Static Mixers for Coagulation and Disinfection

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American Water Works Association, 2001 - 225 pagine
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Static mixers are an attractive alternative for the mixing of chemicals in water treatment plants. The attraction comes from the fact that static mixers do not require an external input of energy and do not have moving parts. Static mixers consist of mixing elements fixed on the inside of a pipe of channel. The elements do not move. Chemicals, added just upstream of the mixers, mix with the bulk fluid because of the complex, three-dimensional fluid motion generated by the elements. The goal of this project is to explore the use of static mixers in two of the key processes in drinking water treatment: for the mixing of coagulants for destabilization and the mixing of disinfectants for the inactivation of Cryptosporidium parvum oocysts in disinfection. The role of mixing in both of these processes is not well understood. But for each process experimental and theoretical evidence suggests that, at least in some circumstances, the mixing environment provided when chemicals are introduced into the flow will affect the resulting destabilization or inactivation.
 

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Indice

INTRODUCTION AND BACKGROUND
1
LITERATURE REVIEW
3
Coagulation and Mixing
4
Turbulence Mixing and Chemical Reactions
5
Static Mixers
6
Disinfection and Mixing
9
Computational Fluid Dynamics
11
PILOTSCALE TESTING OF STATIC MIXERS FOR COAGULANT MIXING
13
DISINFECTION OF CRYPTOSPORIDIUM IN BATCH REACTOR
112
Initial Validation of Model for Batch Reactor
113
Comparing the New Model to Other Models of Disinfection
114
DISINFECTION OF CRYPTOSPORIDIUM IN PLUGFLOW DISPERSION REACTOR
119
SENSITIVITY ANALYSIS
121
SUMMARY AND CONCLUSION
122
COMPUTATIONAL FLUID DYNAMICS PREDICTIONS OF THE FLOWFIELD IN HELICAL STATIC MIXERS
129
Previous Applications of CFD in Water Treatment
131

Source Water
16
Head Loss Experiments
18
Effect of Design Parameters
30
Head Loss Tests
36
SUMMARY AND CONCLUSIONS
38
BENCHSCALE EXPERIMENTS ON THE INACTIVATION OF CRYPTOSPORIDIUMPARVUM OOCYSTS WHEN USING STATIC MIXERS
65
Determining viability
66
MATERIAL AND METHODS
67
Preparing for the Disinfection Experiments
68
Disinfection experiments
70
RESULTS AND DISCUSSION
75
Losses in Filtration Step of Experiments
76
Infectivity Curves
77
Head loss and Gvalues
78
Chlorine Disinfection Studies
79
CONCLUSIONS AND RECOMMENDATIONS
85
Recommendations
87
A NEW PHYSICOCHEMICAL MODEL OF DISINFECTANT MIXING INCLUDING THE EFFECTS OF MIXING ON CRYPTOSPORIDIUM PAR...
103
New View of the Disinfection Process
104
DEVELOPMENT OF THE NEW DISINFECTION MODEL
105
Fluid Transport of the Disinfectant and Pathogens
106
Summary of the Model Derivation
111
Questions in Water Treatment that CFD can Address
132
DESCRIPTION OF THE CFD MODEL
134
Summary of the Numerical Methods
138
VALIDATION OF THE CFD MODEL
140
Validation Results
141
RESULTS AND DISCUSSION OF STATIC MIXER PREDICTIONS
145
More Validation
148
Verification
151
Discussion of the Flowfield Physics
152
APPLYING THE CFD MODEL TO ISSUES IN WATER TREATMENT
159
Rapid Mixing for Coagulation
161
Gvalue for Static Mixers
162
CONCLUSIONS
165
RECOMMENDATIONS FOR FUTURE WORK
167
CONCLUSIONS
189
INACTIVATION OF CRYPTOSPORIDIUM PARVUM USING STATIC MIXERS
190
A NEW MODEL OF MIXING AND DISINFECTION OF CRYPTOSPORIDIUM PARVUM
192
COMPUTATIONAL FLUID DYNAMICS AND THE FLOWFIELD IN HELICAL STATIC MIXERS
193
REFERENCES
197
ABBREVIATIONS
219
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Pagina 218 - JR, 1996. A chemiluminescence immunoassay for evaluation of Cryptosporidium parvum growth in vitro. FEMS Microbiol.

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