Well, this is a subject which I can shed some light. Over 2 decades ago I helped students at a well-known university start a chapter of Engineers Without Borders. Our main interest was local water treatment for developing countries where a water system approach was not appropriate. One of the methods we tested was colloidal silver. Others were chlorine,
solar, and simple filtration. Colloidal silver is an excellent treatment and provides even better residual treatment of the water as it is never actually destroyed in the process, where chlorine will deteriorate. Be careful to use colloidal silver and not some dissolved silver
salt, such as silver nitrate. The nitrate is harmful to infant and enough will even turn an adult a pale blue.
It takes about 1 oz (30 ml) of 36 ppm colloidal silver to treat 158 gal (600 l) of water, but as stated above it will keep the water sweet for an extended period where chlorine will not. The down-side is likely the expense of the colloidal silver. I have not researched it recently but it was always much more than chlorine.
In nearly 30 months in sub-Saharan
Africa over 8 years I used colloidal silver exclusively for
drinking water with no problems. Much of that water looked pretty bad even after filtering through a t-shirt. It was interesting that locals did not accept colloidal silver because they could not see that anything had been done to the water. We ended up mostly using clay filter pots coated on the inside with colloidal silver. They liked the physical process of filtering.
After all that I might point out that I use chlorine - either from the
dock water or I add it if making water or acquiring non-chlorinated water. For drinking and
cooking on the
boat I run the water through a series of filters under the sink to remover particles, remove chlorine with a carbon filter and further treat with a UV light. Much cheaper than
buying colloidal silver. Hope this helped.