There are severally ways to manually purify your own water in an emergency situation. Boiling is one of the easiest options to make water safe to drink, this water can be stored in a cool place for 3 days before it needs to be cleaned again. Bleach can also be added to large amounts of water to assist in killing bacteria and disinfecting the water.
Several factors can affect the quality of your groundwater. This includes your general location and what is nearby where you're drawing water. Is there anything that may be able to pollute surface or groundwater through seepage or runoff?