WHAT'S LEFT AFTER THE ICE MELTS

I purchased a 4kg pkt of ice the other day from the Pick n Pay (company called Cool Ice) they're based in Durban Glen Anil.

What was left in the bottom of the glass after the ice had melted was very disturbing and gross. They say their islce is purified but how is that possible if there's white stuff left at the bottom. I do not drink tap water, only bottled water and I've checked the water, it's not that. So what I think is that they're using tap water and freezing it.