Source of NickelNickel (Ni+2) is common, and exists in approximately 85% of the water supplies, and is usually around 1 ppb (part per billion). The US EPA has classified nickel as a possible human carcinogen based on inhalation exposure. Nickel has not been shown to be carcinogenic via oral exposure. No MCLG (maximum contamination level goal) has been proposed.
Treatment of NickelNickel behaves the same as iron, and can be removed by a strong acid cation exchanger. Activated-carbon filtration can be used to reduce the amount of nickel in drinking water, but may not remove it all. Reverse osmosis will remove 97 - 98% of the nickel from drinking water.