Hygiene control in swimming pools - by addition of a biguanide polymer contg. polymethylene chains

The growth of bacteria and algae in water is inhibited by the addition of 1-200 ppm (4-12 ppm) of a linear biguanide polymer or salt as free base contg. the reducing unit of formula (I): (where X and Y are bridging radicals (polymethylene) with a total of >9 and 17C atoms. The polymer chain chains are terminated at one or both ends by -NHR; and R is 1-18C alkyl). An eample is poly(hexamethylene biguanide) chlorhydrate of MW 1100-1800 used as 20 wt.% soln. in water. The additive is a non-irritant alternative to chlorine.