Is source of Nickel known ...

Is source of Nickel known and can it be curtailed?

I can suggest Lab testing for samples : Try very mild dosage of Sulphuric acid to get Nickel precipitated to a sulphate salt and after filtering the coagulated nickel salt, add Sodium bi-carbonate to correct the Ph.  

Also try in lab whether Ni can react with Bromine to give a filterable Nickel bromide ) and it can be by adding a very small quantity of Sodium or Calcium Bromide or even bubbling small quantity of bromine thru a closed circuit .Only Lab experiment suggested on trial basis for an inexpensive solution.