30 years ago I analysed water for a living. Yeah, you can detect lots of stuff - analytical chemistry has come a long way in the last 30 years. But whether the amounts are meaningful is altogether another matter. There are homeopathic levels of lots of things in tap water - that's why it gets chlorine or chloramine put in it.
Detection limits for things like cocaine are stupid low if you pull out all the stops - parts per billion. 1ppb is 1 milligram of cocaine per ton of water. Now we should drink a couple of litres a day and a typical dose of cocaine is around 15mg. So we need to consume 15 tons of water, 15,000 litres to take one dose of it. Good luck to you getting 15 tons of water into you in any reasonable time - you have maybe an hour.
Detection limits for things like cocaine are stupid low if you pull out all the stops - parts per billion. 1ppb is 1 milligram of cocaine per ton of water. Now we should drink a couple of litres a day and a typical dose of cocaine is around 15mg. So we need to consume 15 tons of water, 15,000 litres to take one dose of it. Good luck to you getting 15 tons of water into you in any reasonable time - you have maybe an hour.