Drawing water from a lake

As someone who has used non potable water for drinking and cooking purposes while away from safe sources, I have on many occasions filled my 30 gallon on board tank with clear river water of water stated as non potable or unsafe to drink, and treated with a ratio of 2 onces of household bleach. Some times the bleach taste comes through as too much was put in. I have also used granulated Spa chlorine not swimming pool chlorine as the Spa chlorine is more convient. One teaspoon to 15 gallons of water. Spa chlorine has a higher percentage of chlorine and has little in the way of non disolvable matter. In both cases the chlorine is mixed with water before pouring into the holding tank. I would submit to you that this procedure would take care of growth of unwanted substances when applied to longer term storage.