weird water question

We have drank from the stream for years and nobody has came down with a case of the " trots" . One a serious note...I contacted someone who has a degree in marine biology and they said that as long as there are no farms using pesticides or fertilizers, or a business that my pump waste water ; we should be fine. They said that any bacteria in the water should be killed off by the salt content of the new water. I am taking a sample to be tested tomorrow and see how I am progressing. It still was the most time consuming thing I have done as far as my tanks. I thought my arm was going to fall off from mixing 255g of water. ( tank + sump ) Wish me luck on the progress of the water. Lord knows I don't want to have to drain and refill that beast again. Have a great day !