Does the SH inactivate giardia and cryptosporidium?
Giardia and cryptosporidium are both protozoa and are resistant to chlorination because they exist in water in a cyst form. The hard coat of the cysts protects giardia and cryptosporidium from being inactivated by chlorine. Cryptosporidium is more resistant to chlorine than giardia. See this inactivation table for more details. Both protozoa, however, are fairly large. Cryptosporidium is approximately 3-5 times the size of the bacteria E. coli, and giardia is approximately 5-10 times the size of E. coli. Cryptosporidium and giardia can thus be removed by filtration. If giardia or cryptosporidium are a significant health problem in the project area, a filtration step (through ceramic, sand, or other filters) can be added before adding the sodium hypochlorite. The Safe Water System intervention has been proven to reduce diarrhea in children, and this intervention does inactivate many of the ones that cause the most severe disease, like cholera, dysentery, and typhoid fever.
