One of the easiest is using UV light from sunlight to do this. On a clear sunny day it takes 6 hours to purify a bottle of water. But use glass bottles. The water should be thorughly filtered before placing it in sunlight.
using charcoal for safe tap water has come to public attention in Japan. Using charcoal can make safe water easily, tasty, and cost-effectively!
It is important to use hard charcoal. Normal black charcoal breaks easily in the water.
Raw charcoal is dirty and not suited for boiling. Wash them under running water. You can use a scrub brush to help in the process of cleaning the charcoal. Do not use any detergent! It will destroy the beneficial effects of the charcoal and will spoil the water.
Sterilize it in boiling water. Use a large uncovered pot. Boil for about 10 minutes.
Put the charcoal into a colander to squeeze out the water and let it cool down. Gently submerge the charcoal in a container poured with tap water or well water. Use about 100 grams of charcoal for every 1 liter of water.
In order to prevent dust from entering, cover it with a dishcloth and let it sit for 1–2 days. It is recommended to use a container made of stainless steel, porcelain enamel, ceramic, or glass.
Pour this water into a vessel and use it for cooking or put it in the refrigerator as a drinking water. This is your sterilized water! Refill the container containing the charcoal with water to make more purified water. You can repeat this process for one week.
Clean the dirt off the charcoal once a week. The method is: boil, let it cool down, and dry it for one week. To use the charcoal again, simply start from number 1 method. It is best to prepare two sets of charcoal and rotate them weekly. In this way, the charcoal can be used for 6 months! But take note that the mineral amount of the charcoal will gradually deplete after 10 days of use.