i the case (i drank water from springs and rivers when i was thirsty for like whole my life, and this goes from jennisej via danube to seine. and i gotten the same comments from collaegues like u, but main problem is that u just have textbook knowledge, and no selfexperience.). Its wise to cook it first if u have to use water from very slow flowing water in great plains, but u wont die or even get a diarhea from it, especially if your body is used to it. Just make the experiment with yourself, u can trink just fine from most lakes / rivers in the western world without catching anything. Now i wouldnt recommend that on some enteramoeba histolytica bearing rainwater pond in the aequator region, but thats a whole other story. And u can cook it just fine in those dangerous regions.
In what field where u working exactly? in this that sells very expensive filter technology that actuelly does nothing because most of the biom in water is actually to small to be filtered? Just do a random dapi test with your "filtered" water u guys export to the 3rd world for much money.
edit: and i forgot all the dogs and cats and horses and cattle and sheep, they die all the time because they drink from rivers.