Page 11 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

x Contents

7.3 Aerated Grit Chambers............................................................................................................................ 148
7.3.1 Principles of Aerated Grit Chamber Operation.......................................................................... 150
7.3.2 Theory of Aerated Grit Chambers.............................................................................................. 150
7.3.2.1 Calculation of Grit Removal....................................................................................... 150
7.3.2.2 Calculation of Spiral Length, DL ............................................................................... 151
7.3.2.3 Empirical Guidelines................................................................................................... 151
7.3.2.4 n Determination .......................................................................................................... 151
7.3.2.5 Algorithm for Calculations ......................................................................................... 152
7.3.3 Practice: Aerated Grit Chambers................................................................................................ 154
7.3.3.1 Guidelines from Five Designs .................................................................................... 154
7.3.3.2 Summary of Guidelines .............................................................................................. 155
7.3.3.3 Pressure in Header Pipe.............................................................................................. 156
7.3.3.4 Blower Power ............................................................................................................. 156
Problems............................................................................................................................................................. 157
Acknowledgments .............................................................................................................................................. 159
Glossary.............................................................................................................................................................. 159
References .......................................................................................................................................................... 160

Chapter 8 Flotation.............................................................................................................................................................. 163
8.1 Development of Flotation........................................................................................................................ 163
8.1.1 Beginning Design Practice ......................................................................................................... 163
8.1.2 Water and Wastewater Applications .......................................................................................... 163
8.2 DAF System Description......................................................................................................................... 163
8.2.1 Synopsis of DAF Process........................................................................................................... 163
8.2.1.1 Coagulation................................................................................................................. 163
8.2.1.2 Flocculation................................................................................................................. 163
8.2.1.3 Contact Zone............................................................................................................... 163
8.2.1.4 Saturator...................................................................................................................... 163
8.2.1.5 Gas Precipitation......................................................................................................... 164
8.2.1.6 Bubble–Floc Agglomerate.......................................................................................... 164
8.2.1.7 Float Layer.................................................................................................................. 164
8.2.1.8 Clarified Water............................................................................................................ 164
8.2.1.9 Further Processing ...................................................................................................... 164
8.3 Principles of DAF Flotation .................................................................................................................... 164
8.3.1 Gas Transfer ............................................................................................................................... 164
8.3.1.1 Henry’s Law................................................................................................................ 164
8.3.1.2 Application of Henry’s Law to Saturator ................................................................... 166
8.3.1.3 Saturator...................................................................................................................... 166
8.3.1.4 Gas Concentration at Nozzle Depth ........................................................................... 167
8.3.1.5 Saturator Mass Balance .............................................................................................. 167
8.3.1.6 Saturator Packing........................................................................................................ 167
8.3.1.7 Hydraulic Grade Line ................................................................................................. 167
8.3.2 Gas Precipitation ........................................................................................................................ 168
8.3.2.1 Bubbles ....................................................................................................................... 168
8.3.2.2 Bubble Size................................................................................................................. 170
8.3.2.3 Bubble Size Distribution............................................................................................. 170
8.3.2.4 Bubble Numbers ......................................................................................................... 170
8.3.2.5 Nozzle Design............................................................................................................. 170
8.3.3 Contact Zone .............................................................................................................................. 171
8.3.3.1 Floc–Bubble Transport and Attachment..................................................................... 171
8.3.3.2 Bubble–Particle Contact ............................................................................................. 172
8.3.3.3 Parameter Values ........................................................................................................ 172
8.3.4 Separation Zone.......................................................................................................................... 172
8.3.4.1 Rise Velocity of Bubbles............................................................................................ 172