Hjem

Preface xvii 1 Introduction 1
1.1 Aquaculture engineering 1
1.2 Classification of aquaculture 1
1.3 The farm: technical components in a system 2
1.3.1 Landbased hatchery and juvenile production farm 2
1.3.2 Ongrowing sea cage farm 4
1.4 Future trends: increased importance of aquaculture engineering 6
1.5 This textbook 6 References 7 2 Water Transport 9
2.1 Introduction 9
2.2 Pipe and pipe parts 9
2.2.1 Pipes 9
2.2.2 Valves 12
2.2.3 Pipe parts: fittings 14
2.2.4 Pipe connections: jointing 15
2.2.5 Mooring of pipes 15
2.2.6 Ditches for pipes 16
2.3 Some basic hydrodynamics 17
2.3.1 Boundary layer theory 17
2.3.2 Bernoulli''s equation 18
2.4 Water flow and head loss in channels and pipe systems 19
2.4.1 Water flow 19
2.4.2 Head loss in pipelines 20
2.4.3 Head loss in single parts (fittings) 23
2.4.4 Gravity feed pipes 23
2.5 Pumps 26
2.5.1 Types of pump 26
2.5.2 Some definitions 26
2.5.3 Pumping of water requires energy 29
2.5.4 Centrifugal and propeller pumps 30
2.5.5 Pump performance curves and working point for centrifugal pumps 32
2.5.6 Change of water flow or pressure 35
2.5.7 Regulation of flow from selected pumps 37 References 39 3 Water Quality and Water Treatment: An Introduction 41
3.1 Increased focus on water quality 41
3.2 Inlet water 41
3.3 Outlet water 43
3.4 Water treatment 44 References 46 4 Fish Metabolism, Water Quality and Separation Technology 47
4.1 Introduction 47
4.2 Fish metabolism 47
4.2.1 Overview of fish metabolism 47
4.2.2 The energy budget 49
4.3 Separation technology 49
4.3.1 What are the impurities in water? 50
4.3.2 Phosphorus removal: an example 51 References 53 5 Controlling pH, Alkalinity and Hardness 55
5.1 Introduction 55
5.2 pH 55
5.2.1 Water dissolves in water 55
5.2.2 What is pH 56
5.2.3 The carbonate system 57
5.2.4 Total carbonate carbon 60
5.2.5 Open or closed system 60
5.2.6 A mathematical approach 63
5.2.7 pH of different water sources 64
5.2.8 Recommended pH for aquaculture 64
5.3 Alkalinity 65
5.3.1 How to avoid pH fluctuations 65
5.3.2 Titration is necessary 65
5.3.3 A buffer 66
5.3.4 The term equivalent weight 68
5.3.5 Alkalinity given as mg/L CaCO3 68
5.3.6 Alkalinity of different water sources 69
5.3.7 Recommended alkalinity for aquaculture 69
5.4 Hardness 69
5.4.1 The concentration of bivalent cations 69
5.4.2 Hardness may lead to precipitation 70
5.4.3 Hardness of different water sources 71
5.4.4 Recommended hardness 71
5.5 Chemical agents to use for regulation of pH, alkalinity and hardness 72
5.6 Examples of methods for pH adjustment 73
5.6.1 Lime 73
5.6.2 Sea water 75
5.6.3 Lye or hydroxides 76
5.6.4 pH regulation in RAS 76 References 77 6 Removal of Particles: Traditional Methods 79
6.1 Introduction 79
6.2 Characterization of the water 80
6.3 Methods for particle removal in fish farming 80
6.3.1 Mechanical filters and microscreens 81
6.3.2 Depth filtration: granular medium filters 84
6.3.3 Settling or gravity filters 87
6.3.4 Integrated treatment systems 90
6.4 Hydraulic loads on filter units 91
6.5 Purification efficiency 92
6.6 Dual drain tank 92
6.7 Local ecological solutions 94 References 94 7 Protein Skimming, Flotation, Coagulation and Flocculation 97
7.1 Introduction 97
7.1.1 Surface tension, cohesion and adhesion 99
7.1.2 Surfactants 102
7.2 Mechanisms for attachment and removal 102
7.2.1 Attachment of particles to rising bubbles by collision, typically in flotation 103
7.2.2 Improving colloid and particle removal rates: pretreatment 105
7.2.3 Attachment of surfaceactive substances, typically in protein skimmers 111
7.2.4 Particle attachment by nucleation 112
7.3 Bubbles 113
7.3.1 What is a gas bubble? 113
7.3.2 Methods for bubble generation 113
7.3.3 Bubble size 115
7.3.4 Bubble coalescence 115
7.4 Foam 116
7.4.1 What is foam? 116
7.4.2 Foam stability 117
7.4.3 Foam breakers 118
7.5 Introduction of bubbles affects the gas concentration in the water 118
7.6 Use of bubble columns in aquaculture 118
7.7 Performance of protein skimmers and flotation plants in aquaculture 119
7.7.1 What is removed in inlet or effluent aquaculture water with the use of protein skimmers? 119
7.7.2 Factors affecting the efficiency of protein skimming in aquaculture 121
7.7.3 Use of ozone 122
7.7.4 Bubble fractionation 123
7.8 Design and dimensioning of protein skimmers and flotation plants 123
7.8.1 Protein skimmers: principles and design 123
7.8.2 Protein skimmers: dimensioning 125
7.8.3 Flotation plant 126
7.8.4 Important factors affecting design of a DAF plant 127 References 129 8 Membrane Filtration 135
8.1 History and use 135
8.2 What is membrane filtration? 136
8.3 Classification of membrane filters 137
8.4 Flow pattern 139
8.5 Membrane shape/geometry 140
8.6 Membrane construction/morphology 142
8.7 Flow across membranes 143
8.8 Membrane materials 143
8.9 Fouling 144
8.10 Automation 146
8.11 Design and dimensioning of membrane filtration plants 146
8.12 Some examples of results with membranes used in aquaculture 149 References 150 9 Sludge 153
9.1 What is sludge 153
9.2 Utilization of the sludge 154
9.3 Dewatering of sludge 155
9.4 Stabilization of sludge 156
9.5 Composting of the sludge: aerobic decomposition 156
9.6 Fermentation and biogas production: anaerobic decomposition 158
9.7 Addition of lime 159
9.8 Drying of sludge 159
9.9 Combustion of sludge 160
9.10 Other possibilities for treatment and utilization of the sludge 161 References 161 10 Disinfection 163
10.1 Introduction 163
10.2 Basis of disinfection 164
10.2.1 Degree of removal 164
10.2.2 Chick''s law 164
10.2.3 Watson''s law 165
10.2.4 Dose-response curve 165
10.3 Ultraviolet light 165
10.3.1 Function 165
10.3.2 Mode of action 165
10.3.3 Design 166
10.3.4 Design specification 166
10.3.5 Dose 168
10.3.6 Special problems 168
10.4 Ozone 168
10.4.1 Function 168
10.4.2 Mode of action 169
10.4.3 Design specification 169
10.4.4 Ozone dose 170
10.4.5 Special problems 170
10.4.6 Measuring ozone content 172
10.5 Advanced oxidation technology 172
10.5.1 Redox potential 172
10.5.2 Methods utilizing AOT 173
10.6 Other disinfection methods 175
10.6.1 Photozone 175
10.6.2 Heat treatment 175
10.6.3 Chlorine 175
10.6.4 Changing the pH 176
10.6.5 Natural methods: ground filtration or constructed wetland 176
10.6.6 Membrane filtration 176 References 176 11 Heating and Cooling 179
11.1 Introduction 179
11.2 Heating requires energy 179
11.3 Methods for heating water 180
11.4 Heaters 181
11.4.1 Immersion heaters 181
11.4.2 Oil and gas burners 183
11.5 Heat exchangers 183
11.5.1 Why use heat exchangers? 183
11.5.2 How is the heat transferred? 184
11.5.3 Factors affecting heat transfer 184
11.5.4 Important parameters when calculating the size of heat exchangers 185
11.5.5 Types of heat exchanger 187
11.5.6 Flow pattern in heat exchangers 189
11.5.7 Materials in heat exchangers 190
11.5.8 Fouling 191
11.6 Heat pumps 192
11.6.1 Why use heat pumps? 192
11.6.2 Construction and function of a heat pump 192
11.6.3 Log pressure-enthalpy ( p-H ) 193
11.6.4 Coefficient of performance 194
11.6.5 Installations of heat pumps 194
11.6.6 Management and maintenance of heat pumps 196
11.7 Composite heating systems 196
11.8 Chilling of water 199 References 201 12 Gas Exchange, Aeration, Oxygenation and CO2 Removal 203
12.1 Introduction 203
12.2 Gas exchange in fish 203
12.3 Gases in water 204
12.4 Gas solubility in water 206
12.5 Gas transfer theory: aeration 210
12.5.1 Equilibrium 210
12.5.2 Gas transfer 212
12.6 Design and construction of aerators 213
12.6.1 Basic principles 213
12.6.2 Change of gas composition in the water for testing purposes 214
12.6.3 Evaluation criteria 215
12.6.4 Example of designs for different types of aerator 217
12.7 Oxygenation of water 223
12.8 Theory of oxygenation 224
12.8.1 Increasing the equilibrium concentration 224
12.8.2 Gas transfer velocity 224
12.8.3 Addition under pressure 224
12.9 Design and construction of oxygen injection systems 225
12.9.1 Basic principles 225
12.9.2 Where to install the injection system 225
12.9.3 Evaluation of methods for injecting oxygen gas 227
12.9.4 Examples of oxygen injection system designs 227
12.10 Oxygen gas characteristics 231
12.11 Sources of oxygen 231
12.11.1 Oxygen gas 231
12.11.2 Liquid oxygen 232
12.11.3 Onsite oxygen