Answer: Soda ash is a particularly poor choice to regenerate a softener. Soda ash is sodium carbonate. By definition, a softener is removing hardness (calcium and magnesium) so, when you try to regenerate with soda ash, the high alkalinity present (due to the carbonate) will form calcium carbonate, which is nearly insoluble and will scale-up the resin, tank and internals. For this reason, common salt (NaCl) is used to regenerate softeners. Calcium and magnesium chlorides are much more soluble than the carbonate salts. Hope this helps.
Drinking water & the immunocompromised
Question: I’m a freelance writer working on a brochure for a drinking water purification system aimed at healthcare providers who work with immunosuppressed patients. I’m wondering if you know of a good resource for statistics that would help to show the importance of providing this population with the purest water possible (i.e., examples of problems this population faces if their drinking water is not of the highest purity level/specific instances of this happening). Thanks so much for your help.
Answer: The following paragraph is a cut from a chapter of a book written by a member of WC&P’s Technical Review Committee, Dr. Debra E. Huffman, a public health microbiologist with the University of South Florida, on crypto-sporidiosis (see “Cryptosporidium: Basic Biology & Epidemiology,” in Encyclopedia of Environmental Microbiology, Gabriel Bitton, et al., eds., John Wiley & Sons, New York, 2002, pp. 650-657). While it does give estimates of the disease in immunocompromised patients, she notes the source of the infection may not be caused by drinking water. Zoonotic transmission—animal-to-human—as well as recreational exposure and person-to-person contact may be responsible for the spread of this disease; however, water is often seen as the predominant mode of transmission.
“It has been estimated that Crypto-sporidium accounts for 13-16% of diarrheal cases in AIDS patients in developed nations with that number climbing to 24-50% in developing nations. A prospective long-term study in Europe suggests that 3-4% of persons with HIV will have cryptosporidiosis when diagnosed with HIV and that an equal number will develop it during the course of their disease. A study in Los Angeles in 1994 suggests that 3.4% of HIV patients in the USA will become infected with cryptosporidiosis during their symptomatic period.”
In an article by Joan Rose, “Environmental ecology of Cryptosporidium and public health implications,” (Annual Review of Public Health, 18:135-161, 1997) it’s enumerated in this manner:
“Three waterborne outbreaks associated with drinking water have revealed that persons with AIDS to be at grave risk. While community-wide exposure did not increase the attack rates in the AIDS patients, the outcome of the disease was severe with 52% to 68% mortality within 6 months to a year after the outbreaks. During the Milwaukee outbreak, in a cohort of 73 AIDS patients (33 with Cryptosporidium) morbidity was also much more severe; 400 of 444 hospital days were logged in by those with the protozoan infection and extra medical costs reached nearly $760,000.”
Additional information on the topic can be found at the following government websites:
• Centers for Disease Control & Prevention: www.cdc.gov/ncidod/dpd/healthywater/immuno.htm
• USEPA: www.epa.gov/safewater/crypto.html
• Drinking Water Inspectorate (UK): www.dwi.gov.uk/pubs/bouchier/pdf/chap008.pdf
• Health Canada: www.hc-sc.gc.ca/hecs-sesc/water/factsheets/giardia_ cryptosporidium.htm
We hope that helps.