You have to bring iodine tablets with you. Chlorine tablets are widely available. The most effective and commonly used version of chlorine is chlorine dioxide, which is tasteless and odorless. Tablets can be bought cheaply and usually 1 tablet is sufficient to purify 1 liter of water. Neutralizing tablets can also be bought to get rid of the smell and taste of chlorine or iodine. This will need to be done for water obtained using hand pumps or in streams during the trek.