All these test kits would check for the presence of small fragments of RNA. If you are applying the test on lots of sewage, it is likely to find some weird fals

All these test kits would check for the presence of small fragments of RNA. If you are applying the test on lots of sewage, it is likely to find some weird false positive that is not COVID-19 in the first. I would find it even more interesting if there were specific agents in sewage, irrelevant from COVID-19, that would cause a false positive.