Silver is used in some home ...

Silver is used in some home treatment devices to reduce microbial growth on the media but NOT to disinfect the water. It is a marginal and very slow acting bacteriostat or bacteriocide for some microbes. . Some of those devices can cause silver to leach into the drinking water. The permissible limit is 100 ppb. Silver is not very toxic. It would require log term exposure to produce argyria, which is significant  darkening of the skin due to silver sulfide deposition. It is a permanent effect. See the WHO guideline discussion.