| OZONE |
|
| Advantages |
Disadvantages |
| Strongest Disinfectant |
No Residual Effect |
| Effective against Cryptosporidium |
Pretreatment required for high organic levels & forms bromates |
| Oxidizes organics fast |
High energy levels required |
| Effective over wide pH and temperatures |
High Maintenance |
| Microflocculation effect |
High Capital Costs |
| Taste & Odor, Color Effectively Reduced |
Requires On-Site Generation |
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| CHLORINE DIOXIDE |
|
|
Advantages
|
Disadvantages |
| Effective against Cryptosporidium & more effective than Chlorine |
More Expensive than Chlorine |
| Effective over Wide pH & Does not react with Nitrogen |
Requires On-Site Generation |
| Prevents TTHMs & Bromate Formation |
Difficult to Analyze Species |
Cheaper than Ozone & more effective for T&O, color, phenols reduction, iron & manganese reduction |
Chlorite by-product |
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CHLORINE |
|
| Advantages |
Disadvantages |
Effective against bacteria, viruses, & Giardia |
Doses for Cryptosporidium kill impractical |
Inexpensive, Easy & Versatile Operation |
Forms TTHMs & HAAs |
Persistent Residual |
Less Effective at Higher pH levels |
| Easy Residual Analysis |
Gas Form Dangerous |
Can be stored easily |
Taste & Odor Problems |
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CHLORAMINES |
|
| Advantages |
Disadvantages |
|
Very Stable Residual
|
Weak Disinfectant & have regrowth problems
|
|
Prevents TTHMs
|
Can Cause Taste & Odors
|
Better for long Contact Times |
Higher HPC and Nitrites can occur |
|
Can be less expensive than chlorine
|
May Form Toxic Iodoacid byproducts
|
Can be used after free chlorine |
Can be more expensive than Free Chlorine |
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| UV |
|
| Advantages |
Disadvantages |
| No Chemicals Added |
Less effective against spores, cysts, and viruses |
| No effect from ammonia |
Pretreatment Needed |
| Taste and Odors are not produced |
No residual present |
| Short Contact Time is effective |
High Energy & Maintenance Required |
| Overdosing is not a problem |
Not effective for Reducing Taste & Odors in Raw Water |