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Activated Sludge Separation Problems

BOOK

Activated Sludge Separation Problems

Valter Tandoi | David Jenkins | Jiri Wanner

(2006)

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Additional Information

Book Details

ISBN
978-1-78040-306-9
Edition
1
Language
English
Pages
218
Subjects
The environment
Environmental science, engineering & technology
Water supply & treatment

Abstract

The Activated Sludge (AS) Process is old technology but is still widely adopted worldwide for its convenience and simplicity: an impressive number (many hundred of thousands) of this kind of system are in operation. Occasionally, problems such as bulking and foaming occur, causing regulation violations and large investment is often required immediately to control them. For this reason, an intense research effort has been made during the last few decades to face these problems, and this report details the work undertaken by the IWA Specialist Group on Activated Sludge Population Dynamics. This Scientific and Technical Report  describes the main reasons fslyuor the growth of the different filamentous microorganisms in activated sludge, and the biological molecular tools available today for the identification of the main biomass components. The wide range of experiences around the world is documented and the methods to avoid the proliferation of these organisms are presented and critically reviewed. Activated Sludge Separation Problems consists of seven chapters, presenting up-to-date technical and scientific aspects of these processes.   Scientific and Technical Report No. 16

Table of Contents

Section Title Page Action Price
Contents 6
1.0 Wastewater characterization 16
1.1 INTRODUCTION 16
1.2 GROSS PARAMETERS 17
1.3 PHYSICAL PROPERTIES 18
1.4 ORGANIC MATTER 18
1.5 INORGANIC MATTER 20
1.6 BIODEGRADABILITY 20
1.6.1 COD, Nitrogen fractionation 20
1.6.2 Evaluation methods 22
1.6.2.1 Carbonaceous substrate (COD) 22
1.6.2.2 Nitrogen and phosphorus 24
1.7 REFERENCES 24
2.0 The Microbiology of Activated Sludge Process 26
2.1 INTRODUCTION 26
2.2 MICROORGANISMS IN ACTIVATED SLUDGE 27
Bacteria: cell structure 27
Inclusions 29
2.3 THE IDENTIFICATION OF BACTERIA 30
Conventional taxonomy 30
Molecular taxonomy 30
Molecular characterization of mixed biomass by molecular probes 32
2.4 FILAMENTOUS BACTERIA 32
2.5 MICROTHRIX PARVICELLA 37
Identification of M. parvicella 37
Physiology of M. parvicella 37
2.6 THIOTHRIX 38
2.7 NOSTOCOIDA LIMICOLA 38
2.8 POLYPHOSPHATE ACCUMULATING ORGANISMS (PAO) 39
2.9 GLYCOGEN ACCUMULATING ORGANISMS (GAO) 39
2.10 NITRIFIERS 40
2.11 DENITRIFIERS 40
2.12 QUANTITATIVE ESTIMATION OF FILAMENTOUS BACTERIA IN ACTIVATED SLUDGE 40
2.13 FISH ANALYSIS 41
Sample fixation 42
Paraformaldehyde fixation (Gram negative cells): 42
Ethanol fixation (Gram positive cells): 42
Quick sample fixation 42
Standard protocol for hybridization on slides 43
Hybridization buffer composition 45
Washing buffer composition 45
Sample examination by epifluorescent microscopy 45
2.14\tREFERENCES 46
3.0 AS Separation problems 50
3.1 INTRODUCTION 50
3.2 “WELL-SETTLING” ACTIVATED SLUDGE 51
3.2.1 Requirements 51
3.2.1.1\tMeasurement of settling and thickening properties 52
3.2.2 Microscopic features of well settling activated sludge 54
3.3 ACTIVATED SLUDGE SEPARATION PROBLEMS 54
3.3.1 Poor floc microstructure 54
3.3.1.1 Dispersed growth 54
3.3.1.2 Unsettleable microflocs 55
3.3.1.3 Viscous bulking 56
3.3.2 Poor floc macrostructure 57
3.3.2.1 Filamentous bulking 57
3.3.2.2 Foaming caused by filamentous microorganisms 58
3.3.3 Other reasons 60
3.3.3.1 Rising sludge 60
3.4 SUMMARY 61
3.5 REFERENCES 61
4.0 Aeration tank and secondary clarifier as one system 62
4.1 INTRODUCTION 62
4.2 \tAERATION TANK AND SECONDARY CLARIFIER INTERACTIONS 63
4.2.1 Activated sludge process 63
4.2.2 Secondary clarifier 64
4.2.2.1 General performance, thickening function 64
4.2.3 Separation function 65
4.2.4 BOD5 65
4.2.5 COD 65
4.2.6 Nitrogen and phosphorus 66
4.3\tTHE IMPACT OF AERATION BASIN EQUIPMENT AND OPERATION ON THE PERFORMANCE OF SECONDARY CLARIFIERS 66
4.3.1 Mechanical vs. diffused-air aeration 66
4.3.2 Mixed liquor mixing 67
4.3.3 Degasification and reflocculation in aeration tanks 67
4.4 FEATURES OF SECONDARY CLARIFIER CONSTRUCTION 68
4.4.1 Inlet structure with a flocculation zone 68
4.4.1.1 Principles of a flocculation zone 68
4.4.1.2 Conventional flocculation zones with tangential flow regime 69
4.4.1.3 Novel flocculation zone with deflectors and a vertical flow regime 69
4.4.2 Outlet structure 70
4.4.2.1 Peripheral vs. internal effluent launders 70
4.4.2.1.1 Circular clarifier, peripheral effluent launder (with inboard weir) 70
4.4.2.1.2 Circular clarifier, internal effluent launder (with inset double-sided weirs) 71
4.4.2.1.3 Effluent launders in rectangular clarifiers with longitudinal flow 71
4.4.3 Scum baffles 71
4.5 EFFICIENT SCUM REMOVAL FROM THE SURFACE OF SECONDARY CLARIFIERS 72
4.5.1 Conventional scum boxes 72
4.5.2 “Travelling” scum boxes 73
4.5.3 Pneumatic systems 74
4.6 REMOVAL OF SETTLED AND THICKENED SLUDGE 74
4.6.1 Effect on the final effluent quality 74
4.6.2 Mechanical scrapers 75
4.6.3 Vacuum sludge removal 75
4.7 REFERENCES 76
5.1 INTRODUCTION 77
5.2 SPECIFIC CONTROL METHODS 78
5.2.1 Bulking due to low F/M 78
5.2.1.1 Continuous plug-flow reactors 79
5.2.1.2 Selectors 81
a) Design based on a biokinetic models 81
b) Design based on empirical criteria 82
c) Enhancing the selector effect: anoxic, anaerobic or compartmentalized selectors 82
5.2.1.3 Sequencing batch reactors 84
5.2.1.4 Role of storage phenomena in microbial competition in substrate gradient processes 84
5.2.2 Bulking due to low nutrient concentration 85
5.2.3 Bulking due to low dissolved oxygen concentrations 86
5.2.4 Bulking due to fatty acids in the influent stream: control methods for Microthrix parvicella 86
5.2.5 Microbial and enzymatic preparations 87
5.3 NON SPECIFIC CONTROL METHODS 87
5.3.1 Oxidising agents 89
5.3.2 Weighting or flocculating agents 91
5.3.3 New findings: use of alluminum salts to control Microthrix parvicella 92
5.4 CONTROL OF NON-FILAMENTOUS BULKING (“VISCOUS BULKING”) 92
5.5 AVOIDING POOR SETTLING PROPERTIES: ALTERNATIVE SEPARATIONS OF ACTIVATED SLUDGE 92
6.0 Experience in various countries 98
6.1 INTRODUCTION 98
6.2 AUSTRALIA 98
6.2.1 General situation 98
6.2.2 Foaming filamentous bacteria in Australian Activated Sludge Plants 100
6.2.3 Foaming and Bulking Filamentous Bacteria in Activated Sludge Plants 102
6.2.4 Do the filamentous populations in activated sludge plants change with time? 105
6.2.5 Which operational factor affect filamentous populations and consequently determine incidents of bulking and foaming 105
6.2.6 Control Measures for Bulking and Foaming 106
6.2.7 An Australian Case Study 107
6.2.7.1 Plant Design Features 107
6.2.7.2 Microscopic Features of the Biomass 107
6.2.7.3 Bulking and Foaming Incidents 108
6.2.8 Conclusions 109
6.3 CZECH REPUBLIK 109
6.3.1 Separation problems - situation up to 1980s 109
6.3.2 Separation problems - situation up to mid-1990s 110
6.3.3 WWTPs screening - 1995 - 2000 110
6.3.3.1 Methodology 110
6.3.3.2 Microscopic analysis and sedimentation properties evaluation 111
6.3.4 Results of separation problems and filamentous micro-organisms screening 111
6.3.4.1 Filamentous micro-organism abundance 111
6.3.4.2 Dominant filamentous microorganisms in sludge and foam 112
6.3.5 Development of filamentous population in Czech activated sludge plants between 1997 - 1998 113
6.3.5.1 SVI and total abundance of filaments 113
6.3.5.2 Dominant filamentous microorganisms in activated sludge mixed liquor and foams 113
6.3.6 Screening of eight nutrient removal plants in 2000 116
6.3.6.1 Characterization of monitored WWTPs 116
6.3.6.2 Activated sludges and settling properties 116
6.3.6.3 Dominant filamentous microorganisms in activated sludge mixed liquor 116
6.3.6.4 Biological foams 117
6.3.7 FOAM CONTROL STRATEGIES 117
6.3.7.1 Water sprays 117
6.3.7.2 Skimming (mechanical removal) of foam 118
6.3.7.3 Return activated sludge manipulation 119
6.3.7.4 Manipulation of SRT 119
6.3.7.5 Additional installation of baffles 119
6.3.7.6 Initial contact zones (“selectors“) 120
6.3.7.7 Chlorination of foam 120
6.4 DENMARK, GREECE AND NETHERLANDS 120
6.4.1 General situation 120
6.4.2 Wastewater composition 120
6.4.3 Process configurations 121
6.4.4 Magnitude of bulking and foaming problems in Denmark, Greece and The Netherlands 122
6.4.5 Settling properties in nutrient removal plants 122
6.4.6 Effect of different process conditions on SVI and the size of the filamentous population 125
6.4.7 Composition of the filamentous population 127
6.4.8 Influence of wastewater composition, process configuration and operating parameters on filamentous microorganisms growth 128
6.4.9 Effects of wastewater composition 128
6.4.10 Effects of process configuration 128
6.4.11 Experience with control measures applied 129
6.4.12 Non specific control measures 129
6.4.13 Specific control measures 131
6.4.14 Conclusions 132
6.5 FRANCE 133
6.5.1 General situation 133
6.5.2 Bulking and foaming characterization 133
6.5.3 Bulking and foaming situation 133
6.5.4 Dominant filamentous microorganisms in bulking and foaming sludges 134
6.5.5 Filamentous microorganisms and relationship with plant operation 134
6.5.6 Successful solutions for bulking and foaming control 135
6.5.7 Contact zone as preventive solution 136
6.5.7.1 Key points of contact zone design 137
6.5.8 Control of bulking by Cl2 addition 139
6.6 GERMANY/AUSTRIA 141
6.6.1 General situation 141
6.6.2 Bulking and scum in municipal and industrial wastewater treatment plants 141
6.6.3 Biology and specific troubleshooting measures of filamentous bacteria 143
6.6.4 Sulfur bacteria 143
6.6.5 Gram-negative filamentous bacteria in highly load plants 144
6.6.6 Experience with selectors for industrial wastes in Austria 144
6.6.6.1 Dimensioning and construction of an aerobic selector 144
6.6.6.2 Storage capacity and substrate removal after shock loads, maximum storage capacity 146
6.6.6.3 Influence of SRT and F/M ratio on the substrate elimination in the selector 146
6.6.6.4 Nutrient supply and substrate elimination 146
6.6.6.5 Adaptation of mixed liquor to a selector 147
6.6.6.6 Microbial growth and storage of substrate in the selector 147
6.6.7 Gram-positive filamentous bacteria in low load WWTP 148
6.6.7.1 M. parvicella 148
6.6.7.2 Nocardioform actinomycetes 149
6.6.8 Eikelboom morphotypes Nostocoida limicola, Types 0041/0675, 1851, and 0092 150
6.6.9 Non-specific control measures for sludge bulking and scum 151
6.6.9.1 Addition of aluminum salts for phosphate precipitation 151
6.6.9.2 Addition of layered silicates 151
6.6.9.3 Addition of lime 151
6.6.10 Decreasing the biomass of filamentous bacteria 152
6.7 ITALY 152
6.7.1 General situation 152
6.7.2 Filament surveys 152
6.7.2.1 Puglia Region, Southern Italy 154
6.7.2.2 Lazio Region, Central Italy 154
6.7.2.3 Industrial wastes, Northern Italy 154
6.7.2.4 Survey on 167 Domestic plants. 155
6.7.3 Control methods 155
6.7.3.1 Non specific methods 155
6.7.3.2 Specific methods 155
6.7.4 Case studies at full scale plants 155
6.7.4.1 Reduction of Type 021N by chlorination at the Bagnuolo (Reggio Emilia) municipal plant 155
6.7.4.2 Controlling growth of Nocardia and M. parvicella by selectors at the Moncasale (Reggio Emilia) treatment plant 156
6.7.4.3 Experiences at Varese – Olona plant (northern Italy) for controlling Nocardia and M. parvicella growth by reducing sludge age 157
6.7.4.4 Type 021N and Thiothrix reduction by an anoxic selector at Area Nolana Treatment Plant 157
6.7.4.5 Selector investigations on four large WWTP in Central Italy 158
6.7.4.6 M. parvicella elimination by poly aluminium chloride at Fusina treatment plant 158
6.8 JAPAN 160
6.8.1 General situation 160
6.8.2 Major Filaments Responsible for problems 162
6.8.3 Research on Fundamental Aspects of Filamentous Bulking in Japan/Thailand 162
6.8.4 Control Measures Applied 163
6.8.5 Case Studies 163
Acknowledgement 164
6.9 SOUTH AFRICA 164
6.9.1 General situations 164
6.9.1.1 Extended aeration plants 164
6.9.1.2 Conventional activated sludge 165
6.9.1.3 Plants treating industrial wastes 166
6.9.2 Plants specifically designed for biological nutrient removal (BNR) 166
6.9.2.1 First generation plants 166
6.9.3 Filamentous organisms in South African activated sludge plants 166
6.9.4 Reasons for the growth of filamentous organisms in SA plants. 167
6.9.5 Methods used for the control of bulking and foaming in South Africa 168
6.9.5.1 Physical removal 168
6.9.5.2 Use of toxicants 169
6.9.5.3 Reduction of sludge age 169
6.9.5.4 Elimination and prevention of surface trapping 170
6.9.5.5 Increase in clarification capacity 170
6.9.5.6 Adjustments of dissolved oxygen levels 170
6.9.5.7 Improvements of reactor configuration 170
6.9.6 A case study 171
6.10 UNITED KINGDOM 172
6.10.1 General situation 172
6.10.2 Current situation 173
6.10.3\tControl measures 173
6.10.4\tCase history 175
6.10.4.1 Background 175
6.10.4.2 Solution Process 177
6.10.5 Conclusion 178
6.11 USA 178
6.11.1\tGeneral situations 178
6.11.2\tControl of filaments in activated sludge systems 179
6.11.3\tOther solids separation problems 182
6.11.4\tFoaming 182
6.11.5\tViscous Bulking and Dispersed Growth 184
6.11.6\tConclusions 187
6.12\tREFERENCES 187

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