Which disinfection method is highly effective against cryptosporidium and leaves no taste or odor, but provides no residual protection in the distribution system?
- AOzonationCorrect
- BChloramination
- CBleaching powder application
- DSodium hypochlorite
Solution
Concept
Ozone disinfection characteristics
Formula
2 O3 -> 3 O2
Step-by-step solution
1. Cryptosporidium oocysts have thick cellular walls resistant to standard chlorine dosages. 2. Ozone is a powerful oxidizer that readily inactivates Cryptosporidium without chlorinated byproducts. 3. Ozone rapidly breaks down into oxygen, leaving no taste, odor, or residual in distribution pipes. 4. Hence, ozonation satisfies all conditions specified. Answer: A
Explanation
Ozone (O3) is an exceptionally strong oxidant capable of inactivating chlorine-resistant pathogens including Cryptosporidium and Giardia oocysts without imparting taste or odor. Because ozone decomposes quickly into molecular oxygen, it provides zero residual disinfectant within the municipal distribution network.
Why the other options are wrong
B) Chloramines provide persistent residual protection and have limited effectiveness against Cryptosporidium. C) Bleaching powder imparts strong chlorine taste and provides residual chlorine. D) Sodium hypochlorite provides residual chlorine and leaves chemical taste.
Shortcut
Cryptosporidium kill + zero residual + no taste/odor = Ozone.
Common mistake
Selecting chloramination because of its durability, ignoring that it leaves residual and is weak against Cryptosporidium.
Correct answer: A) Ozonation