Page 28 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Contents xxvii

20.1.2.2 Wet-Oxidation............................................................................................................. 644
20.1.2.3 Supercritical Water Oxidation .................................................................................... 644
20.2 Oxidation Theory..................................................................................................................................... 644
20.2.1 Fundamentals.............................................................................................................................. 644
20.2.1.1 Definitions................................................................................................................... 645
20.2.1.2 Enumeration of Reaction ............................................................................................ 645
20.2.1.3 Half Reactions............................................................................................................. 645
20.2.1.4 Oxidation Numbers..................................................................................................... 646
20.2.1.5 Thermodynamic Relations.......................................................................................... 646
20.2.2 Oxidants...................................................................................................................................... 647
20.2.2.1 Chlorine....................................................................................................................... 647
20.2.2.2 Ozone.......................................................................................................................... 647
20.2.2.3 Hydroxyl Radical........................................................................................................ 649
20.2.2.4 Permanganate.............................................................................................................. 649
20.2.2.5 Chlorine Dioxide......................................................................................................... 649
20.2.2.6 Titanium Dioxide........................................................................................................ 650
20.2.3 Supercritical Water Oxidation.................................................................................................... 650
20.2.3.1 Critical Point............................................................................................................... 650
20.2.3.2 SCWO In-a-Nutshell................................................................................................... 650
20.2.3.3 Characteristics of Supercritical Water Relevant to Engineering ................................ 651
20.2.3.4 Supercritical Reactors ................................................................................................. 652
20.2.3.5 Research in the 1990s................................................................................................. 653
20.2.3.6 Design Factors ............................................................................................................ 653
20.2.3.7 Case Study: SCWO of Pulp and Paper Mill Sludge .................................................. 653
20.3 Practice .................................................................................................................................................... 655
Problems............................................................................................................................................................. 655
Acknowledgments .............................................................................................................................................. 656
Glossary.............................................................................................................................................................. 656
References .......................................................................................................................................................... 658
Further Reading.................................................................................................................................................. 659

Chapter 21 Precipitation........................................................................................................................................................ 661
21.1 Description............................................................................................................................................... 661
21.1.1 Precipitation In-a-Nutshell.......................................................................................................... 661
21.1.1.1 Definitions................................................................................................................... 661
21.1.1.2 Comparison with Other Processes.............................................................................. 661
21.1.1.3 Process Description..................................................................................................... 661
21.1.2 Applications................................................................................................................................ 661
21.1.2.1 Softening..................................................................................................................... 661
21.1.2.2 Toxic Metals Removal................................................................................................ 662
21.1.3 History ........................................................................................................................................ 662
21.1.3.1 Softening..................................................................................................................... 662
21.1.3.2 Sewage Treatment....................................................................................................... 662
21.1.3.3 Heavy Metals .............................................................................................................. 662
21.2 Precipitation Theory ................................................................................................................................ 663
21.2.1 Equilibria .................................................................................................................................... 663
21.2.1.1 Solubility Law............................................................................................................. 663
21.2.1.2 Application of Solubility Law .................................................................................... 663
21.2.1.3 Listing of Solubility Products..................................................................................... 665
21.2.1.4 Solubility pC–pH Diagrams ....................................................................................... 665
21.2.1.5 pe–pH Diagrams ......................................................................................................... 666
21.2.1.6 General Rules of Solubility ........................................................................................ 667
21.2.2 Hardness ..................................................................................................................................... 667
21.2.2.1 Occurrence of Hardness.............................................................................................. 667
21.2.2.2 Expressing of Hardness as CaCO 3 ............................................................................. 667
21.2.2.3 Other Definitions of Hardness .................................................................................... 668