How to remove Nitrate, Iron and Manganese from water?

We have elevated nitrate, iron and manganese levels in our borehole water. The concentration of these elements is higher than recommended by the WHO drinking water guidelines.  Could someone please suggest a simple removal process for nitrate, iron and manganese? Is it possible to get rid of these elements in a one-step filtration process? Is there a household treatment method for removing all these three elements?