal efficiency Table C-32 Effect of ozone on Color removal efficiency for yeast and bacterial effluent at optimum ozone condition

Color (mg/L) % Color Removal Contact time

(min) Yeast Bacteria Yeast Bacteria

0 330 430 - - 15 85 134 74.2 68.8 30 66 66 80.0 84.7 45 59 42 82.1 90.2 60 41 24 87.6 94.4 75 31 34 90.6 92.1 90 17 13 94.9 97.0 180 15 18 95.5 95.8

5.3 Effect of optimum ozone condition on molecular weight distribution

Table C-33 COD concentration in each fraction based on molecular weight for O3 Yeast at ozone conc. of 75 mg/L, 90 minutes

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD O3 Yeast 100 1,317 1,317 1,159

>50 k 0 0 0 0 10-50 k 9.1 1,147 104.4 9.0 5-10 k 24.9 1,062 264 22.8 3.5-5 k 53.9 1,232 664 57.3 1-3.5 k 10.2 1,019 104 9.0

<1 k 1.9 1,180 22.4 1.9

148

Table C-34 COD concentration in each fraction based on molecular weight for O3 Bact. at ozone conc. of 75 mg/L, 45 minutes

MWCO Volume (mL) COD (mg/L) COD* (mg/L) % COD O3 Bact. 100 1,487 1,487 1,291

>50 k 3.3 1,487 49.1 3.8 10-50 k 13.2 1,062 140.2 10.9 5-10 k 17.4 1,062 184.8 14.3 3.5-5 k 55.9 1,402 783.6 60.7 1-3.5 k 9.3 1,317 122.5 9.5

<1 k 0.9 1,214 10.9 0.8

Table C-35 TOC concentration in each fraction based on molecular weight for YMBR

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC Yeast 100 760 760 722 >50 k 0 0 0 0

10-50 k 2.2 833 18.32 2.54 5-10 k 38.4 734 281 39.0 3.5-5 k 52.3 723 378 52.4 1-3.5 k 4.1 640 26.2 3.64

<1 k 3 581 17.43 2.42

Table C-36 TOC concentration in each fraction based on molecular weight BMBR

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC Bact. 100 614 614 606 >50 k 19.4 655 127.1 21.0

10-50 k 0 0 0 0 5-10 k 19.2 614 118.2 19.52 3.5-5 k 50.2 567 285 47.0 1-3.5 k 9.9 683 67.7 11.17

<1 k 1.3 593 7.7 1.27

Table C-37 TOC concentration in each fraction based on molecular weight for O3 Yeast. at ozone conc. of 75 mg/L, 90 minutes

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC O3 Yeast 100 537 537 538

>50 k 0 0 0 0 10-50 k 9.1 523 47.6 8.85 5-10 k 24.9 533 132.7 24.7 3.5-5 k 53.9 554 298 55.5 1-3.5 k 10.2 490 49.9 9.29

<1 k 1.9 475 9.02 1.68

149

Table C-38 TOC concentration in each fraction based on molecular weight for O3 Bact. at ozone conc. of 75 mg/L, 45 minutes

MWCO Volume (mL) TOC (mg/L) TOC* (mg/L) % TOC O3 Bact. 100 600 600 568

>50 k 3.3 589 19.44 3.42 10-50 k 13.2 574 75.8 13.35 5-10 k 17.4 599 104.2 18.37 3.5-5 k 55.9 565 315.9 55.7 1-3.5 k 9.3 513 47.7 8.41

<1 k 0.9 507 4.56 0.80 Table C-39 Color in each fraction based on molecular weight for YMBR

MWCO Volume (mL) Color (mg/L) Color* (mg/L) % Color Yeast 100 305 305 142.4 >50 k 0 0 0 0

10-50 k 2.2 200 4.4 3.09 5-10 k 38.4 148 56.8 39.9 3.5-5 k 52.3 136 71.1 49.9 1-3.5 k 4.1 143 5.9 4.12

<1 k 3 140 4.2 2.95 Table C-40 Color in each fraction based on molecular weight for BMBR

MWCO Volume (mL) Color (mg/L) Color* (mg/L) % Color Bact. 100 404 404 331 >50 k 19.4 401 77.8 23.5

10-50 k 0 0 0 0 5-10 k 19.2 353 67.8 20.5 3.5-5 k 50.2 330 165.7 50.1 1-3.5 k 9.9 175 17.3 5.24

<1 k 1.3 170 2.21 0.67

Table C-41 Color in each fraction based on molecular weight for O3 Yeast. at ozone conc. of 75 mg/L, 90 minutes

MWCO Volume (mL) Color (mg/L) Color* (mg/L) % Color O3 Yeast 100 12 12 11

>50 k 0 0 0 0 10-50 k 9.1 11 1.00 9.10 5-10 k 24.9 11 2.74 24.9 3.5-5 k 53.9 11 5.93 53.9 1-3.5 k 10.2 11 1.12 10.2

<1 k 1.9 11 0.21 1.90

150

Table C-42 Color in each fraction based on molecular weight for O3 Bact. at ozone conc. of 75 mg/L, 45 minutes

MWCO Volume (mL) Color (mg/L) Color* (mg/L) % Color O3 Bact. 100 51 51 39.6 >50 k 3.3 44 1.45 3.66

10-50 k 13.2 38 5.02 12.66 5-10 k 17.4 44 7.66 19.32 3.5-5 k 55.9 38 21.2 53.6 1-3.5 k 9.3 42 3.91 9.86

<1 k 0.9 40 0.36 0.91

6. The products after ozonation Table C-43 Effect of contact time variation on pH reduction for yeast and bacterial effluent after ozonation at optimum ozone condition

pH Contact time Yeast Bacteria 0 3.52 7.14 15 3.31 6.88 30 3.22 6.74 45 3.16 6.41 60 3.09 5.81 75 3.00 5.15 90 2.94 4.70

151

Appendix D

Results of chemical oxidation of MBR effluent by Ozone plus Hydrogen Peroxide (Perozone)

152

Appendix D: Results of chemical oxidation of MBR effluent by Ozone plus Hydrogen Peroxide (Perozone)

1. Optimization of waiting time after the addition of Hydrogen Peroxide

Table D-1 Optimization of the waiting time after the addition of H2O2 for Yeast effluent

Waiting time (min) COD (mg/L) TOC (mg/L) Color (ADMI) Yeast effluent 2,036 778 324

0 1,209 689 10 10 1,200 591 10 20 1,209 598 10 30 1,200 584 10

Table D-2 Optimization of the waiting time after the addition of H2O2 for Bacterial effluent

Waiting time (min) COD (mg/L) TOC (mg/L) Color (ADMI) Bacterial effluent 1,963 777 438

0 1,400 639 66 10 1,282 639 63 20 1,227 613 41 30 1,282 617 41

2. Optimization of H2O2 concentration in term of H2O2/O3 ratio

Table D-3 Optimization of H2O2/O3 for yeast effluent

H2O2/O3 COD (mg/L) TOC (mg/L) Color (ADMI) Yeast effluent 2,036 778 324

0.1 1,145 654 10 0.2 1,109 670 10 0.3 1,200 670 10 0.4 1,236 708 11.5 0.5 1,254 715 12

Table D-4 Optimization of H2O2/O3 for bacterial effluent

H2O2/O3 COD (mg/L) TOC (mg/L) Color (ADMI) Bacterial effluent 1,963 777 438

0.1 1,245 712 73 0.2 1,218 697 48 0.3 1,227 694 41 0.4 1,227 689 39 0.5 1,264 693 38

153

3. Optimization of Perozone contact time

Table D-5 Optimization of perozone contact time for yeast effluent

Contact time (min) COD (mg/L) TOC (mg/L) Color (ADMI) BOD5 (mg/L)

Yeast effluent 2,100 764 351 58.1 30 1,659 698 41 15 45 1,588 668 53 10 60 1,324 602 20 10 75 1,288 608 23 5 90 1,244 601 18 10

Table D-6 Optimization of perozone contact time for bacterial effluent

Contact time (min) COD (mg/L) TOC (mg/L) Color (ADMI) BOD5 (mg/L)

Bacterial effluent 2,065 688 435 66.3 15 1,765 905 276 32.4 30 1,659 685 107 9.8 45 1,482 700 127 7.0 60 1,456 595 55 11.2 90 1,209 551 20 7.0

4. Comparison of efficiency between ozone and perozone

Table D-7 Comparison between O3 and O3 + H2O2 of yeast effluent in term of COD

Ozone dosage (mg ozone/mg COD)

% COD degradation Contact time (min)

Ozone mass in feed

(mg ozone) O3 O3 + H2O2 O3 O3 + H2O2 0 - - - - - 30 1,350 0.632 0.643 17.1 21.0 45 2,025 0.947 0.964 21.1 24.4 60 2,700 1.263 1.286 38.7 37.0 75 3,375 1.579 1.607 45.4 38.7 90 4,050 1.895 1.928 49.2 40.8

Table D-8 Comparison between O3 and O3 + H2O2 of bacterial effluent in term of COD

Ozone dosage

(mg ozone/mg COD) % COD degradation Contact

time (min)

Ozone mass in feed

(mg ozone) O3 O3 + H2O2 O3 O3 + H2O2 0 - - - - - 15 675 0.348 0.327 16.6 14.5 30 1,350 0.697 0.654 14.0 19.7 45 2,025 1.045 0.981 32.7 28.2 60 2,700 1.393 1.308 24.3 29.5 90 4,050 2.09 1.961 60.3 41.5

154

Table D-9 Comparison between O3 and O3 + H2O2 of yeast effluent in term of TOC

Ozone dosage (mg ozone/mg TOC)

% COD degradation Contact time (min)

Ozone mass in feed

(mg ozone) O3 O3 + H2O2 O3 O3 + H2O2 0 - - - - - 30 1,350 1.695 1.79 7.4 8.6 45 2,025 2.54 2.65 12.2 12.5 60 2,700 3.39 3.54 22.4 21.2 75 3,375 4.24 4.42 32.5 20.4 90 4,050 5.09 5.30 34.5 21.3

Table D-10 Comparison between O3 and O3 + H2O2 of bacterial effluent in term of TOC

Ozone dosage

(mg ozone/mg TOC) % COD degradation Contact

time (min)

Ozone mass in feed

(mg ozone) O3 O3 + H2O2 O3 O3 + H2O2 0 - - - - - 15 675 1.038 0.98 15.4 - 30 1,350 2.08 1.96 29.1 0.436 45 2,025 3.11 2.94 29.9 - 60 2,700 4.15 3.92 36.2 13.54 90 4,050 6.23 5.88 48.2 20.0

Table D-11 Comparison between O3 and O3 + H2O2 of yeast effluent in term of Color

Ozone dosage

(mg ozone/mg Color) % COD degradation Contact

time (min)

Ozone mass in feed

(mg ozone) O3 O3 + H2O2 O3 O3 + H2O2 0 - - - - - 30 1,350 4.09 3.85 80.0 88.3 45 2,025 6.14 5.77 82.1 84.9 60 2,700 8.18 7.69 87.6 94.3 75 3,375 10.23 9.62 90.6 93.5 90 4,050 12.27 11.54 94.9 94.9

Table D-12 Comparison between O3 and O3 + H2O2 of bacterial effluent in term of Color

Ozone dosage

(mg ozone/mg Color) % COD degradation Contact

time (min)

Ozone mass in feed

(mg ozone) O3 O3 + H2O2 O3 O3 + H2O2 0 - - - - - 15 675 1.570 1.55 68.8 36.6 30 1,350 3.14 3.10 84.7 75.4 45 2,025 4.71 4.66 90.2 70.8 60 2,700 6.28 6.21 94.4 87.4 90 4,050 9.42 9.31 97.0 95.4

155

Appendix E

Results of continuous system by combining MBR and Ozonation

156

Appendix E: Results of continuous system by combining MBR and Ozonation

1. COD removal efficiency of MBR system Table E-1 Continuous data of COD elimination from combined system of both effluents

Influent COD (mg/L) Effluent COD (mg/L) % COD Removal Operating day (days) Yeast Bacteria Yeast Bacteria Yeast Bacteria

0 8,400 8,400 2,776 1,970 67.0 76.5 1 8,400 8,400 2,609 2,417 68.9 71.2 2 5,174 5,218 2,609 2,000 49.6 61.7 3 5,174 5,218 2,543 1,988 50.8 61.9 4 3,806 4,970 2,382 1,906 37.4 61.7 5 5,647 4,765 2,240 1,760 60.3 63.1 6 4,800 5,700 2,480 2,000 48.3 64.9 7 5,500 6,500 1,967 1,731 64.2 73.4 8 4,525 4,131 2,676 2,081 40.9 49.6

9 * 5,097 7,646 2,560 2,160 49.8 71.7 10 4,100 4,400 2,000 1,760 51.2 60.0 11 6,800 6,400 2,560 2,040 62.4 68.1 12 8,300 9,800 2,477 1,858 70.2 81.0 13 6,774 6,193 2,400 1,935 64.6 68.8 14 7,548 7,548 2,438 1,981 67.7 73.8 15 6,476 7,429 2,438 1,829 62.4 75.4 16 7,143 6,668 2,439 2,361 65.9 64.6 17 7,645 10,548 2,246 2,284 70.6 78.3 18 7,645 9,193 2,671 2,516 65.1 72.6 19 7,838 7,838 2,419 2,112 69.1 73.1 20 4,704 6,720 2,342 1,997 50.2 70.3 21 6,240 6,336 2,612 2,342 58.1 63.0 22 8,544 6,432 2,625 2,175 69.3 66.2 23 6,188 7,500 2,663 2,100 57.0 72.0 24 6,188 6,000 2,513 2,138 59.4 64.4 25 6,000 5,813 2,380 1,904 60.3 67.2 26 5,851 6,843 2,102 1,785 64.1 73.9 27 4,066 4,264 2,063 1,904 49.3 55.3 28 4,661 4,760 2,261 1,983 51.5 58.3 29 6,446 5,058 2,261 1,904 64.9 62.4 30 5,653 5,851 2,301 2,420 59.3 58.6 31 4918 5,901 2,597 2,282 47.2 61.3 32 5,410 6,000 2,518 2,007 53.5 66.6 33 4,622 4,918 2,557 1,889 44.7 61.6

* Start recirculation

157

Table E-2 COD of leachate before and after ozonation of combined system

COD (mg/L), Combined system YMBR Ozonated YMBR BMBR Ozonated BMBR

Mean 2,418 1,391 2,067 1,473 Max 2671 1,864 2,516 1,928 Min 2,000 1,151 1,760 960

Table E-3 COD of leachate before and after ozonation of original system

COD (mg/L), Original system YMBR Ozonated YMBR BMBR Ozonated BMBR

Mean 2,855 1,765 2,144 1,814 Max 2,973 1,911 2,513 2,176 Min 2,722 1,676 1,934 1,504

158

Appendix F

Results of chemical oxidation of the mixed liquor in MBR reactors by Ozone

159

Appendix F: Results of chemical oxidation of the mixed liquor in MBR reactors by Ozone

1. Effect of ozonation on sludge minimization Table F-1 The fraction of yeast sludge at various ozone dosage

Ozone dose (mgO3/mgSS)

Solubilization, mg/L (SCOD

change)

Mineralization, mg/L (TCOD

change) UMS (mg/L) Residual

(mg/L) % Sludge Reduction

0 0 0 5,250 16,500 0 0.02 2,250 750 4,500 14,250 10.4 0.05 2,625 1,500 6,188 11,438 23.3 0.1 3,750 2,250 7,500 8,250 38.0 0.2 5,625 3,000 7,125 6,000 48.3 0.5 4,500 4,500 9,000 3,750 58.7

Table F-2 The fraction of bacterial sludge at various ozone dosage

Ozone dose (mgO3/mgSS)

Solubilization, mg/L (SCOD

change)

Mineralization, mg/L (TCOD

change) UMS (mg/L) Residual

(mg/L) % Sludge Reduction

0 0 0 7,875 18,375 0 0.02 1,500 3,750 5,250 15,750 10.0 0.05 1,875 3,750 5,625 15,000 12.9 0.1 2,250 2,250 5,438 16,313 7.9 0.2 4,875 3,750 5,625 12,000 24.3 0.5 3,750 4,125 7,313 11,063 27.9

2. Effect of ozonation on the solid concentration

Table F-3 Solid concentration after ozonation at various ozone dosages for both sludge

Yeast sludge Ozone dose (mgO3/mgSS) MLSS (mg/L) MLVSS (mg/L) MLVSS/MLSS

0 24,692 12,425 0.5032 0.02 17,233 10,623 0.6164 0.05 18,500 10,150 0.5486 0.1 20,950 12,033 0.5743 0.2 18,500 9,950 0.5378 0.5 17,167 9,533 0.5553

Bacterial sludge Ozone dose (mgO3/mgSS) MLSS (mg/L) MLVSS (mg/L) MLVSS/MLSS

0 44,383 17,300 0.3897 0.02 29,633 14,300 0.4825 0.05 28,850 14,033 0.4864 0.1 38,517 17,833 0.4630 0.2 42,983 20,950 0.4873 0.5 35,750 18,300 0.5118

160

Table F-4 Settle volume of bacterial sludge after 30 minutes at various ozone dosages

Ozone dose (mgO3/mgSS)

Volume of sludge used (mL)

Settle volume (mL)

Final volume (mL)

0 150 230 1,533 0.02 150 150 1,000 0.05 180 200 1,111 0.1 180 215 1,194 0.2 180 220 1,222 0.5 200 240 1,200

Table F-5 CST results of both sludge before and after ozonation

SS (mg/L) CST (s) CST (s/g SS) Types of sludge Before After Before After Before After

Yeast sludge 15,400 9,800 4,778.5 2,146.3 316.5 219.0 Bacterial sludge 17,700 16,500 5,728.8 3,550.6 323.7 215.2

161

Appendix G

Pictures of the experiments

162

Figure G-1 Experimental set up for Ozonation system

Figure G-3 Ceramic diffuser for ozone column reactor

Figure G-2 Ozone column reactor

163

Figure G-4 Ozone generator type OZ 7510

Figure G-5 Membrane bioreactor system

164

Figure G-6 Yeast and bacterial membrane

bioreactor

Figure G-7 Hg-U tube for pressure measurement

Figure G-8 Ammonia stripping unit

165

Figure G-11 Reactor for sludge ozonation

Figure G-9 Ultrafiltration process for MWCO experiment

Figure G-10 Stirring mechanism inside ultrafiltration unit