Page 18 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Contents xvii

12.4.4 Backwash.................................................................................................................................... 360
12.4.4.1 Manifold Principles..................................................................................................... 360
12.4.4.2 Types of Backwash Systems ...................................................................................... 361
12.4.4.3 Backwash Volume ...................................................................................................... 362
12.4.4.4 Backwash Water Troughs........................................................................................... 363
12.4.4.5 Under-Drain Systems.................................................................................................. 363
12.4.4.6 Bed Fluidization.......................................................................................................... 365
12.4.4.7 Surface-Wash.............................................................................................................. 368
12.4.4.8 Air-wash...................................................................................................................... 369
12.4.4.9 Air–Water Concurrent Backwash............................................................................... 369
12.4.4.10 Collapse Pulsing ......................................................................................................... 370
12.5 Operation ................................................................................................................................................. 371
12.5.1 Filter Operating Cycle................................................................................................................ 372
12.5.2 Filtration Hydraulics................................................................................................................... 372
12.5.2.1 Clean-Bed Headloss.................................................................................................... 372
12.5.2.2 Progression of Headloss with Filter Run.................................................................... 373
12.5.2.3 Negative Pressure........................................................................................................ 374
12.5.2.4 Air Binding ................................................................................................................. 374
12.5.3 Backwash.................................................................................................................................... 374
12.5.3.1 Mudballs and Surface Cracks..................................................................................... 375
12.5.3.2 Floc-to-Grain Bonding................................................................................................ 375
12.5.3.3 Practice........................................................................................................................ 375
12.5.3.4 Operating Protocol...................................................................................................... 375
12.6 Pilot Plants............................................................................................................................................... 375
12.6.1 Equipment................................................................................................................................... 376
12.6.1.1 Contaminant Injection................................................................................................. 376
12.6.1.2 Filter Column.............................................................................................................. 377
12.6.1.3 Pilot Plant System....................................................................................................... 378
12.6.1.4 Data Handling............................................................................................................. 378
12.7 Wastewater Filtration............................................................................................................................... 378
12.7.1 Background................................................................................................................................. 378
12.7.2 Forms of Practice........................................................................................................................ 378
12.7.2.1 As a Unit Process within a Water Treatment Train ................................................... 378
12.7.2.2 As a Stand-Alone Process Following Biological Treatment...................................... 378
12.8 Proprietary Equipment............................................................................................................................. 379
12.8.1 Ancillary Equipment .................................................................................................................. 379
12.8.2 Package Filtration Systems......................................................................................................... 379
12.8.2.1 Deep Bed Filtration—Parkson DynaSandt................................................................ 379
12.8.2.2 Deep Bed Filtration—Culligan Multi-Techt.............................................................. 380
12.8.2.3 Shallow Bed Filtration—ABWt ................................................................................ 380
12.8.2.4 Package Filtration—EPD Wearnes USAt ................................................................. 380
12.8.3 Evaluation of Products ............................................................................................................... 380
Problems............................................................................................................................................................. 381
Acknowledgments .............................................................................................................................................. 382
Appendix 12.A: Filtration in New York ......................................................................................................... 382
Glossary.............................................................................................................................................................. 385
References .......................................................................................................................................................... 391

Chapter 13 Slow Sand Filtration........................................................................................................................................... 395
13.1 Description............................................................................................................................................... 395
13.1.1 Slow Sand Technology .............................................................................................................. 395
13.1.1.1 Filter Box and Appurtenances .................................................................................... 395
13.1.1.2 Sand Bed..................................................................................................................... 395
13.1.1.3 Schmutzdecke .............................................................................................................. 395
13.1.1.4 Design Approach ........................................................................................................ 395