Contents
Disinfectants (Oxidants)
Currently, the most popular disinfectants used in water treatment are: 1. Ozone; 2. Chlorine Dioxide; 3. Chlorine; 4. Chloramines; and 5. UV. Each of these oxidants have their advantages and disadvantages. However, by mixing 1 part of chlorine dioxide with 2/3rds part of chlorine in the same disinfection zone, Dr. Rittmann has published in water treatment research papers that the advantages of each oxidant are maximized while their disadvantages are minimized as shown at the bottom of the table below.
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Advantages |
Disadvantages |
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Strongest Disinfectant |
No Lasting Residual |
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Effective against Cryptosporidium |
Pretreatment required for high organic levels & forms bromates |
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Oxidizes organics fast |
High energy levels required |
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Overtreatment not a problem except in bromide water |
Residual measurement may be difficult |
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Effective over wide pH and temperatures |
High Maintenance |
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Microflocculation effect |
High Capital Costs |
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Taste & Odor, Color Effectively Reduced |
Requires On-Site Generation |
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Advantages |
Disadvantages |
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Effective against Cryptosporidium & more effective than Chlorine |
More Expensive than Chlorine |
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Effective over Wide pH & Does not react with Nitrogen |
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Cheaper than Ozone & more effective for T&O, color, phenols reduction, iron & manganese reduction |
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Advantages |
Disadvantages |
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Effective against bacteria, viruses, & Giardia |
Doses for Cryptosporidium kill impractical |
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Inexpensive, Easy & Versatile Operation |
Forms TTHMs & HAAs |
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Persistent Residual |
Less Effective at Higher pH levels |
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Easy Residual Analysis |
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Can be stored easily |
Taste & Odor Problems |
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Advantages |
Disadvantages |
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Very Stable Residual |
Weak Disinfectant & have regrowth problems |
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Prevents TTHMs |
Can Cause Taste & Odors |
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Better for long Contact Times |
Higher HPC and Nitrites can occur |
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Can be less expensive than chlorine |
May Form Toxic Iodoacid byproducts |
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Can be used after free chlorine |
Can be more expensive than Free Chlorine |
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Advantages |
Disadvantages |
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No Chemicals Added |
Less effective against spores, cysts, and viruses |
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No effect from ammonia |
Pretreatment Needed |
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Taste and Odors are not produced |
No residual present |
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Short Contact Time is effective |
High Energy & Maintenance Required |
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Overdosing is not a problem |
Not effective for Reducing Taste & Odors in Raw Water |
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MIXING DISINFECTANTS USING 3 PARTS OF CHLORINE DIOXIDE TO 2 PARTS OF CHLORINE |
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Increases the inactivation of Cryptosporidium more than chlorine dioxide alone. |
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Lowers TTHMs potential by 1/2 (one-half) compared to chlorine dioxide alone. |
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Increased performance reduces the cost of chlorine dioxide by one-half (1/2) |
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Double-barrier disinfection protection with 2-disinfectants in the same zone |
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Can take CT credit for both disinfectants in the same disinfection zone |
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Lowers Taste & Odors more compared to chlorine dioxide alone. |
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Cost effective as compared to liquid hypochlorite chlorine alone |
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Chlorine more effective as a disinfectant at higher pHs. |
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Prevents TTHMs formation from chlorine |
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Chlorite by-product is decreased more |
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Page Last Revised on 12/05/2006