Page 15 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

xiv Contents

10.3.4 Injection of Coagulant Chemicals.............................................................................................. 260
10.3.4.1 Disparity of Flows ...................................................................................................... 260
10.3.4.2 Advection of Neat Alum ............................................................................................ 260
10.4 Mixing Technologies............................................................................................................................... 261
10.4.1 Impeller Mixing.......................................................................................................................... 261
10.4.1.1 Reactors—Back-Mix and In-Line............................................................................... 261
10.4.1.2 Circulation Criterion for 0.99 Blending in a Back-Mix Reactor ............................... 262
10.4.1.3 Time Ratio, t=Q(reactor), to Attain 0.99 Blending—Experimental Procedure (a)..... 264
10.4.1.4 Impeller Speed, w(impeller), to Attain 0.99 Blending—Experimental
Procedure (b)............................................................................................................... 264
10.4.1.5 Complete-Mix Reactors.............................................................................................. 264
10.4.2 Impellers and Tanks ................................................................................................................... 266
10.4.2.1 Impeller Variety.......................................................................................................... 266
10.4.2.2 Impeller Characteristics .............................................................................................. 266
10.4.2.3 Impeller Pumping........................................................................................................ 267
10.4.2.4 Tanks........................................................................................................................... 269
10.4.2.5 Rushton System .......................................................................................................... 270
10.4.2.6 In-Line Mixers ............................................................................................................ 270
10.4.3 Jet Mixers ................................................................................................................................... 271
10.4.3.1 Flash Mixing by Submerged Jets ............................................................................... 271
10.4.4 Static Mixers............................................................................................................................... 276
10.4.4.1 General Principles....................................................................................................... 276
10.4.4.2 Baffles ......................................................................................................................... 276
10.4.4.3 Static Mixers............................................................................................................... 277
10.5 Summary.................................................................................................................................................. 280
Problems............................................................................................................................................................. 280
Acknowledgments .............................................................................................................................................. 283
Glossary.............................................................................................................................................................. 284
References .......................................................................................................................................................... 288
Bibliography....................................................................................................................................................... 290

Chapter 11 Flocculation ........................................................................................................................................................ 291
11.1 Definitions................................................................................................................................................ 291
11.1.1 Floc............................................................................................................................................. 291
11.1.1.1 Biological Floc............................................................................................................ 291
11.1.1.2 Chemical Floc............................................................................................................. 291
11.1.1.3 Primary Particles......................................................................................................... 291
11.1.2 Flocculation ................................................................................................................................ 291
11.1.2.1 Orthokinetic Flocculation ........................................................................................... 291
11.1.2.2 Perikinetic Flocculation .............................................................................................. 291
11.1.2.3 Flocculent.................................................................................................................... 291
11.2 Applications............................................................................................................................................. 292
11.2.1 Conventional Filtration............................................................................................................... 292
11.2.2 Direct Filtration .......................................................................................................................... 292
11.2.3 Flotation...................................................................................................................................... 292
11.2.4 Activated Sludge Floc Settling................................................................................................... 292
11.2.5 Softening..................................................................................................................................... 292
11.2.6 Tertiary Treatment...................................................................................................................... 292
11.3 History ..................................................................................................................................................... 292
11.3.1 Practice ....................................................................................................................................... 292
11.3.1.1 Quiescent Basins......................................................................................................... 292
11.3.1.2 Langelier’s Paddle Wheels.......................................................................................... 292
11.3.1.3 Design Guidelines....................................................................................................... 293
11.3.1.4 Flocculation Practice, c. 1940..................................................................................... 294
11.3.2 Evolution of Theory ................................................................................................................... 294
11.3.2.1 Langelier ..................................................................................................................... 294