Pool Info: Biguanide Treatment
Originally developed as a pre-surgery anti-microbial scrub, PHMB was patented in 1977, and marketed for pools and spas under the trade name Baquacil. This technology has the distinction and the EPA approval as the only non-halogen sanitizer available for pools and spas. Biguanides, as the class of chemicals is called, is a hydrogen peroxide-polyhexamethylene chemical. You may have heard of using peroxide to bleach your hair or for an ear infection. The formulation is a bit different, but basically in the same chemical family.
Here's a page if you're looking here to find out how to convert back to chlorine or some other sanitizer from a Biguanide treatment.
When the patent expired back in the 90's, Bio Lab introduced a line of biguanide products under the name Soft Swim. A full system for complete halogen free water care, these products are also a stand alone alternative to traditional sanitation methods [chlorine]. The Biguanide itself is combined with algaecides and hydrogen peroxide for periodic oxidation. The system tends to gum up filters, and of course a product is available to de-gum it. Biguanide are not recommended for spas or aerated pools. As long as you don't add any other chemicals but those recommended by the manufacturer, you'll do fine; but add a small amount of chlorine and your pool looks like orange sherbet! :-) Biguanides are also incompatible with TSP, ozone, detergents, ionizers, and other common chemicals, but are not at odds with any water balancing chemicals you may add to adjust pH, Alkalinity or Calcium.